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PART 1: REPEATED QUESTIONS - FREQUENCY ANALYSIS

15-MARK (LONG ESSAY) QUESTIONS - MOST REPEATED

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5-MARK (SHORT NOTE) QUESTIONS - MOST REPEATED

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PART 2: ALL 15-MARK QUESTION ANSWERS

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Q1. IONTOPHORESIS (Most Repeated - 9 Times)

Definition

Type of Current Used

• Constant Direct Current (CDC) / Galvanic current is used
• Current intensity: 0.1 to 0.5 mA/cm² (safe limit)
• Duration: 15-20 minutes
• Polarity: The ion to be introduced must be placed under the electrode of SAME polarity (like charges repel)

Physical Principle (Electrophoresis Principle)

• When two electrodes are placed in a solution and current is passed, ions migrate:
  • Cations (+ve ions) move toward the cathode (-ve pole)
  • Anions (-ve ions) move toward the anode (+ve pole)
• The medicament is placed under the electrode of the same sign as the ion's charge
• The repulsive force drives the ion into the skin

Mechanism

1. Current flows through the electrolyte solution
2. Ions of the drug dissociate in solution
3. Like-polarity electrode repels the drug ions into the skin
4. Ions penetrate through sweat glands, hair follicles, and inter-cellular spaces
5. Ions deposit in skin forming an "ion depot" - slow release occurs over hours
6. Penetration depth: 1-3 mm into the skin

Ions Used and Their Clinical Indications

Treatment of Idiopathic Hyperhidrosis (Hyperhydrosis)

• Ion used: Tap water (H⁺ ions at anode, OH⁻ at cathode)
• The H⁺ ions block the sweat gland pores
• Method: Patient places hands/feet in two trays of tap water; electrodes in each tray
• Polarity alternated to prevent skin burns
• Sessions: 20-30 minutes, 3-4 times/week; 6-10 sessions for results
• Mechanism: Mechanical blockage of sweat ducts by ion accumulation

Therapeutic Uses

1. Hyperhidrosis (excessive sweating) - tap water
2. Calcific deposits (myositis ossificans) - acetate ions
3. Scars and adhesions - iodine ions
4. Wounds and ulcers - zinc ions
5. Inflammatory conditions - dexamethasone
6. Bursitis, tendinitis - salicylate
7. Local analgesia before injections - lidocaine
8. Poor circulation - histamine

Precautions

• Metal on the skin must be removed
• Sensation must be intact
• Current density must not exceed 0.5 mA/cm²
• Avoid over wounds/broken skin unless specifically treating

Contraindications

• Broken/abraded skin
• Metallic implants under electrodes
• Hypersensitivity to the drug
• Malignancy
• Impaired sensation

Dangers

• Chemical burns (acid burn under anode, alkali burn under cathode)
• Galvanic burn if current too high
• Allergic reactions to drug

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Q2. BIOFEEDBACK (7 Times)

Definition

Principle

• The patient is given a signal (auditory beep, visual meter) that represents a physiological parameter
• The patient learns to modify the parameter by trial and error
• Success (desired change) reinforces the behavior
• With practice, voluntary control improves

Parameters Monitored in Biofeedback

Types of Biofeedback

1. EMG Biofeedback - most used in physiotherapy
2. Thermal Biofeedback - temperature of skin
3. GSR (Galvanic Skin Response) Biofeedback
4. EEG Biofeedback (Neurofeedback)
5. Blood pressure Biofeedback

EMG Biofeedback in Physiotherapy

Muscle activity -> Surface EMG electrodes -> Amplifier -> Display unit (visual/auditory)
        ^                                                         |
        |___________________ Patient feedback ___________________|

• Auditory: pitch increases with muscle activity
• Visual: meter deflects or LED bar lights up

Uses / Applications

1. Muscle re-education - facial palsy, post-surgery, nerve injury
2. Relaxation training - tension headache, anxiety, fibromyalgia
3. Muscle strengthening - post-immobilization, knee replacement
4. Spasticity reduction - stroke, cerebral palsy
5. Gait training - drop foot, hemiplegic gait
6. Incontinence - pelvic floor re-education
7. Postural correction - scoliosis, neck pain
8. Biofeedback-assisted relaxation - stress disorders

Advantages

• Non-invasive
• Immediate real-time feedback
• Increases patient motivation
• Applicable to muscles not visible or easily palpated (e.g., pelvic floor, deep muscles)

Precautions/Contraindications

• Intact skin required for electrode placement
• Complete denervation (no EMG signal)
• Cardiac pacemaker (for EMG devices using current)
• Impaired cognition (patient cannot learn from feedback)

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Q3. TENS - Transcutaneous Electrical Nerve Stimulation (6 Times)

Definition

Parameters of TENS

Types of TENS

1. Conventional (High Frequency) TENS

• Frequency: 80-150 Hz
• Pulse width: 50-100 µs
• Intensity: Sensory level (tingling, no contraction)
• Duration: 20-60 min
• Mechanism: Gate Control Theory - activates large diameter Aβ fibres → inhibits pain transmission in dorsal horn
• Best for: Acute pain, post-operative pain

2. Acupuncture-like (Low Frequency) TENS

• Frequency: 1-10 Hz
• Pulse width: 200-300 µs
• Intensity: Motor level (visible muscle twitch)
• Duration: 20-45 min
• Mechanism: Endogenous Opioid Release - β-endorphins, enkephalins released
• Best for: Chronic pain

3. Burst TENS

• Trains of 7-8 pulses at low frequency (1-4 Hz bursts) superimposed on high frequency (70-100 Hz carrier)
• Combines gate control + opioid release
• Better compliance than AL-TENS (less uncomfortable)

4. Intense TENS

• High frequency (80-150 Hz), high intensity (noxious level)
• Short application to trigger point areas
• Mechanism: Hyperstimulation analgesia (C-fibre inhibition)
• Used: Pre-procedure, brief severe pain

Gate Control Theory (Melzack & Wall, 1965)

Peripheral tissue
     |
     |--- Large A-beta fibres (touch, vibration) ---> Substantia Gelatinosa (SG)
     |--- Small A-delta, C fibres (pain) -----------> SG
                                                       |
                                         [SG acts as a GATE]
                                         Large fibre activation = CLOSES gate
                                         Small fibre activation = OPENS gate
                                                       |
                                               Transmission Cell (T cell)
                                                       |
                                            Pain perception (brain)

Methods of Application

1. Segmental: Electrodes placed over the dermatome of the painful area
2. Para-vertebral: Over the spinal segment supplying the area
3. Trigger point/Acupuncture point: Over tender spots
4. Contralateral: Over opposite limb (for nerve injury)
5. Criss-cross: Electrodes placed to cross the painful area

Indications

• Post-operative pain
• Low back pain, neck pain
• Osteoarthritis, rheumatoid arthritis
• Phantom limb pain
• Dysmenorrhoea
• Labour pain
• Neuropathic pain

Contraindications

• Pacemakers (over chest)
• Over carotid sinus
• Epilepsy (near head)
• Thrombophlebitis
• Pregnancy (over abdomen/lower back)
• Impaired sensation
• Malignancy (directly over)

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Q4. STRENGTH-DURATION (SD) CURVE (6 Times)

Definition

Principle

• A muscle responds to a stimulus only if the stimulus has sufficient intensity AND sufficient duration
• Very short pulses require higher intensity; very long pulses can work at lower intensity (rheobase level)

Parameters

• Rheobase: The minimum current required to produce a response when the duration is very long (infinite duration)
• Chronaxie: The minimum duration required to produce a response when the current is twice the rheobase
• Utilisation time: Time needed for a stimulus equal to rheobase to produce a response

Procedure of Drawing SD Curve

1. Patient positioned comfortably
2. Electrodes placed: Active (small) over motor point; Dispersive (large) on proximal area
3. The duration is set at a long value (e.g., 300 ms) and intensity gradually increased until minimal twitch
4. This intensity is recorded - this is the rheobase
5. Intensity set at 2x rheobase; duration reduced until minimal twitch - this is chronaxie
6. Duration is progressively shortened (e.g., 300 ms → 100 ms → 50 ms → 10 ms → 1 ms) and the threshold intensity noted each time
7. Values plotted: Duration (ms) on X-axis, Intensity (mA) on Y-axis
8. Points connected = SD Curve

Characteristics of SD Curve

Intensity (mA)
  |           Normal Innervated Muscle
  |                    ____/
  |              ___/
  |         __/   <-- Kink/Notch here (if partially denervated)
  |    ___/
  |__/ ← Rheobase
  |________________________ Duration (ms)
       ↑ Chronaxie

The Kink (Notch) in SD Curve

• In a partially denervated muscle, the SD curve shows a kink or inflexion point
• The kink separates the innervated fibres (responding to short pulses) from denervated fibres (needing long pulses)
• Normal muscle has no kink; completely denervated has no kink (one smooth curve far right); partial denervation = kink present

Clinical Uses

1. Diagnosis: Differentiates innervated from denervated muscle
2. Monitors progress of nerve regeneration (chronaxie decreasing = good sign)
3. Guides treatment: Helps select appropriate pulse duration for electrical stimulation
4. Determines degree of nerve injury
5. Used in research for nerve physiology

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Q5. INTERRUPTED DIRECT CURRENT / GALVANIC CURRENT (6 Times)

Definition

Types of IDC

• Surged IDC: Current gradually increases (surge) and then drops
• Interrupted IDC: Current switches ON and OFF abruptly
• Pulse durations used: 100-1000 ms (long durations to stimulate denervated muscle)

Physiological Effects on Innervated Muscle

• Motor stimulation → muscle contraction and relaxation
• Stimulation of sensory and motor nerve fibres
• Increases circulation to the muscle
• Prevents muscle atrophy

Physiological Effects on Denervated Muscle

• Denervated muscle CANNOT respond to short-duration Faradic pulses
• IDC uses long-duration pulses (100-300 ms) → denervated muscle fibres directly stimulated
• Direct stimulation of muscle fibres (bypasses nerve)
• Maintains muscle bulk and vascularity during nerve regeneration
• Prevents fibrosis and atrophy
• Improves nutrition to the muscle

Comparison: Faradic vs Galvanic (IDC) Current

Physiological Effects of Constant Direct Current (CDC)

1. Electrochemical effects: Acid forms under anode, alkali under cathode
2. Vascular effects: Hyperemia under cathode (vasodilation), some vasoconstriction under anode
3. Sensory effects: Tingling/pricking sensation
4. Ion movement: Electrolysis - migration of ions in tissue
5. Nerve stimulation: At make (start) and break (end) of current

Therapeutic Effects

1. Reduction of pain (analgesia)
2. Resolution of edema
3. Wound healing (especially cathode increases healing)
4. Iontophoresis medium (deliver drugs)
5. Muscle stimulation via IDC

Precautions and Dangers

• Burns: Acid burn under anode (HCl formed), alkali burn under cathode (NaOH formed)
• Infection risk
• Electrolytic decomposition of tissue proteins

Uses of IDC

1. Stimulation of denervated muscle (main use)
2. Maintenance of muscle bulk during denervation
3. Prevention of joint contracture
4. Improving circulation

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Q6. INTERFERENTIAL THERAPY (IFT) (5 Times)

Definition

Principle

• Current 1: 4000 Hz
• Current 2: 4000 + 1-150 Hz (e.g., 4100 Hz)
• Beat frequency produced = difference between the two frequencies = 1-150 Hz
• This beat frequency is in the therapeutic low frequency range
• Advantage: 4000 Hz carrier easily penetrates deep tissues (low skin impedance at high frequency); therapeutic effect occurs at the beat frequency

Circuit 1: ~4000 Hz ----\
                         > Interference in tissue = Beat frequency (1-150 Hz)
Circuit 2: ~4100 Hz ----/

Modes of IFT

Frequency (Beat Frequency) and Effects

Parameters

• Carrier frequency: 4000 Hz
• Beat frequency: 1-150 Hz
• Amplitude modulation: fixed or sweep (AMF)
• Electrode placement: quadripolar (4 electrodes in X pattern) or bipolar
• Time: 15-20 minutes
• Intensity: Comfortable tingling, no pain

Physiological Effects

1. Analgesia: Gate control at 80-150 Hz; endorphin release at 1-10 Hz
2. Muscle stimulation: Contraction at 1-50 Hz (treats muscle pump)
3. Increased blood flow: Vasodilation, reduction of edema
4. Nerve stimulation: Activates different nerve fibres based on frequency
5. Anti-inflammatory effect: Reduces inflammatory mediators via increased circulation
6. Stimulation of sympathetic fibres: Vasomotor effects

Indications

• Acute and chronic pain (back pain, neck pain, shoulder pain)
• Muscle strengthening
• Edema reduction
• Stress incontinence (pelvic floor stimulation)
• Fracture healing
• Wound healing

Contraindications

• Pacemaker
• Active malignancy
• Thrombophlebitis
• Pregnancy (over abdomen)
• Infections / fever
• Impaired sensation

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Q7. FARADIC CURRENT (4 Times)

Definition

Production (Smart Bristow Faradic Coil)

• Primary coil connected to a battery (DC source)
• Mechanical interrupter breaks the circuit rhythmically
• Secondary coil produces induced AC current by electromagnetic induction
• The induced current is asymmetrical with a sharp spike on one phase

Waveform

        |
        |↑ (short sharp spike - effective phase)
--------|----|----|----|----|---- (time)
                (long slow phase)

Properties

• Frequency: 50-100 Hz
• Pulse duration: 0.1-1 ms
• Surged at: 12-30 surges/minute
• Only stimulates innervated nerve/muscle (cannot stimulate denervated)

Physiological Effects

1. Muscle contraction: Tetanic smooth contraction due to high frequency
2. Sensory stimulation: Tingling sensation
3. Improved circulation: Muscle pump action increases venous return
4. Psychological effects: Patient awareness of muscle activity (biofeedback aspect)
5. No chemical effects: AC current - no ionophoretic effect

Therapeutic Effects

1. Re-education of paralysed/weak muscles (in intact nerve)
2. Prevention of muscle atrophy (disuse atrophy)
3. Reduction of oedema (muscle pump)
4. Reduction of adhesions (passive movement effect)
5. Relaxation of muscle spasm

Indications

1. Muscle weakness (post-immobilisation, disuse atrophy)
2. Nerve injury (neuropraxia only - nerve intact, conduction blocked)
3. Poor circulation, oedema
4. Post-operative muscle inhibition (e.g., deltoid inhibition post shoulder surgery)
5. Re-education after reconstructive surgery

Contraindications

1. Denervated muscle
2. Malignancy
3. Thrombophlebitis
4. Active infection
5. Hemorrhage
6. Over implanted metals/pacemaker

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Q8. PAIN - TYPES, THEORIES AND MODES OF TENS (3 Times)

Definition

Types of Pain

Pain Fibres

Pain Pathway (Ascending)

Nociceptors (periphery)
    → A-delta & C fibres
    → Dorsal Horn of Spinal Cord (Laminae I, II = Substantia Gelatinosa)
    → Spinothalamic tract (contralateral)
    → Thalamus (VPL nucleus)
    → Somatosensory cortex (perception)
    → Limbic system (emotional component)

Theories of Pain

1. Specificity Theory (Von Frey, 1895)

• Specific pain receptors and pathways exist
• Intensity of pain proportional to degree of tissue damage
• Limitation: Does not explain chronic pain, phantom limb pain

2. Pattern Theory (Goldscheider, 1920)

• All receptors can carry pain if stimulus is intense enough
• Pain is determined by the pattern of nerve firing
• Limitation: Does not explain specific pain quality

3. Gate Control Theory (Melzack & Wall, 1965) - MOST IMPORTANT

Large fibres (Aβ) -----> Substantia Gelatinosa (SG) -----> CLOSES gate
                                     |
Small fibres (Aδ, C) -> SG -----> OPENS gate
                                     |
                               T-cell (Transmission cell)
                                     |
                               Ascending to brain = PAIN

• Large fibre (touch, vibration) activity → SG inhibits T-cell → gate closes → pain reduced
• Small fibre (pain) activity → SG excited → T-cell active → gate opens → pain perceived
• Central control from brain can also close the gate (e.g., distraction, anxiety)
• Explains TENS mechanism

4. Endorphin Theory / Opioid Theory

• Stimulation of certain pathways releases endogenous opioids
• β-endorphins, enkephalins, dynorphins bind to opiate receptors (μ, δ, κ)
• This suppresses pain transmission
• Naloxone (opiate antagonist) reverses this effect

5. Descending Pain Inhibition (Diffuse Noxious Inhibitory Control - DNIC)

• Periaqueductal grey (PAG), nucleus raphe magnus
• Serotonin and norepinephrine mediate descending inhibition of dorsal horn
• Counter-irritation mechanism (rubbing an injury reduces pain)

Modes of TENS for Pain

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Q9. PERIPHERAL NERVE INJURIES - TYPES AND MANAGEMENT (3 Times)

Classification (Seddon's Classification)

Wallerian Degeneration

• Occurs distal to the site of axon injury
• Timeline:
  • 24-48 hours: Axon begins to break up
  • 2-3 days: Myelin sheath fragments
  • 1 week: Schwann cells proliferate, phagocytose debris
  • 2-3 weeks: Distal segment fully degenerated
  • After this: Schwann cells form Bands of Büngner (tubes for axon regrowth)

Tinel's Sign

• Percussion of the nerve at the site of injury produces tingling (paraesthesia) in the distribution of the nerve
• Tinel's sign advancing distally = nerve regeneration occurring

Selection of Current for Treatment

Factors Affecting Axon Regeneration

1. Type of injury (neuropraxia > axonotmesis > neurotmesis)
2. Age (younger = faster regeneration)
3. Level of injury (proximal = slower - muscle may atrophy before nerve arrives)
4. Gap size (surgical repair essential for gaps >3 mm)
5. General health, nutrition
6. Vascularity of injured area

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PART 3: ALL 5-MARK QUESTION ANSWERS

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1. IONTOPHORESIS (5 marks)

• Definition: Introduction of drug ions through skin using DC current
• Mechanism: Like poles repel; drug placed under same-polarity electrode; ions driven into skin
• Drug depot forms in skin; slow release
• Ion selection: Cations (+) under anode; Anions (-) under cathode
• Common ions: Iodine (scars), zinc (wounds), dexamethasone (inflammation), tap water (hyperhidrosis)
• Dosage: 1-4 mA, 15-20 min
• Danger: Chemical burns (acid anode, alkali cathode)

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2. PHYSIOLOGICAL EFFECTS OF INTERFERENTIAL CURRENT (IFT)

1. Analgesia: High beat frequency (80-150 Hz) activates A-beta fibres → gate control
2. Opioid release: Low beat frequency (1-10 Hz) stimulates endorphin release
3. Muscle contraction: Stimulates motor fibres at 1-50 Hz
4. Increased blood flow: Vasodilation, reduces edema, aids healing
5. Sympathetic nerve effects: Vasomotor changes at 90-150 Hz
6. Anti-edema: Muscle contractions act as pump

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3. DIADYNAMIC CURRENTS (Bernard's Currents)

• Definition: Low-frequency pulsed DC currents derived from half-wave or full-wave rectification of 50 Hz AC
• Types:
  • MF (Monophasé fixe): Half-wave rectified 50 Hz; 50 pulses/sec; irritant, analgesia
  • DF (Diphasé fixe): Full-wave rectified; 100 pulses/sec; less irritant; analgesia
  • CP (Courte periode): MF + DF alternating every 1 sec
  • LP (Longue periode): MF + DF alternating every 6 sec
  • RS (Rhythme Syncopé): MF with gaps; muscle stimulation
• Uses: Pain relief, muscle stimulation, edema reduction
• Mechanism: Gate control analgesia; vasodilation from pulsed DC
• Application: 15-20 min, over painful area; cathode on pain site for analgesia

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4. PAIN GATE THEORY (Gate Control Theory)

• Proposed by Melzack and Wall (1965)
• Gate in Substantia Gelatinosa (SG) of dorsal horn (Laminae II)
• Large myelinated fibres (A-beta - touch, vibration, TENS) → SG inhibition → gate CLOSES → pain blocked
• Small unmyelinated fibres (A-delta, C - pain) → SG excitation → gate OPENS → pain perceived
• Transmission cell (T cell) sends pain signals to brain
• TENS (high frequency, low intensity) activates A-beta fibres → closes gate → pain relief
• Central control also modulates the gate (anxiety opens; distraction, relaxation close it)

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5. FARADIC-IDC TEST (Faradic-Galvanic Test / Reaction of Degeneration)

Purpose

Principle

• Innervated muscle: responds to both Faradic (short pulse) AND IDC (long pulse)
• Denervated muscle: responds ONLY to IDC (long pulse); does NOT respond to Faradic

Procedure

1. Patient positioned comfortably
2. Test both normal and affected side for comparison
3. Apply Faradic current (0.1-1 ms pulse) to motor point
   • Innervated: brisk, tetanic contraction
   • Denervated: NO response
4. Apply IDC (100-300 ms pulse, DC) to motor point
   • Innervated: brisk response
   • Denervated: slow, worm-like twitch

Reaction of Degeneration (RD)

Significance

• Partial RD = partial denervation
• Complete RD = complete denervation
• Used to monitor nerve regeneration (Faradic response returns as nerve regenerates)

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6. TENS (5 marks)

• TENS = Transcutaneous Electrical Nerve Stimulation
• Parameters: Frequency 1-150 Hz, pulse width 20-500 µs, amplitude 0-50 mA
• Types: Conventional (HF, sensory level, gate control), AL-TENS (LF, motor level, opioids), Burst (both), Intense (noxious level)
• Mechanism: Gate control (HF-TENS), endorphin release (LF-TENS)
• Uses: Post-op pain, back pain, arthritis, neuropathic pain, dysmenorrhoea
• Contraindications: Pacemaker, pregnancy (abdomen), malignancy, over carotid sinus

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7. ELECTROMAGNETIC INDUCTION / TRANSFORMER

Electromagnetic Induction

• Discovered by Michael Faraday (1831)
• Principle: A changing magnetic field induces an EMF (voltage) in a conductor
• Faraday's Law: EMF induced = -dΦ/dt (rate of change of magnetic flux)
• Lenz's Law: Induced current opposes the change that caused it
• Used in: Transformers, generators, Smart Bristow Faradic coil

Transformer

• Based on mutual induction
• Two coils wound on an iron core
• Primary coil: Input voltage (V₁)
• Secondary coil: Output voltage (V₂)
• Turns ratio: V₁/V₂ = N₁/N₂
• Step-up transformer: N₂ > N₁; V₂ > V₁ (used to increase voltage)
• Step-down transformer: N₂ < N₁; V₂ < V₁ (used to decrease voltage to safe levels in clinic)
• Uses in electrotherapy: Isolating transformer (safety), step-down (mains to clinical voltage)

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8. WALLERIAN DEGENERATION

• Process of degeneration of the axon distal to the site of nerve injury
• Timeline:
  • Days 1-2: Axon begins to fragment; Schwann cell reaction begins
  • Days 3-7: Myelin breaks into ovoids, macrophages infiltrate
  • Week 1-3: Complete breakdown of axon and myelin
  • Week 2-3: Schwann cells form Bands of Büngner (longitudinal tubes)
  • Bands of Büngner guide the regenerating axon from proximal stump
• Rate of regeneration: 1-3 mm/day (1 mm/day average)
• Clinically: Electrical excitability of distal nerve lost by 7-10 days
• Tinel's sign follows the regenerating front
• EMG changes: Fibrillation potentials appear in denervated muscle (7-21 days post-injury)

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9. RADIAL NERVE PALSY / WRIST DROP

Radial Nerve

• Arises from posterior cord of brachial plexus (C5-C8, T1)
• Supplies: Triceps, brachioradialis, all wrist extensors, finger extensors

Wrist Drop (Radial Nerve Palsy)

• Wrist cannot be extended (dropped)
• Loss of extension of wrist, fingers, thumb
• Sensory loss: Dorsum of hand (small area - "Saturday night palsy" area)

Causes

• Compression at spiral groove of humerus (Saturday night palsy - sleeping with arm over chair)
• Fracture of mid-shaft humerus
• Honeymoon palsy (pressure from partner's head)
• Injection injury

Physiotherapy Management

1. Splinting: Cock-up splint to maintain wrist in extension (functional position)
2. Electrical stimulation:
   • If neuropraxia: Faradic current to wrist/finger extensors
   • If axonotmesis/neurotmesis: IDC (long pulse) to denervated muscles
3. Passive movements: Prevent joint contracture, maintain range of motion
4. Sensory re-education: If sensation recovering
5. Strengthening: Progressive resistance exercise as nerve recovers
6. Functional training: ADL with splint; grip, pinch training

Assessment

• Test wrist extension (lost), finger extension (lost), thumb extension (lost)
• Check triceps power (if injury at axilla - also lost)
• SD curve to confirm denervation

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10. BELL'S PALSY

Definition

Nerve: CN VII (Facial Nerve)

• Motor to all muscles of facial expression
• Secretomotor to lacrimal, submandibular, sublingual glands
• Taste from anterior 2/3 tongue (chorda tympani)

Features

• All muscles of facial expression affected (upper and lower face)
• Cannot close eye (lagophthalmos) - risk of corneal ulcer
• Drooping of corner of mouth; saliva dribbles
• Loss of nasolabial fold
• Loss of taste (anterior 2/3 tongue)
• Hyperacusis (stapedius paralysis)

Difference: Bell's Palsy vs UMN Facial Palsy

Physiotherapy Treatment

1. Electrical stimulation:
   • Faradic current to facial muscles (if nerve is intact - neuropraxia)
   • IDC if denervated (rarely needed in Bell's palsy - usually neuropraxia)
   • Use small facial electrodes; very low intensity
2. Facial exercises: Voluntary contractions of affected muscles
3. EMG Biofeedback: To re-educate specific facial muscles
4. Eye care: Artificial tears, patching at night (prevent corneal damage)
5. Massage: Gentle effleurage to maintain muscle tone
6. Ice: Reduce inflammation
7. Patient education: Protection of eye, preventing contracture

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11. FUNCTIONAL ELECTRICAL STIMULATION (FES)

• Application of electrical stimulation to produce functional movement by activating paralysed muscles
• Provides a substitute for lost motor function (not just therapeutic stimulation)
• Uses closed-loop feedback: sensors detect limb position → stimulator adjusts accordingly
• Common applications:
  1. Foot drop stimulation: Peroneal nerve stimulation - dorsiflexion during swing phase of gait
  2. Hand grasp: Stimulation of forearm muscles in quadriplegia
  3. Phrenic nerve stimulation: Respiratory assist in high cervical injury
  4. Bladder stimulation: Sacral anterior root stimulation for micturition
  5. Scoliosis (historical)
• Parameters: Similar to faradic; adjustable pulse width, frequency, intensity
• Advantage: Functional gain for patient, not just muscle maintenance

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12. FARADIC FOOT BATH

• A method of applying faradic current to the muscles of the foot and leg via water medium
• Patient places feet in a basin of warm water
• Electrodes immersed in the water; current applied
• Whole foot receives the current simultaneously (unlike focal application)
• Uses:
  1. Flat foot (pes planus) - stimulate intrinsic foot muscles
  2. Weak arch muscles
  3. Poor circulation to feet
  4. General muscle toning of foot intrinsics
• Parameters: Faradic surged; 0.5-2 A (higher because of resistance of water and tissue); 15-20 min
• Precautions: Check for cuts or abrasions; water must be clean; sensation must be intact

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13. NERVE CONDUCTION TEST (NCT / NCV)

Definition

Types

1. Motor nerve conduction velocity (MNCV): Stimulate nerve, record muscle response (CMAP - Compound Muscle Action Potential)
2. Sensory nerve conduction velocity (SNCV): Record sensory nerve action potential (SNAP)

Procedure (Motor NCV - e.g., Median nerve)

1. Recording electrode on thenar eminence (APB muscle)
2. Stimulate median nerve at wrist → record latency (distal latency)
3. Stimulate at elbow → record latency (proximal latency)
4. NCV = Distance / (Proximal latency - Distal latency)

Normal Values

• Motor NCV: 45-65 m/s (upper limb), 40-55 m/s (lower limb)
• Reduced in demyelinating neuropathy
• F-wave and H-reflex assess proximal nerve conduction

Clinical Uses

1. Diagnose peripheral neuropathy (diabetes, alcohol)
2. Locate site of nerve compression (carpal tunnel - reduced at wrist)
3. Differentiate neuropraxia from axonotmesis
4. Monitor nerve recovery after injury
5. Assess severity of nerve damage

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14. EMG BIOFEEDBACK (Electromyography Biofeedback)

• Surface electrodes detect electrical activity (EMG) from muscles
• Signal amplified and converted to auditory/visual feedback in real-time
• Patient uses feedback to learn to increase or decrease muscle activity
• Applications in physiotherapy:
  1. Muscle re-education (Bell's palsy, post-op quadriceps, hemiplegic arm)
  2. Relaxation training (tension headache, neck muscle hypertonicity)
  3. Stress incontinence (pelvic floor - internal electrodes)
  4. Spasticity reduction (stroke)
  5. Gait retraining (drop foot - tibialis anterior feedback)
• Father of EMG biofeedback: Dr. John Basmajian

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15. ACTION POTENTIAL

• Rapid change in membrane potential that travels along nerve/muscle fibre

Phases

1. Resting: -70 mV (K⁺ inside, Na⁺ outside; Na⁺/K⁺ ATPase pump maintains)
2. Depolarisation: Stimulus → Na⁺ channels open → Na⁺ rushes IN → membrane reaches +30 to +40 mV
3. Repolarisation: Na⁺ channels close; K⁺ channels open → K⁺ flows OUT → membrane returns to -70 mV
4. After-hyperpolarisation: Brief period below resting (-80 mV) as K⁺ channels slowly close
5. Refractory period:
   • Absolute: Cannot be stimulated at any intensity (Na⁺ channels inactivated)
   • Relative: Can be stimulated with supramaximal stimulus

All-or-None Law

• Once threshold reached, action potential fires fully or not at all
• Intensity of AP does not vary; frequency of APs encodes stimulus intensity

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16. CHRONAXIE AND RHEOBASE

• Rheobase: Minimum current intensity needed to excite a tissue when the pulse duration is very long (practically infinite)
• Chronaxie: Minimum duration needed to excite a tissue using a current of 2x rheobase intensity
• Normal chronaxie:
  • Motor nerve: 0.08-0.7 ms
  • Skeletal muscle: 0.7-1.0 ms
  • Denervated muscle: >10 ms (much longer)
• Chronaxie increases in denervation (direct index of excitability)
• Clinically used to: Select pulse duration for stimulation; monitor nerve recovery

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17. THERMIONIC VALVES (Triode and its uses)

• Thermionic valve = vacuum tube in which electrons are emitted thermionically (heated cathode)
• Diode: Cathode (heated filament) + Anode; allows current in ONE direction only (rectification)
• Triode: Cathode + Anode + Control Grid; grid controls electron flow
  • Small voltage on grid controls large anode current = amplification
• Uses of Triode:
  1. Amplification of small electrical signals (EMG, ECG)
  2. Oscillators (generate AC signals for therapy machines)
  3. Rectification
  4. Switching in early electrotherapy machines
• Largely replaced by transistors and integrated circuits, but understanding principles is required

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18. PELVIC FLOOR STIMULATION (Faradism of Pelvic Floor)

• Electrical stimulation of pelvic floor muscles using internal vaginal/anal electrodes or external pad electrodes
• Uses:
  1. Stress urinary incontinence (weak sphincter, post-partum)
  2. Urge incontinence
  3. Mixed incontinence
  4. Post-prostatectomy incontinence
  5. Pelvic organ prolapse
• Parameters: 35-50 Hz for stress incontinence (fast twitch fibres); 5-10 Hz for urge incontinence (bladder inhibition)
• Biofeedback: Internal electrode + pressure transducer to show patient pelvic floor activity
• Combination of FES + Kegel exercises most effective

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19. SINUSOIDAL CURRENT

• Pure alternating current (AC), frequency 50 Hz, waveform is a true sine wave
• Produced from AC mains supply directly
• Equal positive and negative phases (no net DC effect)
• Smooth, gradual rise and fall (unlike faradic spike)
• Uses: Muscle stimulation (innervated), pain relief, mild faradism substitute
• Low polar effects (no chemical burns unlike DC)
• Less used today - replaced by more versatile pulse generators

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20. PARAMETERS OF INTERFERENTIAL THERAPY (IFT)

1. Carrier frequency: 4000 Hz (medium frequency)
2. Beat frequency (AMF): 1-150 Hz (therapeutic range)
3. Sweep range: Range of AMF swept to prevent accommodation (e.g., 80-120 Hz)
4. Electrode placement: Quadripolar (4 electrodes) or bipolar (2 electrodes pre-modulated)
5. Intensity: Comfortable sensory tingling to visible muscle contraction
6. Duration: 15-20 minutes
7. Vector rotation: Rotating the field to treat a wider volume of tissue

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SUMMARY: TOP 5 MOST LIKELY EXAM QUESTIONS

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1. Iontophoresis is the single most repeated 15-mark question - know it thoroughly including all ions and uses
2. For SD Curve - draw the graph clearly showing normal vs denervated curve and the kink
3. For Gate Control Theory - draw the diagram of SG, T-cell, large and small fibres
4. For IFT - know the difference between beat frequency ranges and their effects
5. For Faradic-IDC Test - know the Reaction of Degeneration table clearly

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ALL 2-MARK QUESTIONS AND ANSWERS

BPT 3rd Year - Electrotherapy I (LMF / Low & Medium Frequency)

Both PDFs Combined (2011-2025)

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ELECTRICITY / PHYSICS BASICS

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1. Ohm's Law

• V = Voltage (Volts)
• I = Current (Amperes)
• R = Resistance (Ohms)

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2. Joule's Law

• Square of the current (I²)
• Resistance (R)
• Time (t)

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3. Capacitance

• Capacitance is the ability of a body (capacitor) to store electrical charge.
• Unit: Farad (F); clinically microfarad (µF)
• A capacitor has two conducting plates separated by an insulator (dielectric)
• When charged, energy is stored in the electric field between the plates
• Used in electrotherapy machines to produce pulsed currents and waveform shaping

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4. Resistance in Series and Parallel

• Skin acts as resistance to current flow; it decreases when wet (relevant to safe electrotherapy)

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5. Impedance

• Impedance (Z) is the total opposition to flow of alternating current in a circuit.
• Includes resistance (R) and reactance (capacitive + inductive)
• Unit: Ohm (Ω)
• Skin has high impedance to low-frequency currents; high-frequency (4000 Hz IFT) penetrates deeper because impedance is lower at higher frequencies

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6. Fuse

• A fuse is a safety device made of a thin wire that melts and breaks the circuit when current exceeds a safe limit.
• Protects electrotherapy machines and patients from electrical overload
• Should be of correct rating (Ampere value)
• Types: Cartridge fuse, rewirable fuse
• Always placed in the live wire of the circuit

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7. Types of Electric Current

1. Direct Current (DC): Unidirectional flow; e.g., Galvanic current
2. Alternating Current (AC): Reverses direction periodically; e.g., Sinusoidal current
3. Pulsed Current: Interrupted DC or AC; e.g., Faradic, TENS, IFT

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8. Amplitude

• Amplitude is the maximum displacement of a wave from its zero/rest position
• In electrical terms: the peak current (mA) or peak voltage (V) reached by a waveform
• Determines the strength (intensity) of stimulation
• Higher amplitude → stronger stimulus → greater muscle contraction or sensory response

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9. Define Ampere and Ohm

• Ampere (A): Unit of electric current; 1 ampere = flow of 1 coulomb of charge per second
• Ohm (Ω): Unit of electrical resistance; 1 ohm = resistance when 1 volt drives 1 ampere of current

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10. Mutual Induction

• Mutual induction is the phenomenon where a changing current in one coil (primary) induces an EMF in a nearby coil (secondary).
• Basis of the transformer and the Smart Bristow Faradic coil
• Faraday's Law: EMF induced = -M × dI/dt (M = mutual inductance coefficient)

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11. Lenz's Law

• Lenz's Law states that the induced current always flows in a direction to oppose the change in magnetic flux that caused it.
• It is the electromagnetic equivalent of Newton's Third Law
• Explains why the faradic coil produces an asymmetrical current (the self-opposition creates a sharp spike)

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12. Switch

• A switch is a device that opens or closes an electrical circuit.
• Types: Single pole single throw (SPST), double pole, rotary, foot switch
• In electrotherapy: used to start/stop current, change polarity (reversing switch)

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13. Diode Valve

• A diode (thermionic diode) is a vacuum tube with a heated cathode and an anode.
• Allows current to flow in one direction only (from cathode to anode)
• Used for rectification: converts AC to DC
• Modern diodes are semiconductor-based (p-n junction); same function

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14. Triode Valve

• A triode is a vacuum tube with cathode, anode, and a control grid between them.
• Small voltage on the grid controls large anode current = amplification
• Uses: Amplify small biological signals (EMG, ECG), oscillators in therapy machines
• Largely replaced by transistors today

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15. Semiconductors

• Materials that conduct electricity better than insulators but less than metals (e.g., Silicon, Germanium)
• Conductivity can be controlled by adding impurities (doping): p-type and n-type
• Form the basis of transistors, diodes, and all modern electronic circuits in therapy machines

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16. Rheostat

• A rheostat is a variable resistor used to control the flow of current by changing resistance.
• Operated by a sliding contact along a resistance wire
• In electrotherapy: used to smoothly increase/decrease current output
• Prevents sudden surges of current (safety)

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17. Variable Transformer (Variac)

• A variable transformer allows the output voltage to be varied continuously from 0 to maximum
• Used to control intensity in electrotherapy machines
• Sliding carbon brush moves along tapped secondary coil winding

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18. Choke Coil (Inductor)

• A choke coil is an inductor that resists changes in AC current
• Has high inductive reactance to AC but very low DC resistance
• Used to smooth out pulsating DC (filtering) in power supply circuits of therapy machines

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19. Eddy Current

• Eddy currents are induced circulating currents in a conductor when exposed to a changing magnetic field (electromagnetic induction)
• In transformers: eddy currents in the iron core cause energy loss as heat
• Minimized by using laminated iron core
• Used therapeutically in shortwave diathermy (deep heating via eddy currents in tissue)

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20. Medium Frequency Currents

• Currents with frequency range of 1000-100,000 Hz (1-100 kHz)
• Examples: Interferential current (4000 Hz carrier), Russian current (2500 Hz)
• Advantages over low frequency: Lower skin impedance → deeper penetration; less discomfort
• Less polar (electrochemical) effects on skin

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NERVE AND MUSCLE PHYSIOLOGY

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21. Resting Membrane Potential

• The resting membrane potential is the electrical potential difference across the cell membrane at rest: -70 mV (inside negative relative to outside)
• Maintained by:
  • High K⁺ inside the cell
  • High Na⁺ outside the cell
  • Na⁺/K⁺ ATPase pump (3 Na⁺ out, 2 K⁺ in)
  • Negatively charged proteins inside
• This potential is essential for nerve and muscle excitability

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22. Action Potential

• A rapid, self-propagating reversal of membrane potential in response to a threshold stimulus
• Phases: Depolarisation (Na⁺ in, -70 → +40 mV), Repolarisation (K⁺ out, +40 → -70 mV), After-hyperpolarisation (-80 mV briefly)
• Obeys the All-or-None Law
• Propagates along nerve fibre; speed depends on myelination and fibre diameter

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23. Propagation of Action Potential

• Action potential travels along a nerve fibre by local circuit currents
• At the excited area: Na⁺ rushes in → depolarised
• This creates a local current to the adjacent resting membrane → adjacent area depolarises
• In myelinated fibres: Saltatory conduction (jumps node to node of Ranvier) → faster conduction
• In unmyelinated fibres: Continuous propagation → slower

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24. All-or-None Law

• A nerve or muscle fibre either fires a complete, full-sized action potential or it does not fire at all
• Sub-threshold stimulus → no response
• Threshold stimulus → full action potential (no partial APs)
• Intensity of stimulus above threshold does NOT increase the size of the AP; only frequency of APs increases

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25. Refractory Period

• The period after an action potential during which the membrane cannot be re-excited
• Absolute Refractory Period (ARP): No stimulus, however strong, can produce another AP (Na⁺ channels inactivated)
• Relative Refractory Period (RRP): A stronger-than-normal stimulus can produce an AP (K⁺ channels still open, membrane hyperpolarised)
• ARP limits the maximum firing frequency of a nerve

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26. Types of Nerve Fibres

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27. Motor Point

• The motor point is the point on the skin surface that overlies the entry of the motor nerve into the muscle belly - the point of lowest electrical resistance for motor nerve stimulation
• Stimulation here produces the maximum muscle contraction with minimum current
• Located in the proximal one-third of the muscle (where the nerve enters)
• Used for: Diagnostic testing (FG test, SD curve) and therapeutic muscle stimulation

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28. Motor Unit

• A motor unit consists of one motor neurone and all the muscle fibres it innervates
• Small motor units (e.g., eye muscles): few fibres → fine, precise movement
• Large motor units (e.g., quadriceps): many fibres → strong, less precise movement
• Recruitment of more motor units → stronger contraction
• EMG records the Motor Unit Action Potential (MUAP)

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29. Neuromuscular Junction (NMJ)

• The NMJ is the synapse between the motor nerve terminal and the muscle fibre
• Acetylcholine (ACh) released from nerve terminal → binds nicotinic receptors on motor end plate → depolarisation → muscle contracts
• ACh broken down by acetylcholinesterase
• Blocked by: curare, botulinum toxin
• Diseases: Myasthenia gravis (antibodies to ACh receptors)

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30. Synapse

• A synapse is the junction between two nerve cells where information is transmitted
• Types: Chemical synapse (most common) and electrical synapse (gap junction)
• Chemical synapse: Presynaptic terminal releases neurotransmitter → diffuses across synaptic cleft → binds postsynaptic receptor → EPSP or IPSP
• Can be excitatory (glutamate) or inhibitory (GABA, glycine)

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31. H-Reflex

• The H-reflex (Hoffmann reflex) is the electrical equivalent of the monosynaptic stretch reflex (tendon jerk)
• Low-intensity electrical stimulation of a mixed nerve (e.g., tibial nerve behind knee) → activates Ia sensory fibres → monosynaptic reflex arc → motor response recorded in soleus muscle
• H-reflex = assesses integrity of Ia afferents and alpha motor neurones
• Clinically: Absent or delayed in S1 radiculopathy, peripheral neuropathy
• Normal latency: ~30 ms in soleus

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32. F-Wave

• The F-wave is a late motor response obtained by supramaximal stimulation of a peripheral nerve
• Antidromic conduction to motor neurone cell body → "backfires" → orthodromic impulse travels distally → small, late muscle response
• Assesses proximal nerve conduction (nerve roots, plexus)
• Normal latency: 25-32 ms (upper limb), 45-56 ms (lower limb)
• Delayed in Guillain-Barré syndrome, proximal neuropathies

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33. Latency (Latent Period)

• Latency is the time interval between the application of a stimulus and the onset of the muscle response (CMAP)
• Distal latency: From wrist stimulation to muscle response
• Prolonged latency = slowed conduction = nerve compression or demyelination
• Example: Carpal tunnel syndrome → prolonged median nerve distal latency

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34. Fibrillation Potential

• A fibrillation potential is a spontaneous electrical discharge of a single denervated muscle fibre
• Appears 7-21 days after nerve injury (when Wallerian degeneration is complete)
• On EMG: Small amplitude (20-200 µV), short duration (1-5 ms), biphasic/triphasic waveform
• Not visible clinically (unlike fasciculations)
• Indicates denervation; disappears when nerve regenerates

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35. Compound Motor Unit Action Potential (CMAP)

• CMAP is the summation of all muscle fibre action potentials in a muscle recorded during nerve stimulation
• Reflects the number of motor axons and muscle fibres responding
• Amplitude reduced in axon loss (axonotmesis, neurotmesis)
• Normal latency prolonged in demyelination
• Used in Nerve Conduction Study (NCS)

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36. Wallerian Degeneration

• Degeneration of the axon and myelin distal to the site of nerve injury
• Day 1-3: Axon fragments; Day 3-7: Myelin breaks down
• Macrophages and Schwann cells phagocytose debris
• Schwann cells form Bands of Büngner - tubes guiding axon regrowth
• Rate of regrowth: ~1 mm/day
• Fibrillation potentials appear in the muscle within 2-3 weeks

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37. Classification of Nerve Injury (Seddon's)

1. Neuropraxia: Myelin damaged, axon intact → full recovery, responds to Faradic current
2. Axonotmesis: Axon damaged, endoneurium intact → slow recovery (1 mm/day), needs IDC initially
3. Neurotmesis: Complete nerve cut → no spontaneous recovery, needs surgery

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38. Neuropraxia

• Lowest grade of nerve injury (Seddon Grade I)
• Myelin sheath is damaged; axon is structurally intact
• Conduction block: nerve cannot transmit impulses
• No Wallerian degeneration
• Recovery: Complete, spontaneous, within days to weeks
• Electrotherapy: Faradic current (innervated muscle, short pulse) to maintain muscle
• Example: Saturday night palsy (radial nerve compression)

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39. Stimulation of Denervated Muscle

• Denervated muscle cannot be stimulated by Faradic (short pulse) current - nerve is absent
• Requires long-duration pulses (100-1000 ms) of IDC (Interrupted Direct Current)
• Parameters: Pulse width 100-300 ms, intensity sufficient for visible twitch
• Purpose: Maintain muscle bulk, prevent fibrosis, maintain contractility until nerve regenerates
• Confirmed denervation by: No response to Faradic; slow worm-like response to IDC; SD curve shifted right; EMG shows fibrillation potentials

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40. Characteristics of Denervated Muscle

1. Loss of voluntary contraction
2. Wasting and atrophy (muscle bulk reduces)
3. Loss of tone (flaccid)
4. No response to Faradic current (short pulses)
5. Slow, worm-like response to IDC (long-duration pulses)
6. SD curve: Shifted to right, no kink, high rheobase, long chronaxie (>10 ms)
7. EMG: Fibrillation potentials, positive sharp waves; no voluntary MUAPs

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41. Skin Resistance Test

• Skin offers resistance to electrical current
• The skin resistance test uses a galvanometer/ohmmeter to measure skin resistance at various points
• Areas with low resistance indicate: sweat gland openings, acupuncture points, motor points, nerve endings
• Normal dry skin: 100,000 - 1,000,000 Ω
• Wet skin / over motor point: much lower
• Used to locate motor points and acupuncture points before electrotherapy

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42. Tinel's Sign

• Tinel's sign is tingling (paraesthesia) felt distally when the site of nerve injury or compression is tapped
• Positive Tinel's sign at the point of regeneration = nerve is regenerating (advancing Tinel's = good sign)
• Positive Tinel's at wrist (median nerve) = Carpal Tunnel Syndrome
• Used to: Track nerve regeneration progress, detect sites of compression

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43. Kink (Kinked Curve) in SD Curve

• A kink is an inflexion point on the Strength-Duration curve
• Seen in partially denervated muscle
• The kink separates two populations of muscle fibres:
  • Innervated fibres responding to short pulses (left part of curve)
  • Denervated fibres responding only to long pulses (right part of curve)
• Normal muscle: kink present (due to nerve and muscle thresholds)
• Completely denervated: smooth curve, no kink, shifted far right
• Reappearance of kink = nerve regeneration occurring

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44. Factors Affecting Accuracy of SD Curve

1. Patient cooperation (movement artefacts)
2. Electrode placement (must be exactly on motor point)
3. Skin preparation (clean, no thick callus)
4. Current leakage (wet skin, contacts)
5. Patient's pain sensitivity affecting response threshold
6. Experience of the examiner in detecting minimal twitch
7. Position of limb (must be consistent each time)

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45. Advantages and Disadvantages of SD Curve

• Sensitive indicator of denervation
• Monitors nerve regeneration progress
• Guides selection of pulse duration for treatment

• Requires skilled, experienced examiner
• Time-consuming
• Subjective (depends on examiner observing minimal twitch)
• Affected by pain, oedema, thick fat
• Less precise than EMG

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SPECIFIC CURRENTS AND TREATMENTS

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46. Russian Current

• Russian current is a medium-frequency AC at 2500 Hz, delivered in bursts of 10 ms ON and 10 ms OFF (50 bursts/second)
• Developed by Dr. Yakov Kots (Soviet sports scientist) for muscle strengthening in athletes
• Comfortable at high intensities due to medium frequency (less skin impedance)
• Produces strong tetanic muscle contractions without discomfort
• Used for: Muscle strengthening, disuse atrophy, sports rehabilitation, post-surgical muscle training
• Protocol: 10 min, 10 sec ON / 50 sec OFF ratio; 3-4 weeks

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47. Waveform of Faradic Current

• Faradic current produces an asymmetrical biphasic waveform:
  • Sharp, brief spike in the effective phase (cathode negative, ~0.1-1 ms)
  • Long, slow return phase (less effective)
• The sharp spike stimulates sensory and motor nerves
• Total duration: ~10-20 ms
• Frequency: 50-100 Hz
• Waveform produced by electromagnetic induction (Smart Bristow coil or electronic equivalent)

     |  (sharp spike)
     |↑
-----|----\_________/----\_________/---- (time)
           (slow return)

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48. Stimulation Type for Acute Pain (TENS for Acute Pain)

• Conventional (High Frequency) TENS is used for acute pain
• Frequency: 80-150 Hz
• Pulse width: 50-100 µs
• Intensity: Sensory threshold (strong tingling, no muscle contraction)
• Mechanism: Gate Control Theory (Melzack & Wall) - activates A-beta fibres, closes pain gate
• Onset: Fast (within minutes); effect wears off quickly after stopping

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49. Ions Used in Iontophoresis

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50. Dangers of Iontophoresis

1. Chemical burns: Acid (HCl) under anode → acid burn; Alkali (NaOH) under cathode → alkali burn
2. Allergic reaction to the drug used
3. Galvanic burns from excessive current density (>0.5 mA/cm²)
4. Skin irritation and blistering
5. Drug overdose (systemic absorption - rare)

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51. Dosage of Iontophoresis

• Current intensity: 1-4 mA (0.1-0.5 mA/cm² of electrode area)
• Duration: 15-20 minutes
• Total charge: 40-80 mA·min (calculated as: current × time)
• Electrode: Active (drug pad) = same polarity as drug ion; Dispersive = opposite polarity
• Drug concentration: 2-5% solution

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52. Contraindications of Iontophoresis

1. Broken or abraded skin
2. Metallic implants/pins directly under electrodes
3. Known allergy to the drug
4. Active malignancy in the area
5. Impaired/absent sensation
6. Fever, acute infections

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53. Erythema (and how to prevent it)

• Erythema is redness of skin due to vasodilation of superficial blood vessels
• Seen under the cathode (more active) during galvanic current application
• Due to: Histamine release, axon reflex, increased blood flow
• Grades:
  • Grade I: Faint pink (normal reaction)
  • Grade II: Bright red (over-treatment warning)
  • Grade III: Vesicles (burn beginning)
  • Grade IV: Burns
• Prevention: Correct current density (<0.5 mA/cm²), adequate electrode padding, do not exceed treatment time, check skin regularly

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54. Glidemeister Effect (Galvanic Tetanus Ratio)

• The Glidemeister effect describes the change in threshold of a nerve/muscle with continuous DC current:
  • Under cathode: Threshold is lowered (easier to excite) → catelectrotonus
  • Under anode: Threshold is raised (harder to excite) → anelectrotonus
• Galvanic Tetanus Ratio (GTR): The ratio of current needed to produce tetanic contraction vs a minimal twitch; altered in denervated vs innervated muscle
• Used diagnostically to assess nerve integrity

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55. Syncopated Rhythm

• Syncopated rhythm is the pause/gap pattern in surged faradic current
• The surge is rhythmically paused at regular intervals creating a "syncopation" (off-beat rhythm)
• Used to prevent muscle fatigue during prolonged stimulation
• Clinically useful in: Muscle re-education in fatigue-prone conditions

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56. Cathodal Galvanism

• Application of constant direct current with the cathode (negative electrode) as the active electrode
• Effects under cathode:
  • Hyperemia (redness, increased blood flow)
  • Lowered nerve threshold (easier excitation)
  • Formation of NaOH (can cause alkali burn if excessive)
  • Used for: Wound healing, stimulation, increasing circulation

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57. Effects of Chlorine Ionisation (Chlorine Ions in Iontophoresis)

• Chlorine is an anion (negative charge) → applied under cathode
• Drug: Sodium Chloride (NaCl) - liberates Cl⁻ ions
• Effects in tissue: Breaks down scar tissue, softens adhesions, loosens fibrotic tissue
• Used for: Keloid scars, scar softening, adhesions

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58. Wheal

• A wheal is a raised, smooth, pale skin swelling (like a mosquito bite) with surrounding redness
• Produced by: Histamine release in the skin (type I hypersensitivity, or from histamine iontophoresis)
• In iontophoresis with histamine: Wheal and flare reaction = increased local blood flow
• Also seen in: Urticaria, skin prick allergy tests

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59. Acute Pain

• Acute pain is pain that is sudden in onset, short in duration (< 3 months), with a clear cause (tissue damage)
• Protective function: warns of actual/potential tissue injury
• Characteristics: Well-localised, resolves with healing
• Mediators: Prostaglandins, bradykinin, histamine, substance P
• Treatment: TENS (conventional HF), NSAIDs, rest, ice

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60. Edema

• Edema is excess fluid accumulation in the interstitial space
• Causes: Increased capillary pressure, reduced oncotic pressure (low albumin), increased permeability, lymphatic obstruction
• Electrotherapy management:
  • High voltage pulsed current (HVPC)
  • IFT (muscle pump action)
  • Faradic stimulation (improves venous return)
  • TENS (reduces pain, allows movement)

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61. Allodynia

• Allodynia is pain produced by a stimulus that is normally NOT painful (e.g., light touch causing severe pain)
• Seen in: Neuropathic pain, Complex Regional Pain Syndrome (CRPS), fibromyalgia
• Mechanism: Central sensitisation - reduced threshold of pain-signalling neurons
• Clinically differentiated from hyperalgesia (exaggerated pain response to a painful stimulus)

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CLINICAL CONDITIONS

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62. Foot Drop

• Foot drop is the inability to dorsiflex the foot due to weakness/paralysis of the dorsiflexor muscles (tibialis anterior, extensor digitorum longus)
• Cause: Common peroneal nerve palsy (most common), L4-L5 nerve root lesion, stroke
• Gait: High-stepping gait (steppage gait) to clear the ground
• Electrotherapy:
  • Neuropraxia: Faradic to common peroneal nerve / tibialis anterior
  • Axonotmesis: IDC to denervated tibialis anterior
  • FES (functional electrical stimulation): Peroneal nerve stimulator during walking

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63. Wrist Drop (Early Stage)

• Wrist drop = inability to extend wrist due to radial nerve palsy
• Early stage management:
  • Cock-up splint to hold wrist in extension
  • Faradic current (if neuropraxia) to extensor muscles
  • Passive range of motion exercises
  • Sensory protection education

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64. Bell's Palsy

• Unilateral idiopathic lower motor neuron facial palsy (CN VII)
• All facial muscles affected: Cannot close eye, droop of angle of mouth
• Distinguish from UMN: In Bell's palsy, forehead is affected (in UMN - forehead spared)
• Treatment: Steroids (medical), eye protection, Faradic stimulation, facial exercises, EMG biofeedback

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65. Difference between Bell's Palsy and Facial Palsy

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66. Carpal Tunnel Syndrome

• Compression of the median nerve in the carpal tunnel at the wrist
• Features: Paraesthesia (pins and needles) in thumb, index, middle, and half ring finger; pain at night; thenar wasting in severe cases
• Positive Phalen's and Tinel's tests at wrist
• Diagnosis confirmed by NCV (prolonged median nerve distal motor latency)
• Treatment: Wrist splint (neutral position at night), ultrasound, TENS for pain; surgery if severe

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67. Erb's Palsy

• Injury to the upper trunk of brachial plexus (C5, C6 roots)
• Typically from forceful shoulder depression and head deviation (during birth injury)
• Muscles affected: Deltoid, supraspinatus, infraspinatus, biceps, brachioradialis
• "Waiter's tip" position: Arm adducted, internally rotated, elbow extended, forearm pronated, wrist flexed
• Treatment: Physiotherapy, electrical stimulation, passive exercises, splinting

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68. Lumbricals and Interossei

• Intrinsic hand muscles
• Lumbricals (4): Flex MCPJs and extend IPJs; medial two by ulnar nerve, lateral two by median nerve
• Interossei:
  • Dorsal (4): Abduct fingers (DAB)
  • Palmar (3): Adduct fingers (PAD)
  • All interossei supplied by ulnar nerve
• Wasted in ulnar nerve palsy; tested by Froment's sign (compensatory IP flexion for adductor pollicis weakness)

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69. Tardy Ulnar Nerve Palsy

• Late onset ulnar nerve palsy occurring long after an old lateral condyle fracture (cubitus valgus deformity)
• The increased valgus angle stretches the ulnar nerve at the cubital tunnel over years
• Features: Clawing of ring and little fingers, wasting of hypothenar and interossei, loss of grip, sensory loss (medial 1.5 fingers)

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70. Ape Thumb Deformity

• Deformity seen in median nerve palsy (thenar muscle wasting)
• Thenar eminence is flat; thumb lies in the plane of the palm
• Cannot oppose thumb (loss of opponens pollicis)
• Thumb is extended and adducted (looks like ape's thumb)
• Cause: Thenar wasting from median nerve damage at wrist (carpal tunnel) or forearm

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71. SD Curve in Partially Denervated Muscle

• Shows TWO components separated by a kink/inflexion point
• Left part: Innervated fibres responding to short pulses (normal threshold)
• Right part: Denervated fibres needing long pulses (elevated threshold)
• Kink is the most important finding: confirms partial denervation
• As nerve regenerates: kink moves leftward, right component shrinks

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ASSESSMENT AND PROCEDURES

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72. Preparation of Patient for Electrical Stimulation

1. Explain the procedure to the patient (gain consent)
2. Remove jewelry and metallic objects in the area
3. Check for contraindications (pacemaker, malignancy, etc.)
4. Test skin sensation with pin-prick before treatment
5. Clean and dry the skin
6. Position patient comfortably
7. Apply electrodes with adequate padding/gel
8. Start current from zero, increase gradually
9. Observe patient's response throughout

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73. Types of Electrodes (in Electrotherapy)

1. Metal plate electrodes: Zinc/tin, covered with moist lint; used for IDC/galvanic
2. Carbon rubber electrodes: Flexible, used with coupling gel; used for TENS, faradic
3. Suction electrodes: Rubber cups with vacuum; hold themselves in place; used for IFT
4. Facial electrodes: Small, button-type; for facial palsy treatment
5. Vaginal/rectal electrodes: Internal electrodes for pelvic floor work
6. Needle electrodes: For EMG recording

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74. Suction Electrode

• Suction electrodes are rubber cup electrodes that attach to the skin by vacuum suction
• Used mainly in Interferential Therapy (IFT)
• Advantage: Hands-free application; patient can perform exercises during treatment
• The suction also provides a massage effect (vacuum increases local circulation)
• Disadvantage: May cause bruising if suction too high; not for fragile skin

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75. Checking Apparatus for Electrical Muscle Stimulation

1. Check mains supply, fuse condition
2. Test all knobs and switches for smooth functioning
3. Check cables and leads for kinks, breaks
4. Check electrode condition (no holes, good contact)
5. Output meter reading should start from zero
6. Test on oneself before patient (feel tingling, confirm output)
7. Ensure adequate padding for electrodes
8. Check polarity switch and timer function

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76. Placement and Settings for IFT

• Electrode placement: Quadripolar - 4 electrodes placed so the two current circuits cross at the target tissue (e.g., knee pain: one pair above/below, one pair on medial/lateral sides)
• Carrier frequency: 4000 Hz
• Beat frequency (AMF): 80-120 Hz for pain (acute); 1-10 Hz for muscle stimulation; 25-50 Hz for circulation
• Intensity: To comfortable tingling or gentle muscle contraction
• Time: 15-20 minutes

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77. Masking Effect (TENS)

• The masking effect refers to TENS providing pain relief by replacing the pain sensation with a more acceptable tingling sensation (masking of pain by TENS)
• The tingling from TENS is perceived instead of pain
• This is one component of conventional TENS analgesia (alongside gate control)
• The comfortable paresthesia "masks" or overrides the pain signal

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78. Feedback Loop (Biofeedback)

• A feedback loop in biofeedback is the pathway by which the patient receives information about their own physiological process and uses it to voluntarily modify that process
• Loop: Physiological activity → Sensor → Signal processor → Display (auditory/visual) → Patient perception → Motor learning → Modified activity → back to start
• Closed-loop system; continuous and real-time

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79. Latent Period

• The latent period (delay) is the time between stimulus application and the beginning of the observable muscle contraction
• Components: Time for nerve conduction + NMJ transmission + excitation-contraction coupling
• For motor nerve: very short (~1-2 ms)
• Prolonged in: Nerve compression, demyelination, NMJ disorders

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80. Orthodromic Conduction

• Orthodromic conduction is nerve impulse transmission in the normal (natural) direction:
  • Sensory nerve: Periphery → CNS
  • Motor nerve: CNS → Periphery
• Opposite is antidromic (backwards conduction - e.g., F-wave generation)
• Sensory NCV studies use orthodromic conduction (stimulate digit, record at wrist)

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81. Maximum Voluntary Isometric Contraction (MVIC)

• MVIC is the greatest possible force a muscle can generate when it contracts isometrically (no joint movement) at maximum effort
• Used as a reference in:
  • EMG studies (% MVIC used to normalise EMG amplitude)
  • Biofeedback training (target level for feedback)
  • Manual Muscle Testing (Grade 5 = able to hold against maximum resistance)

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82. Advantages of Interferential Therapy

1. Deep tissue penetration (4000 Hz carrier bypasses skin impedance)
2. Less skin resistance = more comfortable at high intensities
3. Minimal polar effects (no chemical burns)
4. Treats large areas with quadripolar electrode arrangement
5. Can combine analgesia and muscle stimulation in one treatment
6. Patient can exercise during treatment (suction electrodes)

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83. Advantages and Uses of IFT (Short)

• Advantages: Deep penetration, comfortable, large area coverage, minimal adverse effects
• Uses: Pain relief (back pain, shoulder, knee), edema reduction, muscle strengthening, incontinence, wound healing

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84. Impedance / Beat Frequency / Medium Frequency Currents (already covered above)

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85. Sinusoidal Current

• Pure AC at 50 Hz with a true sine wave shape
• Smooth, gradual rise and fall
• Equal positive and negative phases (no net DC component)
• Less polar effects than DC
• Stimulates innervated muscle
• Mostly replaced by modern electronic pulse generators
• Used for: Mild faradism, general stimulation, muscle tone

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86. Tinel's Sign (2-mark short form)

• Tapping over a compressed or regenerating nerve produces tingling (paraesthesia) distally
• Positive at wrist = Carpal Tunnel; advancing distally after nerve injury = regeneration occurring

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87. Russian Current (2-mark short form)

• 2500 Hz medium frequency AC in 50 bursts/sec; developed by Kots
• Used for muscle strengthening; comfortable due to low skin impedance at medium frequency

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88. Wallerian Degeneration (2-mark short form)

• Distal axon and myelin degeneration after nerve injury
• Schwann cells form Bands of Büngner → guide regenerating axon
• Rate: 1 mm/day

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89. Current Selection Based on Nerve Injury Type

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90. Resistance in Series and Parallel (2-mark short form)

• Series: R_total = R₁ + R₂ (total increases; current same throughout)
• Parallel: 1/R_total = 1/R₁ + 1/R₂ (total decreases; voltage same across each)

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QUICK FREQUENCY TABLE: MOST REPEATED 2-MARK TOPICS

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Exam Tip: For 2-mark answers, write 2-3 sentences maximum - give the definition + one clinical point. For example: "Resting membrane potential is -70 mV maintained by the Na⁺/K⁺ ATPase pump. It is the baseline electrical state required for nerve/muscle excitability." - That is a perfect 2-mark answer.