Every so often, a client will bring their dog or cat to the veterinarian for an urgent evaluation because of a sudden onset of difficulty walking (almost as if drunk, perhaps complete inability to get up) and a head tilt. Vomiting is sometimes reported. Upon closer examination, nystagmus (eyes going back and forth rapidly) is seen. Clients will comment that they believe that their pet has had a ‘stroke’. Understandably, these pet parents worry that there may be some type of permanent injury and are distressed in watching their companion endure what can be very dramatic symptoms.
We understand a ‘stroke’ from human medicine as a sudden hemorrhage or blood clot to an area of the brain that can lead to weakness, paralysis, potential loss of speech and cognitive functions and potentially, death. While it is not impossible for dogs and cats to develop bleeding problems in the brain, the most common explanation for what is commonly called a ‘stroke’ in small animal medicine is actually vestibular disease.
Vestibular disease (or syndrome) is a general term describing clinical signs consistent with abnormal functioning a part of the nervous system that controls the body’s balance and equilibrium. The vestibular apparatus is the neurological equipment responsible for perceiving your body’s orientation relative to the earth (determining if you are upside-down, standing up straight, falling etc.) and informing your eyes and extremities how they should move. The vestibular apparatus allows us to walk and run on uneven ground without falling, helps us know when we need to right ourselves, and allows our eyes to follow moving objects without becoming dizzy.
In animals and people, balance is controlled by the ears (vestibular receptors of the inner ear) working together with specific areas of the brain. Together they represent the vestibular system. If the vestibular apparatus is not working properly, then you may not accurately perceive your orientation. To put it more simply, you won’t know which way is up, whether or not you are standing up straight or slanted, and you will feel dizzy. The following are signs of vestibular disease:
- Ataxia (lack of coordination without weakness, or involuntary spasms – in other words, stumbling and staggering around)
- Nausea, vomiting (motion sickness)
- Nystagmus (back and forth or rotational eye movements)
- Head tilt
- Falling to one side (you may notice that your pet will only lie on one side and will roll on the floor when attempting to move or when you try to turn him on to the other side)
- Trouble with other nerves controlling the head and face
- Cats may also vocalize due to the imbalance
Many diseases can cause loss of balance – an ear infection, ruptured ear drum, a tumor in the brain or the inner ear, a vascular problem, toxicity to chronic drug administration (e.g., metronidazole), and idiopathic vestibular disease – so it is important that a veterinarian examine the animal to begin to determine the most likely cause. An initial diagnosis is made by the history, general physical exam, ear exam with an otoscope, and by the neurologic examination. If there is a suspicion that something else is going on, your veterinarian might recommend further tests. Additional tests could include blood work, imaging of the middle ear and/or brain (via x-rays and/or CT scan), maybe chest x-rays (to help rule out heart disease or tumors that could contribute to ‘wobbliness’.
A middle ear infection is a likely possibility for vestibular disease especially if there is a history of ear infections. Debris in the external ear, could imply infection in the middle ear as well. However, the absence of debris in the external ear does not mean that a middle ear infection is unlikely. Imaging of the middle ear bones may be in order. One way to evaluate the middle ear is with radiographs called a bulla series, so named because it focuses on an ear bone called the tympanic bulla. If the bulla appears abnormal, the ear may require surgical drainage. The problem is that x-rays are often not sensitive enough to pick up damage in the middle ear and a normal set of films does not rule out disease. In these cases, special imaging such as a CAT scan or MRI is better. These techniques also allow imaging of the brain tissue itself (which radiology does not) thus allowing brain abnormalities to be evaluated as well.
Brain tumors can be a cause of vestibular disease if the signs fit with a lesion of the central nervous system. In these cases, CT or MRI scans are needed to make the diagnosis. Such tumors may be treatable depending on their location.
Idiopathic vestibular disease is the most common form of vestibular disease in dogs (also called ‘old dog vestibular disease’) and cats. The clinical signs happen extremely rapidly, sometimes over a few minutes, and can cause severe incapacitation.
Treatment depends upon the severity of the symptoms and the likely cause. An ear infection would require antibiotic therapy. In some cases in which a cause is not determined, or if it is presumed to be idiopathic disease, symptomatic treatment and supportive care is given. It is not unusual for a dog or cat to be unable to get up and walk because the loss of balance is so severe. It is assumed that your pet feels dizzy and nauseous. With the more severe presentations, hospitalization, fluid support and medications for nausea are advised. If the patient is able to eat and drink, and came move about without needing significant assistance, home care can be appropriate.
Most cases of idiopathic vestibular syndrome improve within several hours to a few days but could take days to weeks to completely resolve. This syndrome can occur again at some point in your pet’s life, however it cannot be predicted. If the patient is not improving, or is worsening, more aggressive diagnostics and treatment would be advised. Despite the severity of the clinical signs and the anxiety of your pet (and you), the chance of recovery is excellent. All your dog or cat needs is some time and your help.