CNs III, V, VII

Question 1

Study the anatomical course, composition and distributions of the trigeminal nerve

Answer 1

Sensory fibres
Motor fibres
Sympathetic fibres from superior cervical ganglion (sweating, vasomotor function)
Sensory fibres - ophthalmic, maxillary, mandibular
Motor fibres - mandibular (muscles of mastication)
Sympathetic fibres - lacrimal, nasal, submandibular, sublingual, parotid

Question 2

Study the anatomical course, composition and distributions of the facial nerve

Answer 2

Arises from pons, through temporal bone, enters internal acoustic meatus (with vestibulocochlear nerve) –> geniculate ganglion
Greater petrosal nerve –> pterygopalatine ganglion –> lacrimal, nasal, oral glands
Chorda tympani (lingual nerve joins) –> submandibular ganglion –> submandibular, sublingual salivary glands and anterior 2/3 of tongue
Nerve to stapedius (muscle stabilises stapes bone)
Exits middle ear through stylomastoid foramen –> posterior auricular, nerve to posterior belly of digastric and stylohyoid.
Parotid –> temporal, zygomatic, buccal, mandibular, cervical (supply muscles of facial expression)

Question 3

Describe cases of common disorders and pathologies affecting the oculomotor nerve

Answer 3

Oculomotor palsy - down and out eye, ptosis
Without pupillary involvement - damage to CN III proper
With pupillary involvement - damage to CN III
Palsy proximal to ciliary ganglion - down and out, ptosis, dilated pupil, loss of accommodation reflex
Palsy distal to ciliary ganglion - down and out, ptosis, normal pupils (pupil sparing third nerve palsy)
*Horner’s syndrome - damage to sympathetic chain –> constricted pupil, anhidrosis, miosis

Question 4

Describe cases of common disorders and pathologies affecting the trigeminal nerve

Answer 4

Harlequin syndrome - damage to pre ganglionic sympathetic fibres at the level of the thoracic cord –> anaesthesia, vasomotor dysfunction, anhidrosis
Varicella zoster infection
Trigeminal neuralgia

Question 5

Describe cases of common disorders and pathologies affecting the facial nerve

Answer 5

Complete palsy –> loss of facial expression, loss of lacrimation and secretomotor function in oral and nasal mucosa, no blink reflex, stasis of tears
Bell’s palsy - temporary (up to 6 weeks)
Bilateral damage - Parkinson’s disease, side effect of certain medication, bilateral damage to nerves
Damage to facial nerve by - forceps delivery of babies, parotid gland tumours, inflammation of nerve within facial canal tympanectomy

Question 6

Study the anatomical course, composition and distributions of the oculomotor nerve

Answer 6

Oculomotor nerve proper:
Leaves midbrain from oculomotor nucleus –> SOF –> superior division (superior palpebral, superior rectus)/ inferior division (medial rectus, inferior rectus, inferior oblique)
Oculomotor nerve:
Leaves midbrain from edinger-wesphal nucleus –> SOF –> ciliary ganglion –> pupillary sphincter
Palsy of CN III proper - down and out eye (unopposed LR/SO muscles), ptosis of upper eyelid (degeneration of LPS)
Palsy of autonomic parasympathetic fibres –> denervation of sphincter pupillae muscle –> unopposed actions of dilator pupillae muscle (supplied by sympathetics)