Cranial Nerves Flashcards
Name the cranial nerves
1 = olfactory 2 = optic 3 = oculomotor 4 = trochlear 5 = trigeminal 6 = abducens 7 = facial 8 = vestibulocochlear 9 = glossopharyngeal 10 = vagus 11 = accessory nerve 12 = hypoglossal
What part of the nervous system are cranial nerves part of?
Peripheral nervous system
Which cranial nerves arise from the brainstem vs the brain?
Brain = optic, olfactory
Brainstem = 3-12
Which cranial nerve supplies structures other than the head and neck?
Vagus nerve = also supplies structures in the thorax and abdo
Cranial nerves can be carrying what types of axons?
General sensory (GS)
Special sensory (SS)
Motor (M)
Autonomic (A)
What is the brainstem?
Part of the brain composed of the midbrain, pons, and medulla oblongata and connecting the spinal cord with the forebrain and cerebrum
Location of majority of CN nuclei
Ascending sensory and descending motor fibres run through the brainstem
Acoustic neuromas have the ability to compress which cranial nerves?
Vestibulocochlear = hearing diff
Facial = loss of facial expression
Trigeminal = loss of sensation in the face
Which 3 cranial nerves pass through the jugular foramen?
Glossopharyngeal
Vagus
Accessory
Which cranial nerves pass through the cavernous sinus?
Oculomotor
Trochlear
Abducens
What branches from the maxillary nerve (trigeminal nerve)?
Infraorbital nerve
Journey = Runs floor of the orbit, through the infraorbital foramen to supply sensation to the cheek/lower eyelid
Clinical points = Blow out fracture forcing orbital contents back = increase pressure in orbital cavity = orbital floor gives way and cracks = infraorbital nerve at risk of damage = reduced sensation of skin below eye
What branches from the mandibular nerve (trigeminal nerve)?
Inferior alveolar N that branches to form the mental N
Lingual N
Discuss the inferior alveolar nerve, a branch of the mandibular nerve (trigeminal nerve)
Journey = mandibular foramen –> through bone of the mandible –> Mental foramen –> emerges as mental nerve (sensation to lip/chin)
Clinical points = Mandibular fracture: test sensation to lip/chin/gums
How many cranial nerves come from each region of the brain?
Forebrain = 2
Midbrain = 2
Pons = 4
Medulla = 4
Outline the Olfactory Nerve (CN I)
Function = olfaction (SS)
Journey = olfactory N –> cribiform foramine –> olfactory bulb –> olfactory tract –> forebrain
Test = smelling salts
Clinical points = anosmia by common cold, head injury
Outline the Optic Nerve (CN II)
Function = vision (SS)
Journey = retina –> optic N –> optic canal –> optic chiasm –> optic tracts –> visual cortex (occipital lobe)
Test = one eye at a time, visual tests, testing pupils
Clinical points = raised ICP seen as papillodema (swollen optic disks), pituitary tumours
Outline the Oculomotor Nerve (CN III)
Function = most extra-ocular muscles, levator palpebrae superioris (M), sphincter pupillae, ciliary muscle (A)
Journey = midbrain –> oculomotor N –> Cavernous sinus –> superior orbital fissure –> Muscles surrounding the eye
Test = inspection of eyelid and pupils
Clinical points = when there is raised ICP the uncus can push over the edge of tentorium cerebelli and squash the oculomotor N.
External compression sees parasympathetic autonomic function lost first as they are on the outside
Outline the Trochlear Nerve (CN IV)
Function = superior oblique muscle of the eye (M)
Journey = dorsal aspect of midbrain –> cavernous sinus –> Superior orbital fissure –> superior oblique
Test = eye movements
Clinical points = diplopia (double vision), raised ICP causes compression
Outline the Trigeminal Nerve (CN V)
Branches = ophthalmic (Va), maxillary (Vb), mandibular (Vc)
Function = main sensory nerve of the face (GS), nerve of mastication (M)
Journey = pons –> Trigeminal ganglion 1) Ophthalmic (S): superior orbital fissure –> Sensation to cornea/conjunctiva, 2) Maxillary (S): foramen rotundum –> cheek, 3) Mandibular: foramen ovale –> mandible
Test = sensation to face, muscles of mastication, corneal reflex
Clinical points = trigeminal neuralgia (sudden severe facial pain), ophthalmic shingles, corneal ulcer
Outline the Abducens Nerve (CN VI)
Function = lateral rectus (M)
Journey = lower pons –> cavernous sinus –> superior orbital fissure –> Lateral rectus
Test = eye movements
Clinical points = diplopia (double vision), raised ICP causes injury via compression
Outline the Facial Nerve (CN VII)
Branches = temporal, zygomatic, buckle, mandibular, cervical
Function = muscles of facial expression (M), taste ant 2/3 tongue (SS), parasympathetic lacrimal/salivary glands (A)
Journey = bottom of pons –> internal auditory meatus –> petrous part of temporal bone –> few branches inside skull (SS) (A) –> exits skull –> 5 terminal branches (M)
Test = facial expression, corneal reflex
Clinical points = close relation ship to middle ear, parotid gland
Outline the Vestibulocochlear Nerve (CN VIII)
Function = hearing (SS)
Journey = pons –> internal auditory meatus –> Cochlear
Test = hearing, enquire about balance
Clinical points = hearing loss, presbyacusis (old-age related hearing loss), pathology involving semilunar canals can cause vertigo, unilateral acoustic neuromas (benign tumour of schwann cells compressing nerve)
Outline the Glossopharyngeal Nerve (CN IX)
Function = sensation of soft palate, tonsils, pharynx, middle ear (GS), posterior 1/3 tongue taste and general sensation (GS/SS), parotid gland (A)
Journey = medulla –> jugular foramen –> down the neck –> tongue, pharynx, carotid sinus, parotid gland
Test = gag reflex, testing in conjunction with vagus nerve
Clinical points = isolated lesions of glossopharyngeal are rare
Outline the Vagus Nerve (CN X)
Function = sensation to lower pharynx, larynx (GS), muscles of soft palate, pharynx, larynx (M), parasympathetic to thoracic, abdo viscera (A)
Journey = medulla –> jugular foramen –> down the neck via carotid sheath –> Branches in the neck –> branches in the thorax
Test = noting speech, swallow, cough, say ‘ahhh’ observing uvula
Clinical points = dysphagia, left recurrent laryngeal (vagus branch) loops under the aortic arch impingement causes horse voice
Outline the (spinal) Accessory Nerve (CN XI)
Function = trapezius, SCM (M)
Journey = spinal roots from medulla -> enters foramen magnum –> exits jugular foramen –> down IJV –> SCM –> trapezius
Test = shrug shoulders against resistance, turn head against resistance
Clinical points = spinal accessory runs though posterior triangle, susceptible to damage in the region
Outline the Hypoglossal Nerve (CN XII)
Function = movement of the tongue (M)
Journey = medulla –> hypoglossal canal –> Runs down neck –> floor of the tongue
Test = move the tongue
Clinical points = damage causes weakness and atrophy of the tongue muscles on ipsilateral side
Which branches of the facial nerve arise within the petrous part of the temporal bone
Chorda tympani branch
Nerve to stapedius
Greater petrosal nerve
What are the parasympathetic functions associated with the oculomotor nerve?
Innervation of the sphincter pupillae
Innervation of the ciliary body
What are the parasympathetic functions associated with the vagus nerve?
Innervation of mucosal glands in the pharynx
Innervation of the cardiac conducting system
Innervation of smooth muscle in the gastrointestinal tract
Innervation of smooth muscle in the respiratory tract
A patient presents with a left facial droop, which the GP suspects is secondary to a facial nerve lesion. What
other problems might the patient complain of/ should the GP look for?
Altered taste
Difficulty closing the eye
Which CN carry SPECIAL sensory nerves?
Olfactory
Optic
Facial
Vestibulocochlear
Glossopharyngeal
Which cranial nerves carry parasympathetic autonomic fibres from the brainstem to structures of the head and
neck?
Oculomotor
Facial
Glossopharyngeal
Vagus
Which of the cranial nerves carry the afferent
(sensory) signals from baroreceptors within the carotid sinus to the brainstem?
Glossopharyngeal
Which cranial nerves are involved in the movement of the eyeball?
Trochlear
Abducens
Oculomotor
Which cranial nerves are purely motor nerves?
Trochlear
Abducens
Hypoglossal
Oculomotor
Accessory
Which is the only cranial nerve to originate from the dorsal aspect of the brainstem?
Trochlear
