Although it’s only the size of a golf ball, your cat’s brain is just about as complex and, when it comes to matters of vital concern, just about as capable as your brain. Of course, a cat uses its brain and the other components of its neurologic system to address needs and desires that are often different from yours. After all, you like to read books and watch movies; your cat likes to torment mice and play with balls of yarn.
Sad to say, a cat’s neurologic system also resembles yours in the wide variety of serious disorders with which it can be afflicted, sometimes with fatal consequences. According to Curtis Dewey, DVM, an associate professor of neurology and neurosurgery at the Cornell University College of Veterinary Medicine, he and his colleagues typically treat four or five neurologically compromised cats each week at the university’s animal hospital.
The feline nervous system, like yours, is made up of two components: the central nervous system, which consists of the brain and spinal cord; and the peripheral nervous system, which comprises the cranial, spinal, and other nerves, as well as muscles. In a healthy animal, the entire arrangement works harmoniously to enable and control vital processes within a cat’s body and to allow the animal to function effectively in its environment.
These processes are facilitated by the instantaneous delivery of electrical signals that are transmitted, via the peripheral nervous system, from tissues throughout a cat’s entire body to its spinal cord and brain. The brain responds by interpreting these signals and transmitting appropriate instructions back through the brain stem and spinal cord to the appropriate destination via the peripheral nerves.
Many functions of the nervous system are under conscious and voluntary control, such as the movement of an animal’s legs or the opening and closing of its mouth. Other functions are involuntary and regulated by the autonomic nervous system, such as those that control the activities of muscles in the digestive tract, lungs and heart, as well as the secretion of hormones.
The hub of all of this activity is the brain, which coordinates these activities. The brain consists of the cerebrum and cerebellum, which govern the array of nervous system activities; and the brain stem, which connects the brain to the spinal cord.
Among those disorders that do occur, some are significantly more common than others, notes Dr. Dewey. Perhaps the most frequently diagnosed of these is a neoplastic disease called meningioma, which is a type of tumor that develops in the thin protective tissue — the meninges — that covers a cat’s brain. Although these growths, which most often affect older cats, are usually benign and well-defined, their continued expansion will eventually result in damage caused by pressure on the brain. “Probably 75 percent of the brain tumors that we see are meningiomas,” says Dr. Dewey.
Fortunately, he notes, such tumors are notably amenable to surgical removal. “Cats that have a meningioma removed usually do very well,” Dr. Dewey says. “The surgery tends to be so successful that we don’t have to follow up with additional therapy, and a lot of the patients will go on to live for several years.” The same cannot be said for another type of brain tumor called a glioma, which develops in a deeper and sometimes surgically inaccessible area of a cat’s brain.
Additional feline neurologic disorders fall generally into the following categories:
Epilepsy — This condition stems from defects in the electrical transmission of nerve signals within a cat’s cerebral cortex, the area of the brain responsible for thought, memory, sensation and voluntary muscle movement. Although this condition can be secondary to head injuries, metabolic irregularities or tumors, a relatively common form is termed idiopathic epilepsy — so named because there is no discernible cause for the violent seizures that an affected cat experiences. Cats with idiopathic epilepsy are typically normal in every other respect, says Dr. Dewey. Fortunately, epilepsy is usually manageable with the daily administration of various medicines.
Congenital disorders — Among the most common of these is a condition affecting the cerebellum, the part of the brain responsible for muscle coordination. Some kittens that are born infected with the feline distemper virus will immediately show a severe lack of coordination. There is no cure for it, but cats with this neurologic problem can live a long life. Another congenital disorder, says Dr. Dewey, is hydrocephalus, a condition in which an abnormal accumulation of fluid can cause enlargement of the skull and compression of the brain. In some cases, he says, the condition can be successfully relieved by surgery that enables the drainage of excess fluid from a cat’s brain to its belly, from which it can then be excreted.
Infectious disease — Cats that are infected with the feline infectious peritonitis virus (FIP) sometimes experience neurologic damage, says Dr. Dewey. “And there’s not too much that we can do to treat it,” he notes. Also, he notes, “We fairly frequently see cats with bacterial infections of the middle- and inner-ear cavities that break through the skull, which can result in a brain infection. Most of these cats will do all right if we catch the infection early.”
Two other factors — trauma and advancing age — can play a substantial role in the sudden or gradual decline of feline neurologic well-being, says Dr. Dewey. “We often see cats that have been hit by cars,” he says. “Most of those that experience head trauma will die at the scene of the accident. But we sometimes see cats that almost escaped being hit but have had their tails run over. This can yank on the nerve roots, and in addition to having a dead tail, a cat that survives is likely to have urinary and fecal incontinence for the rest of its life.”
As for age-related neurologic problems, he says: “We don’t see a lot of them, but it’s well documented that old cats can develop a progressive degenerative disorder that kills brain cells. It’s similar to the problem experienced by elderly humans with Alzheimer’s disease.”