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What is Vestibular Disease?

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so today we're going to talk about

vestibular disease vestibular disease it

refers to a problem in the balanced

systems so we often use the word

vestibular and balance interchangeably

so sometimes I'll say that stimulus

system sometimes I'll say balance system

the vestibular system is the part of the

nervous system responsible for

maintaining balance in general there are

two parts of the balanced system that we

think of the two parts of the balanced

system are what we call the peripheral

vestibular system and the central

vestibular system the peripheral

vestibular system is the parts

associated with the inner ear whereas

the parts of the central vestibular

system are the parts of the balanced

system that are within the brain and the

brain stem so what I've kind of drawn

schematically here this is the dog's

ears the top of the head the other ear

and what we have here is the ear canal

there's basically a vertical part in a

horizontal part and then we get to the

eardrum which is this little line there

what I've tried to draw here is what we

call the middle ear or the tympanic

bulla and then the balanced system

actually starts inside of that so the

parts of the peripheral vestibular

system are the receptors in the inner

ear and the nerve what we call cranial

nerve 8 or the vestibulocochlear nerve

the parts within the brain are the

central vestibular system so that's the

vestibular nuclei that are in the

medulla oblongata and the cerebellum so

it's important for us as veterinarians

to determine is the problem more likely

to be in the central vestibular system

or the peripheral vestibular system

because it affects one what the possible

causes are that affects what the

treatment is and it also affects the

prognosis or the likelihood of us

helping that pet so one of the most

important things we do when presented

with a dog that is showing signs of

vestibular disease is to determine is it

a central versus a peripheral problem

what are the symptoms of a balanced

problem in dogs and cats

the most common symptom is a head tilt

so a head tilt is the head is cocked to

one side where one eyes lower than the

other one

ears lower than the other if the animal

is able to walk it might walk like a

drunken sailor so it might list or lean

or roll or fall to one side sometimes

animals can be very affected and they'll

actually alligator roll in one direction

the next symptom of a balance problem is

what we call nystagmus nystagmus refers

to involuntary rapid eye movements or

involuntary jerks of the eyes usually

they have a slow phase in one way and a

fast jerk in the opposite direction so

we describe nystagmus based off of the

direction of the the rapid jerk or what

we call the fast phase and then the next

symptom of a balance problem is what we

call strabismus or an abnormal eye

position so we can use this and this to

help us better say is the problem inside

the inner ear or is it inside of the

brain because again that affects the

possible causes it affects the the tests

that we choose and it affects the

prognosis and the treatment so when

we're presented with an animal that's

showing symptoms of a balanced problem

we evaluate the head tilt we evaluate

the character of the nystagmus we

evaluate for other cranial nerve

abnormalities we evaluate the level of

meditation and the postural reactions or

the the CPS the conscious proprioception

in an animal that has a peripheral

vestibular problem so again out here in

the inner ear so it's not affecting the

brainstem at all it's just affecting the

inner ear

the head tilt is typically toward the

side of where the problem is

nystagmus is usually horizontal or

rotary with the fast phase away from the

side of the problem we might have other

cranial nerve abnormalities specifically

cranial nerve seven the facial nerve

cranial nerve seven is responsible for

muscles of facial expressions so we

might see a facial droop or inability to

blink on the same side as the head tilt

in animals with peripheral vestibular

disease

just because cranial nerve seven and

cranial nerve eight are right next to

each other similarly while it's not a

cranial nerve the sympathetic

innervation to the eye so the

information that causes the pupil to get

bigger or or dilate that nerve can be

affected in certain causes of peripheral

vestibular disease so sometimes we might

see a small pupil on the same side as

the head tilt because it's not affecting

the brain mentation should be normal

level of consciousness should be normal

and again because the problems in the

inner ear and not affecting the brain

stem our postural reactions should be

normal for animals with peripheral

vestibular disease in contrast animals

that have a problem inside of the brain

or central vestibular disease their head

tilt can be toward or away from the side

of the problem the nystagmus can be

toward or away from the side of the

problem and we might also see things

like vertical nystagmus

so in peripheral vestibular disease we

do not expect the eyes to have

up-and-down movements we only expect

side-to-side or what we call horizontal

nystagmus or rotary where the eye

rotates just a little bit but we do not

expect vertical nystagmus where the eyes

go up and down so vertical and I stagg

miss is a symptom of a central problem

sometimes we can have other cranial

nerve problems so since the problem in

central vestibular disease is affecting

the brain stem we might see other

problems of other cranial nerves that

are right near the vestibular nuclei

many times we could see decreased facial

sensation sometimes we can see atrophy

of the tongue so cranial nerve 5 cranial

nerve seven and cranial nerve 12 are

often affected at the same time in a

central vestibular localization

mentation may be abnormal so the level

of consciousness is affected by many of

the parts of the brain that are in this

same area where the vestibular nuclei

are so a problem here can also cause

things like changes in level of

consciousness and then finally postural

reactions so knowledge of where the limb

is in space that information travels

through this area of the brain so

sometimes dogs with central vestibular

disease may have postural reaction

deficits but it's typically on the same

side as where the problem is lastly

sometimes we can have problems affecting

the cerebellum so cerebellar signs

include intention tremor hyper metria or

high stepping of the limbs so

recognition of cerebellar signs tells us

that the problem is affecting the brain

or the central vestibular system what

are the possible causes of peripheral

vestibular disease so the most common

thing that we see that causes peripheral

vestibular disease is an ear infection

so something affecting the middle or

inner ear we can also have tumors of the

the inner ear hypothyroidism can affect

the peripheral vestibular system and one

of the other common causes of peripheral

vestibular disease is idiopathic old dog

vestibular disease that typically

happens in older dogs comes on suddenly

is usually very severe but usually

improves on its

within a few days examples of diseases

that affect the central vestibular

system or the brain stem are things like

strokes we can get strokes in the

brainstem we can get inflammation in the

brainstem we can get tumors in the

brainstem

sometimes ear infections can be so

severe that they actually invade through

the bone and affect the brain so in

general the things that affect the

central vestibular system like brain

tumors meningitis encephalitis strokes

and brain infections are much more

serious than things like idiopathic and

inner ear infections how do we tell what

the cause is so looking at the pet we

can often tell the difference of

peripheral versus central and that

changes our list of possible causes or

we call our differential diagnosis so we

can come up with that list but the way

that we find out which one it is is by

doing tests usually the first tests

involve blood tests so a complete blood

count a chemistry panel so complete

blood count is going to look at the red

blood cells the white blood cells the

platelets a chemistry panel is going to

look at the internal organs so the blood

sugar the liver or the kidneys and then

we also often do a thyroid profile

because low thyroid can be associated

with certain causes a vestibule ER

disease the next step is often x-rays of

the chest while the x-rays of the chest

aren't necessarily going to tell us

what's going on in the brain certain

causes such as metastatic cancer or

strokes sometimes we can see

abnormalities in the heart and lungs on

our x-rays additionally prior to moving

towards an MRI x-rays of the chest are

important to make sure that your pet is

a good anesthetic candidate

and many times we'll do a blood pressure

just because strokes are a relatively

common cause of festive or their disease

it's very important for us to check the

blood pressure so assuming that one two

and three do not give us an answer the

next step is typically anesthesia and an

MRI and an MRI is going to be the best

way for us to get a picture of the brain

and the inner ear and tell us is it an

inner ear infection is it a tumor is it

a stroke is it inflammation of the brain

etc and by knowing which one of those it

is we have the best chance of treating

your pet specifically and aggressively

many times a spinal tap is necessary to

look for inflammation of the brain or

certain infections and certain types of

cancer a spinal tap is usually done only

after an MRI because sometimes the MRI

will give us the answer and tell us that

we don't need to do the spinal tap

sometimes the MRI will tell us that a

spinal tap would be too risky so we

always do it the MRI prior to deciding

on whether to do a spinal tap or not so

in summary the vestibular system is the

part of the neurological system

responsible for maintaining balance and

posture the symptoms of a balanced

problem include head tilt

leaning falling listing and rolling to

one side abnormal eye movements what we

call nystagmus abnormal eye position

will be called strabismus there are two

basic parts of the vestibular system the

parts outside of the brain what we call

the peripheral vestibular system and the

parts inside of the brain what we call

the central vestibular system it's

important for us to tell the difference

of central versus peripheral because it

affects the possible causes it affects

the tests that we recommend it affects

the treatment and it affects the

prognosis most patients with vestibular

disease we require an MRI to know what

the cause is but sometimes we can find

it before doing an MRI

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