Cranial Nerves

Cranial Nerves
CN I: Olfactory
  • Usually not tested.
  • Rash, deformity of nose.
  • Test each nostril with essence bottles of coffee, vanilla, peppermint.
CN II: Optic
  • With patient wearing glasses, test each eye separately on eye chart/ card using an eye cover.
  • Examine visual fields by confrontation by wiggling fingers 1 foot from pt’s ears, asking which they see move.
    • Keep examiner’s head level with patient’s head.
  • If poor visual acuity, map fields using fingers and a quadrant-covering card.
  • Look into fundi.
CN III, IV, VI: Oculomotor, Trochlear, Abducens
  • Look at pupils: shape, relative size, ptosis.
  • Shine light in from the side to gauge pupil’s light reaction.
    • Assess both direct and consensual responses.
    • Assess afferent pupillary defect by moving light in arc from pupil to pupil. unne). Optionally: as do arc test, have pt place a flat hand extending vertically from his face, between his eyes, to act as a blinder so light can only go into one eye at a time.
  • “Follow finger with eyes without moving head”: test the 6 cardinal points in an H pattern.
    • Look for failure of movement, nystagmus [pause to check it during upward/ lateral gaze].
  • Convergence by moving finger towards bridge of pt’s nose.
  • Test accommodation by pt looking into distance, then a hat pin 30cm from nose.
  • If MG suspected: pt. gazes upward at Dr’s finger to show worsening ptosis.
CN V: Trigeminal
  • Corneal reflex: patient looks up and away.
    • Touch cotton wool to other side.
    • Look for blink in both eyes, ask if can sense it.
    • Repeat other side [tests V sensory, VII motor].
  • Facial sensation: sterile sharp item on forehead, cheek, jaw.
    • Repeat with dull object. Ask to report sharp or dull.
    • If abnormal, then temperature [heated/ water-cooled tuning fork], light touch [cotton].
  • Motor: pt opens mouth, clenches teeth (pterygoids).
    • Palpate temporal, masseter muscles as they clench.
  • Test jaw jerk:
    • Dr’s finger on tip of jaw.
    • Grip patellar hammer halfway up shaft and tap Dr’s finger lightly.
    • Usually nothing happens, or just a slight closure.
    • If increased closure, think UMNL, esp  pseudobulbar palsy.
CN VII: Facial
  • Inspect facial droop or asymmetry.
  • Facial expression muscles: pt looks up and wrinkles forehead.
    • Examine wrinkling loss.
    • Feel muscle strength by pushing down on each side [UMNL preserved because of bilateral innervation].
  • Pt shuts eyes tightly: compare each side.
  • Pt grins: compare nasolabial grooves.
  • Also: frown, show teeth, puff out cheeks.


CN VIII: Vestibulocochlear (Hearing, Vestibular rarely)
  • Dr’s hands arms length by each ear of pt.
    • Rub one hand’s fingers with noise on one side, other hand noiselessly.
    • Ask pt. which ear they hear you rubbing.
    • Repeat with louder intensity, watching for abnormality.
  • Weber’s test: Lateralization
    • 512/ 1024 Hz [256 if deaf] vibrating fork on top of patients head/ forehead.
    • “Where do you hear sound coming from?”
    • Normal reply is midline.
  • Rinne’s test: Air vs. Bone Conduction
    • 512/ 1024 Hz [256 if deaf] vibrating fork on mastoid behind ear. Ask when stop hearing it.
    • When stop hearing it, move to the patients ear so can hear it.
    • Normal: air conduction [ear] better than bone conduction [mastoid].
  • If indicated, look at external auditory canals, eardrums.
CN IX, X: Glossopharyngeal, Vagus
  • Voice: hoarse or nasal.
  • Pt. swallows, coughs (bovine cough: recurrent laryngeal).
  • Examine palate for uvular displacement. (unilateral lesion: uvula drawn to normal side).
  • Pt says “Ah”: symmetrical soft palate movement.
  • Gag reflex [sensory IX, motor X]:
    • Stimulate back of throat each side.
    • Normal to gag each time.
CN XI: Accessory
  • From behind, examine for trapezius atrophy, asymmetry.
  • Pt. shrugs shoulders (trapezius).
  • Pt. turns head against resistance: watch, palpate SCM on opposite side.
CN XII: Hypoglossal
  • Listen to articulation.
  • Inspect tongue in mouth for wasting, fasciculations.
  • Protrude tongue: unilateral deviates to affected side.