Insights into epileptic aphasia: Intracranial recordings in a child with a left insular ganglioglioma

Abstract

Intracranial EEG was recorded during a dialog-based task in a 16-year-old boy with a left insular ganglioglioma, medically intractable epilepsy, epileptic foci in auditory cortex on the lateral superior temporal gyrus (STG) and language deficiencies. Performance of the task was highly erratic, characterized by rapid cycling between providing correct answers, incorrect answers and failure to respond. There was no relationship between performance and the degree of concurrent epileptic activity in auditory cortex. High gamma activity in core auditory cortex (posterior medial Heschl’s gyrus, HGPM) was markedly diminished during listening and, with two exceptions, was less than activity from 17 control subjects. The two exceptions also had seizure onset zones in perisylvian cortex. Responses during listening were of smaller amplitude than those occurring during speaking, a pattern opposite that typically seen in the left HGPM. Within HGPM, lateral STG and pars opercularis of the inferior frontal gyrus, high gamma activity while listening was greatest when questions were correctly answered and least when the subject failed to respond. Alpha activity preceding utterances was lowest in pars opercularis when the subject failed to respond. Comparisons between resting state activity in another cohort of controls and the subject were most disparate in HGPM. Alpha activity during performance of the task was greatest in the mid-anterior cingulate when the subject failed to respond, suggesting dysfunction beyond the speech network and into the salience network. Multiple abnormalities noted in this patient paralleled those seen in epileptic aphasia and Rolandic epilepsy.