Feline Hyperesthesia Syndrome (FHS) – Frequently Asked Questions

What is Feline Hyperesthesia Syndrome (FHS)?

Feline Hyperesthesia Syndrome (FHS), also known as “rolling skin syndrome” or “twitchy cat disease,” is a poorly understood condition characterised by behaviour suggesting heightened sensitivity, especially along the spine. Tail mutilation is also often included under the FHS umbrella although should probably be considered a separate entity and management. With this condition the cat can seriously injure their tail.

Signs of FHS can be extremely distressing. Diagnosis can be challenging especially as “rolling skin” is a normal feline response to itch or emotional irritants i.e. may be observed when a cat has a skin condition or parasites or when a cat is frustrated for example by the presence or smell of another cat. It is also normal for cats to react (negatively) to their lower back being touched especially in stressful environments such as the veterinary clinic - in other words it can sometimes be challenging to confirm spinal pain in a cat (see here for “touch zones” in cats).

FHS is considered a diagnosis of exclusion, meaning that other possible causes of similar clinical signs, such as skin or spinal conditions, should be ruled out. However, skin disease alone will not trigger a severe self-injury to the tail, and this requires urgent management / treatment.

What are the signs of FHS?

Common signs of FHS include:

Lumbar Hyperesthesia: Heightened sensitivity along the lower back, causing the skin to ripple.

Vocalization and Aggression: Vocal outbursts, attacking, or over-grooming behaviours, especially directed at the tail.

Self-Mutilation: Cats may bite, chew, lick, or pluck their hair on the tail or tail base and in extreme cases mutilate the tail.

Personality Changes: Cats displaying signs FHS are often highly aroused, appearing anxious, restless, aggressive, or hypersensitive to touch around the tail and spine.

FHS is reputed to occur more commonly in Siamese, Burmese, Himalayan, and Abyssinian breeds, with clinical signs generally appearing between 1-4 years of age.

For a video of FHS see here.

What causes FHS?

The exact cause of FHS remains unknown, but it appears linked to both physical dysfunction and influence by emotional responses and environmental sensory triggers (for example smells, temperature, wind). The hallmark of FHS is the contraction of the panniculus carnosus (cutaneous trunci) muscle, which is muscle connected to the skin and fascia. This muscle's primary function is to shake off external irritants, leading to the characteristic “rolling” or “twitching” of the skin. However, emotional triggers, like anxiety or frustration, can also lead to similar responses, suggesting a possible link between FHS clinical signs and heightened emotional arousal.

Is FHS a seizure disorder?

Although some cats with signs of FHS will respond positively to medications classified as anti-epileptic drugs, FHS is not considered a seizure disorder or epilepsy by most veterinary surgeons although this remains a popular theory on social media sites.

FHS is unlikely to be a seizure disorder because the cats are fully aware during long lasting episodes and the behaviour is complex and often context related. In true limbic encephalitis there are characteristic autonomic signs (e.g. salivation), with orofacial twitches or behavioural changes suggesting “limbic” dysfunction. One of the reasons why some have suggested that FHS is a seizure disorder is a single case report reporting electroencephalogram (EEG) changes in two affected cats. However, the EEG changes reported could have other explanations and EEG changes do not prove an epilepsy. A response to anti-epilepsy drugs does also not prove an epilepsy as these drugs are non-specific.

For more information on Limbic encephalitis see here

Is FHS a movement disorder?

Movement disorders are a large and eclectic collection of disorders characterised by abnormal, involuntary, or excessive movements (or result in a lack of voluntary movement). There is a suggestion that the movements seen in FHS may be a myoclonus (spontaneous contraction of a group of muscle) or like human restless limb syndrome (a neurological sensory-motor disorder characterized by an uncontrollable urge to move the legs, often accompanied by uncomfortable or unpleasant sensations). This may explain why some cats may appear to sit on tails to stop them moving and appear to get relief from this. This is an alternative explanation to the presence of EEG changes and response to Levetiracetam. Levetiracetam is an anti-epileptic drug which is particularly useful for treating myoclonus.

Is FHS a nociplastic pain disorder?

A nociplastic pain disorder refers to a type of chronic or maladaptive pain that arises from altered pain processing in the nervous system, without clear evidence of tissue damage, inflammation, or nerve injury to explain the intensity or persistence of the pain

There is a strong argument that FHS is a maladaptive pain disorder because the behavioural signs especially tail mutilation could be explained by the cats experiencing abnormal sensations and the most common medications used to (successfully) treat FHS are gabapentinoid drugs such as pregabalin and gabapentin. Although classed as anti-epilepsy drugs these drugs are rarely if ever used for that purpose (in any species) and in cats gabapentinoid drugs are primarily used for their anti-anxiety or pain-relieving effects both of which are thought to help reduce clinical signs of FHS.

More information about neuropathic pain and the drugs used to treat it can be found here (YouTube) and here (scientific paper).

Is FHS an emotional health disorder?

The link between emotional health and pain is complex – poor emotional health can predispose neuropathic and nociplastic pain disorders and chronic pain can cause poor emotional health. There is strong anecdotal evidence that signs of FHS in a predisposed cat can be triggered by environmental factors (compare to humans predisposed to migraines that can be tiggered by certain foods, bright or flickering lights, loud noises, strong odours like perfumes, cleaning products and smoke). Therefore, to optimise management of an FHS cat it is worth exploring these with a veterinary profession that specialises in feline emotional health. Cats with FHS can also be aggressive to their co-habiting humans and other animals and it can be helpful to seek advice on how to manage this.

Is FHS triggered by an infection?

There have been some anecdotal reports of FHS after successful management of feline infectious peritonitis infection with GS-441524: or Remdesivir. There have also been some cases of FHS where the signs have occurred per acutely prompting suggestion of infection. This is an active area of research.

How is FHS diagnosed?

Diagnosing FHS requires ruling out other possible conditions, such as skin diseases or spinal pain, and understanding potential environmental triggers. A systematic diagnostic workup typically includes:

Ectoparasite Control: To ensure clinical signs are not due or compounded by parasitic irritation.

Skin Scrapes and Cytology: To rule out pruritic skin diseases.

Food Trials: A restricted diet trial for 6-8 weeks may reveal allergic responses contributing to clinical signs (for example a hypoallergenic diet or a diet that is exclusively a novel protein and carbohydrate)

Environmental Assessment: Identifying triggers in the home

Some dismiss the necessity of a systematic approach however even cases with true FHS signs will be exacerbated by skin disease and environmental triggers and unless these are identified then successful management may not be possible or the cat may be prescribed medication which is both inappropriate and has potential adverse effects. However, cats with severe self-injury to tails should be started on medication whilst looking for potential triggers.

What is a cat-friendly environment

Managing FHS often begins by addressing the cat’s environmental needs, based on the five “pillars” of a cat-friendly environment. See here for more information on how and why

Safe places to hide.
- Many cats like an elevated resting place; some prefer ground level. Each cat needs access to a safe space that is out of sight of other cats and from which they can monitor their environment
Multiple and separate key environmental resources: water, food, litter box, scratching areas.

- - Remember that although cats may eat together, food is an essential resource, the desire to eat may override other emotions however many cats may be anxious about eating in the presence of other cats.
  - Cats prefer to drink water that distant from the food source – this is because they are carnivores and have evolved a behavioural adaption to avoid water sources that may be contaminated by meat
  - One litter tray per cat and one spare – these should be separate rooms not as one giant litter tray area.
  - Having separate resources is very important in multi-cat households. Cats may successfully share a space but remain their own social unit – in this instance they
    - Do not sleep together with bodies touching (being on the same piece of furniture does not count as sleeping together)
    - Do not groom each other
    - Cats that are one social unit do sleep with bodies touching and groom each other

Opportunities for play including predatory play that mimics natural hunting behaviour. For more information on how to play with your cat see here.
Positive and predictable human social interactions. For more information see here. Remember the CAT acronym

- C – Did I give the cat a CHOICE about whether it wanted to interact with me?
- A – Am I paying ATTENTION and looking out for any subtle signs that the cat is uncomfortable
- T – Where am I TOUCHING the cat and does the cat want me to keep touching?

Smell – we all have personal preferences for our home environment to look and sound a certain way but for cat it is even more important for it to smell a certain way. We can help an environment smell more like a secure home by using pheromone sprays and we also must pay attention to possible negative smells such as the smell of other cats and strong smells including perfumes, cleaning products, smoke and foods.

What is the prognosis for cats with FHS?

The prognosis for FHS can be fair if a thorough diagnostic and treatment approach is taken. Identifying and addressing all underlying triggers, maintaining a stable environment, and carefully selecting medications can help improve the cat’s quality of life.

How is FHS treated?

More information on the drugs used to treat FHS can be found here.

A treatment algorithm for FHS is here. Within the algorithm are links to YouTube videos with more information on the drugs.