1. Cranial Nerves
Matt Vreugde

2. What are Cranial Nerves?
Number
Nerve
Region of origin/Destination I
Olfactory
Cortex II
Optic
Thalamus
III
Oculomotor
Midbrain IV
Trochlear V
Trigeminal
Lateral pons VI
Abducens
Ponto-medullary
VII
Facial
VIII
Vestibulocochlear IX
Glossopharyngeal
Lateral medulla X
Vagus 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, sensory
and autonomic functions

3. CN I - Olfactory SENSORY - Smell
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

4. CN II - Optic SENSORY - Vision
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

5. CN III - Oculomotor Motor – Eye & upper eyelid
Parasympathetic – Pupil constriction
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)

6. CN IV & VI – Trochlear and Abducens
Motor – Eye Movement
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

7. CN V – Trigeminal Sensory – Facial touch, pain and temp
Motor – Muscles of mastication, tensor tympani
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

8. CN VII – Facial
Sensory – external acoustic meatus, taste to ant 2/3 tongue
Motor – Facial expression, stapedius, some muscles in neck
Parasymp – Lacrimal glands & Submandibular+sublingual glands
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)
Two Zulus Bit My Cat

9. CN VIII – Vestibulocochlear
Sensory – Hearing and Balance
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.

10. CN IX – Glossopharyngeal
Sensory – Middle ear, pharynx, post 1/3 tongue taste & sensation
Motor – Stylopharyngeus & laryngeal muscles
Parasympathetic – Parotid Gland
Other – Chemo and bareceptor information from carotid bodies and sinus
Lesions can cause loss of taste and gag reflex ipsilaterally (sign, not symptom), dysphagia.
Test together with vagus nerve

11. CN X – Vagus “The wanderer”
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
“The wanderer”
Test gag reflex (who doesn’t have one?), listen to voice, say AHHH & check uvula.
Symptoms may be hoarse voice, dysphagia.

12. CN XI – Accessory Motor – Spinal: SCM, upper trapezius
Cranial: Striated muscle of soft palate, pharyx and larynx
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)

13. CN XII – Hypoglossal Motor – Tongue muscles 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.