Do a handstand and your body knows that it is upside down. When you fall your body instinctively knows how to try to right itself. Not that it always succeeds but it knows how to try. It does this using a pair of organs located in the middle ear. This is called your vestibular apparatus.
The vestibular apparatus is made up of three semicircular canals filled with a fluid. There are sensory hairs in this fluid that detect the movement of the fluid and inform the brain about rotational movement and the body’s position in space. Within the cochlea of the ear there is a saccule containing a gelatinous material. Within this material are little bony structures called otoliths. These move up and down in the gelatin and trigger small hairs that are attached to sensory nerves. This informs your brain of up and down motion of the body.
If the vestibular apparatus is disrupted by injury or disease we see changes in the way our patients understand their position relative to the outside world. Of the things that can disrupt the vestibular system we can classify them into three broad categories. These are; infections of the middle ear, lesions on the brain and the third category is called idiopathic meaning we do not know the cause.
A dog or cat with vestibular disease will stumble and stagger when they try to walk. They may circle to one side and may get motion sickness. They may also have rapid uncontrolled eye movements and they almost always have a head tilt to one side.
Brain lesions are typically accompanied by other signs that indicate that the problem is affecting more than just the peripheral nerves. Sometimes it can be difficult to preform a complete neurological examination but there will be some subtle clues such as changes in other nerves associated with the head (cranial nerves) on the opposite side of the head tilt that indicate there is something going on in the brain. Many people take these central lesions to be “strokes” and while vascular accidents do occur in our patients they are not terribly common. Typically we recommend advanced imaging of the brain using MRI or contrast CT if MRI is not available to get a better understanding of the problem.
Infections of the middle ear are a bit more common than central brain lesions. Sometimes they will accompany an infection of the external ear or sometimes they come on their own. The best way to diagnose a middle ear infection in general practice is by taking x rays of the middle ear. It is impossible to see the middle ear with an otoscope although sometimes we can infer that there is an infection in the middle ear based on our examination of the external ear canal. Middle ear infections require antibiotics for around 6 -8 weeks and sometimes will not resolve with out surgery to open and clear the middle ear.
The most common cause of vestibular disease in cats and dogs is idiopathic or unknown. These typically show up suddenly and will show signs of improvement over the following three days. It usually takes around 1 to 2 weeks to see complete resolution and it is not uncommon for a slight head tilt to persist. If an infection is not detected and a brain lesion is not suspected it is a good idea to look at tick titers especially in dogs living in areas where tick borne illnesses are common. Fungal titers are also a good idea and ruling out hypothyroidism should also be on the diagnostic list. In fact ruling out hypothyroidism, getting base line blood and urine, taking chest radiographs and (if everything looks ok) waiting three days is our current standard approach to these cases.
After arriving at a diagnosis or ruling everything out and going with an idiopathic diagnosis the best treatment we currently have is to treat and prevent nausea and keep our patients relaxed and calm. This allows them to be comfortable while the condition runs its course.
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