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Neuroanatomy > Vestibule System > Flashcards

Vestibule System Flashcards

1
Q

what is BPPV

A
  • benign paroxysmal positional vertigo
  • Peripheral vestibular system disorder
  • due to otoconia (crystals) from the utricle in the semicircular canals
  • posterior semicircular canal
  • The crystals in the canal affect the movement of the endolymph, affecting the perception of movement and is usually based on position
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2
Q

What are symptoms of BPPV

A
  1. Vertigo/spinning
  2. Loss of balance or unsteadiness
  3. Nausea
  4. Vomiting
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3
Q

what is peripheral vestibular neuritis

A

– a disorder affecting the vestibular nerve such as a bacterial or viral infection

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4
Q

what are the symptoms of peripheral vestibular neuritis

A
  1. Vertigo (sensation of spinning in absence of stimulating movement), not dizziness
  2. Imbalance
  3. Oscillopsia (illusion of movement in visual surroundings)
  4. Nausea
  5. Nystagmus (acute, few days)
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5
Q

what is nystagmus

A

eye movement, beating fast towards the lesion. Amplitude increases when eye moves in direction of fast phase. (alexander’s law)

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6
Q

what is a central vestibular problem

A

brain stem affected

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7
Q

how will a central vestibular problem show differently

A
  1. Nystagmus might be vertical or torsional, which does not occur in peripheral
  2. Saccadic (fast) eye movements are affected. Saccade is fast movement to new target.
  3. Smooth pursuit is affected
  4. Ability to cancel VOR is affected.
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8
Q

what is vestibular schwannoma

A

❖ Tumour arising from the nerve sheath
❖ Tumour on vestibular nerve
❖ Intracranial
❖ Slow onset (months/years)

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9
Q

what are S&S of vestibular schwannoma

A

❖ Hearing loss often first sign

❖ Vestibular signs may accommodate due to slow onset

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10
Q

what is meniere’s disease

A

❖ Disorders of inner ear function that can cause hearing and vestibular dysfunction
❖ Due to distention of endolymphatic compartment of inner ear
❖ Endolymph builds up inside the labyrinth causing spells of hearing loss, tinnitus, vertigo, imbalance and oscillopsia

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11
Q

what is postulated pathogenic mechanisms of menieres disease

A

❖ Increased production of endolymph
❖ Decreased production of perilymph accompanied by compensatory increase in volume of endolymphatic sac and decreased absorption of endolymph due to blockage of endolymphatic pathways

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12
Q

what are vestibular signs of meniere’s disease

A 
❖ Vertigo
❖ Tinnitus
❖ Hearing loss
❖ Fullness in the ear
❖ Imbalance
❖ Spells can last several hours
❖ Physio addresses stable vestibular lesions rather than unstable (spells)
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13
Q

what are the pathways from the vestibular nuclei

A

❖ MLF extra-ocular muscles eye movements
➢ Eyes need to readjust to how your head is moving to gravity allows us to stabilise gaze
❖ Vestibulospinal tract posture
❖ Vestibulocollic tract from spinal accessory nerve head position
❖ Vestibulothalamocortical tract conscious awareness of position
❖ Vestibulocerebella tract
❖ Vestibuloautonomic tract to retinal formation-> nausea and vomiting
➢ Redness, sweating, breathing rate changes, heart rate changes
➢ All autonomic effects

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14
Q

where do inputs to vestibular nuclei come from

A

❖ As well as primary vestibular afferents, inputs to vestibular nuclei include:
➢ Projections from cerebellum via juxtarestiform body
➢ Spinal cord (postural adjustment) also via spinocerebellar tract (as spinovestibular fibres) and reticular formation
➢ Contralateral vestibular nuclei

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15
Q

where is the output from vestibular nuclei

A

❖ Widespread
❖ Primarily projections to:
➢ Spinal cord
➢ Cerebellum
➢ Nuclei of CN’s III (oculomotor), IV(trigeminal) and V(abducens)
❖ Also to thalamus and thereby, cerebral cortex
❖ Finally to reticular formation

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16
Q

explain vestibular pathway from nerve to brainstem

A

❖ Vestibulocochlear Nerve
❖ Synapses with first order neuron found in vestibular ganglion
❖ From there, synapses then connect to vestibular nuclei superior, medial, lateral, inferior
❖ Neuro signals form vestibular nuclei make many important connections:
➢ Ascending connections to abducens, trochlear and oculomotor and thalamus vestibulo-ocular reflex (VOR)
➢ Projections to cerebellum vestibular cerebellar reflexes
➢ Descending connections to spinal cord vestibulospinal reflexes

17
Q

what is the dynamic labyrinth

A

❖ Rotation movements of head
❖ Made up of 3 semicircular canals filled with endolymph enclosed in bony labyrinth
❖ 3 semicircular canals= membranous labyrinth enclosed in bony labyrinth
❖ Each plane situated in a plane in which the head can rotate/move anterior, posterior and horizontal/lateral
❖ All 3 semicircular canals are at right angles to each other
❖ They communicate at both ends with utricle

18
Q

what is the static labyrinth

A

❖ Linear movements of head
❖ Static labyrinth = membranous labyrinth within bony labyrinth
❖ Membranous labyrinth utricle and saccule containing endolymph
❖ Utricle and saccules = otolith organs
❖ Utricle and saccules= canal expansion
❖ Utricle is always closer to canals
❖ Enclosed in bony labyrinth: vestibule
❖ Utricle and saccule separated from vestibule by perilymph

19
Q

what do receptors in static labyrinth respond to

A

Receptors respond to linear acceleration and deceleration of head relative to gravity

20
Q

what do receptors in dynamic labyrinth respond to

A

Receptors respond to angular acceleration and deceleration

21
Q

what does the utricle detect

A

➢ Detects movement in horizontal plane

➢ More sensitive to linear acceleration in this plane forward=backwards, side-to-side

22
Q

what does the saccule detect

A

➢ Detects vertical movements movements in sagittal plane

➢ More sensitive to linear acceleration in this plane fwd-bkwd, up-down

23
Q

what are stereocillia

A

❖ Utricle and saccule has hair cells sensory receptors of vestibular system
❖ On top of each hair cell is a collection of small ‘hairs’ called stereocilia
❖ Stereocilia have calcium carbonate crystals attached on top oh ‘hair’
❖ Crystals are within a viscous gel substance

24
Q

how do steroeocilia detect movement

A

❖ Movement of endolymph through utricle and saccule, causes movement of crystals and hence movement of stereocilia as crystals pull on them
❖ This generates a receptor potential to vestibular nerve carries info to brain

25
Q

what is the vestibular-ocular reflex (VOR)

A

❖ Keeps gaze fixed on an object even though the head is moving or being moved
❖ Different to tracking tracking= keep head fixed and eyes move
❖ Very fast reflex much faster than tracking
❖ Vestibular division of CN VIII forms the afferent limb of the reflex
❖ Rotation of the head in one direction results in contraction of the extraocular muscles to slowly rotate the eyes in the opposite direction

26
Q

what is the optokinetic reflex

A

❖ In order to compensate for the motion of the visual field, the optokinetic system uses the relative velocity of the image of the retina to induce eye movements in the same direction and at the same velocity as the external world to preserve stable vision
❖ As body moves, it adjusts your eye movements to keep a stable gaze
❖ Causes eye movement in response to objects moving in the periphery while the head is stationary
❖ Negative feedback systems associated with the optokinetic reflex enable the retina to achieve and maintain stabilization over time

27
Q

what are some central vestibular pathologies

A
  • Tumour
  • Stroke
  • Trauma, encephalitis, infection, multiple sclerosis
28
Q

what is vertigo

A

Sensation of spinning (specific kind of dizziness)
in the absence of stimulating movement
Specific medical symptom
• Not light headedness, anxiety, floating etc.
• Dizziness does not mean the same as vertigo

29
Q

what is oscillopsia

A

• Visual disturbance in which objects in the visual
field appear to oscillate
• Visual illusion of movement in the environment

30
Q

is acute vestibular hypofunction peripheral or central problem

A

peripheral vestibular disorder

31
Q

what is acute vestibular hypofunction

A

• Viral or bacterial infection of the vestibular nerve or
labyrinth
• Vestibular crisis – sudden onset lasting several days
• Vertigo
• Imbalance
• Oscillopsia (illusion of movement in the visual
surroundings)
• Nausea

32
Q

how do you diagnosis vestibular neuritis

A
  • acute nastagmus–> follows alexanders law

- head thrust test–> abnormal delay

33
Q

how is nystagmus different in central disorders

A

-Any spontaneous nystagmus not meeting the
criteria for Alexander’s Law in the first week
after vestibular crisis – you should send to
someone more experienced for assessment
• Central nystagmus (sinister signs)
• Vertical nystagmus (upbeating or downbeating)
• Direction changing nystagmus
• Gaze evoked nystagmus (at 30°- end range is
normal)

Neuroanatomy (18 decks)

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