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Flashcards in Cranial nerves Deck (117):

What is the organisation of cranial nerve nuclei in the spinal cord

Motor neurones = ventrally in basal plate
Sensory neurones = dorsally in alar plate


Describe organisation of cranial nerve nuclei in brain stem

Similar to spinal cord but alar plate is lateral and basal plate medial .
Motor nerves innervating striated muscles lie medially with those innervating branchial arch derived muscle


Describe organisation of special sensory nuclei in brainstem

The special sensory nuclei associated with hearing and balance lie laterally


Where does sympathetic supply for the head come from

Superior cervical ganglion at top of symp chain


Parasympathetic supply emerges with which cranial nerves

Oculomotor, facial, glossopharyngeal and vagus


Which cranial nerve emerge from forebrain, why are they not proper cranial nerves

1 and 2, (are part of CNS, have oligodendrocytes) so not proper cranial nerves.


Describe sensory, motor and parasympathetic functions of olfactory nerve

Sensory: to olfactory epithelium --> olfaction


Describe the structure of olfactory system

Axons olfactory epitheliual cells pass from olfactory chemoreceptors in nasal mucosa through cribiform plate and synapse in olfactory bulb with output cells, axons projecting along olfactory tract to primary olfactory cortex of temporal lobe or secondary olfactory cortex (orbitofrontal)


How can you test olfactory nerve function

Test sense of smell


Describe the sensory, motor and parasymp functions of optic nerve

Sensory: to retina --> vision


Describe the visual pathway from photoreceptor to optic chiasm, include where optic chiasm is found

Photoreceptor --> retinal ganglion cell --> optic disc --> optic nerve passes through optic foramen --> nerves join = optic chiasm (in anterior cranial fossa)


What happens in optic chiasm why is this important

Axons from medial aspect of retina (i.e. axons from nasal retina)cross midline to join axons from lateral aspect of retina of opposite eye --> info from left and right visual fields segregated into left and right optic tracts


Describe visual pathway from optic tract to visual cortex

Optic tract passes posteriorly around upper brainstem, some fibres --> hypothalamus, some --> midbrain (pretectal nucleus and superior colliculus), most to lateral geniculate nuclei of thalamus for visual perception, axons project as optic radiation --> visual cortex


How do you test optic nerve

Test fields of vision and visual acuity


What happens with lesions of retina/optic nerve

Ipsilateral blindness in affected segment (i.e. in one eye)


What happens in lesion of right optic tract/central parts of visual pathway

Left homonymous defect (loss of left visual field of both eyes)


What happens in lesion of optic chiasm

Bitemporal hemianopia (lose temporal visions on both sides)


What can cause lesion of optic chiasm

Expanding pituitary tumour


Describe the sensory, motor and para symp functions of the oculomotor nerve

Motor: superior, middle and inferior rectus muscles. Inferior oblique eye muscles and levator palpebrae of eyelid.
Parasympathetic: to pupillary constrictor and ciliary muscles of eye --> pupil constriction and accommodation


Describe nuclei for oculomotor nerve

Nucleus of origin at level of superior colliculus (main oculomotor nucleus --> extrinsic eye muscles) and accessory oculomotor nucleus (Edinger Westphal nucleus)


Describe course of oculomotor nerve motor component

Fibres from main nuclei emerge between cerebral peduncles and pierce cavernous sinus, enter superior orbital fissure and divide into superior branch and inferior branch


Describe course of oculomotor nerve para component

Para fibres from EW nucleus innervate ciliary ganglion where parasymp fibres synapse with post ganglionic axons --> supply ciliary muscles


How can you test function of oculomotor, trochlear and abducens nerve function

Examine pupillary reflexes (shine light on one eye, both eyes should get smaller to same extent) + eye movements


How may loss of oculomotor nerve present

Loss of up/down/medial eye movements --> down and out gaze
Pupillary dilation


Why does oculomotor nerve lesion cause ptosis and pupillary dilation

Ptosis: paralysis of levator palpebrae
Pupillary dilation: unopposed symp dilator fibres and loss of pupillary constrictor reflex


Why does oculomotor lesion lead to down and out gaze (eye deviating down and laterally)

Superior oblique and lateral rectus unopposed and rotate eyeball laterally


What are the sensory, motor and para functions of the trochlear nerve

Motor: superior oblique eye muscle --> depression of eye --> move eye out and down


Describe course of trochlear nerve including location of nucleus

Nucleus at level of inferior colliculus (midbrain) emerges on dorsum of pons --> passes to pierce cavernous sinus and enter superior orbital fissure


What happens when you damage trochlear nerve

Vertical diplopia on looking medially and downward (overlapping images)


Which cranial nerve emerge from midbrain

Oculomotor and trochlear


What are the sensory, motor and para functions of trigeminal nerve

Sensory: face, scalp, cranial dura mater, nasal/oral cavities, teeth, tongue (sensation to anterior 2/3), cornea
Sensory: Opthalmic and maxillary afferents in coughing and sneezing (opthalamic --> forehead and nose, maxillary --> upper jaw, mandibular --> lower jaw and face)
Motor: muscles of mastication, tensor tympani and tensor palatini


Where are cell bodies of trigeminal nerve found

Trigeminal ganglion, in depression on petrous temporal bone


Describe roles of different trigeminal nuclei

Principal sensory nucleus = common sensation
Spinal sensory nucleus = pain and temp sensation
(Mesencephalic nucleus for proprioception)
Trigeminal motor nucleus --> motor neurones


Where does ophthalmic division of trigeminal nerve leave skull

Superior orbital fissure


What is the role of ophthalmic division of trigeminal nerve

Purely sensory --> skin of forehead, front of eyeball and nose


Which nerve mediates blink reflex

Ophthalmic division of trigeminal nerve


What is the role of maxillary division of trigeminal nerve

Sensory: innervates upper lip and lateral nose, nerves to upper teeth and lateral face, nasal cavity and palate


Where does maxillary division of trigeminal nerve pass through skull

Foramen rotundum


What is the role of mandibular division of trigeminal nerve

Sensory and motor
Motor: innervates muscles of mastication e.g. temporalis, masseter, medial/lateral pterygoid
Sensory: lower teeth and anterior 2/3 tongue


Where does mandibular division of trigeminal nerve pass through

Foramen ovale


How can you test function of trigeminal nerve

Examine sense of touch in cornea and face
Check jaw closes symmetrically


Symptoms of lateral medullary syndrome

Losses of pain and temp sensation from ipsilateral face and contralateral body


How can lesions of individual divisions of trigeminal nerve be identified

Loss of sensation in corresponding area (and for mandibular --> sensory and motor deficits)


Symptoms of damage to trigeminal nerve

Trigeminal neuralgia --> acute stabbing over corresponding area
Toothache, headache and migraines


Why does damage to trigeminal nerve lead to headaches/migraines on the top of the head

Trigeminal has branch passing through foramen spinosum innervating dura mater superiorly and anteriorly


How is referred pain relevant to trigeminal nerve

Patients with tongue carcinoma (lingual nerve) complain of earache (auriculotemporal nerve) because both innervated by branches of V3


What does abducens nerve pass through

Superior orbital fissure


What part of skull does oculomotor nerve pass through

Superior orbital fissure


What part of skull does trochlear nerve pass through

Superior orbital fissure


What are the para, sensory and motor roles of abducens nerve

Motor to lateral rectus eye muscle, eye ball movement (abduction)


Describe position of nucleus of abducens nerve

In caudal pons


Describe course of abducens nerve fibres

Emerge from pontomedullary junction then pass forward and enter cavernous sinus and to orbit via superior orbital fissure


How is abducens nerve tested

Examine eye movements


How may damage to abducens nerve manifest

Loss of lateral eye movement, diplopia on looking to side, convergent squint


What does facial nerve pass through

Internal acoustic meatus


What is the sensory,motor and para roles of facial nerve

Sensory: anterior 2/3 of tongue (taste)
Motor: muscles of facial expression, stapedius
Para: salivary glands submandibular and sublingual) and lacrimal glands


Describe course of motor supply for facial nerve

Facial nucleus in caudal pons--> fibres loop around abducens nucleus and emerge at cerebellar pontine angle. Motor nerve branches beneath parotid gland and distributes to face and innervates stapedius


Describe course of sensory supply of facial nerve

Sensory neurone cell bodies in geniculate ganglion, innervates anterior 2/3 tongue via chorda tympani, central processes terminate in nucleus solitaries


Sensory neurone cell bodies innervate anterior 2/3 tongue via...

Chorda tympani


Where does taste information (i.e. trigeminal sensory fibres) terminate

Nucleus solitarius


Describe para supply of facial nerve to salivary glands

Submandibular ganglion --> submandibular and sublingual glands via chorda tympani


Describe para supply of facial nerve to lacrimal glands

Pterygopalatine ganglion --regulates tear production by lacrimal glands and mucus secretion from nasal epithelium and palate


How do you test for facial nerve

examine control of facial muscles and test symmetry of expression


What happens when the facial nerve is damaged *

- Hyperacusis (paralysis of stapedius)
- Bell's palsy: loss of expression, hyperacusis, ptosis and dribbling


Potential cause of Bell's palsy

Herpes simplex and influenza


Where does vestibulocochlear nerve pass through

Internal acoustic meatus


What are the sensory, motor and para functions of vestibulocochlear nerve

Sensory: vestibular apparatus of ear --> position of head/movement + cochlea --> hearing


Where are vestibular and cochlear nucleus found

Medulla at level of olives


Where does auditory nerve originate from

Spiral ganglion cells within modiolus of cochlea and vestibular sensory afferents in vestibular ganglion.


How can you test for vestibulocochlear nerve

Examine vestibular function with caloric or rotational tests,
Examine hearing with audiometry (tuning fork to distinguish sensorineural vs conductive hearing loss)


How do you distinguish sensorineural and conductive hearing loss

Tuning fork: Air conduction louder than bone conduction in sensorineural, but reverse true if conductive hearing loss


What do lesions of vestibular division of VC nerve do

Vertigo, nausea, nystagmus


What do lesions of cochlear division of VC nerve do

Unilateral deafness and tinnitus


Give a cause of vestibulocochlear nerve palsy, what are the symptoms

Acoustic neuroma (vestibular schwannoma) in internal acoustic meatus (benign intracranial tumour of Schwann cells of nerve) --> hearing loss, tinnitus, issues with balance


Which cranial nerves emerge from the pons

Trigeminal, abducens Facial nerve, vestibulocochlear nerve


What does glossopharyngeal nerve pass through

Jugular foramen


What are the sensory, motor and para roles of glossopharyngeal nerve

Sensory: oropharynx, external ear. Post 1/3 tongue (sensation and taste) +carotid body/sinus = visceral sensory
Branchial motor: stylopharyngeus
Para (visceral motor): parotid salivary gland (otic ganglion)


Where does branchial motor component of glossopharyngeal nerve arise from

Nucleus ambiguus in medulla


Where does para preganglionic fibres of glossopharyngeal arise from

Inferior salivatory nucleus in pons ( to parotid gland)


Where do neurones providing visceral sensation for glossopharyngeal nerve project to

neurones in petrosal/glossopharyngeal ganglion which terminate in nucleus solitarius of medulla


How can you test glossopharyngeal nerve

Gag reflex, voice and swallowing


What does vagus nerve pass through

Jugular foramen


What are the sensory, motor and para roles of vagus nerve

Sensory to larynx, pharynx, epiglottis, oesophagus, external ear (sensation), external auditory meatus, aortic arch/bodies
Motor: muscles of pharynx/larynx and palatoglossus
Para: skeletal muscle in soft palate, pharynx, larynx and upper oesophagus and organs from neck down to second segment transverse colon (except adrenal glands)


How can gag reflex be elicited (vagus nerve)

Through sensory stimulation in epiglottis or external auditory meatus


What branch of vagus innervates larynx

recurrent laryngeal nerve


Describe role of sensory component of vagus nerve and where it terminates

Visceral sensory supply to foregut and midgut derivatives and project to nucleus solitaries


How does glossopharyngeal nerve innervate parotid gland (describe the course)

Fires arise from inf salivatory nucleus in pons and run in tympanic branch which joins lesser petrosal nerve --> synapse in otic ganglion --> post ganglionic fibres to parotid gland


Where does brnachial motor fibre of vagus nerve arise from

nucleus ambiguus


Describe what vagus nerve does as it passes via jugular foramen

joined by cranial root of accessory nerve


Where do para preganglionic fibres of vagus arise from

Dorsal motor nucleus of vagus in medulla


Describe course of para supply of vagus nerve

Para pre ganglionic fibres from dorsal motor nucleus synapse onto post ganglionic fibres near/on effector organ (i.e. foregut/midgut structures of pharynx/larynx)


Where does visceral sensation of vagus nerve get conveyed yo

Nucleus solitaries


How can you test vagal nerve function

Gag reflex, voice and swallowing , palatal movements


Symptoms of damage to vagus nerve

Hoarse voice as paralysis of muscles controlling vocal cords


Describe sensory, motor and para roles of accessory nerve

Motor to trapezius and sternomastoid


What are the roles of trapezius and sternomastoid

Head and shoulder movements


Which nerve is important for palatal movements

Vagus nerve


Which nerves involved in gag reflex

Glossopharyngeal and vagus


Describe course of spinal accessory nerve

Arises from cell bodies in C2-C6, rootlets join cranial root of accessory nerve before leaving skull through jugular foramen.


Where is cranial part of accessory nerve derived from

Nucleus ambiguus


How can you test for accessory nerve function

Trapezius: ask patient to elevate/shrug shoulders against resistance
Sternomastoid: ask patients to turn face to opposite side against resistance


What happens when accessory nerve is damaged

Paralyse trapezius (can't raise arm above head) and sternomastoid


Where does accessory nerve pass through

Jugular foramen


Where does hypoglossal nerve pass through

Hypoglossal canal


What is the sensory, motor and para function of hypoglossal nerve

Motor to intrinsic and extrinsic tongue muscles except palatoglossus


Where does hypoglossal nerve arise from

Hypoglossal nucleus in medial medulla


Describe course of hypoglossal nerve

Emerge as rootlets between pyramids and olives and passes through hypoglossal canal to reach underside of tongue


How can you test for hypoglossal nerve function

Observe tongue for paralysis and wasting - tongue deviates on protrusion of paralysed site


What can damage to hypoglossal nerve do

Deviation of protruded tongue to affected side and wasted on that side


What can cause damage to hypoglossal nuclei

Medial medullary syndrome from anterior spinal artery lesion.


Concerning vagus nerve..Nucleus solitaries receives...

Visceral sensory info (from vagus) from heart, gut oesophagus, aortic body i.e. autonomic functions


Describe evolution of nucleus ambiguous position

Moved closer to main sensory trigeminal nucleus --> important for reflexes for preventing food down airways --> protects airways as faster subcortical reflex


Where do branchial/somatic sensory afferents of vagus terminate

Branchial sensory afferents terminate in main sensory trigeminal nucleus


What do branchial sensory fibres of vagus convey

information about deep/crude touch, pain, and temperature of the outer ear, and mucosa of larynx)


Describe branchial/somatic sensory component of glossopharyngeal

To oropharynx and cutaneous region behind ear


What nerves do gag reflex test, how

Test branchial sensory from oropharynx and motor from vagus


Where does Vagus and glossopharyngeal nerve pain and temp sensation from larynx come into

Spinal nucleus of trigeminal