Peripheral vestibular dysfunction
Recommended diagnostic procedures in patients determined to have peripheral vestibular dysfunction include
An otoscopic examination of the external ear canal and the tympanic membrane. Examination of the ear is best done with the patient under heavy sedation or anesthesia and by using a magnifying otoscope
or an operating microscope to visualize the tympanic membrane. The ossicles in the middle ear can be seen through the thin
tympanic membrane in a normal ear.
A myringotomy. This procedure can be done to collect a sample from the middle ear for cytologic examination and culture. (See the related link below "Skills Laboratory: How to perform a myringotomy".) Caution must be taken not to injure the sensitive ossicles or the nerves in the middle ear.
Radiography. Radiographs can help you visualize fluid in the tympanic bulla and evidence of processes that cause changes to the osseous
bulla, such as severe infections and neoplasia.
Computed tomography (CT) or MRI. These imaging modalities are ideal for a thorough evaluation of the middle and inner ear.17-20
Idiopathic vestibular dysfunction is diagnosed after ruling out all other causes of peripheral vestibular dysfunction.
Central vestibular dysfunction
Recommended diagnostic procedures in patients determined to have central vestibular dysfunction include
- Cerebrospinal fluid (CSF) analysis
The thick bones of the tympanic bullae frequently cause artifacts on CT, which prevent good visualization of the brainstem.
For this reason, CT is not a good diagnostic tool for imaging animals with central vestibular dysfunction. The CSF tap is
preferably done after the MRI, since the likelihood of cerebellar herniation is greater with a lesion in the caudal fossa
(in the area of the brainstem and cerebellum) than with a lesion in the rostral fossa. If cerebellar herniation is present,
CSF collection may carry a higher risk of death and should not be performed.
TREATMENT AND PROGNOSIS
Treat all patients with vestibular dysfunction with supportive care. In some severe cases of rolling, the patient may need
to be strapped down to a board. Soft padding of the cage is recommended to prevent the patient from injuring itself when rolling
or falling. Patients that are vomiting or are inappetent may feel better if treated with an antihistamine such as meclizine.
General treatments and prognoses for selected causes of vestibular syndrome include
Otitis. The treatment for otitis media or otitis media and interna is any combination of systemic or topical antibiotics, antifungals,
or corticosteroids as directed by clinical signs and diagnostic testing results. If the otitis has not resolved within four
to six weeks, a bulla osteotomy may be necessary to drain the ear.
Neoplasia. The prognosis for ear neoplasia depends on the kind of neoplasia and the extent of neoplasia at the time of diagnosis. Some
neoplasia can be radically removed, and surgery is often followed by radiation therapy.
Primary secretory otitis media. Primary secretory otitis media in cavalier King Charles spaniels is treated with myringotomy and flushing of the ear. Many
times this has to be repeated as the mucus accumulates once the tympanic membrane has healed.8,9
Canine and feline idiopathic vestibular dysfunction. Most dogs with idiopathic vestibular dysfunction recover within a few days to several weeks. Residual head tilt is common.
Recurrence of the disease is rare but can occur. The prognosis for feline idiopathic vestibular dysfunction is good, and most
cats recover within a few weeks.
Metronidazole toxicosis. Patients with metronidazole toxicosis recover within three to 14 days once the metronidazole treatment has been discontinued.
The recovery may be faster if the patient is treated with diazepam; an initial intravenous bolus of 0.5 mg/kg followed by
0.5 mg/kg given orally every eight hours for three days has been recommended.21
Endocrinologic disease. Patients with hypothyroidism or hyperadrenocorticism as a cause of the peripheral or central vestibular dysfunction improve
but do not always completely recover when treated for the underlying disease.
Infarct. If no underlying cause is found for an infarct, the prognosis is in general good for improvement.
Signs of vestibular dysfunction are easily recognized, but it can be difficult to differentiate peripheral from central dysfunction
since a neurologic examination is challenging in severely ataxic patients. However, the diagnostic work-up, treatment, and
prognosis may differ between diseases resulting in peripheral vs. central dysfunction, so the challenge is worth accepting.
Helena Rylander, DVM, DACVIM (neurology)
Department of Medical Sciences
School of Veterinary Medicine
University of Wisconsin
Madison, WI 53706-1102