Medicine : CNS examination

CNS Examination

Higher Functions Examination

1. General Appearance and Behavior

  • Level of consciousness: Alert, drowsy, stuporous, comatose.
  • Mood and affect: Observe emotional state and congruence.
  • Behavior: Cooperative, agitated, withdrawn.
  • Dress and grooming: Appropriate, clean, disheveled.
  • Eye contact: Normal, poor, or avoidant.

2. Orientation

  • Time: Ask date, day of week, season.
  • Place: Ask location, city, hospital name.
  • Person: Ask patient’s name, examiner’s identity.

3. Intelligence

  • Serial 7s: Subtract 7 from 100 repeatedly.
  • Spelling backward: e.g., “WORLD.”
  • Digit span: Recall numbers forward and backward.

4. Memory

  • Immediate recall: Repeat 3 words right away.
  • Recent memory: Recall same 3 words after 5 minutes.
  • Long-term memory: Ask about verifiable life events (e.g., birthplace, school names).

5. Language

  • Fluency: Observe spontaneous speech.
  • Comprehension: Follow simple and complex commands.
  • Naming: Identify objects (pen, watch).
  • Repetition: Repeat set phrases.
  • Reading and writing: Read and follow instructions, write a sentence.

6. Judgment

  • Assessment: Ask hypothetical questions (e.g., “What would you do if you found a money on the ground?”).

Cranial Nerve Examination

Cranial Nerve I – Olfactory Nerve

How to Examine

1. Patient Preparation

  • Ensure both nostrils are clear (ask if there's nasal congestion).
  • Ask the patient to close their eyes and not speak during testing.

2. Test Each Nostril Separately

  • Occlude one nostril with your finger.
  • Bring a non-irritant, familiar smelling substance (e.g. coffee, vanilla, soap) close to the open nostril.
  • Ask the patient:
    • “Can you smell anything?”
    • “Can you identify the smell?”
  • Repeat the same steps for the opposite nostril.

3. Substances Used

  • Use non-irritating, recognizable substances:
    • Coffee
    • Soap
    • Vanilla
    • Clove oil
  • Do NOT use irritants like ammonia or spirit — they stimulate the trigeminal nerve, not olfactory.

4. Interpretation

  • Normal: Patient correctly identifies the smell in both nostrils.
  • Abnormal findings:
    • Anosmia: No perception of smell
    • Hyposmia: Diminished smell
    • Hyperosmia: Increased smell sensitivity
    • Parosmia: Distorted smell perception
    • Cacosmia: Foul smell in absence of stimulus
    • Olfactory hallucinations: Perception without stimulus

5. Clinical Correlation

  • Unilateral anosmia may indicate:
    • Frontal lobe tumour
    • Subfrontal meningioma
  • Bilateral anosmia may be seen in:
    • Neurodegenerative diseases (e.g. Alzheimer’s, Parkinson’s)
    • Head injury
    • Ageing

Cranial Nerve II – Optic Nerve

Examination Includes:

  • Visual Acuity
  • Visual Fields
  • Colour Vision
  • Pupillary Light Reflexes
  • Fundus Examination (Ophthalmoscopy)

1. Visual Acuity Test

  • Purpose: To assess clarity of vision.
  • Tools: Snellen chart (at 20 feet) or near-vision card.
  • Steps:
    • Ask the patient to cover one eye (test each eye separately).
    • Ask them to read the smallest line they can.
    • Record the result (e.g., 20/20, 20/40).
    • Repeat for the other eye.

2. Visual Field Test (Confrontation Test)

  • Purpose: To assess peripheral vision.
  • Steps:
    • Sit or stand at eye level, about 2 feet apart.
    • Ask the patient to cover one eye while you cover the opposite eye (mirror them).
    • Ask them to look directly at your eye.
    • Move your fingers or a small object in from the periphery and ask them to tell you when they first see it.
    • Repeat for all quadrants in both eyes.

3. Fundoscopic Exam (Ophthalmoscopy)

  • Purpose: To visualize the retina and optic disc.
  • Steps:
    • Use an ophthalmoscope in a darkened room.
    • Look for:
      • Optic disc (sharpness, color)
      • Retinal vessels
      • Macula
      • Signs of papilledema, hemorrhages, or optic atrophy

4. Pupillary Light Reflex

Preparation

  • Dim the room slightly to make the pupils more responsive.
  • Ask the patient to look into the distance (to prevent accommodation).
  • Use a penlight or flashlight.
  • Observe both pupils at rest before starting (note size and symmetry).
Direct Light Reflex
  • Definition: Constriction of the pupil in the same eye where the light is shone.
  • Steps:
    • Ask the patient to fix their gaze straight ahead.
    • Shine a light directly into one eye from the side.
    • Observe the illuminated pupil for constriction (miosis).
    • This assesses:
      • Afferent limb: Optic nerve (CN II)
      • Efferent limb: Oculomotor nerve (CN III)
Indirect (Consensual) Light Reflex
  • Definition: Constriction of the opposite eye’s pupil when light is shone into one eye.
  • Steps:
    • Without moving the light, observe the other eye.
    • You should see pupil constriction in the non-illuminated eye as well.
    • This tests the same afferent limb (CN II) but the opposite efferent limb (CN III).

Cranial Nerves III, IV, VI – Oculomotor, Trochlear, Abducens

1. Ocular Movements (Extraocular Movements)

  • CN III (Oculomotor): Controls superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris, pupillary constriction.
  • CN IV (Trochlear): Controls superior oblique.
  • CN VI (Abducens): Controls lateral rectus.
  • How to Examine:
    • Ask the patient to follow your finger with their eyes without moving their head.
    • Move your finger in an “H” pattern.
    • Observe for diplopia, nystagmus, limited movement, or ptosis.

2. Pupillary Light Reflex

  • Tests CN II (afferent) and CN III (efferent).
  • How to Examine:
    • Darken the room slightly.
    • Ask the patient to look straight ahead.
    • Shine a penlight into one eye:
      • Direct response → constriction in the same eye.
      • Consensual response → constriction in the opposite eye.
  • Interpretation:
    • No constriction in either eye → CN II damage (afferent).
    • Constriction only in opposite eye → CN III damage (efferent).

3. Accommodation Reflex

  • Tests CN II (afferent) and CN III (efferent).
  • How to Examine:
    • Ask the patient to look at a distant object.
    • Then ask them to focus on a near object (e.g., your finger 10 cm from nose).
    • Watch for pupil constriction, convergence of eyes.

Cranial Nerve V – Trigeminal Nerve

1. Sensory Function

  • Assess all three divisions for light touch, pain, and temperature.
  • Regions:
    • V1: Forehead and upper scalp
    • V2: Cheek and upper lip
    • V3: Jaw and lower lip

2. Motor Function

  • Only mandibular (V3) has motor fibers.
  • Ask the patient to:
    • Clench their teeth – palpate masseter and temporalis.
    • Open their mouth against resistance – observe for deviation.

3. Reflexes

  • Corneal Reflex: V1 (sensory) + VII (motor).
  • Jaw Jerk Reflex: V3 motor – exaggerated in UMN lesions.

Cranial Nerve VII – Facial Nerve

1. Inspection

  • Look for facial asymmetry, drooping, flattened nasolabial fold, incomplete eye closure, involuntary movements.

2. Motor Function

  • Ask the patient:
    • Raise eyebrows
    • Close eyes tightly
    • Smile/show teeth
    • Puff out cheeks
    • Purse lips/whistle
    • Frown
  • UMN lesion: Forehead spared.
  • LMN lesion: Whole side affected.

3. Taste (Anterior 2/3 tongue)

  • Test with sweet, salty, sour if complaint present.

4. Reflexes

  • Corneal Reflex: Motor limb CN VII.
  • Hyperacusis: Stapedius muscle paralysis.

Cranial Nerve VIII – Vestibulocochlear Nerve

1. Cochlear Function

  • Whisper/finger rub test.
  • Rinne’s test: AC>BC normal/sensorineural, BC>AC conductive.
  • Weber’s test: Conductive → lateralizes to affected ear; Sensorineural → to unaffected.

2. Vestibular Function

  • Ask about vertigo, dizziness, imbalance.
  • Nystagmus: Horizontal = peripheral; Vertical = central.
  • Romberg test: Positive if sway with eyes closed.
  • Unterberger’s test: Turning suggests vestibular dysfunction.

Cranial Nerve IX – Glossopharyngeal Nerve

Examination

  • Gag Reflex: Afferent limb CN IX.
  • Taste posterior 1/3 tongue: Rarely tested.

Cranial Nerve X – Vagus Nerve

Examination

  • Palate Elevation: Say "ah" → uvula deviates away from lesion.
  • Speech/Voice: Hoarseness or nasal tone.
  • Cough: Weak/hoarse cough suggests dysfunction.
  • Gag Reflex: Efferent limb CN X.

Cranial Nerve XI – Accessory Nerve

Examination

  • Sternocleidomastoid: Turn head against resistance.
  • Trapezius: Shrug shoulders against resistance.

Cranial Nerve XII – Hypoglossal Nerve

1. Tongue at Rest

  • Look for wasting, fasciculations (LMN sign).

2. Tongue Protrusion

  • Normal: Midline.
  • LMN lesion: Deviates toward lesion.
  • UMN lesion: Deviates away from lesion (no atrophy/fasciculations).

3. Tongue Movements

  • Ask to move side to side, up/down, press against cheek.
  • Check for asymmetry or weakness.

Examination of Motor System

A. Nutrition (Muscle Bulk)

Examination

  • Inspection: Look for atrophy and hypertrophy.
    Normal: No gross difference in muscle bulk bilaterally.
  • Palpation:
    • Atrophic muscle → flabby
    • Hypertrophic muscle → firm
    • Normal → bilaterally soft
  • Measurement: Circumference of limbs:
    • Upper limbs: 10 cm above & 10 cm below olecranon
    • Lower limbs: 18 cm above patella & 10 cm below tibial tuberosity
    Normal: Equal circumference bilaterally

B. Tone

Definition: Tension in a normally relaxed muscle.

Assessment: By inspection, palpation, and passive movement of joints.

In unconscious patient: Drop test → limb on hypotonic side falls lifeless.

Hypertonia

  • Inspection: Muscles stand out with convex bellies
  • Palpation: Firm consistency
  • Passive movement: Resistance → spasticity or rigidity
Spasticity

Hypertonia more in antigravity muscles → clasp-knife type.
• UL: flexors > extensors
• LL: extensors > flexors
Cause: Pyramidal (UMN) lesion.

Rigidity

Uniform tone ↑ in both agonist & antagonist groups.
Cause: Extrapyramidal lesion.

  • Lead pipe rigidity: Uniform resistance (Parkinsonism, basal ganglia tumor, catatonia)
  • Cog wheel rigidity: Intermittent resistance from tremor (Parkinson’s, drug-induced, CO poisoning)
  • Hysterical rigidity: Resistance ↑ with examiner’s effort (hysteria)

Hypotonia

  • Inspection: Lax, pendulous muscles
  • Palpation: Flabby feel
  • Passive movement: Wide range, little resistance

Causes: LMN lesions (poliomyelitis, polyneuritis, nerve injury), sensory lesions (tabes dorsalis, herpes zoster), combined lesions (syringomyelia, root compression, myopathies), spinal shock, cerebellar disease, chorea, periodic paralysis, REM sleep, drug overdose.

Clonus

Definition: Repetitive contractions after sudden muscle stretch.

Demonstration: Ankle clonus (dorsiflexion), Patellar clonus (push patella down).

  • Sustained clonus: Indefinite → definite pyramidal lesion
  • Ill-sustained clonus: ≤6 beats; can be normal but ≥6 suggests pyramidal lesion

Myotonia

Definition: Delayed relaxation after contraction.

Features: Transverse smile, prolonged hand grip.

Causes: Myotonic dystrophy, Myotonia congenita, Paramyotonia congenita (worsens with cold).

C. Power

Definition: The voluntary force of contraction generated by a muscle.

Testing:

  • Assessed systematically in different muscle groups from head to foot.
  • Weakness is evaluated by comparing with the opposite (normal) side.
  • Distribution of weakness is noted:
    • Proximal muscles (near the trunk)
    • Distal muscles (farther from the trunk)
    • Both proximal and distal

Clinical importance: The pattern of muscle weakness (proximal, distal, or both) helps in diagnosis. Causes are the same as those for muscle wasting.

General principle:

  • Larger muscle groups usually have greater power.
  • Exceptions:
    1. Muscles of mastication (small) have more power than larger pectoral muscles.
    2. In muscular dystrophies → power is weak despite large size (pseudohypertrophy).
    3. In motor neuron disease → muscle wasting is present, but some power is preserved.

MRC Grading of Power:

  • Grade 0: No power
  • Grade I: Flicker of contraction only
  • Grade II: Movement with gravity eliminated
  • Grade III: Movement against gravity
  • Grade IV: Movement against gravity & some resistance
  • Grade V: Normal power

D. Coordination Examination

Coordination of the limbs can be effectively tested only if muscle power is greater than grade 3.

  • The procedure should be explained clearly to the patient.
  • Both limbs are examined and results compared.
  • Tests are first done with eyes open, then with eyes closed (helps detect posterior column lesions).

Coordinated action depends on:

  • Cerebellar control
  • Extrapyramidal system influence
  • Proprioceptive sense & body image

Lesions in these systems → incoordination (ataxia).

Methods of Testing Coordination

a) Upper Limb Tests

  1. Finger-Nose Test
  2. Finger-Finger Test
  3. Dysdiadochokinesis Test: Patient rapidly pronates and supinates one hand against the other.
    Incoordination = inability to perform smooth, rapid alternating movements.

b) Lower Limb Tests

  1. Heel-Knee Test: Patient places heel on opposite knee and runs it down the tibia. Repeated on both sides.
    Incoordination = irregular, wavering movement.
  2. Foot Pat Test: Patient alternately pats the ground with both heels while sitting.
    Incoordination = irregular or clumsy performance.

c) Whole Body

  • Tandem Walking: The patient is asked to walk in a straight line by placing one heel directly in front of the opposite toes, both with eyes open and with eyes closed.
    In sensory ataxia: Walks fairly well with eyes open, but on closing eyes → sways and staggers.
    In vermis lesions: Sways with eyes open, tends to fall in any direction (especially forwards or backwards).
    In unilateral cerebellar hemisphere lesion: Deviates towards the side of lesion.
  • Romberg's Test: The patient is asked to stand with feet closely approximated, first with eyes open and then with eyes closed.
    In sensory ataxia: Able to maintain upright position with eyes open, but sways when eyes are closed → positive Romberg sign.

E. Involuntary Movements

  • Tremor: Rhythmic, distal oscillation
  • Chorea: Jerky, irregular, proximal (caudate)
  • Athetosis: Slow, writhing, distal (putamen)
  • Hemiballismus: Violent flinging, unilateral, proximal (subthalamic nucleus)
  • Dystonia: Twisting postures, stress-induced, disappear in sleep
  • Myoclonus: Sudden jerks, vanish in sleep
  • Fasciculations: Visible twitches, anterior horn disease

F. Gait

Normal exam: Straight walk, posture, swing, step length, turning, stopping.

Abnormal gaits:

  • Circumduction: Hemiplegia, leg swings outward, arm flexed/adducted
  • Spastic gait: Bilateral UMN, stiff scissor walk
  • High stepping: Foot drop (peroneal palsy)
  • High stepping + stamping: Posterior column lesion
  • Ataxic gait: Cerebellar lesion, wide base, reeling
  • Shuffling gait: Parkinsonism, stooped, small rapid steps
  • Waddling gait: Proximal muscle weakness, muscular dystrophy, hip disease

Reflexes

A. Superficial Reflexes

1. Plantar Reflex (S1)

  • Normal response: Flexion of big toe and other toes.
  • Extensor response (Babinski sign):
    • Fanning of small toes
    • Dorsiflexion of big toe
    • Dorsiflexion of ankle
    • Contraction of tensor fascia lata
    • Flexion of knee and hip
  • Causes of extensor plantar response:
    • Pyramidal lesions
    • Deep sleep/coma
    • Normal in infants
    • Transient after seizure
    • Hypoglycemia
    • Metabolic encephalopathy
    • Anesthesia
    • Neuroleptics
    • Neurotoxins
  • Absent plantar reflex:
    • Loss of sole sensation
    • Paralysis of extensor hallucis
    • S1 root lesion
    • Thick plantar skin
    • Cauda equina lesion

2. Abdominal Reflex (T7–T12)

  • Method: Gentle stroking of abdominal wall.
  • Response: Ipsilateral contraction of abdominal muscles, umbilicus moves toward stimulus.
  • Absent in:
    • Obesity, abdominal distension
    • Multiparous women (lax abdomen)
    • Reflex arc lesion (T7–T12)
    • Pyramidal lesion (unilateral loss with hemiplegia)
    • Typhoid perforation (segmental loss)
    • Herpes zoster
    • Post abdominal surgery
    • Early loss in multiple sclerosis
  • Notes:
    • Reflex may persist in motor neuron disease & cerebral palsy despite pyramidal lesion.
    • Beevor’s sign (T10 lesion): Umbilicus pulled upward (loss of lower but preserved upper abdominal contraction).

3. Cremasteric Reflex (L1–L2)

  • Method: Stroking upper medial thigh.
  • Response: Elevation of ipsilateral testis.
  • Absent in:
    • L2 reflex arc lesion
    • Pyramidal lesion
    • Hydrocele
    • Hernia

4. Bulbocavernous Reflex (S2–S4)

  • Method: Pressure on glans penis.
  • Response: Contraction of bulbocavernosus muscle.
  • Absent in:
    • S2–S4 reflex arc lesion
    • Pyramidal lesion

5. Anal Reflex (S4–S5)

  • Method: Stroking/pricking perianal skin.
  • Response: Contraction of external anal sphincter.
  • Absent in:
    • S4–S5 reflex arc lesion
    • Pyramidal lesion

6. Hoffmann’s Sign

  • Method: Flick terminal phalanx of middle finger.
  • Positive response: Flexion & adduction of thumb, flexion of fingers.
  • Significance:
    • Suggests hypertonia (not always pyramidal lesion).
    • May be normal in anxious individuals.
    • If unilateral → likely significant.

7. Tromner’s Sign (Variant of Hoffmann’s)

  • Method: Patient’s hand supinated, examiner pronates and interlocks fingers. Patient pulls against resistance.
  • Normal: Thumb extends.
  • In pyramidal lesion: Thumb flexes and adducts (analogous to Babinski in upper limb).

B. Deep Tendon Reflexes

1. Biceps Jerk (C5: musculocutaneous nerve)

  • Method: Upper limb partially flexed at elbow; press forefinger on biceps tendon in antecubital fossa and strike with hammer.
  • Normal response: Flexion of elbow and visible contraction of biceps.

2. Triceps Jerk (C6–C7: radial nerve)

  • Method: Upper limb flexed at elbow; patient’s hand across trunk; strike triceps tendon 5 cm above elbow.
  • Normal response: Extension of elbow and contraction of triceps.

3. Supinator Jerk (C5–C6: radial nerve)

  • Method: Upper limb partially flexed at elbow, midprone; strike lower end of radius ~5 cm above wrist.
  • Normal response: Contraction of brachioradialis, flexion of elbow, and slight finger flexion.

4. Knee Jerk (L2–L4: femoral nerve)

  • Method: Knees partially flexed and rested on examiner’s forearm; strike quadriceps tendon with hammer.
  • Normal response: Extension of knee and visible contraction of quadriceps.

5. Ankle Jerk (S1: medial popliteal nerve)

  • Method: Leg externally rotated, knee flexed; forefoot gently dorsiflexed and Achilles tendon struck with hammer.
  • Normal response: Plantar flexion of foot and visible contraction of gastrocnemius.

Sensory System examination

Classification of Sensation

  • A. Superficial: Pain, temperature, superficial touch (carried by spinothalamic pathway).
  • B. Deep: Crude touch, joint position, vibration (carried by dorsal column pathway).
  • C. Cortical: Can be tested only when other sensations are intact.

1. Touch

  • Method: Tested with cotton wool or head of a pin on all body parts.

2. Pain

  • Superficial pain: Tested with pin prick on all body parts, areas of decreased sensation noted.
  • Deep pain: Tested by pressing calves, tendo Achillis, or testes.
  • Findings:
    • Lost in tabes dorsalis.
    • Calves are tender in peripheral neuritis.

3. Temperature

  • Method: Two test tubes (one with hot water, one with crushed ice) placed on body parts; patient asked to identify temperature.

4. Position

  • Method: With eyes closed, limb is placed in a definite position; patient asked to describe position or mirror it with opposite limb.

5. Joint Sense

  • Method: With eyes closed, examiner fixes joint, moves finger/toe up or down at terminal joint (sides held, pulp not touched). Patient asked to identify direction.

6. Vibrations

  • Method: A 128 Hz tuning fork placed on bony prominence; patient asked to confirm perception of vibrations.

7. Cortical Sensations

a) Point Localisation (Tactile Localisation)

  • Method: Touch with fingertip or pin → patient identifies location with finger.
  • Notes: Painful stimuli not used. More precise distally than proximally.

b) Tactile Extinction / Sensory Inattention (Rivalry)

  • Method: Bilateral simultaneous stimulation at analogous sites.
  • Finding: Sensation extinguished consistently on one side during bilateral stimulation (but intact when tested separately) = extinction phenomenon.
  • Significance: Indicates contralateral parietal lobe lesion.

c) Two-point Discrimination

  • Method: Ability to distinguish two simultaneous contact points.
  • Normal distances:
    • Finger pulp & lips → 3–5 mm
    • Palm → 2–3 cm
    • Sole → 4 cm
    • Dorsum of foot → ≥5 cm
    • Legs → ≥5 cm
    • Back → ≥5 cm
  • Abnormal: Loss of two-point discrimination with intact posterior column → parietal lobe lesion.

d) Stereognosis

  • Definition: Ability to recognise an object by feel of its shape and size.
  • Test: With eyes closed, patient asked to identify objects (coin, key, pen).
  • Abnormal: Failure (astereognosis) or delayed recognition → cortical dysfunction.

Identification of Textures

  • Method: With eyes closed, patient asked to identify materials (paper, cloth, wood, metal).
  • Significance: Tests ability to differentiate surface quality and material type.

e) Graphaesthesia

  • Definition: Ability to recognise letters/numbers traced on skin with blunt point.
  • Sites: Palm, forearm, thigh, lower leg.
  • Test: Clear shapes (8, 4, 5) first; difficult (6, 9, 3) as finer test.
  • Abnormal: Loss with intact peripheral sensation → parietal lobe lesion (agraphaesthesia).
  • Note: Cortical sensory loss may be more prominent in subcortical lesions (e.g., posterior limb of internal capsule).

f) Sensory Dissociation

  • Definition: Pinprick and temperature sensations lost, but touch preserved.
  • Indicates: Spinothalamic tract involvement, esp. with unilateral lesions.
  • Causes:
    • Intramedullary lesions: Hydromyelia, Syringomyelia.
    • Small fibre neuropathy (Pseudosyringomyelia): Leprous neuritis, hereditary sensory neuropathy, amyloid neuropathy, diabetic polyneuropathy.
    • Anterior spinal artery thrombosis: Posterior column spared.
    • PICA syndrome.
    • Brown–Sequard syndrome.

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