Source and Clinical Significance of Rhythmic Mid-Temporal Discharges in Partial Epilepsy. A MEG Study.
Abstract number :
1.233
Submission category :
Year :
2001
Submission ID :
330
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
Y-Y. Lin, MD, PhD, The Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan; Z-A. Wu, MD, The Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan; H-Y. Yu, MD, The Neurological Institute, Taipei Veterans General Ho
RATIONALE: To evaluate the exact source location and clinical significance of rhythmic temporal theta activity of drowsiness by MEG in patients with partial epilepsy.
METHODS: We enrolled two consecutive patients with complex partial seizures who were found to have bursts of rhythmic mid-temporal theta discharges (RMTD) on scalp EEG recordings. Patient 1 has been a victim of medically refractory epilepsy with 3-5 fits monthly for 5 years. Patient 2 has suffered from paroxysmal episodes of bizarre behavior with inappropriate laughing for 3 years without definite diagnosis and treatment before. Simultaneous MEG and EEG measurement was conducted with a whole-scalp 306-channel neuromagnetometer (Vectorview[tm] Neuromag Ltd). We visually detected the RMTD activity and interictal spikes on both MEG and EEG channels, and then localized their sources by MEG source modeling. Intensive video/EEG evaluation confirmed the diagnosis of right temporal lobe epilepsy in patient 1 (TLE patient) and right frontal lobe epilepsy in patient 2 (FLE patient). MEG recordings were repeated 3 months after right anterior temporal lobectomy (ATL) in the TLE patient; one month after anticonvulsant medication in the FLE patient. We analyzed RMTD activity and clinical outcome of seizure control before and after above treatment intervention.
RESULTS: In both patients, some bursts of RMTD activity were present during drowsiness over the left temporal channels of both MEG and EEG recordings contralateral to the epileptogenic side. RMTD was localized to the left inferior temporal gyrus by MEG source modeling. The TLE and FLE patients became seizure free after right ATL and anticonvulsant medication, respectively. MEG/EEG follow-up did not show epileptic spikes, but RMTD activity was still found in left MEG and EEG channels localized to the left inferior temporal gyrus. Postoperative MEG recording in our TLE patient also showed appearance of RMTD over bilateral temporal regions instead of unilateral distribution observed preoperatively.
CONCLUSIONS: The source of RMTD activity is located in the fissural cortex of inferior temporal gyrus. As a physiologic rhythm related to dampened vigilance, RMTD has no relation to epileptogenic activity. In patients with partial epilepsy, RMTD may occur more likely over the side contralateral to epileptogenic focus. Following appropriate treatment, the appearance of RMTD associated with normalized electromagnetic background over the epileptogenic side may reflect underlying functional recovery.
Support: This study was funded by grant VGH-443-(3) and VGH-370 of Taipei Veterans General Hospital.