Physiologic alterations during prolonged tonic-clonic seizures include hyperpyrexia, systemic hypotension with resultant systemic and cerebral hypoperfusion and hypoxia, and acidosis. Sequelae include circulatory collapse, pulmonary edema, renal failure, aspiration, electrolyte disturbances and myoglobinuria. Focal sclerotic changes have been identified within the brain histologically. The primary therapy of epilepsy is pharmacologic, and the majority of patients with primary generalized seizures are well-controlled medically. However, some patients cannot be controlled pharmacologically or suffer intractable side-effects such as marrow suppression.
Resectional surgery requires accurate identification of the seizure focus.
In most cases, injection and imaging are performed in the inter-ictal state. In the typical case of a patient with complex partial seizures, the abnormal finding is unilateral inter-ictal hypometabolism, or decrease in cerebral metabolic rate of glucose, located in the temporal lobe. Such a finding is closely correlated with the presence of a lesion histologically in surgically resected cases, and can be present even in cases where no lesion is detectable on MRI scanning. When visible on both modalities, the apparent size of the lesion is greater on PET than on MRI, probably due to a combination of physiologic and technical factors. Many centers combine the PET and MRI images into fusion images for better anatomic localization.