Feline Hyperesthesia (FHS)

Ever since the earliest days of human-cat interactions, cats have had a reputation for being mystical, spiritual beings, either divine or possessed. It isn’t hard to understand why. Cats have the propensity to gaze unblinking in people’s eyes, to appear to see things that aren’t there, to run crazily around for no apparent reason, and to go from quiet to ferocious in a moment.

Some of these attributes, in an extreme form, are components of the syndrome known as feline hyperesthesia. Cats affected by this syndrome show the most bizarre character changes, sometimes appearing to hallucinate, act manic, schizophrenic, or even “possessed.”

Clinical Signs of Feline Hyperesthesia Syndrome (FHS)

• Sudden bouts of bizarre hyperactive or aggressive behavior
• Frenetic self-directed grooming, directed along the flank or tail (possibly leading to hair loss)
• Tail swishing, fixation with tail, tail chasing, or vicious attacks directed toward the tail
• Large pupils/strange look to the eyes
• Skin rippling/rolling (this disorder is sometimes referred to as “Rolling Skin Disease”)
• Apparent hallucinations – seemingly following the movement of things that are not there or running away from some unseen adversary
• Vocalization, crying, loud meowing
• Exquisite sensitivity to touch (“hyperesthesia”) along the spine – stroking can precipitate a bout of the behavior
• Sudden mood swings – e.g. from extremely affectionate to aggressive
• Any or all of the above signs progressing to seizures (falling over, leg paddling, salivating)
• Bouts occurring almost constantly, all day, every day, or once every few days

Possible Causes

FHS tends to arise for the first time in mature cats. No one really knows what causes FHS, but there are a few possibilities:

• Because some cats display grand mal seizures during or following a bout of FHS, it is possible that the condition arises as a result of aberrant electrical activity in areas of the brain that control emotions, grooming, and/or predatory behavior (i.e. there may be partial seizure activity). In support of this explanation, some affected cats respond to anticonvulsant (anti-epileptic) therapy.
• FHS could be a form of feline obsessive-compulsive disorder (OCD) in which the obsession relates to grooming, and/or aggression, plus concerns for personal safety. The apparently compulsive nature of self-directed grooming and a positive response to anti-obsessional medication supports this etiology.
• Seizure activity leading to obsessive-compulsive manifestations (almost half of human bulimics have abnormal brain waves). This hypothesis provides a way of unifying the seemingly disparate etiologies described above.
• An inherited tendency for mania precipitated by stress. Certain breeds are more susceptible to FHS and its expression does seem to be stress-linked.
• Some affected cats have been reported to have pathological lesions in the muscles along their spine. It is assumed that the lesions may cause local irritation, altered sensitivity, and/or pain.

Diagnosis

There is no definitive “rule in” test that confirms FHS. If the clinical picture fits the description above, the diagnosis is confirmed by exclusion of possible medical causes and by a positive response to treatment for FHS. To this end, your veterinarian should obtain a careful behavioral history regarding your cat, perform a thorough physical examination, and take a blood sample for complete blood count, chemistry profile, and thyroid hormone level (T4). Medical conditions that may be confused with FHS include hyperthyroidism (thyroid gland overactivity), brain infections, brain trauma, brain tumors, some poisonings (e.g. lead, strychnine), heavy parasitic infestations of the skin, nutritional deficits (e.g. thiamine), and severe allergy.

Treatment

Optimize the affected cat’s environment to minimize stress (stress could be – probably is – a factor in every expression of the syndrome). Recommendations include:

• Provide daily aerobic exercise for the cat by playing with the cat using a feather wand toy or toys dragged along on a string.
• Feed the cat frequently and on a regular schedule to minimize stress over food.
• Train the cat to perform one new trick each month (come for food, sit for food, jump up, jump down). Click and treat training is the best way to accomplish this goal.
• Consider getting a friendly companion cat for your cat. You should probably arrange a “trial marriage” first.
• Address any infighting between existing cats in the home.
• Arrange predatory play activities to allow the cat to “blow off steam” and dissipate any unvented prey drive. The feather wand type of toys mentioned above are appropriate for this purpose as are “laser mice” toys, ping-pong balls kicked or dragged around, Cat Dancer toys, and so on.
• Make life interesting for your cat: spend more quality time with them and make the environment more “cat friendly.” Provide a three dimensional environment by adding cat perches strategically placed so that they can sit up on high and have a good view of the world. Buy a fish tank or get some birds in a cage, but make sure the little ones are always safe and secure. Get a window bird feeder. Provide an assortment of cat toys – moving interactive toys are best. Catnip mice appeal to some cats.

Anti-Obsessional/Antidepressant Therapy

Drugs that help are potent serotonin-enhancing medications. In the brain, the neuromodulator, serotonin, stabilizes mood and has anti-obsessional and anti-aggressive effects. Drugs that have been found effective include clomipramine (Clomicalm®) and fluoxetine (Prozac®) though, theoretically, any potent serotonin-enhancing drug, including paroxetine (Paxil®), sertraline (Zoloft®), and fluvoxamine (Luvox®) should all work. These drugs take a while to become effective. Typically nothing much is seen for the first three weeks. Then, by four weeks, owners might notice a 50% reduction in the incidence and severity of bouts of FHS. Typically, the improvement may reach 75% at eight weeks, 85% at 12 weeks, and 95% by sixteen weeks. Complete cure is rare and most cats need to remain on medication long term to suppress the FHS behavior. This need not be a problem since the doses employed are small, therefore inexpensive, and medical complications of treatment are rare. Nevertheless, it makes sense to have treated cats checked by the veterinarian, including appropriate bloodwork, at least once per year.

Anti-Convulsant Therapy

When anti-obsessional therapy is ineffective or only marginally effective, anti-convulsants can be tried. The drug of first choice is usually phenobarbital. Phenobarbital takes three weeks to peak, after which a “trough” blood sample (one taken when the level is expected to be lowest) should be taken to measure the phenobarbital level in plasma. If the level is appropriate for control of seizures, and yet no improvement has occurred, alternative measures will have to be employed. It is possible to combine phenobarbital treatment with anti-obsessional therapy, if necessary.

Conclusion

With appropriate environmental and pharmacologic treatment, affected cats can often be rehabilitated and can lead a normal life. On treatment, most appear much happier than they were previously while suffering the full brunt of their affliction.