Vestibular syndrome

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What is it?

Vestibular syndrome is a neurological condition which affects the brain's ability to sense balance. Structures in the inner ear are involved in sensing head position and movement, and this information is passed to the brain along nerves. Any problem affecting the inner ear, middle ear, sensory nerves or parts of the brain responsible for sensing balance can therefore affect balance and coordination of movement. Vestibular syndrome or "old-dog vestibular syndrome" is a sudden-onset problem that can develop in elderly dogs, which is often idiopathic, meaning there is no known cause for why it occurs.

Why is it important?

Vestibular syndrome is a common condition in older dogs. Whilst it is frequently idiopathic, there are many possible underlying causes, and as such investigations to establish the cause and appropriate treatment may be required to resolve signs. The signs can be severe and distressing for both the pet and owner.

What’s the risk?

Vestibular disease can be a side effect of certain antibiotics and drugs, either given as medication by mouth or into the ear. Diseases of the middle and inner ear, most commonly infections, but also polyps and tumours are also potential causes. Dogs with hypothyroidism (an underactive thyroid) may also be predisposed to vestibular syndrome. Conditions affecting the brain and nerve supply to the inner ear can also cause vestibular disease. These conditions include brain tumours, cysts, strokes and inflammation of the brain and the membranes surrounding it (meningoencephalitis). However, the majority of cases appear to be due to a “malfunction” of the sense organs and are linked to old age.

What happens to the dog?

Some dogs are more severely affected than others. The animal may be very wobbly and uncoordinated when walking, or be unable to stand or walk at all. They will usually have a tilt of the head and prefer to circle or roll in one direction. They also develop a nystagmus, which is a flicking movement of the eyes. The eyes may flick from side to side, up and down, or in circles. Frequently they will feel nauseous and so may vomit. Sometimes other nerves will also be affected and if this occurs there may be additional signs such as a drooping of the face, inability to blink or difference in size of the pupils.

How do you know what’s going on?

The vet will take a history, asking questions about what medication the dog is on and whether or not they have a history of ear disease for example. They will then perform an examination of the animal. This will include a neurological examination, which is performed to assess the function of nerves to the eyes and face, as well as the rest of the body. Information from the examination will help the vet work out whether the vestibular syndrome is likely to be due to problems with the 'peripheral vestibular system' i.e. ear and nerve supply to the ear, or 'central vestibular system' i.e. the brain.

If your dog is elderly, and shows classic signs, your vet may diagnose the dog with "idiopathic old dog vestibular syndrome". There is no specific test that will confirm this, but in this situation all tests for other causes will be negative.

Further testing may be required if an underlying cause is suspected. This may include blood tests, including for thyroid function. If the dog has a history of ear problems, the ears may be examined using an otoscope to assess whether or not the eardrum is ruptured and samples may be taken for culture to check for infection in the middle ear. It may not be possible to tell for sure if there is disease in the middle or inner ear without some form of imaging. X-rays may be taken to examine the tympanic bullae, which are round bony structures in the middle ear, for signs of disease. CT and MRI scans are more sensitive ways to image the middle and inner ear, and can also be used to examine the brain if it is suspected the vestibular syndrome may be caused by a brain tumour or other disease in the brain.

What can be done?

In cases of "idiopathic old-dog vestibular syndrome", there is no specific treatment, but usually dogs will show a significant improvement within 2-3 days, being able to walk unassisted by this point, and signs will resolve in most cases within 2-3 weeks. Nursing care will be required to assist animals with going to the toilet, eating and drinking. Regular turning is needed and a well-padded bed to avoid pressure sores. Anti-nausea medication may be given by the vet. In general, the prognosis is good. However, some dogs will be left with a residual head tilt, some dogs may have repeated vestibular syndrome episodes in future, and a few dogs do not recover fully, or take longer than 2-3 days to regain their ability to walk.

In cases with an underlying cause, specific action may be needed to treat the condition, such as antibiotics for an ear infection, thyroid supplementation medication, or surgery if there is a polyp or tumour in the middle ear. If the dog is severely affected to the point they have a poor quality of life and there is an underlying cause which cannot be treated, or treatment is unsuccessful, euthanasia may be recommended.

What can I do to protect my pet?

Unfortunately as this syndrome is often idiopathic, there is nothing that can be done to prevent episodes. Ensuring outer ear infections are properly treated and prevented will help to reduce the risk of middle ear infections developing.