Feline Hyperaesthesia Syndrome

Introduction

The incidence of hyperaesthesia is not known, but it may be more common than once thought and could play a significant part in other behaviour 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. Historically 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. Analysis of specific incidents will show that play or grooming began to initiate bouts of hyperaesthesia, which then lead to aggression [often by the other cat].

The behaviour is highly bizarre but is often overlooked by the owner as a quirk of the cat’s personality. They may consider it to be playful or amusing, unless it becomes frequent or involves self-trauma. The fact that the cat suffers from hyperaesthesia may only come to light as a result of investigating some other behavioural problem. 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.

Diagnosis

Feline hyperaesthesia is relatively poorly understood and there are a number of medical differentials that should be excluded before a behavioural investigation.

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

Signs

Signs indicative of hyperaesthesia are very variable, but include:

• Skin or muscle twitching or rippling [commonly thoracolumbar or at the tail base].
• Sudden bouts of intense grooming, self-mutilation or attacks on rear quarters, feet or tail.
• Freezing, with tail swishing, and then sudden turning or darting movements.
• Ear twitching [often as if the cat is alert to a sound behind it].
• Sudden bouts of increased arousal, with the cat dashing about and jumping as if pursued or pursuing an invisible ‘opponent’.
• Bouts are often accompanied by vocalisation.

During these attacks, the cat’s behaviour is generally indicative of a state alarm and as if it is reacting to hallucinatory visual, auditory or tactile stimuli. The bouts may occur without any obvious 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.

When deciding on treatment it is important to examine situations in which the attacks are most likely to occur. Specific triggers should be identified, such as:

• Human contact

1. Stroking certain places [usually the back]
2. Grooming
3. Play

• Contact with other cats

1. Play
2. Allogrooming

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. 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 the cat along its back or in other areas that trigger an attack of hyperaesthesia.
• Avoid grooming.
• 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 cat does not become the victim of predatory 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 once an attack has started, 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.

Drug Therapy

Drug therapy is frequently beneficial for hyperaesthetic cats, which respond well to serotonin reuptake inhibitor drugs like Clomipramine [Clomicalm, Novartis] and the more serotonin selective drug Fluoxetine [Prozac]. These drugs are commonly used to treat compulsive disorders and do appear to provide considerable relief for hyperaesthetic cats. Onset of action is 4 or more weeks. The dose of Clomipramine may need to be increased from an initial dose rate of 0.25mg/kg once daily, to 0.5mg/kg once daily or greater if initial response is insufficient after 6-8 weeks. Higher doses are associated with increased adverse effects such as sedation and it is important that genuine response to therapy is not confused with undesirable profound 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 petit mal type 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. Response to normal touch should be diminished 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. Care must be taken if there is any risk that disinhibition may release aggressive behaviour during handling.

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 over at least 4 weeks. Recidivism during dose reduction indicates that drug therapy should be reintroduced at the lowest dose that produced complete relief from symptoms. Another attempt to wean the cat off medication may be attempted after a further month at this dose. In some cases medication will need to be permanent.

Once long-term drug therapy is producing 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.

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