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Detailed CNS Examination — MBBS Clinical Medicine

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PRELIMINARY OBSERVATIONS

• Facial expression: Hypomimia (masked face) → Parkinsonism; worried/astonished look → Progressive supranuclear palsy
• Posture & spontaneous movements: Hemiplegia posture, tremor, dystonia, chorea, myoclonus
• Speech pattern: Dysarthria, aphasia, spasmodic dysphonia
• Ptosis: Suggests myasthenia gravis or brainstem lesion
• Gait (if ambulant): Observe before formal examination

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1. HIGHER MENTAL FUNCTIONS (Cognitive / Mental Status Examination)

Consciousness & Orientation

Speech & Language

• Articulation: Rate, rhythm, prosody — detect dysarthria
• Naming: Ask patient to name parts of a watch/pen (successive detail)
• Repetition: "No ifs, ands, or buts"
• Comprehension: Follow a 3-step verbal command
• Reading: Follow a written command
• Writing: Write a spontaneous sentence

Memory

1. Immediate: Repeat a 3-item list immediately
2. Short-term: Recall same 3 items at 5 min and 15 min
3. Long-term: Coherent chronological illness/personal history

Other Cognitive Domains

• Fund of information: Major historical/current events
• Insight & Judgment: Response to situational scenarios ("What would you do if you found a wallet?")
• Abstract thought: Similarities (apple vs. orange; poetry vs. sculpture); listing 4-legged animals
• Calculation: Serial 7s from 100 (or 3s from 20); simple word problems

— Harrison's Principles of Internal Medicine 22E, p. 3422–3424

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2. CRANIAL NERVE EXAMINATION (CN I–XII)

CN I — Olfactory

• Tested only in suspected inferior frontal lobe disease (e.g., meningioma), head injury, or suspected Parkinson's disease
• Method: Eyes closed → sniff mild odorant (toothpaste, coffee) → identify it

CN II — Optic

• Visual acuity: Snellen chart for each eye (with correction)
• Visual fields: Confrontation — examiner at 0.6–1 m, hands at periphery, patient fixes gaze at examiner's face
• Fundoscopy: Optic disc (pallor, papilloedema, cupping), retinal vessels, macula
• Relative Afferent Pupillary Defect (RAPD): Swinging flashlight test

CN III, IV, VI — Oculomotor, Trochlear, Abducens

• Pupils: Size, symmetry, direct & consensual light reflex, accommodation reflex
• Extraocular movements: Saccades and smooth pursuit in H-pattern; look for nystagmus, diplopia, lid lag
• Ptosis: Assess lid position

CN V — Trigeminal

• Sensory: Pin-prick and light touch in all 3 divisions (V1: forehead; V2: cheek; V3: jaw) bilaterally
• Corneal reflex: Cotton wisp approaching from lateral → blink; tests V1 afferent, VII efferent
• Motor: Open/close jaw against resistance; jaw deviated to side of lesion

CN VII — Facial

• Upper motor neuron (UMN): Forehead spared (bilateral cortical supply)
• Lower motor neuron (LMN): Entire ipsilateral face involved (Bell's palsy)
• Test: "Raise eyebrows, close eyes tight, show teeth, puff cheeks"

CN VIII — Vestibulocochlear

• Auditory: Whispered voice test; Rinne and Weber tests
• Vestibular: Nystagmus, head-impulse test (HIT), HINTS exam if acute vestibular syndrome

CN IX, X — Glossopharyngeal, Vagus

• Ask patient to say "Aah" → palate elevates symmetrically; uvula deviates away from lesion
• Gag reflex (IX afferent, X efferent)
• Note hoarseness (X — recurrent laryngeal nerve)

CN XI — Accessory

• Sternocleidomastoid (SCM): Turn head against resistance; ipsilateral SCM contracts
• Trapezius: Shrug shoulders against resistance

CN XII — Hypoglossal

• Protrude tongue — deviates toward side of LMN lesion; toward opposite side if UMN

— Harrison's Principles of Internal Medicine 22E, p. 3424–3425; Bradley and Daroff's Neurology in Clinical Practice

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3. MOTOR SYSTEM EXAMINATION

Inspection

• Muscle wasting/atrophy: Thenar, hypothenar, interossei, quadriceps, tibialis anterior
• Fasciculations: Fine involuntary twitching → LMN disease (motor neurone disease)
• Abnormal postures: Hemiplegia posture (flexed arm, extended leg)

Tone

• Passively flex/extend limbs at all joints
• Hypotonia: LMN lesion, cerebellar disease
• Spasticity (clasp-knife): UMN lesion — velocity-dependent resistance
• Rigidity (lead pipe/cogwheel): Extrapyramidal/Parkinson's disease

Power (MRC Grading 0–5)

• Upper limb: Shoulder abduction (C5), elbow flexion (C5/6), elbow extension (C7), wrist extension (C7), finger extension (C7), finger abduction (T1), grip (C8)
• Lower limb: Hip flexion (L1/2), knee extension (L3/4), knee flexion (L5/S1), ankle dorsiflexion (L4/5), plantar flexion (S1/2)

Involuntary Movements

• Tremor: Rest (Parkinsonism), intention (cerebellar), postural (essential)
• Chorea: Irregular, jerky
• Dystonia: Sustained abnormal posture
• Myoclonus: Brief, shock-like jerks

— Bradley and Daroff's Neurology in Clinical Practice

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4. DEEP TENDON REFLEXES (DTRs)

• Hyperreflexia → UMN lesion
• Hyporeflexia/areflexia → LMN, peripheral neuropathy, cerebellar disease

Pathological Reflexes

• Plantar response (Babinski sign): Stroke lateral sole heel-to-toe → normal = plantar flexion (downgoing); extensor (upgoing + fanning = Babinski positive) = UMN lesion above S1
• Clonus: Rapid sustained dorsiflexion of ankle → rhythmic beats = UMN lesion
• Hoffman's sign: Flicking terminal phalanx of middle finger → thumb and index flex = UMN lesion in upper limbs
• Jaw jerk: Tap jaw → brisk response = bilateral UMN lesion above pons (pseudobulbar palsy)
• Grasp reflex: Frontal lobe release sign

— Harrison's Principles of Internal Medicine 22E, p. 3425; Ganong's Review of Medical Physiology 26E

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5. SENSORY EXAMINATION

Primary Modalities

Cortical Sensation (test only if primary intact)

• Two-point discrimination: Two points on fingertip (normal ≤5 mm)
• Stereognosis: Identify object by touch alone (coin, key)
• Graphesthesia: Identify number/letter written on palm
• Double simultaneous stimulation: Touch both hands simultaneously — extinction = parietal lobe lesion

Romberg Test

• Eyes open: Maintained balance (tests motor/cerebellar)
• Eyes closed: Loss of balance = positive Romberg = dorsal column/proprioceptive defect (not cerebellar — cerebellar ataxia is present with eyes open)

— Harrison's Principles of Internal Medicine 22E, p. 3425

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6. CEREBELLAR / COORDINATION EXAMINATION

Finger-Nose Test (Upper Limb)

• Intention tremor (tremor worsens near target) + dysmetria (past-pointing) = cerebellar

Heel-Knee-Shin Test (Lower Limb)

• Incoordination = ipsilateral cerebellar lesion

Rapid Alternating Movements (Dysdiadochokinesia)

• Upper limb: Rapidly pronate/supinate hand, or tap index finger on thumb
• Lower limb: Tap foot rapidly
• Irregular, slow = cerebellar

Other Cerebellar Signs

• Rebound phenomenon: Push arm down; overshoots when released
• Nystagmus: Horizontal, direction toward the side of lesion
• Speech: Scanning/staccato dysarthria
• DANISH: Dysdiadochokinesia, Ataxia, Nystagmus, Intention tremor, Speech changes, Hypotonia

— Harrison's Principles of Internal Medicine 22E, p. 3425

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7. GAIT & STATION

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8. SIGNS OF MENINGEAL IRRITATION

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QUICK SUMMARY: UMN vs LMN

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• Harrison's Principles of Internal Medicine 22E (2025) — Cranial nerve, motor, sensory, coordination, and reflex examination
• Bradley and Daroff's Neurology in Clinical Practice — Screening neurological examination
• Adams and Victor's Principles of Neurology 12E — Brief and complete neurological examination
• Ganong's Review of Medical Physiology 26E — UMN vs LMN signs