A parenchymal brain granuloma is the final consequence of a localized inflammatory reaction against an infectious agent, particularly parasites. In humans, these lesions are frequent causes of epilepsy. We studied the pattern of seizures induced by pentylenetetrazol (PTZ) in cats with a chronic granuloma induced 1 year earlier by injection of silicates into the brain amygdala. Compared with controls, the seizure threshold to myoclonic seizures was significantly decreased in cats with granuloma, while the threshold for tonic-clonic seizures was not altered. Thus, the difference in PTZ doses between the initial and final components of the seizure became significantly enlarged (P < 0.001). Our results indicate that a granulomatous lesion in amygdala facilitates the generation and propagation of myoclonic seizures, whereas other components of PTZ-induced seizures are not affected.