Vestibular syndrome describes any illness that affects a dog’s vestibular system – the body’s apparatus that keeps him balanced and upright. A problem with his vestibular system causes a dog to seem dizzy and disoriented.
Vestibular syndrome in a dog can be one of two types: peripheral or central. Peripheral vestibular syndrome affects the components of the middle and inner ear. Central vestibular syndrome affects the parts of the brain responsible for coordinating movement of the eyes, head, and limbs.
Your veterinarian will complete a full physical and neurologic exam of your dog to determine if his vestibular syndrome is peripheral or central (or if his symptoms are caused by a seizure or syncope – these conditions can look similar). Determining the type of vestibular syndrome narrows down the list of potential causes. It also helps determine which diagnostics will be useful in identifying the cause of your dog’s vestibular syndrome.
Causes of peripheral vestibular syndrome
There are a number of quite disparate causes of peripheral vestibular syndrome:
- Idiopathic vestibular disease. The most common cause of peripheral vestibular syndrome is also known as old-dog vestibular syndrome. Idiopathic vestibular disease tends to affect older dogs and can affect any breed. Dogs with this condition have no change in their mentation; they are still bright, alert, and want to be with their people. They look as though they are on a boat at high seas!
The signs of idiopathic vestibular disease typically begin to subside after three days. It may take up to two weeks for an affected dog to return to normal, although he may have a persistent head tilt for two months or more. There is no known cause or treatment for idiopathic vestibular disease. Your veterinarian may prescribe medication to address the nausea associated with his vertigo while he recovers.
You can help your dog during his recovery from idiopathic vestibular disease by keeping him away from stairs or other places where he may fall and hurt himself. You may need to support your dog while walking or posturing to urinate and defecate. You can provide him with support with bath towels slung under his chest and belly or an orthopedic harness (like the Help ‘Em Up Harness).
— Middle ear infection (otitis media) or an inner ear infection (otitis interna). Collectively, these ear infections are the second most common cause of peripheral vestibular syndrome. These infections are different from the more common external ear infections (otitis externa). Otitis externa affects the ear canal and sometimes the eardrum (tympanum); these are the parts your veterinarian can see when examining your dog’s ear with an otoscope. Otitis media and interna affect the part of the ear on the other side of the tympanum – the part that cannot be seen with an otoscope.
Diagnosis of otitis media/interna can sometimes be made by examining the tympanum with an otoscope. A bulging, discolored, or even ruptured tympanum is consistent with otitis media/interna. But a dog with otitis media/interna may have a normal-appearing and intact tympanum. If your veterinarian is suspicious that your dog has otitis media/interna but the tympanum appears normal, she may order radiographs or CT of the skull to examine the middle and inner ear.
Treatment of otitis media/interna may require a 4- to 6-week course of antibiotics. Your veterinarian may collect a sample of pus from your dog’s ear and submit it to the laboratory for a bacterial culture and sensitivity. This ensures that the correct antibiotic has been selected to treat your dog’s infection.
— Less common causes of peripheral vestibular syndrome. These include tumors of the inner ear, recent head trauma, and hypothyroidism (low thyroid hormone). Recent administration of ototoxic drugs – such as the antibiotics gentamicin and amikacin – can also cause peripheral vestibular syndrome. A rare congenital condition seen in German Shepherds, English Cocker Spaniels, and Doberman Pinschers can cause peripheral vestibular syndrome in puppies.
Causes of central vestibular syndrome
Central vestibular syndrome is a rare condition in dogs. Dogs with this condition will have many of the same symptoms as peripheral vestibular syndrome but with a few key differences. There may also be blindness, facial paralysis, rigidity of the forelimbs or all of the limbs, flaccid paralysis of two or more limbs, or a recent behavior change.
— Cerebral ischemic events (strokes) and intracranial masses (brain tumors) are the two most common causes of central vestibular syndrome.
Dogs who have suffered a stroke will often start to improve on their own over the course of a few hours to a few weeks. The neurologic changes that occur with a stroke have an acute onset. Strokes can recur, causing more damage each time they wreak havoc on the brain. Therefore, it is important to look for an underlying cause of the stroke to minimize the risk of recurrence.
Brain tumors may cause a sudden and rapid decline in a dog’s neurologic status. Unlike a stroke, brain tumors can cause gradual changes in a dog’s behavior, such as staring off into space, walking into corners, barking without explanation, and aggression toward family members (both human and animal). Depending on the location of the tumor, there may also be gradual loss of vision, gradual and progressive loss of control over their limbs, and gradual and progressive facial paralysis.
If your veterinarian suspects that your dog has a brain tumor, she may order advanced imaging of his brain, such as MRI or CT. Since brain tumors can be primary (originate in the brain) or secondary (metastasize from other locations in the body), she may also order chest x-rays, bloodwork, and an abdominal ultrasound to screen for cancer elsewhere in the body. Treatments for a brain tumor include surgical removal of the mass, radiation therapy, chemotherapy, or palliative therapy with steroids.
— Less common causes of central vestibular syndrome. These include infections that affect the brain, an inflammatory condition known as granulomatous meningoencephalitis, congenital malformations (such as hydrocephalus or Chiari-like malformation), long-term administration of high-dose metronidazole (an antibiotic), and recent head trauma. Infections that affect the brain can be viral (such as canine distemper), bacterial (such as tick-borne diseases), protozoal (like toxoplasmosis or neosporosis), or fungal (including cryptococcosis, coccidiodomycosis, and blastomycosis).
Diagnosing one of the less common causes of either peripheral or central vestibular syndrome may require advanced imaging (such as CT or MRI), obtaining a sample of cerebrospinal fluid to look for infectious or inflammatory conditions, and thyroid function testing.
Prognosis for dogs with vestibular syndrome
The prognosis for dogs with idiopathic vestibular syndrome is generally good, while the prognosis for other causes is variable depending on the underlying cause. This is one of the few times that we welcome a syndrome with no specific cause!