Cranial Nerves
CN 5 function
*Sensory*: Sensation of face, head cornea of eye, & inner oral cavity---pain, temp, disc touch *Motor* Innervates jaw muscles that control chewing
the midbrain contains which 4 cranial nerves?
1,2,3,4
describe the general process of smelling
1. vaporized chemicals reach nostrils and dissolve 2. specialized receptors in olfactory epithelium (olfactory receptor neurons) detect odor 3. transmit to olfactory bulbs in back of nose 4. bulbs have receptors that are part of the brain and send messages to limbic system structures and "higher centers" (neo-cortex).
sense of smell is X times more sensitive than any other sense
100,000 times and immediate!
the pons contains which 4 cranial nerves?
5,6,7,8
eye movement is controlled by how many muscles
6- high degree of coordination
cn ___ is sensory to heart cn ___ is motor to heart
9, 10
the medulla contains which 4 cranial nerves?
9,10,11,12
Case: -Patient has poorly controlled HTN and Type 2 DM -partial ptosis and inferiolateral deviation of left -eye and unable to move eye past midline ptosis, unsteady gait, headache, and left eye pain Most likely diagnosis? A. Aneurysm of the posterior communicating artery. B. Diabetic third nerve palsy. C. Myasthenia gravis. D. Orbital myositis. E. Vertebrobasilar occlusion
B. diabetic third nerve palsy (levator palpebrae and 4 EO muscles) caused by microvascular infarction MRI should be performed!
an intraventricular lesion of the 4th ventricle can hurt which cranial nerves?
CN 6 and 7
a pontine brain stem lesion would most likely result in a lesion of which 2 cranial nerves?
CN 6 and CN 7
lesion in internal acoustic meatus cleaves what two nerves
CN 7 and CN 8
What is Claude syndrome?
Damage to the dorsal midbrain involving the superior cerebellar peduncle and producing a contralateral ataxia in addition to ipsilateral CN III palsy
LMN lesion
Hyporeflexia, hypotonia, atrophy, fasciculations
aortic aneurysm can affect which N
LEFT recurrent laryngeal
a patient presents with a widened mediastinum, bruit, and aortic arch on CXR patient also has a hoarse voice what do you expect?
LEFT recurrent laryngeal nerve lesion and aortic aneurysm
a patient presents with weakness when rotating head to the right as well as downward lateral rotation of the scapula and shoulder drop, what type of lesion might you expect?
LMN lesion of CN 11 on opposite side damage cn 11 can happen during radical neck surgery weakened head rotation AWAY from side of lesion
CN 6 function
LR6
eye muscle cranial nerves
LR6(SO4)3
what is lateral medullary infarction?
Lateral medullary syndrome is a neurological disorder causing a range of symptoms due to ischemia in the lateral part of the medulla oblongata in the brainstem. The ischemia is a result of a blockage most commonly in the vertebral artery or the posterior inferior cerebellar artery.
What is the L5 dermatome?
Lateral shin, dorsum of foot, toes (except little toe).
what is Weber's test?
Lateralization. Apply vibrating fork to the forehead or on top of the head
OS refers to?
Left eye
what is the treatment for anosmia?
No specific treatment, only education and exploration of causes decongestants, quit smoking.
What is Wallenberg syndrome?
Occlusion of PICA or VA (Lateral Medullary Syndrome) Ipsilateral ataxia, ipsilateral loss of pain on face, contralateral loss of pain in body, n/v, nystagmus, hoarseness, decreased gag reflex
what arteries does CN3 run in between?
Posterior cerebral A, superior cerebral A
What is the S1 dermatome?
Posterolateral thigh, lateral calf, lateral ankle and foot, and little toe.
OD refers to?
Right eye
CN 4 function
SO4
What is acoustic neuroma?
Schwan cell tumor of CN 8 dizziness, nausea, vomiting, tinnitus, decreased balance followed by IPSILATERAL deafness also affects CN 7- decreased facial expression, decreased tase anterior 2/3 tongue, dry salivary and mucosal lacrimal gland on affected side.
CN 9 function
Sensory - taste on the POSTERIOR aspect of tongue Motor - swallowing
What is the Rinne test?
Test measuring hearing using bone conduction and air conduction
what is carotid sinus massage?
The Czermak-Hering test is a vagal maneuver consisting of the application of external digital pressure to the carotid sinus. The test is performed at the patient's bedside by imposing moderate pressure with the fingers, repeatedly massaging the left or the right carotid arteries a test to possibly slow and "reset" the cardiac rhythm CN 9 and 10
What is Benedikt's syndrome?
This is a syndrome of ipsilateral 3rd nerve palsy and contralateral choreiform movements: it involves the red nucleus and neighboring third nerve. -occlusion of PCA perforators @ midbrain tegmentum
what is the most famous disease of the trigeminal nerve?
Tic Douloureux (trigeminal neuralgia) cause unknown
what are the three divisions of the trigeminal nerve
V1 ophthalmic V2 maxillary V3 mandibular OMM
what is one of the main problems of thyroid surgery?
Vocal cord paresis or paralysis due to iatrogenic injury of the recurrent laryngeal nerve (RLNI)
Patient presents to you with Ipsilateral ataxia, ipsilateral loss of pain on face, contralateral loss of pain in body, n/v, nystagmus, hoarseness, decreased gag reflex - what do you suspect?
Wallenberg's Syndrome (CN V, IX, X, and XI)
what is a "Crossed tract" sign?
a cranial nerve deficit on one side with body deficits on the opposite side , usually indicate a brainstem lesion.
a patient presents to you with a tongue deviation to the right - what do you suspect?
a lesion in the hypoglossal nerve on the same side as the deviation
What is Foster Kennedy Syndrome?
a tumor forms and 1) compresses one optic nerve (visual field loss), 2) increases ICP (papilledema iin opposite eye), 3) pressure on CN1 (anosmia)
what is the action of the abducens nerve?
abducts the eye
what muscles does CN10 supply
all MM of the pharynx and soft palate except stylopharyngeus IX and tensor palati (V3)
what is the function of the lateral vestibular tract?
allowing eyes to maintain fixation on an object while the skull moves and maintains antigravity muscles --> aka MLF
a patient presents with trapezius weakness on one side and sternocleidomastoid weakness on the contralateral side - what does this indicate?
an UMNL ipsilateral to the involved SCM and above the oculomotor nerve nucleus
what things can affect cn 3
aneurysms, midbrain stroke, meningitis, temporal lobe herniation, cavernous sinus lesion, LMNL --> oculomotor ophthalmoplegia
how do you differentiate between myasthenia gravis and other ischemic palsies bc MS can present as a pupil sparing third nerve palsy with ptosis
apply ice for 2 minutes which will relieve ptosis and point to myasthenia gravis.
what the function of CN 8?
auditory information from the cochlea balance information from the semicircular canals
what medications should you avoid in patients over 60 years old to avoid a vasovagal reflex?
beta blockers and anticholinerggics
what type of lesion can cause bilateral weakness of voluntary jaw movement?
bilateral lesions of the hemisphere or brain stem above the 5th nerve nucleus --> they supply temporals, masseter, pterygoid (above brainstem= hyper chewing reflexes)
what are symptoms of 4th ventricle lesions?
bilateral, lateral rectus palsies in addition to ipsilateral CNVII facial paralysis
what is initial treatment of trigeminal neuralgia? other treatments?
carbamazepine oxcarbazepine, baclofen, lamotrigine, or pimozide
What are cones responsible for?
color vision and acuity, (fewer in number, located centrally )
what muscles are responsible for parasympathetics of eye (pupil size, lens shape)
constrictor pupillae, ciliary muscles
UMN lesions of CN VII
contralateral lower quadrant paralysis
describe the visceral motor component of the facial nerve
controls all facial glands through superior saltatory nucleus except skin and parotid
what is Villaret's syndrome?
damage to CN IX, X, XI, and XII in the posterior retroparotid space
What is homonymous hemianopsia?
damage to optic track after cross over --> loss of half of the field of view on the same side in both eyes
What are rods responsible for?
dim light (retina is made of rods and cones)
What is parosmia?
distorted sense of smell (CN1)
what clinical symptoms are associated with vestibular damage?
dizziness, falling, nystagmus nausea, vomiting (connections with vagus nerve)
oculomotor nerve palsy clinically presents as an eye that is....?
down and out
a patient presents with hoarseness and dysphagia, what do you expect to find on physical exam?
drooping of soft palate and uvula deviates towards the unaffected side, (unilateral loss of elevator palitini) (CN 10 lesion)
what is the function of the glossopharyngeal nerve on the pharynx?
elevates pharynx during swallowing and speech -brachial motor
CN 3 function
eye movement
describe the signal route for the optic nerve
eyes --> optical canal --> middle cranial fosse --> chiasm --> crossover (1/2 fibers) --> lateral geniculate body in thalamus. small amount foes to midbrain for reflexes larger amount go to optic radiations in cerebral hemispheres through internal capsule near calcimine fissure in occipital lobes
CN 7 function
facial nerve facial motor function taste to anterior 2/3 of tongue tears saliva
the mandibular division of the trigeminal nerve emerges from where?
foramen ovale
the maxillary division of the trigeminal nerve emerges from where?
foramen rotundum
a patient presents with severe shooting paints at the root of the tongue - what do you suspect?
glosspharyngeal neuralgia
CN 11 function
head and shoulder muscles
CN 8 function
hearing and balance
UMN lesion
hyperreflexia hypertonia spasticity
what is hyperosmia?
increased ability to smell (CN1)
what muscle is responsible for upward gaze?
inferior oblique
what muscle is responsible for downward gaze?
inferior rectus
what are signs and symptoms of a midbrain stroke of CN3?
ipsilateral ophthalmoplegia contralateral hemiplegia (weber's syndrome) contralateral tremor (red nucleus) - Benedikt's syndrome
LMN lesions of CN VII
ipsilateral upper and LQ paralysis (crocodile tears, decreased conjunctival reflex, lips can't purse, food collects in cheeks)
LMN cell bodies of CN 11 enter the cranium via what?
jugular foramen
what does CN9 exit out of
jugular foramen
What is the C5 dermatome?
lateral arm
the abducens nerve innervates what muscle?
lateral rectus
weakness of both the trapezius and SCM on the same side might indicate what?
lesion in the contralateral brainstem, ipsilateral high cervical cord, or an accessory nerve lesion peripherally before the nerve bifurcates
a patient presents to you with trapezius weakness but associated sparing of the SCM - what might this indicate?
lesion in the ventral BS, lower cervical cord, or lower spinal accessory roots
a patient presents with hoarseness s/p thyroidectomy - what do you suspect?
lesion of recurrent laryngeal nerve
a patient presents to you with ipsilateral sensory loss to pain and temperature in the face as well as similar sx in contralateral body. what do you suspect?
lesion of the trigeminal nucleus in the pons or medulla as well as they near spinothalamic tract "lateral medullary infarction"
a patient presents with ipsilateral loss of facial sensation to pain and temperature - what do you suspect?
lesions of the trigeminal nuclei in the brainstem (primary sensory fibers do not cross before entering nucleus)
What is tic douloureux?
lightening like excruciating, shooting pains through parts of the face.
describe the general sensory innervations of the various divisions of the trigeminal nerve
look at slides 60-63 for more info
what muscle adducts the eye?
medial rectus
which part (rule of 4s) is CN 9 in?
medulla
CN supplies motor and sensory to:
motor: inferior salvatori nucleus, parotid gland sensory: hrt --> carotid N --> NTS--> cardiac/resp reflexes
Vertebrobasilar occlusion aka posterior ischemia ss
nausea, vertigo bilateral ptosis , neuro déficits
what kind of signals do the olfactory N vs optic N use
olfactory: chemical via olfactory bulb optic: electrical via retina
when testing the olfactory nerve you always test how many nostrils at a time?
one!
sensory to cn 10
pain, touch, temp from larynx, pharynx, external ear, set auditory meatus, ext surface of TM, meninges of posterior cranial fossa
CN XII supplies all muscles of the tongue except which one?
palatoglossus muscle (CN X)
ophthalmoplegia, hemiplegia
paralysis/weakness of extraoccular eye muscles, paralysis/weakness of half the body
describe the compensation associated with a trochlear nerve lesion
patient tilt to the UNAFFECTED side causing the normal eye to intort and line up with the extorted abnormal eye (Bielschowsky's sign) **trochlear nerve palsy is #1 cause of vertical diplopia
CN 6 palsy of the left eye can be caused by what? what might the patient also have?
poorly controlled diabetes diplopia bc MR is overtaking LR
What is cacosmia?
presence of disagreeable odors (CN1)
What is the gag reflex?
prevents entry of foreign objects into the alimentary and respiratory passages. The reflex is initiated by CN IX which relays sensation of the presence of a foreign object from the back of the mouth. The information is relayed to cranial nerve nuclei X and XII so that respiratory and alimentary passages are closed and the tongue protrudes to expel the object.
what is the action of the hypoglossal nerve?
protrude the tongue straight out, baby: reflexive swallowing, sucking, chewing
how do you test CN 11?
resistance of shrugging shoulders and turning head to CL side
CN 10 function
sensorimotor thoracic/abdominal viscera
the corneal reflex is mediated by what 2 cranial nerves?
sensory - CN 5- ophthalmic motor - CN 7
how do you test CN 7?
show me your teeth wrinkle your forehead smile, puff cheeks
CN 2 funciton
sight
PSVT (Paroxysmal Supraventricular Tachycardia) AKA: AV nodal Re-entrant Tachycardia
simultaneous activation of A & V - retrograde P waves almost lost in QRS
other causes of ansomnia
sinus infection, nasal polyps, head trauma, toxic chemicals, medications, antidepressants, heart meds, cocaine, old age, Alzheimers, Parkinson's, MS, CA radiation
what is the small cutaneous sensory component of CN 7?
skin of the concha of the external ear
causes of ipsilateral anosmia
skull fracture parallel to sagittal suture can cut olfactory fibers going across cribriform plate. cribriform plate fracture (trauma), frontal lobe tumor, dementia, old age
CN 1 funciton
smell
what muscles does CN 11 innervate?
sternocleidomastoid and trapezius
what are LMNL associated with CN 3?
strabismus ptosis dilation (decrease tone in constrictor pupillae) downward, abducted eye position accommodation paralysis OCULOMOTOR OPHTHALMOPLEGIA
the ophthalmic division of the trigeminal nerve emerges from where?
sup. orbital fissue
what muscle is responsible for upward gaze and lid raising?
superior rectus, acts with elevator palpebral superiors
CN 12 function
tongue muscles
T/F CN 7 and 8 are usually involved together
true
a patient presents with hoarseness and dysphagia, you suspect a lesion where?
vagus nerve (unilateral)
LMNL of the trigeminal nerve can be caused by what? what symptoms would present clinically?
vascular damage/skull fracture (foramen ovale) paralysis/atrophy of mastication muscles on affected side with a downward bite on that side
what are some symptoms of damage to the vagus nerve?
vocal changes (hoarse, tongue movements) loss gag reflex dysphagia digestive problems deafness cardiovascular problems like arrhythmia urinary incontinence
What is Weber's syndrome?
• *Contralateral hemiparesis* --> CST • *CN III palsy* --> ipsilateral gaze weakness and diplopia (LMN) PCA @ level of midbrain
