Introduction: Benign adult familial myoclonus epilepsy (BAFME) (Yasuda, 1991) is an autosomal dominant disease characterized by cortical tremor and infrequent generalized seizures. The precise pathological mechanism of cortical tremor (Ikeda et al., 1990) of BAFME is uncertain so far. We aimed to clarify the cerebral generator mechanism of cortical tremor in BAFME by means of corticomuscular coherence.
Methods: We employed 15 BAFME patients diagnosed based on clinical and electrophysiological findings (IRB #E1284). Electroencephalography (EEG), electromyography (EMG) and accelerometer were simultaneously recorded in all 15 patients. In addition, magnetoencephalography (MEG), EEG and EMG were also simultaneously recorded on different occasions in 3 patients. Patients were instructed to keep the hand with the outstretched posture in the air and also to do so with loading 500 g weight on the hand. Fourier Transform was applied for the frequency analysis. We compared the power spectrum between tasks to judge whether the tremor was of cerebral or peripheral origin.
Results: No significant corticomuscular coherence was observed at the frequency of cortical tremor in 12 patients. The frequency of significant corticomuscular coherence was consistent with that of peak power spectrum of cortical tremor in 2 patients. No significant coherence was observed in another patient.
Conclusion: The frequency of corticomuscular coherence and that of the peak of power spectrum did not show consistency in 12 out of 15 BAFME patients. Thus, the frequency of cortical tremor in BAFME could not be made directly by cerebral cortex but possibly modulated by other structures such as subcortical or cerebellum structures.