Cornell Feline Health Center
Cornell University College of Veterinary Medicine
Ithaca, New York 14853
A generally healthy and typically agile cat suddenly seems to be having trouble getting up on all four legs and maintaining its balance. The animal eventually manages to stand, but its appearance is startling. Although its vision seems to be all right, its head is oddly tilted to one side, and its eyes dart back and forth wildly. And after taking a few steps, it abruptly lists to one side and tips over again.
The cat may be experiencing a transitory problem with its vestibular system—the complex arrangement of nerves and other components that governs its sense of balance and coordinates the movement of its head and eyes. Such a disorder and its alarming manifestations are typically temporary and ultimately harmless. In some cases, however, the signs of what is known as vestibular disease may be due to a more serious problem—so immediate veterinary consultation is certainly in order.
The vestibular system’s essential components are housed in two interconnected locations, explains Marnie FitzMaurice, VMD, PhD, an instructor in the department of biomedical sciences at Cornell University’s College of Veterinary Medicine and a consultant at the Cornell Feline Health Center. One is the vestibular apparatus, located deep within the inner ear, adjoining the cochlea; the other is centered in the lower area of the brain (medulla), which is situated at the top of the spinal cord. The vestibular apparatus consists of several fluid-filled canals that contain specialized nerve cells and receptors.
These receptors, which are connected to nerves leading to the medulla, respond to changes in movement of the fluid that is in the chambers. The fluid shifts as the animal’s head changes position, and corresponding signals are instantaneously sent to the brain; these signals register the position of the head relative to gravity. The vestibular apparatus tells the animal whether its head is motionless or moving and, if the head is moving, which way it is moving. A cat’s sense of balance is normally maintained because the system also compensates for changes in position. If the animal turns one way or another, a signal is automatically sent to the muscles on one side of its body to adjust for the change in position, thus preventing the cat from tipping over.
The most common clinical signs of vestibular disease include circling or falling to one side, a pronounced head tilt, and nystagmus—the rapid and involuntary oscillating movement of the eyeballs. Facial drooping may occur if there is a tumor or inflammatory disease of the inner or middle ear because the facial nerves are closely associated with the middle ear, which is next to the inner ear.
Disorders that precipitate vestibular system malfunction can range dramatically in severity, Dr. FitzMaurice points out. They can include, for example, bacterial infections; inflammatory disease; adverse reactions to certain drugs, including some antibiotics; and a variety of growths such as polyps, tumors, cysts, and cancer. In most cases, however, the cause of vestibular malfunction will remain unknown and may be referred to, therefore, as idiopathic vestibular syndrome.
The clinical signs of this mysterious disorder may be seen in both male and female cats of any age or breed. Although the signs are typically the same as those associated with other types of peripheral vestibular disease, they are transitory, arising abruptly and then gradually improving over the course of several days. Most cats will be completely recovered within two or three weeks. “The condition is not very common,” notes Dr. FitzMaurice, “but any veterinarian will see it now and then.”
Diagnosis of vestibular dysfunction, she says, requires a thorough medical history and physical examination of the patient, including a neurologic exam and an otoscopic exam that explores the cat’s ears for signs of infection, inflammation, or tumors. In some cases, advanced imaging (CT or MRI) might be used to test for problems deeper within the ear or skull, Dr. FitzMaurice adds.
Treatment of vestibular disease depends on the cause. If the condition is secondary to infection, tumor, or toxicity, the primary disease must be treated. In the case of idiopathic vestibular disease, there is no specific treatment. Animals must be kept confined in a safe place where they will not injure themselves. Supportive care may include assisted feeding and fluid administration if the cat cannot eat and drink. And anti-nausea medication may be used if the cat is vomiting. In most cases, the signs of idiopathic vestibular syndrome will vanish within a short time and will never reappear.
By Tom Ewing
December 20, 2010