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Feline audiogenic reflex seizures
Introduction
- Cause: suspected neuro-degenerative condition of geriatric cats.
- Signs: noise-induced myoclonic or generalized tonic-clonic seizures, hearing loss, decreased cognitive function, weight loss.
- Diagnosis: no definitive test, observation (potentially via video) of noise induced myoclonic seizures.
- Treatment: avoid sound trigger, oral levetiracetam.
- Prognosis: slowly progressive condition over a median time of 2-3 years, poor prognosis.
Presenting signs
- Seizures Seizures in response to noise (often high-pitch noises):
- Myoclonic seizures - an involuntary jerk of the legs and/or body that can be likened in appearance to a brief electric shock. This sign is a pre-requisite for a diagnosis of feline audiogenic reflex seizures (FARS).
- Generalized tonic-clonic.
- Absence seizures (or 'petit mal') - a temporary loss of awareness, staring vacantly into space and being unresponsive.
- Hearing loss or deafness Deafness: acquired.
- Decreased cognition.
- Weight loss.
- Incoordination/weakness.
- Inability to jump.
Geographic incidence
- Worldwide.
Age predisposition
- Clinical signs exclusively appear in the second decade of life (median age 15 years).
Breed/Species predisposition
- Any breed of cat.
- Approximately one third of affected cats are Birmans Birman suggesting a predisposition in this breed (notably in blue and seal points only).
Special risks
- Consideration should be given to concurrent disease in cats undergoing investigation under sedation or anesthesia due to the high prevalence of concurrent diseases in older cats.
Pathogenesis
Etiology
- Unknown.
- Audiogenic seizures in mice have been found to be associated with deafness as a result of a mutation in GIPC3. This mutation has not been found in cats with audiogenic seizures.
Pathophysiology
- Many of the sounds causing these seizures are relatively innocuous to us (ie they are quiet, high-pitched sounds).
- Suggested that the reason they may cause seizures is that cats have an ultrasonic hearing range, allowing them to catch mice that communicate with each other in this ultrasonic frequency range.
- These domestic noises that precipitate seizures have a high component of ultrasonic frequencies and so this may be a reason for the exaggerated response in these cats.
Timecourse
- Signs usually develop in cats over 10 years old and slowly progress.
- First observable signs are infrequent myoclonic (twitches) seizures which can progress to generalized tonic-clonic seizures and disorientation with time.
- Volume of the sound is proportional to the severity of the seizures.
- A persistent sound can cause repeated jerks (myoclonic seizures) of the body that may culminate in a full generalized tonic-clonic seizure - this phenomenon is known as audiogenic kindling in which lots of small sound stimuli culminate to produce a larger response, in this case a generalized tonic-clonic seizure.
- Repetitive sound-induced seizures (audiogenic kindling) gradually induce the transference of epileptic activity from brainstem (or myoclonic seizures) to forebrain structures (generalized tonic-clonic seizures) along with behavioral changes in these cats.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Lowrie M, Thomson S, Bessant C et al (2015) Levetiracetam in the management of feline audiogenic seizures: a randomized, controlled, open-label study. J Fel Med Surg 19 (2), 200-206 PubMed.
- Lowrie M, Bessant C, Harvey R J et al (2015) Audiogenic reflex seizures in cats. J Fel Med Surg 18 (4), 328-336 PubMed.
- Charizopoulou N, Lelli A, Schraders M et al (2011) Gipc3 mutations associated with audiogenic seizures and sensorineural hearing loss in mouse and human. Nat Commun 2, 201 PubMed.
Other sources of information
- Lowrie M (2015) 'Tom and Jerry' Syndrome. Veterinary Times May 18 2015, 21-22.