VESTIBULAR DISEASE IN THE CAT AND DOG
By Maggie Vandenberg, DVM, DACVIM
Neurology
Practice Points

In central vestibular disease concurrent mental dullness and
dysfunction, as well as other cranial nerve deficits are often observed.

In peripheral vestibular disease, otitis media/interna and idiopathic
peripheral vestibular disease are the most common causes in both cats
and dogs.

Magnetic resonance imaging is the gold standard diagnostic test for
soft tissue imaging and preferred imaging for vestibular disease.

Computed tomography (CT) should be considered in patients with otic
disease causing vestibular signs.

Patients with otitis media/interna will have a history of head shaking,
bulla pain, and/or ear infection.
(*put vestibular patient photo at beginning)
Vestibular disease is one of the most commonly seen neurologic
condition seen in general and/or specialty practice. This is a general term
for neurologic conditions affecting the balance center. The balance center is
located within the brainstem, cerebellum, first three cervical spinal
segments, or inner ear. Animals with vestibular disease often have several
neurologic abnormalities. These abnormalities include head tilt, abnormal
nystagmus, dull mentation, vomiting, ataxia, proprioceptive deficits, and/or
become unable to stand or walk. Oftentimes, due to the severity of clinical
signs, it is very difficult to determine by neurologic exam where the location
of or what is the underlying cause of the vestibular dysfunction. Careful
observation, attention to historical information, and a systematic approach is
crucial in order to appropriately treat and determine the underlying cause of
dysfunction in our patients.
Vestibular disease is separated into two main categories based on the
disease localization. The two categories of disease are peripheral and
central. With peripheral vestibular disease the underlying problem is
occurring within the bony and membranous labyrinth of the petrous
temporal bone (inner ear). With peripheral vestibular disease you can
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additionally observe ipsilateral dysfunction of the post-ganglionic
sympathetic innervation to the eye, and/or dysfunction in cranial nerve VII.
In central vestibular disease the underlying problem is occurring within the
brain (brainstem, cerebellum) or first three cervical spinal cord segments.
With central vestibular disease concurrent mental dullness and dysfunction
in other cranial nerves (cranial nerves V, VII, IX, XII) is often observed.
Cats and dogs have very different etiologies of vestibular dysfunction.
Peripheral vestibular disease has many underlying causes. The two most
common causes of peripheral vestibular dysfunction in both species include:
otitis media/interna and idiopathic peripheral vestibular disease. Patients
with otitis media/interna will have a history of head shaking, bulla pain,
and/or otic discharge/infection. Otic examination will be abnormal. If there
are not any apparent abnormalities on otic examination than another cause
should be sought out. It is very important to recognize that topical otic
medications can be extremely ototoxic especially when the integrity of the
tympanic membrane is compromised. So ideally they should not be used at
all. Additionally, horner syndrome or facial nerve paralysis is commonly
seen along with otitis media/interna as these nerves pass within the inner
ear in close association with the vestibular receptors. Idiopathic vestibular
disease is seen in both cats and dogs. In both species it’s onset is acute and
clinical signs (head tilt, ataxia, vomiting) can be quite severe. In this
disorder cranial nerve VII and/or horner syndrome will not be seen. It is
seen in dogs over 5 years of age and can occur in cats of any age. Aural
neoplasms are seen in both species and tend to be more malignant (85% of
the time) in cats. Nasopharygeal polyps are found in young cats (1-5 years
of age). They are usually unilateral and removal by traction polypectomy
through the mouth or external ear canal typically results in a 30-40%
recurrence rate. A bulla osteotomy can reduce recurrence to ~10%.
Hypothyroidism is a condition that causes peripheral cranial neuropathy in
dogs. Commonly cranial nerves VII and VIII are affected together.
Supplementation with thyroid hormones usually results in improvement
within a few months.
Central vestibular disease should definitely be considered if
proprioceptive deficits, dull mentation, and/or other brainstem signs are
observed. These conditions are often more insidious and/or chronic in
nature. They can be acute though with cerebrovascular disease. Conditions
that cause central vestibular dysfunction are hypothyroidism (dog),
intracranial tumors, non-infectious inflammatory disease (granulomatous
meningoencephalitis), infectious disease (fungal, protozoal, viral, rickettsial),
metronidazole toxicity (dogs), metabolic diseases (portosystemic shunts,
hypothyroidism), cerebrovascular disease (more commonly in the dog), and
degenerative diseases (lysosomal storage diseases).
Work up for both forms of vestibular disease is similar. Getting a
baseline blood chemistry, complete blood count, urinalysis, and blood
pressure is essential in every patient. Typically patients are not in a lifethreatening situation and taking the time to adequately assess your patient
is essential. Supportive therapy should be initiated as soon as possible.
Typically patients have vertigo and may be vomiting. In these patients it is
recommended to start intravenous fluid support, anti-emetics, and
appropriate nursing (turning, passive range of motion, supported
ambulation). Steroids are not indicated in the initial nursing period. In
many instances they are not necessary and if given they will interfere with
future diagnostic testing (i.e., cerebrospinal fluid analysis, magnetic
resonance imaging). If an otic infection is confirmed, appropriate testing
(myringotomy, culture, cytology) and administration of antibiotic therapy
should be performed. In the persistently hypertensive patient, underlying
causes of hypertension should be sought out. Testing such as
protein:creatinine, ACTH stimulation test, abdominal ultrasound, +/echocardiography can be considered if indicated by the laboratory results
and initial assessment.
If the initial diagnostics do not reveal an underlying cause, a
neurologic consultation should be performed. At that time magnetic
resonance imaging (MRI) of the brain (FIGURE 1) +/- cerebrospinal fluid
(CSF) analysis should be considered. Computed tomography (CT) (FIGURE
2) could be considered for otic disease causing only peripheral signs but is
not ideal in patients with central vestibular disease. With CT, the beam
hardening artifacts caused by the bone can preclude visualization of small
lesions within the brainstem, cerebellum. Thus MRI is the preferred method
of imaging for vestibular disease as it is the gold standard diagnostic test for
soft tissue imaging.