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Vestibular System Examination (view source)
Revision as of 16:06, 9 March 2011
, 16:06, 9 March 2011Created page with "====The Vestibulocochlear Nerve==== * Cranial nerve VIII is the vestibulocochlear nerve. * The vestibulocochlear nerve carries ** Auditory, or cochlear, signals. ** Balance, or ..."
====The Vestibulocochlear Nerve====
* Cranial nerve VIII is the vestibulocochlear nerve.
* The vestibulocochlear nerve carries
** Auditory, or cochlear, signals.
** Balance, or vestibular, signals.
* Signals from CN VIII are relayed to the vestibular nuclei in the brainstem.
** The nuclei in turn relay information to
*** The eyes
*** The body and limbs
*** Higher centres.
* Many efferent signals are controlled in part by cerebellar input.
====Unilateral Vestibular Disease====
* Horses with unilateral vestibular lesions often have a head tilt towards the side of the lesion.
* If nystagmus is absent, determining whether a horse with a head tilt is also weak is helpful in deciding whether vestibular disease is central or peripheral.
** In peripheral diease, the horse may be ataxic but weakness is not normally seen.
=====Acute=====
* In the acute stages of vestibular disease, spontaneous nystagmus may be present.
** The appearance of nystagmus is different depending on the type of vestibular disease present.
*** Central vestibular disease
**** Nystagmus often is variable; i.e. rotary, horizontal and vertical.
*** Peripheral vestibular disease
**** The fast phase of the nystagmus is away from the side of the lesion.
=====Chronic=====
* Nystagmus may resolve in more chronic lesions.
** However, it may return with changes in head position.
*** I.e. positional nystagmus.
* Visual accomodation improves ataxic movements.
** However, these may return dramatically on blindfolding.
====Bilateral Vestibular Disease====
* An observable head tilt may not be present.
* Movements are likely to be markedly ataxic.
** This is probably due in part to involvement of ascending proprioceptive and descending motor pathways that run through the brainstem.
[[Category:Cranial Nerve Examination - Horse]]
* Cranial nerve VIII is the vestibulocochlear nerve.
* The vestibulocochlear nerve carries
** Auditory, or cochlear, signals.
** Balance, or vestibular, signals.
* Signals from CN VIII are relayed to the vestibular nuclei in the brainstem.
** The nuclei in turn relay information to
*** The eyes
*** The body and limbs
*** Higher centres.
* Many efferent signals are controlled in part by cerebellar input.
====Unilateral Vestibular Disease====
* Horses with unilateral vestibular lesions often have a head tilt towards the side of the lesion.
* If nystagmus is absent, determining whether a horse with a head tilt is also weak is helpful in deciding whether vestibular disease is central or peripheral.
** In peripheral diease, the horse may be ataxic but weakness is not normally seen.
=====Acute=====
* In the acute stages of vestibular disease, spontaneous nystagmus may be present.
** The appearance of nystagmus is different depending on the type of vestibular disease present.
*** Central vestibular disease
**** Nystagmus often is variable; i.e. rotary, horizontal and vertical.
*** Peripheral vestibular disease
**** The fast phase of the nystagmus is away from the side of the lesion.
=====Chronic=====
* Nystagmus may resolve in more chronic lesions.
** However, it may return with changes in head position.
*** I.e. positional nystagmus.
* Visual accomodation improves ataxic movements.
** However, these may return dramatically on blindfolding.
====Bilateral Vestibular Disease====
* An observable head tilt may not be present.
* Movements are likely to be markedly ataxic.
** This is probably due in part to involvement of ascending proprioceptive and descending motor pathways that run through the brainstem.
[[Category:Cranial Nerve Examination - Horse]]