Cranial Nerves

• Sensory - smell
• Arise from cell bodies in olfactory epithelium
• Enters skull through cribriform plate

Head trauma with anosmia = suspected cribriform plate fracture

• Sensory - vision and afferent limb of pupillary light reflex
• Arise from cell bodies in the retina
• Enters skull through optic canal
• Decussates at the optic chiasm sending the medial fibres to the contralateral hemisphere

• Motor and parasympathetic
• Arises in the midbrain
• Parasympathetic fibres synapse in the ciliary ganglion
• Enters orbit through superior orbital fissure

Supplies

• Superior rectus
• Inferior rectus
• Medial rectus
• Inferior oblique
• Levator palpabrae superioris

Parasympathetics

• Via Edinger-Westphal nucleus
• To the ciliary muscles for accommodation
• To the sphincter of the iris for pupil constriction

When damaged, the eye points 'down and out' and there may also be ptosis

Loss of pupillary light reflex is an early sign of oculomotor nerve compression

• Motor
• Arises from cell bodies in the midbrain
• Only nerve to arise from posterior surface of brainstem
• Passes through superior orbital fissure

Supplies

• Superior oblique

When damaged, the patient has double vision when looking down

• Sensory and Motor
• Sensory to skin of face
• Motor to masseter and temporalis
• Arises from lateral pons
• Sensory cell bodies found in trigeminal ganglion

Sensory branches

• V1 Ophthalmic - Superior orbital fissure
• V2 Maxillary - Foramen rotundum
• V3 Mandibular - Foramen ovale

Sensation of the anterior 2/3 of the tongue is V3, but taste is chorda tympani from CN 7

The jaw reflex triggers afferents of V3 that synapse directly in the motor nucleus with the motor fibres to masseter and temporalis

Here's our post on trigeminal neuralgia

• Motor
• Arise from cell bodies in the pons
• Long, tortuous journey making it vulnerable to compression

Supplies

• Lateral rectus

When damaged, the eye will deviate medially and the patient gets double vision when looking anywhere other than laterally to the other side

• Motor, sensory and parasympathetic
• Arises from junction of pons and medulla
• Two roots - motor and intermediate
• Pass through internal acoustic meatus and facial canal in the petrous temporal bone
• Join at the geniculate ganglion
• Leaves skull via stylomastoid foramen
• Passes through parotid gland

Motor supply to

• Facial muscles
• Scalp muscles
• Stapedius
• Stylohyoid
• Posterior belly of digastric

Parasympathetics

• Sublingual gland
• Submandibular gland
• Lacrimal gland
• Other glands of nose and palate

Upper motor neurone lesions usually spare the forehead as these muscles have bilateral motor supply

• Sensory
• Arises from vestibular and cochlear nuclei in the pons
• Passes through internal auditory meatus
• Pierces temporal bone into inner ear
• Vestibular nerve carries sensation of balance
• Cochlear nerve carries sensation of hearing

Fibres from the vestibular nerve to the lateral reticular formation of the medulla are involved in the vomiting reflex

• Motor, sensory and parasympathetic
• Arises from lateral medulla
• Passes through jugular foramen

Motor supply

• Stylopharyngeus
• Gag reflex

Sensory supply

• External ear (tympanic nerve)
• Posterior third of tongue (sensory and taste via lingual, tonsillar and pharyngeal nerves)
• Carotid sinus nerve (baroreceptors and chemoreceptors)

Parasympathetic supply

• Parotid gland

• Motor, sensory and parasympathetic
• Arises from lateral medulla
• Passes through jugular foramen

Motor supply

• Pharyngeal constrictors (except stylopharyngeus)
• Intrinsic muscles of the larynx
• Muscles of palate (except tensor veli palatini)
• Muscle of superior 2/3 oesophagus

Sensory supply

• Taste from epiglottis and palate
• Auricle
• External auditory meatus
• Dura mater of posterior cranial fossa
• Visceral sensory from base of tongue, pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach and proximal intestine

Parasympathetic supply

• Smooth muscle of trachea and bronchi
• Digestive tract
• Myocardium

• Motor
• Two roots
• Cranial root arises from the nucleus ambiguus in the medulla
• Spinal root arises from spinal nuclei in C1 - C5
• Passes through jugular foramen

Motor supply

• Sternocleidomastoid
• Trapezius

• Motor
• Arises from hypoglossal nucleus in the medulla
• Passes through hypoglossal canal

Motor supply

• Genioglossus
• Hyoglossus
• Styloglossus
• Thyrohyoid
• Geniohyoid

Lesions of the hypoglossal nerve produce deviation of the tongue towards the affected side, as genioglossus acts to 'push' the tongue forward

• Jugular foramen syndrome
• Compression of nerves at jugular foramen due to tumour, aneurysm etc
• Presents with dysfunction of nerves 9, 10 and 11