Feline Hyperesthesia Syndrome (FHS) isn’t a single disease but rather a set of symptoms that indicate a skin, neurologic or behavioral problem. Hyperesthesia is the opposite of anesthesia – instead of lack of sensation, a cat with hyperesthesia appears to have too much sensation from the skin or muscles under the skin. Like tickling, it starts out a bit pleasant but rapidly becomes painful or distressing to the cat.
The classic symptoms of FHS are episodes of skin twitching or rolling that can escalate into excessive grooming and chewing at themselves. The cat will usually appear distressed, with dilated pupils or staring into space. Episodes may last a few seconds or several minutes.
Some affected cats seem to be painful when petted, especially along the lower back. Cats with milder disease may lick or bite themselves. This often leads to shortened hair or baldness where they are licking themselves excessively. Some cats will attack their tails or their lower back. Others will lick or chew at their paws. With severe symptoms they may cry or run screaming through the house, and they may mutilate their tails. FHS can even cause seizures to occur if a cat is petted or touched in a certain way.
Cats who are normally calm may become aggressive to humans while having a hyperesthesia episode, or aggressive cats can become more calm. Episodes most commonly occur in the morning or evening, the dawn and dusk times when a cat in the wild would be actively out hunting.
Diseases that cause itching can trigger hyperesthesia. Allergy to pollen, food, fleas or mites are possibilities. Cats with skin allergies are treated with steroids, usually prednisolone, and any parasites the cat is reacting to should be eliminated. Cats with food allergy may need a special diet. Ringworm, which is not a worm at all but a fungal disease of the skin, can also be a cause. To diagnose these diseases we will usually do skin scrapings to look for mites, fungal culture to test for ringworm, and apply Revolution ointment to kill fleas, Cheyletiella mites and Sarcoptic mites. If Demodex mites are found on the skin scraping your cat will need lime-sulfur dips. Allergic cats usually respond quickly to steroid treatment, so giving this medication often dramatically relieves symptoms. Antihistamines such as doxepin may be helpful as well.
If testing and treatment for skin diseases doesn’t fix the problem we will then want to rule out a neurological problem. This would be a problem affecting the spinal cord or the nerves to the back or tail. Spinal x-rays, referral to a neurologist and possibly a CT or MRI scan may be needed. Cats with neurological disease may have other symptoms besides FHS – weakness or unsteady gait, pain in the neck, legs or back, or difficulty with jumping or stairs. They may improve with pain medication. In some cats the symptoms seem almost like seizures, so anti-seizure medication, usually Phenobarbital, may be used to treat them. Gabapentin, which decreases neurological pain, may be effective for some cats. We would start with a higher dose and once it is working we would decrease the dose gradually over 4-6 months to find the lowest effective dose. Both Phenobarbital and gabapentin can take several weeks to start working so it’s a slow process to figure out what works best for a particular cat.
When we can’t find a dermatological or neurological problem to explain the symptoms we are seeing we then assume the problem is a compulsive disorder. It is thought that compulsive disorders arise because of a lack of the neurotransmitter serotonin. Medications called selective serotonin reuptake inhibitors (SSRI) can be used to increase the amount of serotonin in the brain and reduce the symptoms. Prozac (fluoxetine) is an SSRI that often works well for cats. It is available as a chewable tablet for dogs which can be crushed into canned food or broth for cats. Other medications that may be effective include clonazepam, sertraline, paroxetine and citalopram. (None of these drugs is FDA approved for use in cats. Blood tests for liver and kidney function should be done to ensure these medications are being tolerated by the cat. Side effects can occur as well.) It takes trial and error to find the drug that works best for the individual cat.
Stress and conflict, such as aggression between two cats in a household, often worsen symptoms of hyperesthesia, especially when it has a behavioral cause. To reduce stress:
• Food and feeding times should be predictable – changes in diet and schedule can be very stressful to cats
• Regular play sessions, especially with target-type toys the cat can chase or bite are especially helpful
• Provide tall hiding and perching places – cats feel safer when they are higher up
• Provide plenty of litter pans and food bowls in multiple-cat households, so a timid cat doesn’t have to worry about being picked on by a more aggressive one when trying to eat or eliminate
• Anticipate stressful situations and try to avoid them and redirect behavior with training or playing
When hyperesthesia is caused by skin or neurological disease it will start when the underlying disease occurs. When symptoms are behavioral, they often begin around the age of one to four years. Any breed of cat can be affected but Siamese, Burmese, Himalayan and Abyssinian cats are most commonly affected, so some breeds are genetically predisposed to FHS. Symptoms can be triggered by a painful event (such as declawing or an abscess) or the above-mentioned skin or nerve problems.