A _potentiallyconfusing aspect is thatin order totest muscles individually: SR & IR are tested with the eye_abducted_ _(even though_ _one_ _action of the muscle is_ _adduction) and SO & IO are tested with the eye_ _adducted (even though the_ _one_ _action of the muscle is_ _abduction)!
CN palsy effects:
III – Eye is down & out, with dilated pupil unreactive to direct light, ptosis
IV – Eye elevated (hypertropia). Head tilted to unaffected side.
VI – Eye may be turned inward (esotropia). Head turns laterally on looking to affected side.
Conjugate gaze abnormalities – gaze centres in frontal & occipital lobes connect to CN nuclei (III & IV in midbrain, VI in pons). Horiz conjugation relies on co-ordination between VI & III via the medial longitudinal fasciculus & vert by III & IV coord.
Deviation of both eyes to one side (causes: ipsilat frontal stroke or tumour, contralat brainstem lesion or contralat frontal epileptic stim)
E.g. Steele-Richardson (Vert & then horiz, EPE, neck rigidity, dementia)
Distinguished from CN palsy by:
Affects both eyes
Pupils often fixed & unequal
Usually no diplopia
Reflex movements (on neck ext/flexion) are intact
V – Trigeminal Nerve (Ophthalmic, maxillary & mandibular divisions)
Corneal sensation & reflex (afferent component)
Facial sensation (pin prick & light touch) in each division
Muscles of mastication (clench teeth, resist mouth closure)
Jaw jerk (increased in pseudobulbar palsy)
VII – Facial Nerve
Look up & wrinkle forehead (preserved in UMN lesion)
Tightly close eyes
Purse lips and blow out cheeks
Grimace – contracting platysma
Corneal reflex (efferent component)
VIII – Vestibulocochlear Nerve
Whisper a number in one ear while distracting the other
Rinne’s test – 256Hz tuning fork on mastoid process then next to EAM. Sound becomes louder unless conductive deafness.
Weber’s test – 256Hz tuning fork on centre of forehead. If nerve deafness sound heard more on side of normal ear, if conductive deafness then sound heard more on affected side.
Hallpike test if vertigo
Examine external auditory canal/tympanic membrane if indicated.
IX – Glossopharyngeal Nerve
Gag reflex (sensory component)
Sensation to pharynx
X – Vagal Nerve
Elevation of soft palate – Say “Ahh”
Gag reflex (motor component)
XI – Accessory Nerve
Shrug shoulders against resistance
Turn head against resistance (right SCM turns head to left & vice versa)
XII – Hypoglossal Nerve
Examine for wasting or fasciculation of tongue
Tongue protrusion – deviation is towards the lesion if unilateral LMN
Multiple Cranial Nerve Lesions
Unilateral V, VII & VIII palsies suggest cerebellopontine angle lesion (tumour)
Unilateral IX, X & XI palsies suggest a jugular foramen lesion
Bilateral X, XI, XII suggest bulbar palsy if LMN changes or pseudobulbar palsy if UMN signs.
Weakness of eye & facial muscles esp with repetition suggests myasthenia.