Ataxia: Vestibular Dz Flashcards Preview

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Flashcards in Ataxia: Vestibular Dz Deck (33):

How do the hairs detect yaw movement?

both sides affected oppositely when fluid flows and pushes hairs


What is the main output from the vestibular system?

Extensor muscles
- so if lost, extensor muscle tone lost


Outline angular acceleration head motion pathway

- semicircular canals
- vestibular nuclei
- forebrain... to compelte








What other inputs are there to the vestibular nuclei?

- cerebellum: primarily INHIBITORY
- spinal cord
- pontine reticular formation
- contra-lateral vestibular nuclei


Which side is the lesion on with nystagmus?

SLOW phase (weak side)


What is pendular nystagmus? Which breeds are predisposed?

- siamese, burmese and himalayan
- congential abnormaltiy
(^ no. fibres cross chiasma)
- cerebellar disorders and visual defects
- no slow phase


What is jerk nystagmus?

- horizontal, vertical or rotary
- ??


- What is searching nystagmus?

- blindness


What is positional strabismus?

- affected side doesnt realise head has moved up for eg. so eye stays looking down and eye rolls


What clinical signs are associated with Horner's? Cause?

- loss of sympathetic innervation to the eye
- enopthalmus
- 3rd eyelid protrusion
- ptosis
- miosis
- congested vessels (hotter ear that side)


How does horner's syndrom differ in horses?

- ptosis (look for eyelashes)
- miosis
- enopthalmus
- prominant TE
- conjnctival and nasal hyperaemia
- *sweating*


Where in the symathetic system is usually affected for horners?

LOOK UP (diagram on lecutre echo )


Outline regional sweating patterns in horses

If the lesion is cranial to where the sympathetic chain splits into the spinal nerves of the thoraco lumbar region and courses back up the neck as the sympathetic chain(?) then sweating will be observed alongthe length of the sympathetic interuption. If further along the sympathetic trunk then sweating will be more localised.
- horses ^ sweat d/t vasodilation and ^ adrenaline so if sympathetic innervation lost -> vasodilation and sweating.


Which clinical signs are affected with a central vestibular problem?

- paresis: posible
- concious proprioceptive deficits: possible
- conciousness: normal/obtunded/stuperous/coma
- CN deficits: V-XII
- Horner's: Rare
- Horizontal nystagmus: Yes
- Rotational nystagmus: Yes
- Vertical nystagmus: Yes
- Nystagmus with head position changes: Yes


Which clinical signs are afected in a peropheral vestibular lesion?

- paresis: No
- concious proprioceptive deficits: No
- conciousness: Alert/disorientated
- CN deficits: VII only
- Horner's: Possible
- Horizontal nystagmus: Yes
- Rotational nystagmus: Yes
- Vertical nystagmus: No
- Nystagmus with head position changes: No


Why differentiate cenral and peropheral lesions?

peripheral can be tx in private practice, central needs referral


Most important aspects to localise central and peropheral vestibular lesions?

Mentation and proprioception


What will happen to nystagmus over time?

Decreases as animal compensates


What is a myrnigotomy?

Penetrate tympanic membrane and remove fluid from inner ear
- r/o infection etc.


Look at lecture for peripheral vestibular problem algorithm

> ototoxic drugs? - ototoxicity (if signs stop when withdrawn)
> normal otoscope exam? - idiopathic, 4-7d no improvement: advanced imaging needed
> abnormal otoscopic exam: Myringotomy- supparative (otitis media/interna, tx Abx), if no bacteria -> MRI/CT to r/o polyps, neoplasia, trauma


What is seen with bilateral vestibular disease?

- Stevie wonder sign (swaying head)
- no nystagmus
- no occulovestibular response


Which anials often get bilateral vestibular disease?

elderly cats d/t middle ear disease


What is paradoxical vestibular syndrome?

- proprioceptive deficiency on side of lesion ALWAYS
- head tilt should be TOWARDS lesion, but can be AWAY in paradoxical vestibular dz
- d/t lesion between the cerebellum and nuclei (usually d/t cerebellar dz)


What do vestibular nuceli innervate?

- extensor muscles (mainly)


How doesthe cerebellum affect the vestibular nuclei?

Inhibits the vestibular nuclei


Where does the position of the lesion differ in paradoxical and normal vestibular dz?

- between nuceli and muscles = vestibular dz
- between cerebellum and nuclei = paradoxical (loss of inhibition -> oher side appears to be affected)


Clinical signs of cerebellum disease?

> rostral lobe
- opisthotonus, forelimb hyperextension, hindlimb hip flexion, - hindlimb extension if lesion includes ventral part of vermis
> caudal lobe
- hypotonia, hypermetria, intention tremor
> Flocclunonodulalr lobe
- Dysequilibrium - drunken, broadbased stanc, staggering gait, loss of balance, abnormal nystagmus
> caudal cerebellar peduncle
- paradoxical vestibular signs
> cerebellar nuclei fastigial and interposital
- dilated pupil, TE protrusion, enlarged palpebral fissure


Clinical signs of cerebellar syndrome

- spastic, dys- and hyper- metric ataxia (goose stepping)
- intention tremor
- ipsilateral menace deficit and normal vision
- broad-based stance
- postural reactions delayed with exaggerated responses
- menace deficit (ipsilateral) with normal vision
+- anisocoria (pupil dilated contralateral to side of lesion)
+- opisthotonus (rare)
+- vestibular signs


What is the occulovestibular reflex?

Eyes remain central and then snap on to next focus point when muscles stretched


What are the 3 regions of the cerebellum?

- vestibulocerebellum
- spinocerebellum (most axial)
- cerebrocerebellum (most lateral, advanced)


Function of the cerebellum?

- maintainence of equilibrium
- regulation of muscle tone (to preserve normal postiion at rest/movement)
- coordination of movement