Vestibular disease can be a distressing affliction to your pet’s health.
Clinical signs may be as mild as a head tilt to severe as inability to stand. You may notice nystagumus (sporadic eye movement, see video here), running into walls, difficulty walking, dragging of the feet, incoordination, or flailing. These signs may be seen in both an acute and chronic onset. Click here for a video showing the incoordination of a cat with vestibular disease. Note the head tilt towards the left. In addition, you will see the cat lose his balance about half-way through the video, a common symptom of vestibular disease in the cat.
Before one can truly understand vestibular disease, one has to understand the anatomy of the ear and its relation to the vestibular apparatus. There are numerous differences between the cat and human ear.
The most pronounced difference is the cat’s ear canal has two distinct portions, a vertical and
horizontal part. This creates a 90 degree angle within the canal. As the canal dives deeper into the head, it passes the tympanic membrane (ear drum) to enter the middle ear. Protected by bone even deeper, the inner ear houses all of the neurologic components of the vestibular and hearing systems. This includes the two branches of the main nerve involved in balance/hearing (the vestibule-cochlear nerve). In addition, a number of other major nerves and blood vessels pass through this area.
Normal Vestibular Function
Beyond knowing the anatomical structures, understanding their functions will allow better insight into disease processes in this area. Balance, in most mammals, comes from three neurologic pathways. There are hair cells in the middle ear that respond to fluid (endolymph) changes that come from moving the head and body. These hair cells communicate to the brain how the head is oriented. The other two pathways are the visual system for orientation, and gravity receptors in the skin. With the information gained from all of these systems, the brain is able to orient the body properly. If there are issues with any of these three systems, signs of vestibular disease may present.