Neuro9 Cranial Nerves Flashcards
Cranial nerve nuclei
Located in tegmentum portion of brain stem (between dorsal and ventral portions) .
Lateral nuclei = sensory (alar plate). - Sulcus limitans-
Midbrain
nuclei of CN III, I V
Pons
nuclei of CN V, VI, V II, VIII
Medulla
nuclei of CN IX, X, XII
Corneal Cranial nerve reflex
Afferent: V1 ophthalmic (nasociliary branch)
Efferent:
VII (temporal branch: orbicularis oculi)
Lacrimation Cranial nerve reflex
V 1 (loss of reflex does not preclude emotional tears)
VII
Jaw jerk Cranial nerve reflex
V3 (sensory-muscle spindle from masseter)
V3 (motor-masseter)
Pupillary reflex
Afferent: II
Efferent: III
Gag
Afferent: IX
Efferent: IX, X
Vagal nuclei: Nucleus Solitarius
Visceral Sensory information (e.g., taste,
baroreceptors, gut distention).
VII, IX, X.
Vagal nuclei: Nucleus aMbiguus
Motor innervation of pharynx, larynx, and upper esophagus (e.g., swallowing, palate elevation) .
IX, X, XI.
Vagal nuclei:Dorsal motor nucleus
Sends autonomic (parasympathetic) fibers to heart, lungs, and upper GI.
Cranial nerve and
vessel pathways
Cribriform plate (CN 1).
Middle cranial fossa (CN II-VI) -through
sphenoid bone:
l . Optic canal (CN II, ophthalmic artery,
central retinal vein)
2. Superior orbital fissure (CN III, IV, V1,
VI, ophthalmic vein, sympathetic fibers)
3. Foramen Rotundum (CN V2)
4. Foramen Ovale (CN V3)
5. Foramen spinosum (middle meningeal
artery)
Posterior cranial fossa (CN VII-XII) - through
temporal or occipital bone :
I. Internal auditory meatus (CN VII, VIII)
2. Jugular foramen (CN IX, X, XI, jugular
vein)
3. Hypoglossal canal (CN XII)
4. Foramen magnum (spinal roots of CN
XI, brain stem, vertebral arteries)
Divisions of CN V exit owing to Standing Room
Only.
Cavernous sinus
A collection o f venous sinuses o n either side of
the pituitary. Blood from eye and superficial
cortex goes to cavernous sinus goes to internal jugular
vein.
CN III, IV, V1, V2, and VI and postganglionic
sympathetic fibers en route to the orbit all
pass through the cavernous sinus. Cavernous
portion of internal carotid artery is also here.
The nerves that control extraocular muscles
(plus V1 and V2) pass through the cavernous
sinus.
Cavernous sinus syndrome (e.g., due to mass
effect) - ophthalmoplegia, ophthalmic and
maxillary sensory loss.
CN XII lesion (LMN)
tongue deviates toward side of lesion (lick your wounds) due to weakened tongue muscles on the affected side
CN V motor lesion
jaw deviates toward side of lesion due to unopposed force from the opposite pterygoid muscle.
CN X lesion
uvula deviates away from side of lesion. Weak side collapses and uvula points away
CN XI lesion
weakness turning head to contralateral side of lesion (SCM). Shoulder droop on side of lesion (trapezius)
Conductive hearing loss
abnormal Rinne test (bone > air); Weber test localizes to affected ear
Sensorineural hearing loss
normal Rinne test (air > bone); Weber test localizes to unaffected ear.
Facial Nerve UMN lesion
Lesion of motor cortex or connection between cortex and facial nucleus. Contralateral paralysis of lower face only, since upper face receives bilateral UMN innervation.
Facial Nerve LMN lesion
Ipsilateral paralysis of upper and lower face.
Bell’s palsy
Complete destruction of the facial nucleus itself
or its branchial efferent fibers (facial nerve
proper) .
Peripheral ipsilateral facial paralysis with
inability to close eye on involved side.
Can occur idiopathically; gradual recovery in
most cases.
Seen as a complication in AIDS, Lyme disease,
Herpes simplex, Sarcoidosis, Tumors, Diabetes
(Alexander graHam Bell with STD) .
Mastication muscles
3 muscles close jaw: Masseter, teMporalis,
Medial pterygoid. 1 opens: lateral pterygoid.
All are innervated by the trigeminal nerve
(V3).
