Feline Hyperaesthesia Syndrome

Key Points
Feline Hyperaesthesia is an under-presented problem. Signs overlap with a number differentials. Aetiology and prevalence are not known. Treatment with SRI/SSRI drugs is often effective. Drug therapy must be supported with environmental enrichment.

Introduction

The prevalence of feline hyperaesthesia syndrome (FHS) is not known, but it is thought to be more common in oriental breed cats such as the Burmese. It may be more common than once thought and can play a significant part in other behavioural problems such as inter-cat aggression.

Age of onset varies, but if the condition starts in early adulthood, it can cause the breakdown of previously excellent relationships between cats sharing a household. Affected cats will begin to resent play or contact with conspecifics, becoming progressively more irritable and aloof from them. The cat may also begin to resent human contact and show aggression when stroked or handled during a bout of hyperaesthesia.

Owners may regard the cat's behaviour as bizarre, or even amusing, but rarely regard hyperaesthesia itself as a problem until it becomes really severe. A diagnosis is usually only considered when hyperaesthesia results in self trauma or behavioural problems. It is unknown whether hyperaesthesia occurs in discrete bouts or, in fact, produces an ongoing altered perception of touch contact. The fact that bouts maybe triggered by contact implies that touch sensation is persistently altered in some way.

Investigation

The aetiology of FHS is not known, and many of its signs overlap with other physical and behavioural health problems. Other causes should be excluded before reaching a diagnosis of FHS.

Clinical Signs

During bouts of FHS, the cat’s behaviour is generally indicative of a state of alarm and as if it is reacting to hallucinatory visual, auditory or tactile stimuli. The bouts may occur without an external trigger, in which case the first sign may be skin twitching. Bouts also occur during handling or stroking by the owner, or grooming and play by other cats.

Signs indicative of hyperaesthesia are variable, but include:

• Mydriasis
• Touch sensitivity
• Ear twitching (often as if the cat is alert to a sound behind it)
• Tail thrashing
• Skin or muscle twitching or rippling (commonly thoracolumbar or at the tail base)
• Vocalisation
• Bouts of intense grooming, self-mutilation or attacks on rear quarters, feet or tail
• Sudden bouts of increased arousal, with the cat dashing about and jumping as if pursued or pursuing an invisible ‘opponent’

Episodes vary in length, most often lasting a few minutes, and end spontaneously. There is often a progression in level of activity during a bout, beginning with mydriasis and ear twitching, to self-directed nipping/licking, and then into increasingly frantic darting around and self-directed pouncing. Prior to an episode, cats may become anxious and more attentive to their owners, suggesting that more subtle sensory or emotional changes precede an attack. Anecdotally, bouts are more common in the evening.

Specific triggers should be identified, so that a treatment and management plan can be designed. Triggers may include:

• Human contact

1. Stroking certain places (usually the back)
2. Grooming
3. Play

• Contact with other cats

1. Play
2. Allogrooming

Differentials

• Allergic skin disease (atopy, food allergy)
• Ectoparasites
• Epilepsy (petit mal type – limbic location)
• Local or referred pain (spinal lesion, intermittently luxating patella, etc)
• Hyperthyroidism
• CNS pathology

Treatment

The number and character of attacks should be recorded during the 7-14 days before treatment begins, to give a baseline of frequency and severity.

Environmental Enrichment

The cat’s environment should be improved in accordance with general recommendations, especially if social stress in a multi-cat household is thought to be an underlying factor. The aim should be to introduce activities that use up the cat’s time and energy budget and give it greater control over access to resources. For example, introduce activity feeding using toys that dispense portions of the cat’s daily food allowance as they are played with. Making these changes in multi-cat households will help to reduce overall competition and social stress, which can only be beneficial to all of the cats.

Avoidance of Triggers

Specific triggers of the behaviour should be identified and prevented, for example:

• Stop stroking or grooming the cat if this triggers bouts of hyperaesthesia or aggression.
• Redirect play between cats using fishing toys or laser pointers so that the hyperaesthetic cat is not pushed or pounced on during play.
• Keep other cats amused using activity feeders and play so that the hyperaesthetic is less likely to be the focus of play.

If the attacks usually require some kind of triggering event, these first steps may substantially reduce their frequency. These cats will also possess a number of conditioned associations between normal activities and the initiation of a hyperaesthetic attack. For example, the approach of a person or another cat may predict when a bout is likely to occur. This kind of negative association heightens stress and anxiety, which may in turn contribute to the worsening of the condition. Reducing factors that trigger hyperaesthetic attacks will therefore have direct and indirect effects on the frequency of attacks.

Redirection of Behaviour

It is sometimes possible to redirect the cat onto an alternative behaviour at the first onset of an attack of FHS, by calling the cat and engaging it in play or some other non-tactile distraction. A ‘recall’ type response can be easily conditioned by calling the cat before offering a food treat or playing a game. This strengthens the response during distraction. Distraction of this kind may be useful in cases that involve self mutilation.

Drug Therapy

Drug therapy is frequently beneficial for hyperaesthetic cats, which respond well to serotonin reuptake inhibitor (SRI) drugs like Clomipramine and the more selective serotonin reuptake inhibitor (SSRI) drug Fluoxetine. These drugs are commonly used to treat anxiety, compulsive disorders and neuropathic pain in humans, although the precise action in feline hyperaesthesia is not understood. Onset of action is 4 or more weeks. The dose of Clomipramine may need to be increased if the response is insufficient after 6-8 weeks. Higher doses are associated with increased adverse effects such as sedation and urinary retention. It is important that a genuine response to therapy is not confused with sedative effects which will suppress all sorts of behaviour, including the reaction to hyperaesthetic sensations. SRI drugs like Clomipramine reduce the threshold for seizures, which makes it particularly important to rule out epilepsy as a differential.

The effect of serotonergic drugs is to reduce the severity and frequency of the hyperaesthetic attacks, and it may become easier to distract the cat from the behaviour. Touch sensitivity should be reduced so that the cat may then be desensitised and counter-conditioned to the stimuli and events that previously triggered an attack, such as stroking and grooming.

Drug treatment should continue until there has been a period of at least 2 months without hyperaesthetic attacks and until the cat is able to tolerate normal tactile contact with people and conspecifics. The drug may then be phased out gradually. Recidivism during dose reduction indicates that drug therapy should be reintroduced. Further attempts to withdraw medication may be attempted but in some cases medication will need to be permanent.

Once long-term drug therapy has produced a stable improvement, there should be a regular 6-monthly case review to make sure that beneficial environmental changes remain in place and drug therapy is still effective. Otherwise there is a significant chance of relapse. If permanent therapy is required, then drug dose and type may need to be changed more than once during the cat’s lifetime in order to maintain effectiveness.

Summary of Treatments for Feline Hyperaesthesia Syndrome

• Record baseline rate and severity of hyperaesthetic attacks as a comparison for future reassessment.
• Provide an enriched environment.
• Identify and minimise exposure to events or stimuli that trigger hyperaesthetic attacks.
• Consider use of an SRI (Clomipramine) or SSRI (Fluoxetine) drug.
• Desensitise and counter-condition responses to approach, touch, grooming and other activities that may be associated with hyperaesthetic attacks.

Prognosis

The prognosis is best if the cat is treated thoroughly early in the course of the condition. The use of medication, environmental enrichment and other treatments should all be introduced as soon as a diagnosis is reached. There is usually some progression unless environmental and social underlying factors can be addressed successfully. Clients must be made aware that behavioural and/or drug treatment will need to be continued throughout the cat’s life.

The creation of this content was made possible by Ceva Santé Animale as part of the feline behaviour project.

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