While veterinary neuroscientists continue to make progress in diagnosing and treating many feline afflictions associated with the brain, some conditions remain a mystery. Such is the case with hyperesthesia syndrome, a bizarre disorder that can affect cats of all ages, although its onset most often occurs in mature animals.
The clinical signs typically occur in brief bursts of odd behavior lasting perhaps only a minute or two at most. Alexander de Lahunta, DVM, emeritus professor of anatomy at Cornell University’s College of Veterinary Medicine, describes a typical episode as follows: “You’re sitting in a chair, with the cat dozing on the floor in front of you. You reach down to scratch its back in the lumbar region, just in front of its pelvis. All of a sudden, the cat wakes up. Its tail is twitching, its eyes wide open, pupils dilated, very focused—and it begins scratching itself like the dickens with its back paws. Of course, you get your hand out of the way to avoid being scratched yourself. Then, after 20 or 30 seconds, the cat abruptly stops the abnormal behavior, stretches out on the floor, and goes back to sleep.” Instead of scratching, some cats will obsessively lick or bite at their flank, back or tail. Many of these cats will follow up the scratching or grooming behavior with a frantic run around the house.
In addition to obsessive scratching or grooming and running about, another frequently observed sign of hyperesthesia syndrome is a rippling or rolling of the skin on an affected cat’s back. “That’s because there is a skeletal muscle called the cutaneous trunci under the skin that is hyperresponsive when you scratch it,” Dr. de Lahunta explains, “and that makes the skin ripple. The skin can’t move by itself—it has to be stimulated by the muscle.”
Other signs may include salivation, alarming vocalization, and uncontrolled urination. Although no one knows what prompts this potentially self-mutilating behavior, says Dr. de Lahunta, “Some people believe that it belongs to the general obsessive-compulsive group of conditions. But I believe it is a seizure disorder.” This view is supported, he notes, by the fact that many cats show signs of epileptic seizures soon after an episode of the compulsive scratching behavior. Whether the disorder has a genetic basis also remains unknown. “But it’s something to think about,” observes Dr. de Lahunta, “since there appears to be an increased risk for this condition in certain breeds—Siamese cats, for example.”
Some of the behavioral manifestations associated with hyperesthesia resemble clinical signs sometimes observed in other feline health disorders affecting the nervous system, skin, and muscles. Painful spinal problems that can cause similar signs include arthritis, pinched nerves or slipped disks. Skin disorders to rule out include flea or food allergies, fungal infections and mite infestations. Categorically ruling out the presence of such disorders will require a variety of diagnostic steps, including a general physical and neurologic examination, blood chemistry and urine analyses, x-rays and perhaps magnetic resonance imaging. Other measures may be needed as well. For example, says Dr. de Lahunta, “If you want to know if there’s some sort of myopathy (muscle disease) present, you would have to have a muscle biopsy done.”
Recommended treatment for a cat that is diagnosed with hyperesthesia syndrome is likely to include a behavioral component aimed toward reducing any anxiety that the animal might be experiencing. Regularly scheduled feeding times and play periods, for example, may help keep an insecure cat relaxed and well exercised. And any type of physical activity that may irritate or overstimulate the cat—such as scratching its back—must certainly be avoided. For some patients, a veterinarian may prescribe a serotonin-enhancing drug—amitryptyline or fluoxetine, for example—to stabilize a cat’s mood; an anti-seizure drug, such as phenobarbital; an anti-inflammatory medication, such as prednisolone; or a combination of drugs. Gabapentin, a drug with both analgesic and anti-seizure properties, is a recent addition to the arsenal of drugs potentially useful for treating hyperesthesia syndrome.
Overall, says Dr. de Lahunta, “Hyperesthesia is a relatively mild condition. I’m not aware that a cat has ever died from it. Once it has established itself, it doesn’t progress very much, and the prognosis is pretty good as long as the scratching doesn’t result in a serious infection.”