Detailed Examination of Cranial Nerve

I. Olfactory Nerve (Smell)

• Preparation: Ensure the patient's nostrils are patent.

• Substances: Use familiar, non-irritating substances like coffee powder . Avoid irritants such as ammonia, which can stimulate the trigeminal nerve and lead to an incorrect assessment.

• Procedure:

  • Test each nostril separately.

  • Ask the patient to close one nostril and sniff the test substance.

  • Repeat with the other nostril.

  • First, ask if the patient can appreciate any smell, then ask them to identify it.

• Observation: Note the presence of parosmia (distorted smell perception) or olfactory hallucinations.

II. Optic Nerve (Vision)

1. Visual Acuity

• Tools: Ideally, use a Snellen's chart. A modified bedside chart (Rosenbaum chart or modified Snellen's chart) can also be used.

• Procedure:

  • Test each eye separately, covering (but not closing) the opposite eye.

  • Literate patients: Ask the patient to read printed material at a specified distance.

  • Impaired reading: Assess finger counting at one meter.

  • Further impairment: Look for perception of hand movement.

  • Severely impaired: Check for perception of light.

  • Distant vision: Ask the patient to read a number on top of the opposite bed.

2. Visual Field

• Purpose: To chart visual fields and detect scotomata (blind spots) or field defects.

• Method (Confrontation):

  • Test each eye separately and explain the procedure to the patient.

  • The examiner should sit one meter from the patient, with their eyes at the same level.

  • To test the patient's right eye, ask them to cover their left eye and gaze directly into your left eye. You should cover your right eye and gaze into the patient's right eye.

  • Hold your left hand midway between you and the patient. Move your finger from the periphery to the center, using both moving and stationary fingers.

  • Test all four quadrants in both eyes (not diagonally).

  • Finally, test both eyes together to check for any visual inattention.

• Menace Reflex (for bedridden patients):

  • Ask the patient to fix their gaze on the roof.

  • Rapidly bring your hand (kept at an angle) towards the patient's eye from each quadrant (being careful not to blow air into the eye) and observe for reflex eye closure.

  • Alternatively, bring the examiner's finger from the sides towards the center and assess when the patient can see them.

3. Colour Vision

• Assessment: Check if the patient can appreciate red, green, yellow, and blue colors.

• Tools: Ideally use Ishihara's letter charts. Colored papers can be used if charts are unavailable.

4. Optic Fundus (Ophthalmoscopy)

• Preparation: Dim the room illumination. The patient can be sitting or supine.

• Procedure:

  • Ask the patient to look at a distant, clearly defined point, and instruct them not to look at the ophthalmoscope's light.

  • Use your right eye to examine the patient's right eye and your left eye for their left eye.

  • Ensure your eye, the scope's aperture, and the patient's pupil are in a straight line.

  • First, focus on the iris and pupil, looking for the red reflex.

  • Bring the scope as close as possible to the patient's eye and direct the light beam slightly nasally.

  • Avoid shining the light directly on the macula initially, as this can cause pupillary constriction.

• Observation: Look for:

  • Disc: color, contour, shape margins, and crossing vessels.

  • Optic Cup and cup-to-disc ratio.

  • Peridiscal area.

  • Retina: vessels, hemorrhages, and exudates.

  • Macula: edema, degeneration, and star.

III, IV, VI. Oculomotor, Trochlear, Abducent Nerves (Eye Movements)

The actions of these nerves are closely linked and are considered together.

1. Inspection of the Eyes for Abnormalities

• Eyelid:

  • Lid retraction.

  • Partial ptosis (e.g., Horner's Syndrome: look for ptosis, miosis, enophthalmos, anhydrosis, and absence of ciliospinal reflex).

  • Complete ptosis (indicative of 3rd nerve palsy).

  • Proptosis (protrusion of the eyeball).

  • Squint: convergent or divergent.

2. Eye Movements (Extraocular Muscles)

• Procedure:

  • Ask the patient to keep their head still and follow your finger or a penlight with their eyes only.

  • Move your finger in a wide 'H' pattern to test all six cardinal gaze positions.

  • Observe for smooth pursuit, saccades (rapid eye movements), and nystagmus (involuntary eye movements).

  • Nystagmus: Note the direction (horizontal, vertical, torsional), amplitude (fine, medium, coarse), and frequency (slow, fast).

3. Pupillary Reflexes

• Light Reflex:

  • Direct light reflex: Shine a light into one eye and observe the constriction of the pupil in that eye.

  • Consensual light reflex: While shining the light into the same eye, observe the constriction of the pupil in the opposite eye.

  • Repeat for the other eye.

• Afferent Pupillary Defect (Marcus Gunn pupil): Use the swinging flashlight test.

  • Shine a torch into the abnormal eye; there will be no direct or consensual pupillary reflex.

  • Shine the torch into the normal eye; it will show a direct pupillary reflex and a consensual reflex in the abnormal eye.

  • Swing the light back to the abnormal eye; the pupil will dilate because it was already constricted by the consensual reflex from the normal eye.

• Accommodation Reflex: This is discussed along with convergence.

V. Trigeminal Nerve (Sensation and Mastication)

1. Motor Part

• Muscles tested: Temporalis, Masseter, and Pterygoids.

• Inspection: Note the symmetry of the temporal fossae and the angles of the jaw.

• Palpation:

  • While clenching the teeth, palpate the masseters and the temporalis muscles.

  • Apply resistance while the patient attempts to open their mouth to test the pterygoids.

2. Sensory Part

• Procedure: Each side of the face is tested separately for pain, light touch, and temperature sensations.

• Areas to test: Care is taken to avoid midline structures. Test the forehead and upper part of the side of the nose and scalp anterior to the vertex (ophthalmic division), the malar region and upper lip (maxillary division), and the chin (mandibular division).

3. Reflexes

• Corneal Reflex:

  • Method: Explain the procedure. Ask the patient to look up and out. Support your hand on the patient's malar eminence. Using a wisp of sterile cotton, touch near the limbus (do not touch the central part of the cornea).

  • Response: Normally, a sudden, brisk blinking of the same eyelid (direct corneal reflex - afferent 5th nerve and efferent 7th nerve) and simultaneous contraction of the opposite eyelid (consensual corneal reflex - afferent 5th and efferent 7th).

  • If ptosis is present, keep the eyelids open with fingers and elicit the reflex, feeling for lid contraction.

• Conjunctival Reflex: This involves touching the bulbar conjunctiva. The procedure is similar to the corneal reflex. Both reflexes should be checked as dissociation can occur.

• Jaw Jerk:

  • Method: Ask the patient to keep the jaw slightly open. Place your forefinger or thumb below the lower lip. Tap in a downward direction with a percussion hammer.

  • Response: Normally, there is a slight palpable upward jerk. Both afferent and efferent pathways involve the 5th nerve. It may be absent in many normal individuals.

VII. Facial Nerve (Facial Expression, Taste, Secretion)

1. Motor Part (Muscles of Facial Expression)

• Observation: Note if facial palsy is present (unilateral or bilateral).

• Differentiation: Determine if it's an Upper Motor Neuron (UMN) or Lower Motor Neuron (LMN) type palsy. In UMN facial palsy, only the lower half of the face is involved, while in LMN palsy, both the upper and lower halves of the face are involved.

• Specific Tests:

  • Wrinkling of forehead: Reduced on the affected side in LMN palsy.

  • Naso-labial fold: Less prominent on the affected side in both LMN and UMN palsy.

  • Smile/show the teeth: The angle of the mouth will deviate to the side opposite the palsy (risorius muscle).

  • Blowing the cheek: Ask the patient to purse their lips and blow their cheek. Observe for symmetry and attempt to expel air by pressing on either side (buccinator muscle).

  • Whistling: Ask the patient to whistle (orbicularis oris).

  • Platysma: Ask the patient to bare their teeth and open their mouth simultaneously. Look and palpate for contraction of the platysma along the inferior border of the mandible and lateral aspect of the neck. Demonstrate the action if needed.

• Involuntary movements: Look for any twitching movements or contractures.

2. Nerve to Stapedius

• Assessment: Ask for hyperacusis (increased sensitivity to sound). A subjective assessment is usually sufficient.

3. Secretomotor Function

• Assessment: Look for any drying of the eyes (xerosis). Salivary secretion is generally not tested.

4. Sensory Part (Special Sensation - Taste)

• Location: Taste in the anterior two-thirds of the tongue.

• Substances: Use strong solutions of common tastes: sugar, salt, sour, and bitter. For bedside testing, sugar and salt solutions are usually sufficient. Use freshly prepared solutions.

• Procedure: Describe the procedure to the patient. Tell the patient to show or write the tastes as 1, 2, and 3 for Sugar, Salt, and "Don't know," respectively.

• Protrude the tongue of the patient.

VIII. Vestibulocochlear Nerve (Hearing and Balance)

1. Cochlear Part (Hearing)

• Gross Hearing:

  • Voice Test: Stand 60 cm away from the patient (one arm's length) and occlude one ear. Whisper or speak in a normal voice, asking the patient to repeat numbers. If this isn't heard, use a conversational voice.

  • Watch Test: Use a ticking watch and note the distance at which it is heard.

• Tuning Fork Tests: Use a 512 Hz tuning fork.

  • Rinne Test:

    • Place the vibrating tuning fork on the mastoid process until the sound is no longer heard (bone conduction - BC).

    • Immediately move the vibrating fork near the external auditory meatus and ask if it can be heard again (air conduction - AC).

    • Normal (Positive Rinne): AC > BC.

    • Conductive hearing loss (Negative Rinne): BC > AC.

  • Weber Test:

    • Place the base of the vibrating tuning fork on the vertex (top of the head), forehead, or bridge of the nose.

    • Ask the patient where they hear the sound (left, right, or center).

    • Normal: Sound is heard equally in both ears (not lateralized).

    • Conductive hearing loss: Sound lateralizes to the affected ear.

    • Sensory neural hearing loss: Sound lateralizes to the unaffected ear.

• Auscultation of Squama: Place the stethoscope on the squamous part of the temporal bone and ask the patient to count loudly. This can assess loud speech.

2. Vestibular Part (Balance)

• Nystagmus: Observe for nystagmus (spontaneous or induced).

• Romberg Test:

  • Ask the patient to stand with their feet together, first with eyes open, then with eyes closed.

  • Positive Romberg: Patient sways or falls with eyes closed but not with eyes open, indicating a proprioceptive or vestibular defect.

• Gait: Observe the patient's walking pattern. Look for a broad-based gait or staggering.

• Past-pointing: (Also discussed under cerebellar signs, but relevant here).

  • Patient sits or stands opposite the examiner, holding arms forward horizontally, touching the examiner’s finger.

  • They then raise their hand vertically and bring it back to the original position, first with eyes open, then with eyes closed.

  • In unilateral vestibular lesions, the ipsilateral and contralateral hands deviate to the affected side.

• Caloric Test: (A more specialized test for vestibular function)

  • Irrigate the external auditory canal with warm (44°C) or cold (30°C) water.

  • Warm water: Produces nystagmus with the fast component towards the irrigated ear.

  • Cold water: Produces nystagmus with the fast component towards the opposite ear.

  • "COWS" mnemonic: Cold Opposite, Warm Same (referring to the direction of the fast component of nystagmus).

IX. Glossopharyngeal Nerve & X. Vagus Nerve (Swallowing, Voice, Gag Reflex)

These nerves are generally tested together due to their intertwined functions.

1. Voice

• Assessment: Listen for hoarseness, nasal quality (rhinolalia aperta), or paralytic dysarthria.

• Procedure: Ask the patient to speak and vocalize "ah".

2. Palate

• Inspection: Ask the patient to open their mouth and vocalize "ah".

• Observation: Observe for symmetrical elevation of the soft palate and deviation of the uvula. The uvula deviates to the healthy side if one side is paralyzed.

• Palate Reflex: Touch the soft palate with a tongue depressor and observe for elevation.

3. Swallowing

• Assessment: Ask the patient if they have difficulty swallowing solids or liquids (dysphagia).

• Procedure: Ask the patient to swallow a small amount of water. Observe for coughing, nasal regurgitation, or delayed swallowing.

4. Gag Reflex

• Procedure: Touch the posterior pharyngeal wall with a tongue depressor.

• Response: Normally, there is a gagging or retching response. This reflex can be absent in some normal individuals.

• Significance: Absence of the gag reflex may indicate a lesion of the IX and X cranial nerves.

XI. Accessory Nerve (Shoulder and Neck Movement)

1. Trapezius Muscle

• Inspection: Observe for wasting or fasciculations (fine muscle twitches). Look for drooping of the shoulder and winging of the scapula.

• Power Testing:

  • Shrugging shoulders: Ask the patient to shrug their shoulders against your resistance.

  • Abduction of arm beyond 90 degrees: Test this movement.

2. Sternocleidomastoid Muscle

• Inspection: Observe for wasting or fasciculations.

• Power Testing:

  • Head rotation: Ask the patient to turn their head against resistance, first to one side then the other. The opposite sternocleidomastoid muscle is tested (e.g., turning head to the left tests the right sternocleidomastoid).

  • Head flexion: Ask the patient to flex their head forward against resistance. Both sternocleidomastoids are tested.

XII. Hypoglossal Nerve (Tongue Movement)

1. Inspection of the Tongue (at rest in the mouth)

• Observation:

  • Note the size of the tongue.

  • Look for wasting (atrophy).

  • Observe for fasciculations (worm-like movements), which are indicative of a lower motor neuron lesion.

2. Tongue Protrusion

• Procedure: Ask the patient to protrude their tongue fully.

• Observation:

  • Deviation: The tongue deviates towards the paralyzed side if there is a lower motor neuron lesion (e.g., XII nerve palsy). This is because the genioglossus muscle on the healthy side pushes the tongue towards the weak side.

  • In upper motor neuron lesions, the tongue deviates to the side opposite the lesion.

  • Midline vs. Deviation: Note if the tongue protrudes in the midline or deviates.

3. Power of the Tongue

• Procedure: Ask the patient to push their tongue into their cheek, and palpate the cheek to feel the strength of the push. Repeat on both sides.

• Involuntary movements: Look for any involuntary movements of the tongue