Nonthalamic Generalization of Ictal Spikes in Atypical Absence Seizures

Reported here is the case of a boy who had a thalamic hemorrhage as a neonate and developed symptomatic focal epilepsy at 3 years of age. At the onset of focal epilepsy, the interictal spikes were localized in the occipital regions; over time, they gradually expanded, and atypical absences developed at the age of 6 years. When the patient was hospitalized at the age of 7 years 11 months, the spatiotemporal distribution of the synchronous spikes was assessed for each generalized spike-and-wave discharge observed on ictal electroencephalography. The occipital spikes were always the first to appear, and most spikes had posterior-to-anterior distribution. Occasionally, the frontopolar spikes appeared before the frontal spikes. These results indicate that the generalized spikes observed during atypical absences were formed by rapid generalization of the focally generated spikes from the occipital region through the cortex and the long association fibers, but not through the thalamus.