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CN and brain stem reflexes Flashcards

1
Q

what most commonly causes an impairment in CN 1

A

mucosal swelling and inflammation during sinusitis or an upper respiratory infection

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2
Q

what can cause a permanent loss of smell

A

severe head trauma where the olfactory nerve branches are sheared or torn where they pass through the bony cribriform plate

or a tumor near the olfactory lobe at the skull base (i.e. meningioma)

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3
Q

how do you test CN III, IV, VI

A

pt tracking a target up and down and side to side

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4
Q

what eye movements is the superior oblique responsible for

A

depresses and abducts the eye and medial rotation

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5
Q

what eye movements is the inferior oblique responsible for

A

elevates and abducts they eye, and lateral rotation

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6
Q

what eye movements is the superior rectus responsible for

A

elevates and adducts the eye and medially rotates

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7
Q

what eye movements is the inferior rectus responsible for

A

depresses and adducts the eye and laterally rotates

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8
Q

if a patient cannot fully elevate the eye which muscles are you concerned are not functioning and how would you differentiated

A

superior rectus or inferior oblique

if the patient turns his eye inward (adducts) and has weakness then its mainly the inferior oblique

weakness of elevation when the eye is turned outward (abduction) is mainly the superior rectus

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9
Q

if a patient cannot fully depress the eye which muscles are you concerned are not functioning and how would you differentiated

A

superior oblique or inferior rectus

weakness when eye is turned outward = inferior rectus

weakness when the eye is turned inward = superior oblique

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10
Q

starting with the eye out/abducted which muscle are you testing by having the patient look up

A

superior rectus

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11
Q

starting with the eye out/abducted which muscle are you testing by having the patient look down

A

inferior rectus

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12
Q

starting with the eye in/adducted which muscle are you testing by having the patient look down

A

superior oblique

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13
Q

starting with the eye in/adducted which muscle are you testing by having the patient look up

A

inferior oblique

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14
Q

what are the signs of a CN III lesion

A
  • complete ipsilateral ptosis (paralysis of leavator palpebrae superioris m)
  • eye abducted
  • pupil is large and unreactive to light directly and consensually
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15
Q

what are signs of a CN IV lesion

A

impairment of downward gaze - best seen when the involved eye is in the adducted position

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16
Q

where does CN IV exit the brainstem and what is unique about its pathway

A

exits the brainstem dorsally and decussates to innervate the contralateral superior oblique m

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17
Q

what does a CN VI lesion affect

A

the ipsilateral lateral rectus muscle impairing abduction of the affected eyeball

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18
Q

what causes binocular diplopia

A

the eyeballs are not perfectly aligned in primary position or when conjugately moving to other positions

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19
Q

how can binocular and monocular diplopia be differentiated

A

covering one eye will correct binocular diplopia

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20
Q

what CN lesions can cause binocular diplopia

A

CN III, IV, VI (or a lesion of their related muscles)

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21
Q

what is more common binocular or monocular diplopia

A

binocular - monocular is very rare

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22
Q

what is a nystagmus

A

repetitive, oscillatory, jerky eye movements

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23
Q

what causes a normal/physiological nystagums

A

suddenly stopping someone rotating in a chair

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24
Q

what causes an asymmetrical pathologic nystagmus

A

pathologic nystagmus could be due to a lesion of the vestibular system, brain stem, or cerebellum - all upset normal control or balance on conjugate eye movements (usually asymmetric and position dependent)

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25
what causes a symmetrical pathologic nystagmus
drug toxicity - usually present with all eye movements
26
what is internuclear opthalmoplegia (INO)
paralysis of extraocular muscles (opthalmoplegia) due to a lesion between the nuclei (internuclear) involved with lateral gaze (oculomotor and abducens nuclei) which interrupts the ascending medial longitudinal fasciculus (MLF)
27
what syndrome is associated with an internuclear opthalmoplegia
MLF syndrome
28
describe the path of the MLF
it connects the PPRF (paramedian pontine reticular formation) and the contralateral oculomotor nucleus - it decussates early then rises from the pons to the midbrain
29
what would a lesion in the left MLF cause
paralysis of adduction of the left eye with nystagmus of the abducting right eye - since the left CN III nucleus never gets the MLF signal causing an impairment in right lateral gaze. the left medial rectus still functions and both eyes will be able to converge via the near reflex
30
what are the 2 most common causes of a MLF lesion
young pts - MS | old pts - ischemic infarct
31
what is the pathway involved in the consensual pupillary response
retinal ganglion cells projecting bilaterally to the pretectal area (rostral to the superior colliculus) which then projects to the Edinger-Westphal nucleus of CN III
32
describe pupillary direct and consensual response with an optic nerve lesion
when light is shined into the affected eye there is no direct or consensual response when light is shined in the other eye both pupils respond
33
describe pupillary direct and consensual response with a CN III lesion
when light is shined in the affected eye there is no direct response but the other eye has a consensual response when light is shined in the other eye there is a direct response but no consensual response
34
what causes a relative afferent pupillary defect (RAPD)
a partial optic nerve or retinal lesion
35
what are the pupillary responses with a RAPD
both pupils may initially constrict to light but after moving the light source from the normal to affected eye there may be dilatation due to the relatively decreased afferent input
36
what 3 things occur during the near reflex
pupillary constriction, lens accommodation and convergence of the eyes
37
what is a dissociation of light and near reflexes (light-near dissociation)
when there is disruption of the pupillary light reflex pathway at the pretectal area but the near reflex is preserved pupils constrict during the near reflex but not to a light stimulus
38
what are 2 causes of light-near dissociation
dorsal midbrain syndrome and Argyll Robertson pupils in neurosyphilis
39
what is the dorsal midbrain syndrome
aka Parinaud's syndrome, classically refers to a pineal tumor compressing the dorsal midbrain but may also occur from an ischemic infarction there
40
what other deficit may be seen with dorsal midbrain syndrome in addition to light-near dissociation
impairment of upward gaze do to involvement of the midbrain's centers for vertical gaze
41
what causes Horner's syndrome
a lesion disrupting the oculosympathetic pathway
42
what are the symptoms of Horner's syndrome
Miosis (constricted pupil), anhidrosis (lack of sweat), and mild ptosis (drooping of eyelid)
43
where is a lesion in Horner's syndrome
*  lateral medullary infarction aka Wallenberg syndrome (first order neuron) * tumor of the apex of the lung (2nd order neurons) * neck trauma (3rd order neuron)
44
where would you suspect a lesion affecting V1, CN III, CN IV, CN VI
superior orbital fissure or nearby cavernous sinus
45
what in Trigeminal neuralgia
painful syndrome of irritation or inflammation of one of the trigeminal nerve sensory branches causing it to "short circuit" or "misfire"
46
what are the symptoms of Trigeminal neuralgia
sharp episodic pain several times daily that may be provoked by talking, chewing or touching the face no sensory or other CN deficits are found on exam
47
what causes Trigeminal neuralgia in younger patients
MS lesion at the trigeminal nerve entry regoin into the pons
48
what causes trigeminal neuralgia in older patients
a trigeminal nerve branch is often compressed by a tortuous or kinked blood vessel (often in the superior cerebellar artery) this can be surgically repositioned or padded
49
what are treatments for trigeminal neuralgia
if due to compression - surgery | oral anticonvulsants i.e. carbamazepine, gabapentin or others
50
what are signs/symptoms of a LMN lesion of the trigeminal motor nerve
atrophy and weakness in the ipsilateral muscles of chewing (the masseter and temporalis) and jaw deviation towards the side of the lesion
51
what are the signs of an UML of the trigeminal nerve
there is bilateral innervation so no atrophy, weakness or deviation is seen in a bilateral UMN lesion here there may be hyper-reflexia of the jaw jerk
52
what is the sign/symptoms of a CN VII lesion at or near the stylomastoid foramen (or a lesion in its nucleus)
severe paralysis of the entire ipsilateral half of the face
53
impaired taste over the anterior 2/3 of the tongue indicate a lesion where
involving the chorda tympani branch of the facial nerve.
54
hyperacusis is seen with a lesion involving what
the branch of CN VII that goes to the stapedius muscle
55
what would symptoms of lesion at the internal auditory meatus or cerebelloponine angle cause
facial weakness hyperacusis hearing impairment and tinnitus (involves CN VII and VIII, commonly caused by an acoustic neuroma)
56
A lesion of CN VII in the pons is likely to also involve what other nerve, causing what sign?
CN VI -causing a weakness of lateral gaze
57
where is the lesion in Bell's palsy
its idopathic
58
what are the symptoms of Bell's palsy
facial nerve paralysis - may occur suddenly | may have ipsilateral hyperacusis and impaired taste as well
59
how do yo treat Bell's palsy
short course of oral corticosteroids and maybe antivirals since it is thought to possibly be due to inflammation of the facial nerve mediated by HSV-1 or other viruses
60
what is the distribution of weakness for an UMN CN VII lesion
facial paralysis of the lower part of the contralateral face (spares the forehead)
61
a lesion of what cranial nerves could cause difficulty speaking or swallowing and how could you differentiate clinically?
CN IX or X gag-reflex or elevation of the palatal arch
62
how is a gag-reflex interpreted clinically
can try to differentiate between CN IX and X deficits with a gag reflex test- a decreased gag reflex when touching one side of the pharynx suggest a CN X lesion on that side (very difficult to differentiate)
63
how does a LMN CN X lesion present
impaired speech and swallowing absent gag-reflex ipsilateral drooping or sagging of the palatal arch (uvula points toward the normal side) horse voice
64
a horse voice could be due to a lesion involving what nerve
X
65
what is seen with a LMN lesion of CN XI
decreased elevation or shrugging of the shoulder and weakness when turning the head to the opposite side
66
what does the CN XII innervate
tongue muscles most importantly the genioglossus muscle which protrudes each side of the tongue forward
67
what clinical sign of a LMN lesion of XII
the protruded tongue will point toward the side of the lesion. over time there is atrophy and fasiculation and fibrillation of the tongue
68
what way would the tongue point in an UMN lesion of CNXII
in most patients toward the side of the lesion but in some patients the UMN is controlled by the opposite side
69
what is a crossed brain stem syndrome
cranial nerve involvement on one side and an adjacent fiber tract lesion creating a sensory or motor deficit on the opposite side of the body
70
what symptoms would be expected with a right pontine lesion
* LMN paralysis of the right face (CN VII) | * UMN paralysis of the left upper and lower limbs (rt CST)
71
where could a lesion be located causing deficits of pain and temperature over the left face and right limbs and body
Lesion of the left lateral medulla | Involves the Left descending spinal tract of CN V and the left STT
72
what is weber syndrome aka
the medial midbrain syndrome
73
what could cause the medial midbrain syndrome
ischemic infarction from an occluded branch of the posterior cerebral artery
74
What CNs and tracts are affected in a medial midbrain syndrome
CN III and the cerebral peduncle (CST and corticobulbar tracts)
75
what are the symptoms of a medial midbrain syndrome
ipsilateral oculomotor nerve lesion and upper motor neuron weakness of the contralateral face and limbs
76
what is the other name for the lateral medullary syndrome
wallenberg syndrome
77
what causes a lateral medullary syndrome
ischemic infarction from an occluded vertebral artery or its PICA branch
78
what are the symptoms of a lateral medullary syndrome
pain and temperature impairment in the ipsilateral face and contralateral limbs and body others: hoarseness, vertigo, nausea and vomiting, clumsiness there may be nystagmus, ipsilateral limb dysmetria, ipsilateral Horner's syndrome and ipsilateral palatal and coal cord paralysis
79
what is preserved in a lateral medullary syndrome
position sense and strength

Neuro (11 decks)

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