vestibular Flashcards
which are the mechanical sensors of the vestibular system
canals and otoliths
what are the mechanical forces that canals and otoliths respond to
movement and gravity (input info)
what are the responses/ outputs generated form these mechanical sensory inputs in the vestibular system?
ocular reflex (maintaining gaze)
postural control
(reflexes)
where is the input info integrated to generate the reflex responces
in CNS
how many semi circular cannals does a person have
3 pairs/ 3 each ear/ 6 total
what are the names of each canal? (explain which name is for which direction thinking of yes and no movement and the “odd one out”)
anterior semicircular canal: yes
posterior: no
lateral : the other movement
what is found on one end of each canal
ampula that links to utricle
List the components of the vestibular organ
Semi circular canals (and ampulas at the end)
Vestibule: saccule and utricle (centre)
What are the physical connections between canals, saccule, utricule and cochlea
Ampulas of canals connected to utricle
Utricle and saccule are joined by a conduit
Saccule joined to cochlea
(think sketch linear with cannals starting, then utricle then sacule then (cochlea (isnt vestibular organ but links to sacule)
Which are the otolith organs?
Utricle and saccule
On what structure do the hair cells sit on in otoliths?
On the maculae
How are the hair cells/ maculae placed in space in the saccule and utricle?
Horizontally in utricle and verticaly in saccule
List the layers of structures in the maculae of otoliths from deep to out
Hair cells
Gelatinous matrix
Otolith (helps hair deflection)
Where are the hair cells in the canals located?
In ampula, the rest of the canal is filled with endolymph
Explain ampula structure
-ampullary crista: hair cells are on there
- cupula in centre helps hair cell movement
What is endolymph rich in?
Potassium
State which canals are horizontal and which vertical (in relation to eachoter)
Anterior and posterior vertical
Lateral is horizontal
(Think of the face as the main wall- horizontla plane- the others are vertical to this)
The canals of which ear depolarize when you move head to right
Right
Vestibular system functions 3
Detect and inform about head movements
Keep images fixed in the retina during head movements
Balance
What are the vestibular reflexes?
Vestibulospinal reflex
Vestibulooccular reflec
Where do the eyes move when head moves to right? (Vestibulooccular refelx) how fast and how much do they move?
Left, equal velocity and amplitude as head movement
What is the role of the occulomotor reflex
Keep images fixed in retina
What neurological connection makes the vestibulooccular reflex possible?
Cestibular nuclei link with oculomotor nuclei
What is the largest cilium called?
Kinocilium
When were not moving what is the potential of hair cells?
Resting potential: basal discharge to nerve
Movement towards or away from kinocilium is depol
Towards, increases nerve discharge and depol
what happens when cilia move away from kinocilium
Hairs moving away from the kinocilium generates hyperpolarization and a reduction in nerve discharge.
where do primary afferents in the vestibular nerve end?
in the brainstem (pons)
Vestibular disorders – 2 factors that help categorise them in relation to symptoms and the possible presentations based on these factors
laterality and timing:
acute AND unilateral
chronic AND unilateral or any bilateral loss
presentation of acute and unilateral
vertigo, dizziness, imbalance and nausea
presentation of slow and uni or bilateral
imbalance and nausea
(DEF NOT VERTIGO)
Balance disorders: state the two possible areas of pathology
1) peripheral vestibular disorders: vestibular organ or CN 7
2) central vestibular disorders: CNS (brainstem/ cerebellum)
which are the common peripheral vestibular disorders?
vestibular neuritis
benign paroxysmal positional vertigo (BPPV- crystals thing)
Meniere’s disease
what are the central vestibular disorders
stroke (cerebellar)
multiple sclerosis
tumours
what are the most common vestibular diagnoses in general?
BPPV
Vestibular Neuritis
Vestibular Migraine
Stroke (cerebellar)
what body parts does the core exam for vestibular disorder involve?
eyes
ears
legs
what are some red flags relevant to vestibular disorders?
symptom related:
headache
gait problems
hearing loss
timing related:
hyper acute onset
prolonged symptoms (>4days)
what is the altering cover test?
covering one eye and observibgn the other, abnormal movement is up down
which disorders are acute?
vestibular neuritis
stroke
which disorders are intermittent?
benign paroxysmal
positional vertigo (BPPV)
WHICH DISORDERS are recurrent
Migraine
(Meniere’s Disease)
which disorders are progressive
Schwannoma vestibular (VIIIth nerve)
Degenerative conditions (MS)
what is reccurent and what is intermittent?
reccurent: regular pattern, something happens again anad again
intermittent meaning it comes on repeatedly but with no regular pattern
what presentation do doctors do hints exam for?
acute dizziness
what does HINTS exam involve?
Head-ImpulseTest
abnormal for Vestibular Neuritis
less likely to have this with stroke
how you do it: Horizontal rotational VOR: (vestibulooccular reflex)
(Meaning you move rapiudly patients head to one side of the “No” nod)
normal is if eyes stay fixed to centre, abnormal is if they follow
Nystagmus
(eyes just drift to one direction)
Vestibular organ Vs Cerebellar/brainstem nystagmus
Test-of-SkewDeviation
Vertical misalignment - usually absent in peripheral pathology
(alternating cover test, you repeatedly cover one then other eye and look for VERTICAL- UP DOWN eye movements= abnormal!!)
when is Dix- Hallpike tets done?
to diagnose Intermittent vestibular disorders
