Vestibular and Cerebellar Disease Flashcards
What is the role of the vestibular system?
Maintains balance, limb position, detects head motion and innervates muscles throughout the neck & body
Which specific structure of the vestibular system detects head position and linear acceleration and how?
In the utricle and saccule- the glycoprotein layer is displaced by gravity which distorts the cilia on the hair cells and activate the axonal endings of CN VIII to initiate an action potential
How is angular acceleration (head rotation) detected?
The semi-circular ducts in the inner ear are located at right angles to each other- unequal activation of left and right vestibular nerve leads detects the movement
What are the four vestibular nuclei found in the medulla oblongata and what do they join with?
Rostral, Medial, Lateral, Caudal
Join with axons from the cochlea to form the vestibulocochlear nerve
What are the efferent outputs of the vestibular system? (5)
UMN spinal cord tracts- stimulate extensor muscles (inhibit opposite side)
Connects to nuclei of CN III, IV and VI to innervate ocular muscles
Cerebellum- head position
Cerebral cortex- conscious perception
Vomiting Centre
Cerebellar efferent output is ______ to the vestibular nuclei
inhibitory
What are some common clinical signs of vestibular dysfunction?
Head tilt
Vestibular Ataxia
Tight Circling
Nausea
Positional Strabismus
In cases of vestibular dysfunction, the head tilt is …. why?
towards the side of the lesion because there’s decreased extensor tone on the side of the lesion and increased tone on the opposite side
[basically the direction of head tilt and falling are to the side with the least vestibular nuclei activity]
How does disrupted vestibular input lead to pathological nystagmus?
Unequal input to the vestibular nuclei is perceived as the head turning when at rest resulting in jerking eye movements away from the compromised duct
Peripheral vestibular dysfunction primarily effects which nerves?
CN VII and innervation to the eye (so can cause Horner’s)
Central vestibular dysfunction primarily presents as what?
Proprioceptive Ataxia
Tetraparesis
Vertical Nystagmus
Obtunded or Comatose
[all CN can be affected]
Which group most commonly suffer from Idiopathic Vestibular Disease?
Older dogs
{also known as geriatric vestibular syndrome}
How do we treat Idiopathic vestibular disease?
Antiemetics & supportive care- prognosis is good- usually resolves in 1-3 weeks with possible residual head tilt long term
Give an example of an infectious cause of vestibular disease?
Otitis Media/ Interna
How would we diagnose and then treat vestibular disease caused by Otitis Media?
CT/ MRI and then antibiotics (systemic and topical)
What is the Arbor Vitae?
tree-like white matter tracts that provide afferent and efferent (incoming and outgoing) sensory and motor information to and from the cerebellum.
Cerebellar afferent and efferent information is ipsilateral.
What does this mean?
Left side of cerebellum receives information from left side of head and body which controls movement on the left side
What are some clinical signs of cerebellar dysfunction?
Wide based stance
Intention tremor
Abnormal menace response
Truncal ataxia (swaying of the body)
Cerebellar ataxia
What are the three forms of Ataxia?
Vestibular
Cerebellar
Proprioceptive
Cerebellar ataxia presents as…
inability to regulate rate, range and force of movement- so may see
Jerky movements, Exaggerated movements (think marching soldier)
Why would cerebellar dysfunction cause increased muscle tone?
Rostral lobe of the cerebellum is inhibitory to UMN’s so a lesion to this area means there’s no inhibitory signals telling the muscles to relax- causes rigid extension of the limbs aka Decerebellate Posture
What is an intention tremor?
Failure to coordinate activity of the agonist and antagonist muscles acting around a joint especially during a goal orientated movement
How can a cerebellar lesion cause vestibular disease?
Can cause paradoxical vestibular disease- cerebellum is inhibitory to vestibular nuclei so suppresses the activation of extensor muscles- when damaged there’s less inhibition of vestibular nuclei (so more activity) on side of the lesion and the brain perceives this as the animal turning towards the lesion so will lean/ fall to the opposite side of the lesion to attempt to counterbalance (hence paradoxical)
How can we recognise a paradoxical vestibular lesion?
e.g. if one the right side, it would cause a left head tilt (away from lesion) with a right sided postural reaction deficit and right sided cerebellar signs
What causes cerebellar cortical degeneration?
What is the treatment?
type of postnatal degeneration- genetical causes
no treatment
Give an example of an infectious cause of Cerebellar disease?
Neospora caninum
How do we treat Neospora Caninum?
Serology to detect antibodies to Neospora
MRI
CSF analysis
How is Neospora treated and what’s the prognosis?
Clindamycin (3-4 week course)
Improvement with treatment but permanent neuro deficits are possible
