The vestibular apparatus is the neurological equipment responsible for determining if you are upside-down, standing up straight, falling etc. and informing the eyes and limbs how they should move accordingly.
The vestibular apparatus allows us to walk, even run, on very uneven ground without falling, helps us know when we need to right ourselves, and allows our eyes to follow moving objects without becoming dizzy.
Instructions are carried by nerve cells to the legs and neck muscles, and eye muscles so that we may orient ourselves immediately. The information about being upside down (or in some other abnormal orientation) is also sent to the hypothalamus (an area of the brain) so that we can become consciously aware of our position.
If there is trouble in the vestibular apparatus, then you may not properly 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 very dizzy.
Signs you will see:
- Ataxia (lack of coordination without weakness or involuntary spasms-in other words, stumbling and staggering around)
- Motion sickness
- Nystagmus (back and forth or rotational eye movements) The movements will be slower in one direction. This is the side where the neurological lesion is likely to be.
- Head tilt (usually toward the side of the lesion)
- Falling to one side (usually toward the side of the lesion)
- Trouble with other nerves controlling the head and face
Causes of Vestibular Disease
In order to determine prognosis and choose treatment, we need to figure out what has happened to the vestibular system. The first step is to determine whether the lesion is in the brain (central) or in the inner ear (peripheral). There will be some hints in the clinical examination, but if your vet is unsure they may suggest further tests.
Canine idiopathic vestibular disease (also called "Old dog vestibular disease") and, its feline counterpart, feline idiopathic vestibular disease, begin suddenly and resolve suddenly. Usually improvement is evident within 72 hours and your pet is back to normal in 7-14 days, possibly with an occasional head tilt persisting. These two conditions are idiopathic, meaning we do not know why they occur. We do know that they represent problems in the nerves of the middle ear rather than in the actual brain. Idiopathic Vestibular Disease is the most common form of vestibular disease in dogs and cats.
Middle ear infection is a likely possibility for vestibular disease especially if your pet has a history of ear infections. When an otoscope is used to visualize the external ear of an animal with vestibular disease and debris is seen, this would be a good hint that there is infection in the middle ear as well. However, just because debris is not seen in the external ear does not mean that a middle ear infection is unlikely. X-rays of the middle ear bones may be in order if this is suspected.
Brain tumours can be a cause of vestibular disease if the signs fit with a central lesion. The brain can be imaged using MRI scans but this requires visiting a specialist neurologist. Such tumours may be treatable depending on their location.