Investigation Neurology

Examination of the Cranial Nerves

Examination of the Cranial Nerves

Examination of the Cranial Nerves

OLFACTORY NERVE (I)

Test with alcowipes, coffee etc.
Unilateral anosmia may be significant
Bilateral anosmia: commonest cause viral
Classical pathology:olfactory groove meningioma
Basal skull fractures another potential cause (unilateral or bilateral)

OPTIC NERVE (II)

Visual acuity
Visual fields to confrontation
Pupillary reflexes (II and III)
Fundoscopy (papilloedema, optic atrophy, retinitis pigmentosa)

VISUAL ACUITY

CORRECTED (ie brain not lens)
Each eye separately
Snellen charts for distance and near vision reading charts for near vision
Best approximation: small print (or equivalent) at normal reading distance
If unable, finger counting, hand movements, perception of light

VISUAL FIELDS

Often forgotten but very important
First do a bilateral screening test: will uncover the majority of significant visual field defects immediately
Go on to check each eye separately, ask about scotomata
Mention checking for blind spot enlargement

COMMON FIELD DEFECTS

HOMONOMOUS HEMIANOPIA: lesion posterior to the optic chiasm (eg posterior cerebral artery territory infarction)
BITEMPORAL HEMIANOPIA: lesion at the optic chiasm (eg pituitary tumour)
BLINDNESS ONE EYE: lesion in eye, retina or optic nerve

PUPILLARY RESPONSES

Light reflex is the clinically significant one
Afferent limb = II, efferent limb = III
Look at pupillary sizes
Direct and consensual response
Look for afferent pupillary defect (optic nerve lesion)

Read more in the Attached Lecture

Examination of cranial nerves ppt