Diagnosis of primary generalized epilepsy in a cow

On the basis of history, electrodiagnostic and neuropharmacologic studies, and results of laboratory testing and necropsy, a seizure disorder of 1.5 years' duration in an 8-year-old Hereford cow was diagnosed as primary generalized epilepsy. Evidence of metabolic, toxicologic, head trauma, or genetic cause of the seizures was not found. A morphologic cause for the convulsions also was not detected. One naturally occurring seizure was recorded electroencephalographically, but interictal EEG abnormalities were not seen. Attempts to evoke a seizure with photostimulation or therapeutic doses of acepromazine, ketamine, tripelennamine, and estradiol cypionate were unsuccessful. The seizure threshold for the CNS stimulant pentylenetetrazol was found to be less than 6 mg/kg, IV; the seizure threshold in a control cow was found to be greater than 12 mg/kg, IV. The pharmacologic protocol used for this cow may be useful for diagnosis of epilepsy in other animals.