The patient went on to have a hippocampectomy. 

Histology

Sections of the mesial structures confirm mesial temporal sclerosis, which is represented by a profound depletion of neurons within CA1. A localized aggregate of neurocytic cells is observed, equivalent to focal microdysgenesis. No other diagnostic neuropathologic findings are seen. Subpial gliosis is evident.

Final diagnosis:  mesial temporal sclerosis