Audiogenic reflex seizures

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Feline audiogenic reflex seizures (FARS) are characterized by generalised tonic–clonic seizures, myoclonic seizures and absence seizures.

There appears to be no sex bias, although cats exclusively suffer from FARS later in life within their second decade. The sounds responsible are high-pitched sounds, often relatively quiet sounds, with increasing loudness and persistence of a sound only serving to enhance the severity of epileptic seizures. Myoclonic jerks or seizures with or without impairment of consciousness appear as one of the cardinal signs of FARS, frequently occurring prior to a GTCS in this population[1].

FARS occurs in both pedigree and non-pedigree cats, with Birmans over-represented.

A pattern of audiogenic kindling has been observed in rats, with myoclonic seizures initiated following numerous exposures to sounds, leading to spread of neuronal discharges from teh brainstem to forebrain structures (e.g. caudal colliculus, hippocampus, amygdala and neocrotex)[2]. It is thought that this pattern may occur in cats.

Clinically affected cats usually present with the cat falling to one side with the legs stretched out and the head back. Vocalisation, head twitching, spontaneous urination and ptyalism may also be observed. The seizures often progress to clonic seizures, characterized by rhythmic movements of limbs and chomping of jaw. Absent seizures may occur, characterized by sudden and temporary loss of consciousness with no motor activity.

One-third of the population was diagnosed with concurrent diseases; however, this most likely reflected the age of the population rather than a causal relationship. This rationale is made on the basis of the static or improving nature of the epilepsy in the cats with concurrent medical conditions. However, 50% of the population were reported to have hearing impairment or were deaf.

Traditional treatment involves use of drugs such as phenobarbital or diazepam, with the former more suitable.

Therapeutic trials with levetiracetam suggest this may be more suitable than phenobarbital to control myoclonic seizures and GTCSs associated with this condition[3].

The recommended dose for levetiracetam for treatment of FARS in cats is 20 - 25 mg/kg every 48 hrs.

Although seizures remained relatively non-progressive, other signs developed that were slowly progressive exclusively in cats suffering this epilepsy syndrome for >2 years.


References

  1. Lowrie M et al (2016) Audiogenic reflex seizures in cats. J Feline Med Surg 18(4):328-336
  2. Kesner, RP (1966) Subcortical mechanisms of audiogenic seizures. Exp Neurol 15:192-205
  3. Lowrie, M et al (2017) Levetiracetam in the management of feline audiogenic reflex seizures: a randomised, controlled, open-label study. JFMS 19(2): 200-206