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Complete cns examination in medicine
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I now have comprehensive content from two authoritative textbooks. Let me compile the complete CNS examination.
Complete CNS (Neurological) Examination in Medicine
The neurological examination is organized into 7 major components. Every central nervous system region, peripheral nerve, muscle, sensory modality, and reflex must be assessed systematically.
1. GENERAL OBSERVATION (before touching the patient)
Begin assessing from the moment the patient enters. Note:
- Facial expression - lack of expression (hypomimia) suggests Parkinsonism or depression; worried/astonished expression suggests progressive supranuclear palsy
- Ptosis - suggests myasthenia gravis or brainstem lesion
- Speech pattern - dysarthria, aphasia, or spasmodic dysphonia
- Abnormal involuntary movements - tremor, dystonia, chorea, athetosis
- Gait - observe as patient walks in
2. HIGHER MENTAL FUNCTIONS (Mental Status)
- Consciousness level - alert, confused, stuporous, comatose
- Orientation - time, place, person
- Memory - immediate, recent, remote
- Attention and concentration
- Speech and language - assess for aphasia, dysarthria
- Mood and behavior
- Cognitive functions - calculation, abstraction, judgment
Glasgow Coma Scale (GCS) - used to quantify level of consciousness:
| Component | Score |
|---|---|
| Eye Opening: Spontaneous / To speech / To pain / None | 4 / 3 / 2 / 1 |
| Verbal Response: Oriented / Confused / Inappropriate words / Sounds / None | 5 / 4 / 3 / 2 / 1 |
| Motor Response: Obeys / Localizes / Withdraws / Abnormal flexion / Extension / None | 6 / 5 / 4 / 3 / 2 / 1 |
Total = 3-15; score ≤8 = coma.
3. CRANIAL NERVE EXAMINATION (CN I - XII)
CN I - Olfactory Nerve
- Ask patient: can you smell? Test each nostril separately with familiar substances (coffee, vanilla)
- Anosmia: suggests olfactory groove meningioma or frontal lobe tumour
- Parosmia (perversion of smell): suggests uncinate gyrus lesion
CN II - Optic Nerve
- Visual acuity: ask patient to read different letter types, or count fingers at distance
- Visual fields by confrontation: patient gazes at a fixed point; move a white pin/finger from periphery to centre both horizontally and vertically. Test each eye separately
- Fundoscopy: look for papilloedema, optic atrophy, hypertensive/diabetic changes
- Swinging flashlight test: detects relative afferent pupillary defect (RAPD)
| Visual Field Defect | Lesion Location |
|---|---|
| Monocular blindness | Optic nerve (ipsilateral) |
| Bitemporal hemianopia | Optic chiasm (e.g. pituitary tumour) |
| Homonymous hemianopia | Optic tract / radiation (contralateral) |
| Upper quadrantic defect | Pituitary tumour pressing chiasm from below |
| Lower quadrantic defect | Suprasellar cyst pressing chiasm from above |
CN III, IV, VI - Oculomotor, Trochlear, Abducent Nerves
- Pupils: size, shape, symmetry. Normal = 3-4 mm, equal, round
- Dilated pupil + loss of light/accommodation reflex = CN III palsy
- Pinpoint pupils = pontine lesion
- Pupillary reflexes: direct and consensual light reflex; accommodation reflex
- Ocular movements: ask patient to follow your finger in all 6 directions (H pattern). Note any limitation
- Diplopia: ask if patient sees double in any direction
- Ptosis, squint, nystagmus: nystagmus indicates cerebellar or vestibular lesion
- Conjugate deviation: in cerebral hemisphere lesions, eyes deviate toward the side of a paralytic lesion; in pontine lesions, eyes deviate away from the paralytic side
CN III palsy: ptosis, eye deviated down and out (external-inferior squint), dilated pupil, diplopia
CN IV palsy: inability to look down and inward; vertical diplopia
CN VI palsy: internal squint, inability to abduct the eye, diplopia on lateral gaze
CN V - Trigeminal Nerve
- Motor: feel masseter and temporalis while patient clenches teeth; ask patient to open mouth - jaw deviates toward affected side (pterygoid paralysis)
- Sensory: test pinprick and light touch in all 3 divisions (V1: forehead; V2: cheek; V3: chin/jaw). Also test anterior 2/3 of tongue
- Corneal reflex: touch cornea lightly with cotton wool - both eyes should blink (afferent: CN V; efferent: CN VII)
- Jaw jerk: tap the chin with mouth slightly open - exaggerated jaw jerk = bilateral upper motor neurone lesion
CN VII - Facial Nerve
Inspect for flattened nasolabial fold and drooping of angle of mouth.
Motor testing (ask patient to):
- Show teeth - angle of mouth drawn to healthy side in paralysis
- Puff out cheeks - paralysed side balloons more
- Close eyes tightly - cannot close on affected side; eyeball rolls upward (Bell's phenomenon)
- Raise eyebrows / wrinkle forehead - forehead spared in UMN lesion (bilateral cortical representation); forehead involved in LMN lesion
Upper vs Lower Motor Neurone lesion:
- UMN (central): lower face only affected, forehead spared
- LMN (peripheral, e.g. Bell's palsy): entire ipsilateral face affected including forehead
CN VIII - Vestibulocochlear (Auditory) Nerve
- Hearing: use a ticking watch or whispered voice; note distance at which patient can hear
- Rinne's test: tuning fork (512 Hz) - air conduction vs bone conduction
- Normal/Sensorineural loss: AC > BC (Rinne positive)
- Conductive loss: BC > AC (Rinne negative)
- Weber's test: tuning fork on vertex - lateralises to the affected ear in conductive loss; lateralises to the normal ear in sensorineural loss
- Vestibular function: nystagmus, Romberg's test, Dix-Hallpike
CN IX - Glossopharyngeal Nerve
- Test sensation over posterior 1/3 of tongue and back of pharynx (probe/orange stick)
- Note asymmetry between left and right sides
- Gag reflex: touch posterior pharynx (afferent: CN IX; efferent: CN X)
CN X - Vagus Nerve
- Ask patient to open mouth, depress tongue with spatula
- Say "Aah" - observe palate movements; in paralysis the affected half remains immobile
- The uvula deviates away from the paralysed side
- Voice: hoarseness suggests recurrent laryngeal nerve involvement
CN XI - Accessory Nerve
- Sternocleidomastoid: ask patient to turn face to opposite side against resistance from examiner's hand; paralysed SCM does not stand out
- Trapezius: ask patient to shrug shoulders against resistance
CN XII - Hypoglossal Nerve
- Ask patient to protrude tongue - tip points toward paralysed side
- Patient unable to move tongue to opposite side
- In long-standing cases: hemiatrophy of the tongue
4. MOTOR SYSTEM EXAMINATION
a) Inspection
- Wasting/atrophy: measure limb circumference if asymmetry suspected
- Fasciculations: spontaneous muscle twitching at rest = LMN lesion
- Abnormal posture
b) Tone
- Assess resistance to passive movement at each joint
- Hypotonia (flabby, decreased resistance): LMN lesion, cerebellar lesion
- Spasticity (velocity-dependent increase): UMN lesion - clasp-knife character
- Rigidity (constant throughout range): Parkinson's disease
- Lead-pipe rigidity: uniform resistance
- Cogwheel rigidity: tremor superimposed on rigidity
c) Power (MRC Grading Scale)
| Grade | Description |
|---|---|
| 0 | No movement |
| 1 | Flicker of contraction only |
| 2 | Movement with gravity eliminated |
| 3 | Movement against gravity, not against resistance |
| 4 | Movement against some resistance |
| 5 | Normal power |
Test all major muscle groups systematically (shoulder abduction, elbow flexion/extension, wrist extension, grip, hip flexion, knee flexion/extension, ankle dorsiflexion/plantarflexion).
Quick screening tests:
- Patient can do a push-up, rise from floor without using hands, walk on toes and heels - power is normal
- Hold arms extended in supination with eyes open - pronator drift indicates contralateral UMN lesion
d) Coordination
| Test | What It Detects |
|---|---|
| Finger-nose test | Cerebellar dysmetria (eyes open then closed) |
| Heel-shin test | Lower limb cerebellar ataxia |
| Rapid alternating movements (pronation/supination) | Dysdiadochokinesia (cerebellar lesion) |
| Tandem gait (heel-toe walking) | Cerebellar or proprioceptive ataxia |
e) Involuntary Movements
Observe for:
- Tremor: resting (Parkinsonism), intention (cerebellar), postural/essential
- Chorea: brief, random, flowing movements
- Athetosis: slow writhing movements
- Myoclonus: sudden, brief muscle jerks
- Tics: repetitive, stereotyped movements
- Hemiballismus: violent flinging movements (subthalamic nucleus lesion)
5. SENSORY SYSTEM EXAMINATION
Always test with patient's eyes closed.
a) Superficial/Primary Sensations
- Light touch: cotton wool
- Pain/Pinprick: pin; compare both sides, proximal to distal
- Temperature: test tubes of hot/cold water
b) Deep/Proprioceptive Sensations
- Vibration sense: 128 Hz tuning fork on bony prominences (great toe, malleoli, tibial tuberosity, iliac crest)
- Joint position sense (proprioception): hold digit at sides; move up or down; ask patient to identify direction. Start distally
c) Cortical/Discriminative Sensations (test if primary sensations intact)
- Stereognosis: ability to recognize objects placed in hand by touch alone (failure = astereognosis in parietal lobe lesions)
- Graphesthesia: ability to identify numbers/letters written on skin
- Two-point discrimination: minimum distance at which two stimuli perceived as separate
- Sensory extinction: present simultaneous bilateral stimuli; neglect of one side = parietal lobe lesion
d) Romberg's Test
Patient stands with feet together - perform with eyes open, then closed.
- Positive Romberg (falls with eyes closed, stable with open): dorsal column/proprioceptive deficit
- Cerebellar ataxia: falls with eyes both open AND closed (not a positive Romberg)
6. REFLEXES
Deep Tendon Reflexes (DTR)
| Reflex | Level | Method |
|---|---|---|
| Biceps | C5, C6 | Tap examiner's thumb on biceps tendon |
| Triceps | C7 | Tap just above olecranon with elbow flexed |
| Supinator (brachioradialis) | C5, C6 | Tap radial styloid |
| Knee jerk (patellar) | L2, L3, L4 | Tap ligamentum patellae; leg extends briskly |
| Ankle jerk | S1, S2 | Foot slightly dorsiflexed; tap Achilles tendon |
Grading: 0 (absent) | 1+ (diminished) | 2+ (normal) | 3+ (brisk) | 4+ (clonus)
Clonus: rhythmic involuntary contractions at ankle/knee = UMN lesion
Interpretation:
- DTR exaggerated + superficial reflexes absent/altered: pyramidal (UMN) lesion
- DTR diminished/absent: LMN lesion, peripheral neuropathy, cerebellar lesion
Superficial/Skin Reflexes
| Reflex | Level | Response |
|---|---|---|
| Plantar reflex | S1 | Normal: flexion of big toe. Babinski's sign (extensor plantar = UMN lesion): big toe extends, other toes fan out |
| Abdominal reflexes | T7-T11 | Stroke abdominal wall; umbilicus moves toward that quadrant. Absent in UMN lesion |
| Cremasteric reflex | T12 | Scratch inner thigh; testis draws upward |
| Corneal reflex | CN V, VII | Touch cornea; bilateral blink |
Primitive/Pathological Reflexes
- Babinski's sign: extensor plantar response - most important sign of UMN lesion
- Hoffmann's sign: upper limb equivalent of Babinski; flick terminal phalanx of middle finger
- Jaw jerk: exaggerated = bilateral UMN lesion above pons
- Grasp reflex: persistent grasping to palm touch = frontal lobe lesion
7. GAIT AND STANCE
Observe gait carefully - often the most revealing part of the examination.
| Gait Pattern | Description | Lesion |
|---|---|---|
| Hemiplegic | Arm flexed, leg circumducts (circumduction gait) | UMN - contralateral hemisphere |
| Paraplegic / Scissor | Legs stiff, cross each other (scissor gait) | Bilateral UMN |
| Steppage | High stepping, foot slap (foot drop) | LMN / peripheral nerve (common peroneal) |
| Cerebellar ataxic | Wide-based, unsteady, reeling | Cerebellum |
| Sensory ataxic | Wide-based, stamps feet, worse in dark | Dorsal columns |
| Parkinsonian | Shuffling, small steps, stooped, festinant | Basal ganglia |
| Waddling | Pelvic tilting side to side | Proximal myopathy / muscular dystrophy |
| Antalgic | Limp, reduced weight bearing | Pain |
Tandem gait (heel-to-toe walking): tests cerebellar function and proprioception.
Summary: UMN vs LMN Lesion Features
| Feature | UMN Lesion | LMN Lesion |
|---|---|---|
| Wasting | Mild (disuse) | Severe |
| Fasciculations | Absent | Present |
| Tone | Spasticity (clasp-knife) | Hypotonia/flaccidity |
| Power | Weak (pyramidal distribution) | Weak (affected muscle groups) |
| DTR | Exaggerated, clonus | Diminished or absent |
| Plantar reflex | Extensor (Babinski +ve) | Flexor (normal) |
| Abdominal reflexes | Absent | Normal |
Sources: Bradley and Daroff's Neurology in Clinical Practice; S Das A Manual on Clinical Surgery 13th Ed; 22nd Edition Pye's Surgical-Handicraft
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