Seizures in Cats
Seizures in cats are less frequent and more often due to organic disease of the brain than in dogs, i.e., idiopathic epilepsy is much less common in cats than in dogs as a cause for seizures. The most common type of seizure seen in cats is a complex partial seizure, not a generalized grand mal type as is typical for dogs.
Generalized motor seizures in cats are infrequently seen but tend to be more violent than in dogs. They are non-localizing , generally last from 30 sec to 120 sec. They may throw themselves around a room, develop contusions, bite their tongue and rip off their claws during a violent grand mal convulsion. Severe piloerection is common. Varying periods of post-ictal activity (from hyperactive to sleepy) occur in cats as in dogs and can last from minutes to hours.
Mild generalized motor seizures (non-convulsive) are characterized by decreased awareness, bilaterally symmetrical mild motor activity without recumbency, and have a duration of a few seconds. They may stop activity and sit motionless for a few seconds. Pupillary dilitation, and bilateral facial twitching are common. They may shake their head, joints or body. Partial seizures are more common in cats and have lateralizing signs preceeding or during the ictus. They may be simple or complex.
Partial simple seizures are characterized by normal mentation but lateralized motor activity of a part of the body or the whole body. Partial complex seizures, however, have altered consciousness plus lateralizing signs with or without stereotypical behavioral or motor activities. Cats may exhibit a glazed look and be poorly responsive to commands. Motor signs are associated with unilateral facial twitching which may involve one ear, one eyelid or the whiskers, turning of the head to the side, or movements of the fore or rear limbs on the same side of the body. Owners may feel the cat is hallucinating because they hiss, growl, lick or smack their lips and attack imaginary or real objects, startle for no obvious reason, and run frantically. They may blindly collide with objects. Compulsive behaviors such as circling, self-chewing, and biting are also occasionally seen. They are differentiated from obsessive-compulsive disorders by the coexisting motor activity or progression of signs to a generalized convulsion.
Status epilepticus occurs in cats but is more often non-generalized partial or mild generalized (non-convulsive) in type and may not be recognized as status epilepticus by owners or veterinarians.
Idiopathic epilepsy is rare in cats compared to organic causes for seizures. Inflammatory infectious causes in cats include: Toxoplasmosis, FIP, FeLV, crypttococcosis, and presumed viral meningoencephalitis. However, if seizures occur and the cat has a normal physical and neurological exam, only FIP or viral meningoencephalitis should still be on your differential list. The most common proposed cause for seizures in a large series of cases was meningoencephalitis of unknown origin (47%). The cause was presumed to be an unidentified virus. Cats generally had a good prognosis with therapy. The second most common cause was feline cerebral infarction (substantiated on MRI). These cats did not have the typical severe, peracute lateralized cerebral cortical dysfunction as was originally reported for this disease. Most of these cats also responded well, in general, to phenobarbital therapy.
The diagnostic approach involves a thorough history and physical exam (including a neurological evaluation). In addition, a CBC, chemistry profile (usually normal), fundic exam, CSF and advanced imaging (CT or MRI) may be indicated. CSF findings for cats with ischemic encephalopathy tend to have mild increases in protein <200 mg/dl) and total WBC of <10, with an increased percent of lymphocytes. Cats with CNS FIP have total protein concentrations of > 200 mg/dl, and total WBC of >100 (primarily neutrophils). They also generally have multifocal neurological abnormalities. In suspected viral disease (non-FIP), the total protein in CSF was < 100 mg/dl and total WBC <50. Cats tended to be less than 4 years old and had focal neurological signs.
Therapeutic approaches to cats involves trying to identify a cause and treat it specifically, if possible. While a diagnosis is being established therapy may be instituted to decrease the severity, frequency and number of seizures. Generally, therapy is indicated for cats that seizure more than once every 6 to 8 weeks, those that cluster seizure, or cats that have a single episode of status epilepticus.
Phenobarbital is the drug of choice for chronic therapy of feline epilepsy. Serum trough levels optimally should be between 23 and 30 ìg/ml. Sedation and ataxia are common when serum levels exceed 32 ìg/ml. Generally cats are administered 3 to 5 mg/kg/day in divided dosages (BID). Others recommend a starting dosage of 7.5 mg BID. Serum trough levels are measured at 10 to 14 days and dosages adjusted accordingly. Some cats require 15 mg BID to attain therapeutic concentrations. Sedation and ataxia are common during the initial phase of therapy. Cats generally adapt after a week or two to the medication. Polyphagia and weight gain are common, as is seen in dogs on phenobarbital. No hepatotoxicity has been documented, but no long-term studies are available. Isolated observations of possible adverse reactions include facial pruritis, thrombocytopenia and neutropenia with swelling of the feet.
Diazepam is a second choice drug for long-term control of cats with seizure disorders. Starting dosages of 0.5 to 1 mg/kg divided BID or TID are used. Gradually work up to these dosages to reduce the sedation associated with initial administration of diazepam. Acute hepatic necrosis associated with an idiosyncratic toxicity to diazepam has been reported in cats. It is generally fatal. If any pre-existing liver disease is present this drug should not be given. In addition, it is recommended to obtain a biochemical profile within 5 days of initiating therapy to monitor for elevated hepatic enzymes. If an increase from pre-treatment values is seen, diazepam should be stopped immediately.
Status epilepticus in cats is treated initially with intravenous diazepam at 0.5 to 1 mg. You must stop generalized motor activity in grand mal convulsions and stop or 18 significantly decrease abnormal neurological activity in cats with non-convulsive status epilepticus. A second dose of diazepam should follow the first if seizures are not stopped in 5 to 10 minutes. The bolus therapy is followed by a constant rate infusion of diazepam at 0.5 mg/kg/hour added to the cats maintenance fluids. Once seizures have been controlled for 6 hours the animal is weaned off the drug for a duration equal to the time it took to control the seizures. Some cats need intensive monitoring and IV infusions of diazepam for 2 to 4 days.
Phenobarbital can be added to the diazepam at a dosage of 0.5 to 1 mg/kg/hour. Heavy sedation is often required to stop the seizures. Oral anticonvulsants (phenobarbital) is started as soon as the cat can swallow, or is given intramuscularly if the animal cannot swallow.
The prognosis for cats with seizures is directly related to the underlying cause. For those with FIP or neoplasia, the prognosis is grave. It appears that FeLV, FIV and Toxoplasmosis are relatively rare causes for feline seizures. Idiopathic epilepsy also is a very rare syndrome in the cat. Other causes for seizures may respond well to anticonvulsant therapy but be difficult to stabilize if status epilepticus occurs. However, the prognosis for cats with viral meningoencephalitis or ischemic encephalopathy is unpredictable. If status epilepticus can be managed, many of these cats can ultimately be released on medication and live good quality lives.