Abstracts

Rationale: Language impairment sometimes co-exists with epilepsy in particular patients in childhood with epileptic encephalopathy: e.g. Landau-Kleffner syndrome, sequelae of hypoxic-ischemic encephalopathy and acute encephalopathy. Identification of language development should be categorized objectively, but ideal methods have not been specified. And the identification of language area is very important when they are considered to be a candidate of the epilepsy surgery. We evaluated progress of language functions in developing subjects and the instance of language acquisition using magnetoencephalography (MEG). Methods: The subjects are four children with language impairment (congenital myopathy, Angelman syndrome, sequelae of acute encephalopathy and cryptogenic language impairment). Each patient underwent multiple MEG and evaluated the chronological change. Three normal adult volunteers have been evaluated as control. All patients and their parents, and volunteers are Japanese speakers. All volunteers were right handed. MEG was performed in a magnetically shielded room using a 204-channel planner type gradiometer and 102ch magnetometer (Vector View System, Elekta AB, Stockholm, Sweden). The Japanese traditional character "HIRAGANA" -phonetic alphabets- superimposed on with the favorite animation films of the subjects. Subjects could not been ordered to keep attention to the stimulator: "HIRAGANA", since subjects are mentally retarded. The animation films were presented to keep the attention of children. Three HIRAGANA characters and random dots were presented alternately, 50 times per 10 minutes. Averaged language related evoked magnetic fields were estimated with base line from -500msec to 0msec of trigger stimuli. The MEG data within 1,000msec from the triggers were divided into 3 frequency bands as followings: 5-9 Hz, 9-12 Hz, 13-15 Hz bands, and evaluated the each event related desynchronization (ERD) and event related synchronization (ERS). ERDs and ERSs were presented in nine pixels represented nine brain regions (bilateral frontal regions, anterior midline, bilateral parietal regions, central midline, bilateral occipital-lateral regions and posterior midline). Results: Volunteers: ERDs were observed in the left occipial-lateral regions. These were projected to the representation of the language areas. Patients: In one patient, ERDs were observed in the left occipial-lateral region in accordance with language acquisition. Though, wide variability was observed within same study, sometimes there were no ERDs or ERSs. This issue might be originated by the grade of attention to the stimulation. In adult volunteers, the results were constant in the subjects, so the reliability of this method should be confirmed. Though in children, the results varied widely. It might be due to the concentration of children for the test. Conclusions: Our trial to assess the perceptive language function using MEG should be reliable to demonstrate the language area and the instance of language acquisition. Funding: none