Osteology

Question 1

Describe some of the causes and consequences of cranial nerve damage

Answer 1

I - fracture of cribiform plate –> anosmia, CSF rhinorrhea
II - fracture of optic canal –> loss of papillary constriction
III - aneurysms, oculomotor palsy –> dilated pupil, ptosis, down and out eye
IV - fracture of orbit, raised intracranial pressure –> double vision
V - injury to terminal branches in roof of maxillary sinus –> loss of touch and pain sensations, paraesthesia, no contraction of masseter and temporalis muscles, deviation of mandible to side of lesion when mouth is opened
VI - fracture involving cavernous sinus –> inability to more eye lateral, double vision on lateral gaze
VII - laceration/tumour in parotid region, fracture of temporal bone, intracranial haematoma –> paralysis of facial muscles, loss of taste on anterior 2/3 of tongue
VIII - tumour (acoustic neuroma) –> progressive unilateral hearing loss, tinnitus
IX - brainstem lesion, deep laceration of neck –> loss of taste of posterior 1/3 of tongue, loss of sensation on soft palate
X - brainstem lesion, deep laceration of neck –> deviation of uvula to normal side, hoarse voice
XI - laceration of neck –> drooping of shoulder
XII - laceration of neck, fracture of cranial base –> tongue deviates to affected side, dysarthria

Question 2

List the foramina through which cranial nerves exit through

Answer 2

I - cribiform plate of ethmoid bone
II - optic canal
III, IV, VI, V1 - superior orbital fissure
V2 - foramen rotundum
V3 - foramen ovale 
VII, VIII - internal acoustic meatus
IX, X, XI - jugular foramen
XII - hypoglossal canal

Question 3

List the cranial nerves and their functions

Answer 3

I Olfactory - special sense of smell
II Optic - special sense of vision
III Oculomotor - ciliary muscles, sphincter pupillae, extrinsic eye muscles
IV Trochlear - superior oblique muscle of eye
V Trigeminal - sensory of face, oral, nasal, mucosa, anterior 2/3 of tongue, motor of muscles of mastication
VI Abducens - lateral rectus muscle of eye
VII Facial - motor muscles of facial expression, digastrics, stylohyoid, stapedius muscle, PS submandibular, sublingual, lacrimal, nasal, palatine glands, special sense of taste from anterior 2/3 of tongue, soft palate
VIII Vestibulocochlear - sense of equilibrium, motion and hearing
IX - Glossopharyngeal - motor of stylopharyngeus muscle, PS parotid gland, special sense of taste from posterior 1/3 of tongue, sense of pharynx, dorsum of palate, auditory tube, mastoid antrum
X Vagus - motor and sensory of palate, pharynx, larynx, trachea, bronchial tree, heart, GI tract –> left colic flexors
XI (Spinal) Accesory - motor of sternocleidomastoid and trapezius
XII Hypoglossal - motor of muscles of the tongue, strap muscles of the neck

Question 4

Which cranial nerves carry parasympathetic fibres and to which structures do these innervate?

Answer 4

CN III - edinger-westphal (pre-ganglionic) –> ciliary ganglion (terminates) –> sphincter pupillae (constricts), ciliary muscles (accommodation)
CN VII - superior salivary nucleus (pre-ganglionic) –>pterygopalatine/submandibular ganglion (terminates) –> lacrimal, submandibular, sublingual
CN IX - inferior salivary nucleus (pre-ganglionic) –> otic ganglion (terminates) –> parotid, oropharynx
CN X - dorsal vagus motor nucleus (pre-ganglionic) –> laryngopharynx, larynx, oesophagus, trachea