Signalment, history, ictal pattern, and clinical and neurologic findings were examined in cats with recurrent seizures that were classified as either primary epilepsy (PE) or secondary epilepsy (SE). Patients in the study underwent thorough physical and neurologic examinations. PE was considered in cats with normal diagnostic workups or in cats older than 1-year-postseizure onset with incomplete workups or interictal neurologic deficits. Cats with PE did not have any evidence of neurologic disease other than seizures and were reevaluated at least 12 months postdiagnosis. The SE diagnosis was based on a history of seizures along with confirmed pathologic findings in hematology, serum biochemistry, cerebral spinal fluid analysis, or morphologic changes of the brain. A total of 125 cats with recurrent seizures (78 with SE and 47 with suspect PE) were evaluated in the present study. The most common SE etiologies were intracranial neoplasia (16), hippocampal necrosis (14), toxicosis (8), and encephalitis (7). Significant differences between PE and SE were identified in age, body weight, duration of seizures, occurrence of status epilepticus, and neurologic deficits. Results suggested that SE was more likely if the first seizure occurred after 7 years of age; complete diagnostic workup with advanced diagnostic imaging was strongly recommended in these cases. Seizures that occurred during resting conditions with observed rapid running suggested that PE was the likely diagnosis. Mydriasis during ictus and postictal blindness/deafness were more frequently identified in the PE group. Other ictal signs, including tremors, facial twitching, vocalization, urination, defecation, salivation, and postictal signs, including polyphagia, polyuria/polydipsia, and ataxia, did not differ between the 2 groups. These results suggested that PE is an important etiology for seizure in cats.

Commentary: Idiopathic epilepsy (IE) has long been considered an uncommon cause of seizures in cats compared with dogs. However, this study confirms recent data suggesting that IE is important in the feline differential diagnosis, particularly in cats younger than 7 years of age. Results from this study suggested that seizures that occur during periods of rest or involve “wild running behavior” were statistically more likely in patients with IE. Older cats, those with longer seizure duration, or those with any interictal neurologic abnormalities were significantly more likely to have SE. This study demonstrates that a full medical workup, including advanced imaging if indicated, should be recommended for all older cats with a new onset of seizures, especially those with interictal abnormalities.—Mark Troxel, DVM, Diplomate ACVIM (Neurology)

Clinical comparison of primary versus secondary epilepsy in 125 cats. Pákozdy A, Leschnik M, Sarchahi AA, et al. J FEL MED SURG 12:910-916, 2010.

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