Abstracts

Rationale: Functional mapping of language plays a major role in the preoperative assessment of patients with pharmacologically intractable epilepsy. To date, several predictors of atypical language representation have been described in epileptic patients. Among those factors, the relatively acute (i.e. non-post-ictal) effect of seizures on language localization remains poorly understood, due to the unpredictable nature of seizures, as well as the complexity to study language during or following a seizure with current neuroimaging methods. These difficulties can be overcome by functional near-infrared spectroscopy (fNIRS), a relatively new and promising neuroimaging technique in the field of epilepsy. Methods: We used a newly developed high-channel simultaneous fNIRS-EEG system, composed of 128 fNIRS channels and 20 EEG channels to continuously monitor cortical hemodynamic changes during a semantic language task in a patient with bitemporal epilepsy admitted to the EMU. Results: Following an acute seizure, the language task was performed three times (at 5 min, 60 min and after 3 days). Few minutes after the seizure, language task elicited a significant decrease in HbO2 and a relatively small increase in HbR was present over both Broca areas but more predominately over the right hemisphere. In the following hour, we observed an increase in HbO2 and decreased in HbR more importantly in the right hemisphere suggesting right language lateralization. Finally, a third evaluation, a few days later, showed a different hemodynamic response with an increase in HbO2 and decreased in HbR mainly over the left hemisphere suggesting left language lateralization. fMRI and Wada testing confirmed that latter. Conclusions: Acute seizures have the potential to interfere with language localization especially in patients with temporal lobe epilepsy. We cannot emphasize enough the importance to include EEG during functional evaluation of language in epileptic patients. Funding: No funding was received for this abstract