Object: The goal of this study was to examine the sensitivity and specificity in preoperative localization of hand motor cortex by imaging regional event-related desynchronization (ERD) of brainwaves in the beta frequency band (15-25 Hz) involved in self-paced movement.
Methods: Using magnetoencephalography (MEG), the authors measured ERD that occurred before self-paced unilateral index finger flexion in 66 patients with brain tumors, epilepsy, and arteriovenous malformations.
Results: The authors applied an adaptive spatial filtering algorithm to MEG data and found that peaks of the tomographic distribution of beta-band ERD sources reliably localized hand motor cortex compared with electrical cortical stimulation. They also observed high specificity in estimating contralateral hand motor cortical representations relative to somatosensory cortex. Neither presence nor location of tumor changed the qualitative or quantitative location of motor cortex relative to somatosensory cortex.
Conclusions: An imaging protocol using ERD obtained by adaptive spatial filtering of MEG data can be used for extremely reliable preoperative localization of hand motor cortex.