Magnetoencephalography (MEG): Its application to moyamoya disease

The re-build-up phenomenon in electroencephalography (EEG) was first described as a pathognomonic phenomenon of moyamoya disease in 1977 (in Japanese) [1] and in 1979 (in English) [2]. Slow wave discharges are known to build-up during hyperventilation used as a routine provocation method in clinical EEG. Moreover, slow wave discharges also appear a few minutes after the termination of hyperventilation exclusively in patients with moyamoya disease. This re-build-up phenomenon was once thought to occur only in pediatric patients [1, 2], but was later also found in adult patients. Interestingly, the re-build-up phenomenon is often accompanied by ischemic symptoms. However, the cortical or deep structural origin of the generator mechanism remains controversial.