By Yao Yao, VMD
MSPCA-Angell West, Waltham
The vestibular apparatus is located in the middle/inner ear and part of the brain, and it is responsible for maintaining normal balance. The vestibular apparatus achieves this by allowing the body to perceive its orientation relative to the earth and in turn directs the legs, neck, and the eyes to move appropriately. If the vestibular system is not working correctly, the patient may feel disoriented and dizzy. Vestibular disease often presents as an acute disturbance of balance, and it is more commonly seen in older dogs.
Vestibular disease is fairly commonly seen in the veterinary emergency room. Common signs of vestibular disease include:
- Head tilt
- Ataxia (stumbling and staggering when walking)
- Circling, falling and leaning to one side
- Some dogs will become reluctant/unable to stand and walk
- Jerky eye movements called nystagmus; sometimes nystagmus is only seen when the patient is in certain position, such as lying upside down
- Vomiting, decreased appetite
There are many causes of acute vestibular disease. Your veterinarian will try to determine if the vestibular disease is peripheral (related to the middle/inner ear), or central (related to the brain). Some causes of peripheral vestibular disease include middle/inner ear infection, drugs that are toxic to the middle/inner ear, trauma, hypothyroidism, and tumors. When no cause is found, the condition is called idiopathic vestibular disease, also referred to as old dog vestibular disease. These cases tend to improve with time and supportive care. When central vestibular disease is suspected, patients often have additional neurologic signs including mentation change, additional cranial nerve deficits, proprioceptive/postural reaction deficits (trouble knowing where their paws are), etc. Central vestibular disease can be caused by vascular event/stroke, brain tumor, brain inflammation or infection, etc.
A number of diagnostics may be indicated to further understand the cause of a patient’s vestibular disease. For peripheral vestibular disease, an otoscopic exam may be used to visualize the external ear canal. If there is evidence of an ongoing external ear infection, or if a patient is historically prone to having ear infections, the infection may have extended to the middle/inner ear, causing the patient’s vestibular signs. However, it is important to note that even if the external ear looks normal, it does not rule out a middle/inner ear infection. Sometimes advanced imaging (CT scan or MRI) is needed to ascertain if there is an ongoing inner/middle ear infection. Other diagnostics including blood work to look for hypothyroidism and concurrent systemic diseases may be indicated. When central vestibular disease is suspected, imaging of the brain using MRI would be useful in determining the nature and extent of the brain lesion to guide further therapy. General anesthesia is required for MRIs. Other diagnostics indicated in central vestibular disease include systemic blood work, urinalysis, abdominal ultrasound, and chest radiographs to look for evidence of cancer, kidney disease, endocrine disease, protein-losing disease, etc. Blood pressure may be measured to look for evidence of high blood pressure.
Treatment of vestibular disease depends on the underlying cause. For idiopathic vestibular disease, patients are usually given medications to help with nausea or motion sickness. Antibiotics may be used to cover possible middle or inner ear infections. In severe cases, hospitalization and intravenous fluids may be needed until the patient can eat and walk better. If hypothyroidism is diagnosed, a patient will need to start taking thyroid supplementation. Otherwise, underlying systemic diseases need to be addressed as needed. Some brain lesions can be treated surgically, and certain cases may also require follow up chemotherapy or radiation therapy.
The prognosis of vestibular disease depends on the underlying cause. For idiopathic vestibular disease, the clinical signs tend to be the most severe during the first several days before gradual improvements are seen. Some patients improve rapidly, with their clinical signs resolving within days, others can take weeks to months to recover, and some patients have a mild, persistent head tilt.