CRANIAL NERVESMatt Vreugde

What are Cranial Nerves?

Number NerveRegion of

origin/Destination

I Olfactory Cortex

II Optic Thalamus

III Oculomotor Midbrain

IV Trochlear Midbrain

V Trigeminal Lateral pons

VI Abducens Ponto-medullary

VII Facial Ponto-medullary

VIII Vestibulocochlear Ponto-medullary

IX Glossopharyngeal Lateral medulla

X Vagus Lateral medulla

XI Accessory Spinal cord C1-C5

XII Hypoglossal Ventral medulla

Nerves originating directly from the brain & brainstem

12 in total

Carry a range of motor, sensoryand autonomic functions

CN I - Olfactory• Frequently gets damaged,

frequently regenerates

• Dysfunction = anosmia

• Ask “has there has been any change in your sense of smell or taste”?

• Test each nostril separately with familiar, non-pungent odours

SENSORY - Smell

CN II - Optic• Site of lesion determines

signs and symptoms

• Test if vision is intact in both eyes • acuity (snellen chart), visual

fields (direct confrontation), colour vision (ishihara plates), pupillary light reflexes, accommodation, fundoscopy.

• Learn the pathway, don’t forget left and right

SENSORY - Vision

CN III - Oculomotor• Superior, medial & inferior recti,

inferior oblique & levator palpebrae superioris

• Ciliary muscle – constrictor pupillae

• Test eye movements – H pattern

• Check for ptosis

• Look if pupils are equal and appropriately dilated

• Check for nystagmus (slow)

Motor – Eye & upper eyelid

Parasympathetic – Pupil constriction

CN IV & VI – Trochlear and Abducens

• Trochlear => Superior oblique

• Dysfunction can cause torsional diplopia and strabismus

• Abducens => lateral rectus

• Dysfunction causes inability to abduct eye

• Diplopia when looking towards side of affected eye

Motor – Eye Movement

CN V – Trigeminal

• Sensation:• Va – top of head, forehead and

ocular regions, bridge of the nose, nasal cavity, lacrimal glands, BLINKING!

• Vb – temple, lower eyelid, cheek and upper mandible (palate, upper pharynx, upper teeth and upper lip)

• Vc – lower jaw, lower face, side of head and ant 2/3 tongue, and floor of mouth

• Test by prodding the face or blowing into their eye

• Palpate maseter and temporalis and clench jaw

Sensory – Facial touch, pain and temp

Motor – Muscles of mastication, tensor

tympani

CN VII – Facial

• Lesions can be transient (Bell’s Palsy), ask patient to smile

• TEST: Eyebrows up, eyes shut, puff your cheeks, smile you….• Test against resistance

• Ask about taste changes, tinnitus/hyperacusis • (no, don’t yell in their ears)

Sensory – external acoustic meatus, taste to ant 2/3 tongue

Motor – Facial expression, stapedius, some muscles in neck

Parasymp – Lacrimal glands & Submandibular+sublingual glands

Two Zulus Bit My Cat

CN VIII – Vestibulocochlear

• If isolated sensorineural lesion think acoustic neuroma or other cerebellopontine angle tumour

• TEST: Rinne’s and Webers

• Ask about vertigo, difficulty with their balance etc.

Sensory – Hearing and Balance

CN IX – Glossopharyngeal

• Lesions can cause loss of taste and gag reflex ipsilaterally (sign, not symptom), dysphagia.

• Test together with vagus nerve

Sensory – Middle ear, pharynx, post 1/3 tongue taste & sensation

Motor – Stylopharyngeus & laryngeal muscles

Parasympathetic – Parotid GlandOther – Chemo and bareceptor

information from carotid bodies and sinus

CN X – Vagus

• “The wanderer”

• Test gag reflex (who doesn’t have one?), listen to voice, say AHHH & check uvula.

• Symptoms may be hoarse voice, dysphagia.

Sensory – larynx, oesophagus, bronchi, lungs, heart, foregut&midgut

Motor – Pharyngeal & laryngeal muscles, vocal cords

Parasympathetic – Heart, lungs, gastric system, abdominal viscera (foregut/midgut)

Other – Aortic body chemoreceptors and aortic arch baroreceptors

CN XI – Accessory

• Really anatomists?

• Easily damaged in neck surgery.• Check for wasting of trapezius

then ask patient to shrug shoulders and rotate neck against resistance

• Symptoms are weakness of shoulder and arm elevation, and weakness of head when turning.

• Remember your LMN (ipsilateral) and UMN (contralateral)

Motor – Spinal: SCM, upper trapezius

Cranial: Striated muscle of soft palate, pharyx

and larynx

CN XII – Hypoglossal

• Girl’s best friend

• To test, stick tongue out and assess. Wasting, fasciculations, power (push inside of cheek), is it deviating?

• Difficulty in chewing, speaking and swallowing. Patient will have atrophy of the tongue.

Motor – Tongue muscles