Spike morphology in childhood focal epilepsy: relationship to syndromic classification

The waveform morphology of interictal spike activity associated with uncontrolled childhood focal epilepsy was quantified in 40 patients by a computer-based technique. The findings were then analyzed with respect to epileptic syndromes. Samples of spike activity from each patient were characterized by determination of average amplitude (A), duration (D), and sharpness (S). A single morphologic index, the composite spike parameter (CSP), was also derived from the basic spike parameters (CSP = A x D/S). The spikes of patients in the benign focal epilepsy category differed from those of patients in other syndromic categories (symptomatic, cryptogenic, and Landau-Kleffner). Specifically, they were higher in amplitude, longer in duration, less sharp, and had a higher CSP value. The pretreatment spike parameters did not differ significantly in patients who responded favorably to initial antiepileptic drug (AED) therapy as compared with those whose seizures were harder to control. The findings suggest that quantitative assessment of interictal spike morphology may help develop a more objective basis for classifying patients according to epileptic syndrome.