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ENT > Function and examination of the vestibular system > Flashcards

Function and examination of the vestibular system Flashcards

1
Q

what does function and examination of the vestibular system involve?

A

-vestibular function
examination of the vestibular system
peripheral and central vestibular syndrome and their diagnosis

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2
Q

what is the basic function of the vestibular system?

A

-maintain equilibrium of human body in standing and in walking

-stabilisation of retinal picture and keeping visual sharpness in movement

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3
Q

wha are the basic vestibular reflex circles?

A

-vestibulo-occilar reflex
-vestibulo spinal reflex-> helps keep head and body in an upright position due to vestibulospinal system

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4
Q

how is the vestibular system associated with equilibrium ?

A

-Interaction of eye, vestibular- semicircular system, proprioception and cerebellum on keeping balance

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5
Q

what are the three afferent sources of equilibrium ?

A

eye
proprioception
vestibular system

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6
Q

what do the vestibular disorders manifest as ?

A

-vertigo
-disturbed balance
proprioceptive information disorders
visual information disorders
vestibular information disorders

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7
Q

what is vertigo?

A

partial or complete loss of spatial orientation
e.g. apparent movement of the environment as a result of spontaneous vestibular nystagmus

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8
Q

what des disturbed balance mean?

A

an inability to maintain balance, stand upright or walk properly

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9
Q

what do disorders of proprioceptive information indicate?

A

loss of control over the ability to stand upright and walk straight causes a balance disorder

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10
Q

what do disorders of visual information indicate ?

A

loss of optical control of the visually field occasionally leading to dizziness due to discrepancy between visual and vestibular information causing disorientation

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11
Q

what do disorders of vestibular information indicate?

A

disorders of vest information occur due to involvement of spatial orientation and stabilisation of the gaze axis leading to contraindicatory vestibular visual and kinesthetic information and dizziness

-if central compensation of the loss of vestibular function is also absent there is also a balance disorder.

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12
Q

what occurs in the examination of the vestibular system?

A

-case history and analysis of symptoms
-examination of the vestibulospinal reflexes
-examination of vestibulo ocular reflexes

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13
Q

what is the general purpose of case history

A

-vestibular system problems can lead to dizziness
-case history gives a structured analysis and allows diagnostic classification of

-peripheral vestibular dizziness
-central vestibular dizziness
-non vestibular dizziness

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14
Q

what is involved in a case history?

A

-questions about:

previous illnesses and meds
type of dizziness -> how it feels, duration and intensity
dizziness causing factors
secondary symptoms

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15
Q

what is the purpose of examination of vestibulospinal reflexes?

A

-using tests to check the influence of vestibular stimulation on body posture and balance

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16
Q

what are the pathologies of the vestibular system ?

A

peripheral vestibular lesions
central vestibular lesions

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17
Q

what does the body do when there is a peripheral vestibular lesion?

A

body’s centre of gravity is displaced to the side on which the labyrinth lesion is located

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18
Q

what does the body do when there is a central vestibular lesion?

A

there is a disturbance of balance
with symptoms like unsteady gait, irregular direction of falling (unlike peripheral vestibular lesions)

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19
Q

what are the tests to examine the vestibulospinal reflexes ?

A

-romberg test
hautant test
target pursue test
walking in a straight line
unterberger stepping test

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20
Q

what happens in the romberg test?

A

pt stands with feet together and eyes closed
observe for any unsteadiness or tendency to fall
a loss of balance is a POSITIVE ROMBERG TEST

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21
Q

what happens in the Hautant test?

A

the patient is seated, arms extended and palms up
observe if patients lose balance
drop their arms
pronate the palms

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22
Q

what happens in the target pursue test?

A

-arms are stretched out and the index finger of the hand is brought to the tip of the nose with eyes closed

-observe for any overshooting which indicates a disorder in the positional sense

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23
Q

what do we observe for in walking in a straight line?

A

-any abnormal gait and or deviation of the body

24
Q

what is the unterberger stepping test ?

A

patient stands on one foot with arms raised forward and eyes closed

-if there is a peripheral vestibular disorder the body will rotate on the body axis towards the side fo the labyrinth lesion lesion (at least 45 degrees for it to be pathological)

-in central lesions the deviation are irregular

25
Q

what is the purpose of the vestibulo-occular reflex ?

A

-the function of the reflex is to stabilise the images on the retina during head movement by producing eye movements in the opposite direction of the head movement

-this preserves the image on the centre of the visual field

26
Q

what are the examinations of the vestibulo occular reflex?

A

-examination of eye moveemnts
-examination of spontaneous nystagmus
examination of semi spontaneous nystagmus
examination of provoked nystagmus

27
Q

what is involved in the examination of eye movements?

A

observe if there are any abnormal eye movements
e.g. nystagmus

28
Q

what are the tests involved in the examination of the spontaneous nystagmus?

A

frenzel glasses
video occulography
electronystagmography

29
Q

what is a spontaneous nystagmus ?

A

nystagmus that occurs randomly
regardless of external stimulation of vestibular system

30
Q

how do the frenzel glasses work ?

A

the glasses are used to disable the patient’s ability

to visually fixate on an object whilst at the same time allowing the the examiner to adequately visualise the eye

the reason for this is because the patient can suppress the nystagmus caused by peripheral vestibular lesions by fixing the vision

31
Q

how does vide-occulography work ?

A

-video based method of measuring horizontal,vertical and torsional movements of both eyes

-its some cameras that film eyes and then a computer finds out if there’s any involuntary movements of the eyes

32
Q

how does electronystagmography feel?

A

test is performed by attaching electrodes around the eyes

-the cornea is electropositive and the retina is electronegative

when the eye moves the electrodes can meausre changes in the electric field -> this method can be used to find involuntary movements such as a nystagmus

33
Q

what tests are involved in the examination of a semi spontaneous nystagmus?

A

positional testing (static)
positional testing (dynamic)
Head shaking

34
Q

what is involved in static positional testing?

A

-the nystagmus is induced by adoptiong different body positions in slow motion
->lying on back, on the side, hanging head over the edge of the bed

-this influences the utricle and saccule

35
Q

what is involved in dynamic positional testing?

A

-nystagmus is induced by moving the head in different positions quickly

-this influences the semicircular canals especially

-very usefull to diagnose paroxysmal positional vertigo (PPV)

36
Q

what is involved in head shaking?

A

-spontaneous nystagmus can be provoked by gentle , passive , horizontal shaking of the patient’s head

37
Q

what are the tests involved in a provoked nystagmus ?

A

caloric reflex test
rotatory test

38
Q

what is involved in the caloric reflex test

A

-involves irrigating cold water into the external auditory canal
-this creates connvective currents (in the fluid due to temp differences) in the endolymph of the nearby horizontal semicircular canal

39
Q

what happens under a cold stimulus?

A

-endolymph moves away from ampulla
-eyes turn to the ipsilateral side
nystagmus to the contralateral side

40
Q

t happens in a warm stimulus ?

A

-endlolymph moves towards the ampulla
eyes turn to the contralateral side
nystagmus to the ipsilateral side

41
Q

what happens in the rotatory test?

A

-angular acceleration as the stimulus for investigating the sensitivity of the semicircular canals

-rotation around an axis passing through the head stimulates one or more semicircular canals on each side depending on the head position

42
Q

what are the results of the rotatory test?

A

whatever direction the chair is rotated-> the left and right vestibular apparatus are stimulated in opposing direction

as the eye reaches a peripheral point in the orbit-> a corrective response attempts to move it back to the centre of the orbit

-the nystagmus that is observed MOVES INT THE SAME DIRECTION as the chair ( ROTATORY NYSTAGMUS)
when the rotation stops the nystagmus reverses to the opposite direction in an oscillating fashion

43
Q

what can we use the rotatory test for ?

A

-to determine whether the vestibular apparatus is working correctly

44
Q

what does the peripheral and central vestibular syndrome and their diagnosis involve?

A

-overview of vestibular components
-vertigo types a.k.a. dizziness

45
Q

what is the peripheral component of the vestibular system and what is the function?

A

-the membranous labyrinth
-the vestibular portion of the vestibulo cochlear nerve are the peripheral vestibular components of the inner ear

function of the utricle and sacule is to detect gravity and linear acceleration

the semicircular canals function is to detect head rotation

46
Q

what is the central component of the vestibular system and what is the function?

A

central part of the vestibular system include the structures within the brainstem and the cerebellum

-the vestibular portion of the 8th cranial nerve connects to the vestibular nuclei of the medulla and neurons of the cerebellum

-the vestibular nuclei are connected to the
occulomotor
trochlear
abducens nerves and aid int control of eye movements

vestibular nuclei are also connected to neurons of the spinal cord via descending pathways which adjust tone in the muscles of neck, trunk and limbs to oppose gravity and maintain posture

47
Q

how do you diagnose cases with vestibular system abnormalities ?

A

-the localisation of the lesion
-determining whether the lesion is in the peripheral or central vestibular system is critically important for making differential diagnosis and predicting the prognosis

48
Q

what are the 2 types of vertigo

A

peripheral and central

49
Q

how is peripheral type of vertigo characterised ?

A

-feeling of rotation of self or surroundings, direction of rotation is usually into healthy part, loss of stability or feeling of swimming

50
Q

how is central type vertigo characterised ?

A

blackouts, inability to walk
sudden dizziness attacms
fluctuating dizziness with loss of consciousness
drop attacks
double vision and other disturbances of vision
dizziness with dysarthria and change of personality

51
Q

what is the pathogenesis of central vestibular disorders

A

central vestibular disorders are usually the result of multifocal lesions of the brainstem

-they are therefore usually accompanied by symptoms of disorders of visual occulomotor and somatosensory system

52
Q

what is the pathogenesis of central vestibular disorders

A

central vestibular disorders are usually the result of multifocal lesions of the brainstem

-they are therefore usually accompanied by symptoms of disorders of visual occulomotor and somatosensory system

53
Q

what are the symptoms or peripheral nystagmus?

A

nystagmus -horizontal rotatory side of most reactive labyrinth

tonic deviation- on side of weak labyrinth in relation to position of head

eye fixation - in the absence of eye fixation nystagmus is growing

cranial nerves - without lesions
cerebellar symptoms-not present

hearing disorder- usually could be present

central compensation- intensity of vertigo correlates with nystagmus intensity and tonic deviations

postural reaction deficits - no
mental stat -normal

head tilt -towards side of lesion

54
Q

what are the symptoms of central nystagmus?

A

nystagmus -other than horizontal rotatory

tonic deviation- without relation to head position

eye fixation - in the absence of eye fixation nystagmus not changed

cranial nerves - lesion of cranial nerves present
cerebellar symptoms- could be present

hearing disorder- could be present

central compensation-not present , disharmonic symptoms

postural reaction deficits - yes possible usually same side as lesion
mental stat - depressed

head tilt -either side

55
Q

what are the peripheral causes of vertigo?

A

LABYRINTH
benign paroxysmal positional vertigo
mernieres disease
perilymphatic fistula
cogans syndrome

VESTIBULAR NERVE
vestibular neuritis
accoustic neuroma
ramsay hunt syndrome
vestibular paroxysmia

56
Q

what are the central causes of vertigo?

A

VASCULAR
stroke
lateral medullary syndrome
cerebellar infarct

NON VASCULAR
vestibular migraines
multiple sclerosis

ENT (11 decks)

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