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Neuro > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

vestibular system function

A

maintain equilibrium/postural control

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2
Q

primary input to the vestibular nuclei

A
  1. peripheral vestibular system - inner ear/CN 8 pathways
  2. visual pathways
  3. proprioceptive/mechanosensory pathways
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3
Q

central vestibular pathways

A

located in midbrain at junction of pons and medulla
vestibular nuclei process all vestibular input and coordinate all vestibular responses through connections to other areas of the CNS

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4
Q

peripheral vestibular system

A

inner ear R/L - semicircular canals - otolithic organs: utricle and sccule
vestibulocochlear nerve (CN8) - transits vestibular information from inner ear to the vestibular nuclei

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5
Q

bony labyrinth

A

convoluted space located with petrous portion of temporal bone
contains: perilymphatic fluid similar to CSF, auditory structure = cochlea, vestibular structures = semicircular canals: 3 in each ear, otolithic organs (utricule, saccule)

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6
Q

membranous labyrinth

A

contains membranous portions of the 3 semicircular canals, as well as the utricle and saccule
filled with endolymph-resembles intracellular fluid

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7
Q

vestibular structures

A

semicircular canals: horizontal, posterior, anterior
otolithic organs: utricle, saccule

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8
Q

semicircular canals

A

three semicircular canals lay in three different plans and are arranged perpendicular to each other in each ear
1. horizontal
2. posterior
3. anterior (superior)

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9
Q

function of semicircular canals

A

monitor ROTATIONAL acceleration/deceleration movement - “speed” of rotational movement

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10
Q

receptors of semicircular canals

A

ampulla - enlarged area that contains recpetors in each semicircular cancal
the receptors are hair cells that emerge from crista ampullaris
the hair cells embedded in a gelatinous mass known as the cupula
hair cells are connected to CN 8
endolymph - fluid in the semicircular canals
rotation of head causes endolymph to shift in the semicircular canal and “bend” (displace) the cupula
the change in cupula position bends (moves) the hair cells which stimulates an action potential in vestibular nerve
movement in all three canals allows the brain to determine the axis and speed of rotation

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11
Q

semicircular canals coplaner pairs

A

horizontal canals work together
L posterior and R anterior work together
R posterior and L anterior work together

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12
Q

otolithic organs: utricle and saccule function

A

head movement and linear acceleration/deceleration
changing head position tilts the macula causing the otoliths to shift and displace the gel layer
the change in gel layer bends (moves) the hair cells which stimulates an action potential in vestibular nerve

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13
Q

otolithic organs: utricle and saccule location

A

located within the vestiule of each membranous labyrinth
located almost perpendicular to each other
saccule: vertical
uticle: horizontal

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14
Q

macula

A

recepetors in utricle and saccule
structure: hair cells embedded in a layer of gell like substance, otoliths (ear stones) small, granular-like crystaks that lay on top of the gel layer

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15
Q

otolithic organs: utricle

A

located in the vestibule
contains receptors known as macula
endolymph flows in the bony labyrinth
slightly superior and lateral to saccule
linear movement -> anterior/posterior - like a car in traffic
lies horizontally, hair cells on floor

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16
Q

utricle function

A

monitor head position and linear acceleration/deceleration
they DO NOT monitor rotation

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17
Q

otolithic organs: saccule

A

located in the vestibule
slightly inferior to utricle
contain recpetors known as macula
endolymph flows in the bony labyrinth
vertically oriented - hair cells located on medial wall
senses vertical acceleration (still linear) - like an elevator

18
Q

saccule function

A

monitor head position and linear acceleration/deceleration
they DO NOT monitor rotation

19
Q

semicircular canals

A

monitor rotational acceleration/deceleration of head

20
Q

otolithic organs - utricle and saccule

A

monitor head position and linear acceleration/deceleration of head

21
Q

Benign Paroxysmal Positional Vertigo (BPPV)

A

peripheral vestibular disorder
most common peripheral vestibular disorder
most common cause of vertigo in adults

22
Q

symptoms of BPPV

A

acute/sudden onset of vertigo and nystagmus
paroxysmal - sudden

23
Q

onset/duration of BPPV

A

sudden onset that lasts seconds to minutes (1-2)

24
Q

BPPV incidence and risk factors

A

affected women outnumber men by a ration of 1.6:1
peak age of onset in the 6th decade of life
low vitamin D levels associated with recurrence

25
Q

BPPV causes

A

idiopathic: 50-70%
head trauma: 7-17% - more common to have more than one canal involved

26
Q

BPPV etiology

A

otoliths dislodge from the macular of the utricle/sacule & travel to semicircular canal
the otoliths accumulate near the cupula and disrupt the endolymph flow/hair receptor signaling which causes vertigo nystagmus, etc.
*most common cause of BPPV is accumulation of otoliths in posterior semicircular canal
*may occur spontaneously or after head trauma or infection (upper respiratory illness)
posterior>horizontal>anterior

27
Q

canalithiasis

A

otoliths accumulate in endolympth near in semicircular canal, generally near cupula
free flowing otoconia in semicircular canal - delay of onset of symptoms - symptoms less than 60 seconds

28
Q

cupulolithiasis

A

otoliths accumulate (get stuck) in cupula
otoconia adhered to cupula - no delay in symptoms with testing - symptoms more than 60 seconds

29
Q

nystagmus

A

rapid, uncontrollable eye movements, generally bilaterally
occuring in multiple directions
side to side: horizontal
up and down: vertical
in a circle: torsional or rotary

30
Q

dix-hallpike/test

A

procedure to assess for posterior canal BPPV
- pt seated, rotate head 45 degrees
- safely, passively and quickly bring pt into supine with head extended 30 degrees
- observe for nystagmus or complaint of vertigo
- testing ear that is down
- position creates an abnormal or mismatch of semicircular canal signaling between coplaner pair between non-involved side and the involved side with the displaced otoliths
- the abnormal/mismatch of vestibular signaling stimulates nystagmus and vertigo symptoms

31
Q

dix-hallpike test results

A
  • “positive test” if maneuver provokes nystagmus that is upbeating and torsional to the side involved and pt complains of vertigo or “dizziness”
    slight delay in symptom onset = latency
    symptoms typically last 5-30 seconds = duration
  • negative test if no symptoms reported, no nystagmus observed
32
Q

BPPV treatment

A

particle repositioning maneuvers (PRM)
- repositioning of patient in an attmept to redirect fluid flow in the posterior semicircular canal in such a way that the otoliths are “released” and flow back to macula
- several variants of PRM, including the Epley maneuver, Semont maneuver, and many others

33
Q

Meniere’s Disease

A

peripheral vestibular disorder
symptoms: sensation of fullness/hearing loss, tinnitus, vertigo, +/- nausea, and vomiting
onset/duration: slow chronic onset, lasts for 2-3 days with gradual improvement over 2 weeks

34
Q

meniere’s disease etiology

A

not completely understood
associated with abnormal endolymph fluid pressures within inner ear
low sodium diets are often used to manage
*PT does not treat
40 to 60 yr old age group, nearly 1:1 male:female
familial occurrence - autosomal-dominant

35
Q

vestibular hypofunction

A

can occur unilateral (more common) or bilaterally
due to infection, trauma, vascular events
Unilateral Vestibular Hypofunction (UVH)
- due to mismatch in firing between coplainer pairs
- vestibular neuritis
- labyrinthitis

36
Q

vestibular neuritis

A

acute unilateral vestibulopathy is the second most common cause of vertigo
viral infection is common and usully affects the vestibular nerve unilaterally
absense of cochlear involvement - normal hearing
presence of vestibular symptoms: dizziness/vertigo, nausea, vomiting
onset of vestibular symptoms are often about 2 weeks post infection

37
Q

vestibular neuritis treatment

A

medications: antihistamines, anticholinergic agents, antidopaminergic agents, steroids, antivirals
glucocorticoids administered within 3 days after onset of vestibular neuronitis improves long-time recovery of vestibular function and reduces length of hospital stay
symptom resolution over 6 weeks to 3 months

38
Q

labyrinthitis

A

inflammation of the membranous labyrinth
due to infection bacterial or viral
causes inflammation to BOTH branches of CN 8
- changes in hearing, vertiginous symptoms: dizziness, imbalance, vertigo

39
Q

labyrinthitis treatment

A

medications: steroids, antiemetics-symptom management
glucocorticoids administered within 3 days after onset of vestibular neuronitis improves long-time recovery of vestibular function and reduces length of hospital stay
prognosis: symptoms should resolve within days to weeks

40
Q

perilymphatic fistula

A

an abnormal communication of the inner and middle ear spaces - causing vertigo
vestibular symptoms or hearing loss may be major presenting complaint
more common with conenital malformations or prior ear surgery
damage can also result from an increase in the pressure of the CSF
easing of symptoms at rest and increase with activity
sensorineural hearing loss

Neuro (21 decks)

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