Visiting Veterinarian : FHS explained
You may have met a cat like Norman. A seemingly normal feline, he jumps up on the couch for attention. You pat his head, scratch behind his ears. He leans in, purring vociferously. "What a nice kitty," you think, moving your hand down his neck. But as you reach to touch his back, Norman's skin begins to ripple. His eyes dilate. Without warning he wheels around, fiercely sinks his teeth into your hand, then lets out an unearthly yowl and races off madly around the house.
People experiencing this phenomenon for the first time often think Norman has a back injury or that they hurt him in some way to elicit such a reaction. They may decide Norman has gone psycho or that he is just an evil kitty. Well, could be, but the more likely explanation is that Norman has an odd affliction known as feline hyperesthesia syndrome (FHS).
FHS goes by many other names: psychomotor epilepsy, neurodermatitis, pruritic dermatitis of Siamese, rippling, rolling, or twitchy skin disease. Affected cats exhibit a wide range of behaviors which may include rolling, crouching with hindquarters stuck up in the air, excessive licking, biting, or fur-pulling along the back and tail, rippling skin, muscle spasms, yowling, running, jumping, and possible hallucinations. Seen most commonly in cats between the ages of one and five, it can occur at any age and in any breed, although Siamese, Persians, Burmese, and Abyssinians have a higher incidence than your typical alley cat. There is not one specific cause, but it is thought to be a unique behavioral response to a variety of different factors.
The first possibility is that Norman has some kind of skin condition that makes his back highly sensitive to touch. Fleas, food or inhalant allergies, bacterial, fungal, or parasitic infections are all proposed causes. The second possibility is that Norman has a musculoskeletal problem causing back pain such as inflammatory diseases of the nerves or muscles, or intervertebral disk disease. The third possibility is that Norman has a brain lesion that is creating the bizarre behavior, such as a brain tumor, or an unusual form of epilepsy. All of these options can be pursued diagnostically by your veterinarian with a thorough physical and neurologic examination, followed by tests. Lots of tests. Blood work, fungal cultures, skin scrapings, radiographs, allergy tests, hypoallergenic food trials, MRIs, CAT scans, muscle biopsies. Maybe you'll opt to do all of these, or maybe just the most basic.
"My cat is freaking out," a client once called me, hysterical. "He's leaping around the house like a wild animal." The cat, Alfred, had been acting increasingly agitated over the last few days, she explained. Then, right before she called, kitty had come bounding in from the hall, jumped frantically onto the table, then catapulted himself to the top of the refrigerator, sending papers flying and dishes crashing. "He's acting like he's on fire, like he's afraid to touch the ground with his feet," she cried.
After I calmed the owner and made suggestions for how to safely corral the cat, she managed to get Alfred into the carrier and bring him in for an exam. It was a five-second diagnosis. "Do you have wall-to-wall carpet?" I inquired. The owner nodded, mystified. "Is Alfred the only animal in the house?" I continued. Nodding again, she added "My son's golden retriever used to live with us, but he took her back to college last month."