Abstracts

Rationale: Stereotactic EEG (SEEG) is a viable but understudied tool for mapping language functions in patients who are being considered for epilepsy surgery. Factors associated with successful identification of language positive areas through SEEG mapping likely go beyond location of implanted electrodes. The current study aims to identify such factors (e.g., demographic factors, epilepsy-specific factors, and stimulation related variables) associated with our ability to identify eloquent language cortex.


Methods: A consecutive series of 30 adult and pediatric epilepsy patients (age range 7-52 years; mean 20 years) implanted with SEEG who underwent a functional stimulation study at Minnesota Epilepsy Group between 9/2017 and 5/2023 were evaluated. All patients had previously completed formal neuropsychological evaluation, with a broad range of abilities (FSIQ mean = 83, range= 51 - 116) and 47% demonstrating language impairment (e.g., Boston Naming Test standard score < 70). Localization of seizure onset varied across the subjects examined, with 70% having suspected left hemisphere seizure onset. 83% of the sample were being considered for surgery involving either temporal lobe. Electrical stimulation mapping (ESM) was performed using the following parameters: 50 Hz, 3 μs pulse duration, 0.5– 10 mA, and 5 second train duration with different language tasks. Language tasks (e.g., picture naming, repetition, reading) were selected on the basis of hypothesized language functions at any given electrode site. Electrode contacts were scored as language positive if stimulation reliably interfered with speech/language functions in the absence of after-discharges. Positive language sites were examined for their association with various factors: demographic factors (e.g., age, intellectual level, language ability level, bilingualism, etc.), epilepsy-specific factors (e.g., age of onset, hemisphere of onset, temporal lobe involvement) and stimulation-related variables (e.g., % of total electrodes stimulated)