EEG findings in an adult with severe case of alobar holoprosencephaly

Holoprosencephaly is a category of congenital brain malformation that is frequently associated with epilepsy. Epileptic spasms and partial seizures are reported with a variety of electrographic ictal and interictal EEG findings. We report a case of severe alobar holoprosencephaly with cortical tissue limited to inferior-anterior-frontal areas and a thin mantle over the posterior areas, and no appreciable connective fibers to the subcortical structures. Interictal EEG consisted mainly of 2-3 Hz irregular delta activity during wakefulness and sleep. Clinical seizures had two different semiologies: (1) epileptic spasms lasting 0.5s during state change and (2) prolonged tonic spasms lasting 5-8s followed by appendicular clonic activity, abnormal nystagmoid eye movements and eye flutter lasting 5-8s. Preceding the epileptic spasms, there was 1-2s of electrodecrement in the EEG. During prolonged tonic spasms there was also electrodecrement in the EEG. No other electrographic activity was seen. Due to lack of any appreciable connecting fibers between cortical and subcortical structures, these findings suggest an increase in brain stem excitability with inefficient (or lack of) cortical modulation as a possible underlying mechanism for epileptic spasms in this patient.