Vestibular and Cerebellar Disease

Question 1

What is the role of the vestibular system?

Answer 1

Maintains balance, limb position, detects head motion and innervates muscles throughout the neck & body

Question 2

Which specific structure of the vestibular system detects head position and linear acceleration and how?

Answer 2

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

Question 3

How is angular acceleration (head rotation) detected?

Answer 3

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

Question 4

What are the four vestibular nuclei found in the medulla oblongata and what do they join with?

Answer 4

Rostral, Medial, Lateral, Caudal
Join with axons from the cochlea to form the vestibulocochlear nerve

Question 5

What are the efferent outputs of the vestibular system? (5)

Answer 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

Question 6

Cerebellar efferent output is ______ to the vestibular nuclei

Answer 6

inhibitory

Question 7

What are some common clinical signs of vestibular dysfunction?

Answer 7

Head tilt
Vestibular Ataxia
Tight Circling
Nausea
Positional Strabismus

Question 8

In cases of vestibular dysfunction, the head tilt is …. why?

Answer 8

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]

Question 9

How does disrupted vestibular input lead to pathological nystagmus?

Answer 9

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

Question 10

Peripheral vestibular dysfunction primarily effects which nerves?

Answer 10

CN VII and innervation to the eye (so can cause Horner’s)

Question 11

Central vestibular dysfunction primarily presents as what?

Answer 11

Proprioceptive Ataxia
Tetraparesis
Vertical Nystagmus
Obtunded or Comatose
[all CN can be affected]

Question 12

Which group most commonly suffer from Idiopathic Vestibular Disease?

Answer 12

Older dogs
{also known as geriatric vestibular syndrome}

Question 13

How do we treat Idiopathic vestibular disease?

Answer 13

Antiemetics & supportive care- prognosis is good- usually resolves in 1-3 weeks with possible residual head tilt long term

Question 14

Give an example of an infectious cause of vestibular disease?

Answer 14

Otitis Media/ Interna

Question 15

How would we diagnose and then treat vestibular disease caused by Otitis Media?

Answer 15

CT/ MRI and then antibiotics (systemic and topical)

Question 16

What is the Arbor Vitae?

Answer 16

tree-like white matter tracts that provide afferent and efferent (incoming and outgoing) sensory and motor information to and from the cerebellum.

Question 17

Cerebellar afferent and efferent information is ipsilateral.
What does this mean?

Answer 17

Left side of cerebellum receives information from left side of head and body which controls movement on the left side

Question 18

What are some clinical signs of cerebellar dysfunction?

Answer 18

Wide based stance
Intention tremor
Abnormal menace response
Truncal ataxia (swaying of the body)
Cerebellar ataxia

Question 19

What are the three forms of Ataxia?

Answer 19

Vestibular
Cerebellar
Proprioceptive

Question 20

Cerebellar ataxia presents as…

Answer 20

inability to regulate rate, range and force of movement- so may see
Jerky movements, Exaggerated movements (think marching soldier)

Question 21

Why would cerebellar dysfunction cause increased muscle tone?

Answer 21

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

Question 22

What is an intention tremor?

Answer 22

Failure to coordinate activity of the agonist and antagonist muscles acting around a joint especially during a goal orientated movement

Question 23

How can a cerebellar lesion cause vestibular disease?

Answer 23

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)

Question 24

How can we recognise a paradoxical vestibular lesion?

Answer 24

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

Question 25

What causes cerebellar cortical degeneration?
What is the treatment?

Answer 25

type of postnatal degeneration- genetical causes
no treatment

Question 26

Give an example of an infectious cause of Cerebellar disease?

Answer 26

Neospora caninum

Question 27

How do we treat Neospora Caninum?

Answer 27

Serology to detect antibodies to Neospora
MRI
CSF analysis

Question 28

How is Neospora treated and what’s the prognosis?

Answer 28

Clindamycin (3-4 week course)
Improvement with treatment but permanent neuro deficits are possible