Interictal temporal lobe epileptiform discharges and their relationship to secondarily generalized epilepsy

In a previous study of epileptic phenomena in 19 patients with partial complex seizures, it was noted that seizures of left temporal lobe origin had a higher incidence of secondary generalization. To evaluate this observation further, we retrospectively reviewed reports of EEGs for evidence of focal interictal epileptiform discharges (FIED) of temporal lobe origin and correlated this finding with seizure type. Of 3,276 EEG reports reviewed, 195 showed FIED. The medical records of these patients were reviewed and 79 had sufficient information therein to enable seizure classification. Of 79 patients, 61 had secondary generalized seizures, 45 with left temporal FIED, 16 with right FIED. Of 79 patients, 18 had partial seizures, 13 with right temporal FIED, 5 with left FIED (p less than 0.001). These findings suggest that seizures of left temporal lobe origin may have a higher incidence of secondary generalization. The significance of this observation and its relevance to medical and surgical treatment of complex partial seizures is discussed.