Abstracts

Rationale: Electrical stimulation mapping (ESM) is often used to identify essential language cortex prior to resection of epileptogenic tissue in the language dominant hemisphere. Although considered the "gold standard" for language localization, there is limited information concerning the reliability of the procedure, particularly over long time intervals. We present a case report of a young man with refractory left temporal lobe epilepsy who underwent intraoperative language mapping at age 14 years and again at age 25 years. Methods: This patient developed focal seizures at age 13 and was found to have a left temporal dysembryoplastic neuroepithelial tumor (DNET), consistent with scalp vEEG evidence of left (dominant) temporal seizure onset. He underwent surgical resection of the tumor and epileptogenic cortex at age 14, with poor seizure outcome. Following multiple medication trials he underwent further resection at age 25. Intraoperative stimulation mapping was conducted prior to both resections. Tasks included visual object naming and auditory description naming. For both mapping procedures the neuropsychologist administering language tasks was blind to the location of the stimulation. Sixteen sites were tested during the first procedure, 10 sites were tested during the second procedure. Results: Results from the first mapping identified a positive auditory naming site approximately 5cm from the temporal pole on the superior temporal gyrus, just at the anterior aspect of the tumor. No reliable visual naming areas were identified. Stimulation over the tumor was not associated with any language difficulties. Results from the second intraoperative mapping again identified a positive auditory naming site on the superior temporal gyrus approximately 5cm from the temporal pole. Stimulation at other tested sites was not associated with changes in speech or language. The location of the positive language (auditory naming) site initially identified at age 14 was replicated 11 years later at age 25. Conclusions: Repeat ESM following an 11-year interval provided a unique opportunity to investigate the reliability of ESM-identified language areas. Although with caveat given the limited ability to generalize from a single case study, this finding of the same type of language site in the same location supports the reliability of the procedure and suggests intra-individual reliability in the location of language cortex over a prolonged time interval.