CNS examination: topic map

1. General observation and vital signs
2. Level of consciousness and Glasgow Coma Scale
3. Higher mental functions
   • Orientation, attention, memory, speech, calculation, judgement
4. Cranial nerves I-XII
5. Motor system
   • Bulk, tone, power, involuntary movements
6. Reflexes
   • Deep tendon reflexes, plantar response, clonus
7. Sensory system
   • Pain, temperature, touch, vibration, proprioception, cortical sensory tests
8. Coordination and cerebellar signs
9. Gait, stance, and Romberg test
10. Meningeal signs and autonomic/spinal examination, when indicated

• Complete CNS examination
• Cranial nerve examination
• Motor, sensory and reflex examination
• CNS examination case presentation format

Step-by-step complete CNS examination

1. Preparation

1. Introduce yourself, confirm the patient's identity, explain the examination, obtain consent.
2. Wash hands.
3. Ensure adequate exposure while maintaining dignity:
   • Face and upper limbs initially
   • Lower limbs later
4. Position the patient sitting upright or at 45 degrees, with both sides accessible.
5. Equipment:
   • Pen torch
   • Tendon hammer
   • Cotton wool
   • Neurotip or disposable pin
   • Tuning fork, 128 Hz
   • Ophthalmoscope, if available
   • Snellen chart or reading card
   • Tongue depressor
6. Ask if the patient has pain, visual or hearing impairment, or mobility limitations.

2. General inspection and observations

• Level of alertness and engagement
• Posture, facial expression, speech, mood, and behaviour
• Mobility aids, walking pattern, tremor, involuntary movements
• Muscle wasting, fasciculations, abnormal posturing
• Scars, especially cranial, spinal, or peripheral nerve surgery
• Skin signs such as café-au-lait spots, neurofibromas, shingles, or rash
• Urinary catheter or other clues to neurological disability

3. Higher mental functions and consciousness

A. Level of consciousness

• Eye opening: /4
• Verbal response: /5
• Motor response: /6

B. Mental status

1. Appearance and behaviour
   • Grooming, eye contact, agitation, apathy, appropriateness.
2. Speech and language
   • Fluency, articulation, comprehension, naming, repetition, reading and writing if needed.
   • Dysarthria: impaired articulation.
   • Dysphasia/aphasia: impaired language.
3. Orientation
   • Ask name, age, location, date, day, month, and year.
4. Attention and concentration
   • Months backward.
   • Serial 7s.
   • Digit span.
5. Memory
   • Immediate recall: repeat three objects.
   • Short-term recall: recall them after about 5 minutes.
   • Long-term memory: relevant personal or historical events.
6. Executive and cortical functions, where appropriate
   • Similarities, for example “How are an apple and orange alike?”
   • Following a three-stage command.
   • Praxis: ask the patient to mime using a key or comb.
   • Visuospatial function: copy intersecting pentagons or draw a clock.
   • Neglect: line bisection or double simultaneous stimulation.

4. Cranial nerve examination

Cranial nerve I: Olfactory

1. Ask about change or loss of smell.
2. Ensure each nostril is patent.
3. With eyes closed, test each nostril separately using a familiar non-irritating smell, such as coffee or soap.
4. Do not use ammonia, as it stimulates trigeminal nerve endings.

Cranial nerve II: Optic

1. Visual acuity
   • Test each eye separately with a Snellen chart or reading card, with glasses if normally used.
2. Visual fields
   • Sit opposite the patient at eye level.
   • Cover the opposite eye to the one being tested.
   • Bring fingers into each quadrant from the periphery and compare with your own visual field.
   • Test for visual inattention using double simultaneous stimulation if relevant.
3. Pupils
   • Inspect size, shape, and equality.
   • Test direct and consensual light reflexes.
   • Test accommodation: ask the patient to look into the distance, then at your finger brought toward their nose.
4. Fundoscopy
   • Examine optic disc, vessels, retina, and macula if indicated.
   • Look for papilloedema, optic atrophy, haemorrhages, exudates, and diabetic or hypertensive changes.

Cranial nerves III, IV and VI: Oculomotor, trochlear, abducens

1. Inspect for ptosis and abnormal eye position.
2. Ask about diplopia.
3. Test eye movements in an H pattern.
4. Observe for restriction of movement, diplopia, nystagmus, or pain.
5. Assess convergence by moving your finger toward the nose.
6. Reassess pupil responses because CN III mediates pupillary constriction.

Cranial nerve V: Trigeminal

1. Sensory
   • Ask the patient to close their eyes.
   • Test light touch in the three divisions bilaterally:
     • V1: forehead
     • V2: cheek
     • V3: jaw
   • If abnormal, test pinprick similarly.
2. Motor
   • Palpate masseter and temporalis while the patient clenches teeth.
   • Ask the patient to open the jaw against resistance.
   • Observe for jaw deviation, which is toward the side of a weak pterygoid muscle.
3. Corneal reflex
   • Not routinely performed in an alert patient.
   • Afferent limb is V1; efferent limb is VII.

Cranial nerve VII: Facial

1. Raise eyebrows.
2. Close eyes tightly. Attempt to open them.
3. Smile and show teeth.
4. Puff out cheeks.
5. Whistle, if appropriate.

Cranial nerve VIII: Vestibulocochlear

1. Ask about hearing loss, tinnitus, vertigo, and imbalance.
2. Test gross hearing by whisper or finger rub in each ear.
3. If impaired, perform:
   • Rinne test: air conduction should exceed bone conduction.
   • Weber test: normally heard centrally.
4. Assess vestibular function if indicated:
   • Nystagmus
   • Head impulse test
   • Romberg test
   • Gait and tandem walking

Cranial nerves IX and X: Glossopharyngeal and vagus

1. Listen for hoarseness, nasal speech, or dysarthria.
2. Ask the patient to say “ah.”
   • Observe symmetrical palatal elevation.
   • Uvula may deviate away from the weak side in unilateral vagal weakness.
3. Ask about swallowing, choking, nasal regurgitation, or altered voice.
4. Gag reflex is not routinely necessary and can be distressing.

Cranial nerve XI: Accessory

1. Inspect sternocleidomastoid and trapezius bulk.
2. Ask the patient to shrug shoulders against resistance.
3. Ask them to turn their head against your hand on each side.
   • Right sternocleidomastoid turns the head to the left, and vice versa.

Cranial nerve XII: Hypoglossal

1. Inspect tongue at rest for wasting or fasciculations.
2. Ask the patient to protrude the tongue.
   • It deviates toward the weak side in a lower motor neuron lesion.
3. Ask them to move it side to side.
4. Listen to articulation of lingual sounds, such as “la-la-la.”

5. Motor system examination

A. Inspection

• Muscle bulk and wasting
• Fasciculations
• Involuntary movements: tremor, chorea, dystonia, myoclonus
• Contractures
• Abnormal posture

B. Tone

• Shoulder
• Elbow flexion and extension
• Wrist flexion and extension
• Forearm pronation and supination

• Hip rolling
• Knee flexion and extension
• Ankle dorsiflexion and plantarflexion

• Spasticity: velocity-dependent increase in tone, typical of upper motor neuron pathology.
• Rigidity: uniform or cogwheel resistance, often extrapyramidal.
• Hypotonia/flaccidity: can occur with lower motor neuron, cerebellar, or acute upper motor neuron lesions.

C. Power

D. Pronator drift

1. Ask the patient to hold both arms outstretched, palms upward.
2. Ask them to close their eyes for 10 to 20 seconds.
3. Observe for pronation and downward drift, suggesting subtle corticospinal tract weakness.

6. Reflexes

A. Deep tendon reflexes

B. Clonus

1. At the ankle, briskly dorsiflex the foot and maintain pressure.
2. Sustained rhythmic beats suggest upper motor neuron pathology.
3. Knee clonus may also be tested when indicated.

C. Plantar response

1. Stroke firmly along the lateral sole from heel toward little toe, then across the forefoot medially.
2. Normal adult response: flexion/down-going toes.
3. Extensor response: great toe extension with fanning of other toes, suggesting corticospinal tract dysfunction.

7. Sensory system examination

A. Primary sensory modalities

1. Light touch
   • Use cotton wool.
   • Test face, upper limbs, trunk, and lower limbs.
2. Pinprick
   • Use a disposable neurotip.
   • Test sharp versus dull if required.
3. Temperature
   • Usually tested only if pain sensation is impaired or a spinothalamic lesion is suspected.
4. Vibration
   • Use a 128-Hz tuning fork.
   • Start distally:
     • Upper limb: distal interphalangeal joint of index finger
     • Lower limb: interphalangeal joint of great toe
   • If abnormal, move proximally to ankle, tibial tuberosity, anterior superior iliac spine, or sternum.
5. Joint position sense
   • Hold the sides of the distal phalanx of a finger or great toe.
   • Move it slightly up or down.
   • Ask the patient to identify the direction.

B. Cortical sensory testing

1. Stereognosis
   • Identify a familiar object placed in the hand.
2. Graphesthesia
   • Identify a number traced on the palm.
3. Two-point discrimination
   • Test ability to distinguish one from two points.
4. Extinction/inattention
   • Touch corresponding areas on both sides simultaneously.
   • Failure to perceive one side suggests sensory neglect.

8. Coordination and cerebellar function

Upper limbs

1. Finger-nose test
   • Ask the patient to touch their nose, then your finger repeatedly.
   • Move your finger to different positions.
   • Look for intention tremor and past-pointing.
2. Rapid alternating movements
   • Ask the patient to rapidly pronate and supinate hands on thighs.
   • Alternatively, tap thumb to each finger quickly.
   • Slowness or irregularity is dysdiadochokinesia.
3. Rebound phenomenon
   • Only if safe and necessary.

Lower limbs

1. Heel-shin test
   • In a supine patient, ask them to place heel on the opposite knee and run it down the shin.
   • Look for wavering or inability to maintain contact.

9. Gait, station, and balance

1. Observe normal gait:
   • Base, stride length, arm swing, turning, foot clearance, symmetry.
2. Ask the patient to walk:
   • On heels: assesses dorsiflexion, mainly L4-L5.
   • On toes: assesses plantarflexion, mainly S1-S2.
   • Heel-to-toe tandem gait: sensitive for cerebellar or vestibular dysfunction.
3. Romberg test
   • Patient stands with feet together.
   • First with eyes open, then closed for about 20 seconds.
   • Stand close enough to prevent a fall.
   • A positive Romberg sign is increased sway or falling after eye closure, suggesting impaired proprioception or vestibular dysfunction. It is not a primary cerebellar sign.

10. Meningeal irritation and spinal examination, if indicated

Meningism

• Neck stiffness: gently assess passive neck flexion.
• Kernig and Brudzinski signs have limited sensitivity and do not exclude meningitis when absent.

Spine and sacral examination

• Inspect and palpate spine.
• Check lower-limb motor, sensory, and reflex function.
• Assess perianal sensation and anal tone only with clear indication, consent, chaperone, and appropriate privacy.
• Ask about urinary retention, incontinence, bowel dysfunction, and saddle sensory loss.

Example normal examination summary

Patient is alert and orientated to time, place and person, with normal speech and cognition. Cranial nerves II-XII are intact. There is normal bulk, tone and power of 5/5 throughout, with no tremor, fasciculations or pronator drift. Reflexes are symmetrical and 2+ throughout; plantar responses are flexor bilaterally. Sensation to light touch, pinprick, vibration and joint position sense is intact. Coordination is normal, with no dysmetria or dysdiadochokinesia. Gait, tandem gait and Romberg testing are normal.