Feline audiogenic reflex seizures (FARS)

Feline audiogenic reflex seizures (or FARS, also known as ‘Tom and Jerry syndrome’) is a recently discovered and important type of epilepsy in cats. It appears to be more common in older cats and Birmans, and is triggered by various high-pitched noises.

Discovering FARS

International Cat Care had received a number of enquiries about cats having seizures, seemingly in response to certain high-pitched sounds. The charity sought help from veterinary neurologists at Davies Veterinary Specialists (UK) in looking into the problem. After looking into the cases, the team found this was a new, previously undescribed problem in cats.

The team, working with International Cat Care, were able to identify hundreds of owners across the globe with cats affected by the condition, and were able to collect detailed information about many of these cats.

The team has now been able to publish a scientific study describing the condition, which is now a recognised and distinct syndrome in cats. This scientific paper was published in International Cat Care’s veterinary journal (the Journal of Feline Medicine and Surgery) and is freely available to read by clicking this link: click here

Naming FARS

The name given to this syndrome is feline audiogenic reflex seizures (FARS); with ‘reflex’ referring to the fact that the seizures are brought on by a stimulus, and ‘audiogenic’ referring to the fact that this stimulus is a sound. However it has also been dubbed ‘Tom and Jerry syndrome’ after the cartoon character Tom who has a strong startle reflex and often reacts with involuntary jerks to sounds (see below for more information about myoclonic seizures).

Causes

How the condition develops in a cat is unclear, although it is seen more commonly in older cats and in certain breeds (Birmans) suggesting there may be an inherited component. The FARS study found that cats typically developed the syndrome at around 15 years of age. Around half the cats in the FARS study were also found to be deaf (or at least partially deaf). Losing the sense of hearing can be part of getting older, and it is usually the ability to hear lower pitched sounds that is lost first, and this might partially explain why high-pitched sounds may be more startling to them.

Triggers

The sounds that trigger seizures vary between individual cats, and a huge variety of different sounds were identified as triggers. Some of the more common trigger noises included:

  • crinkling tin foil
  • a metal spoon clanging in a ceramic feeding bowl
  • chinking or tapping of glass
  • crinkling of paper or plastic bags
  • tapping on a computer keyboard or clicking of a mouse
  • clinking of coins or keys
  • hammering of a nail
  • clicking of an owner’s tongue

Types of seizures

There are three types of seizure associated with FARS:

  • generalised tonic-clonic seizures
  • myoclonic seizures and
  • absence seizures.

Generalised tonic-clonic seizures

A generalised tonic–clonic seizure is what most people regard as a ‘classic’ seizure. The cat will lose awareness, fall to the ground and exhibit shaking/paddling of the legs, chomping and chewing, foaming at the mouth, and will sometimes pass urine or stools. The seizure usually last no more than a few minutes but the cat may be very disorientated afterwards.

Myoclonic seizures

Myoclonic seizures are seizures often only last for a fraction of a second, and many cats will appear to remain conscious throughout. The seizure is characterised by brief involuntary muscle jerks or spasms, and this was the type of seizure seen in almost 95% of the FARS cats studied.

Absence seizures

The third type of seizure is called an absence seizure (sometimes called a petit mal seizure). With this seizure, cats may simply lose awareness of their surroundings for up to 20 seconds or so. The may stare vacantly into space and not respond. Absence seizures were only occasionally seen in the FARS study, but they can also be difficult to spot at times.

Treatment

Phenobarbitone is the drug most commonly used to treat different forms of epilepsy in cats. While it may help some cats with FARS, the team investigating this condition found another drug – levetiracetam – appeared to be more helpful. Levetiracetam reduced the number of myoclonic seizures in cats by at least half and improved the cat’s quality of life while also having fewer side effects than phenobarbitone.

While levetiracetam has been shown to reduce myoclonic seizures, the team’s next step is to investigate whether it can also prevent generalised tonic-clonic seizures in affected cats.

Your vet may tell you that levetiracetam is not licensed for use in cats. Many medicines are not licensed for cats because it costs such a great deal of money (millions) and this drug would not have been considered for use in cats. As long as the vet explains this to you and relies on good evidence (as in Mark's published scientific papers), then the drug can be used. Vets have to use what is called the 'drug cascade' where, if there is a medication which is appropriate for the species, then it must be used. If there are no treatments available in the cascade, then drugs made for other species can be used. This is common in cats as there are fewer drugs licensed for use in cats.