Intraoperative neurophysiology in DBS for dystonia.

Deep brain stimulation (DBS) of the internal segment of the globus pallidus (GPi) has been demonstrated to be an effective therapy for the treatment of primary dystonia as well as tardive dystonia. Results for other forms of secondary dystonia have been less consistent. Although a number of target sites have been explored for the treatment of dystonia, most notably the motor thalamus, the target of choice remains the sensorimotor portion of the GPi. Although the optimal site within the GPi has not been determined, most centers agree that the optimal site involves the posteroventral lateral "sensorimotor" portion of the GPi. Microelectrode recording (MER) can be used to identify boundaries of the GPi and nearby white matter tracts, including the corticospinal tract and optic tract, and the sensorimotor GPi. However, whether or not the use of MER leads to improved outcomes compared with procedures performed without MER has not been determined. Currently, there is no evidence to support or refute the hypothesis that mapping structures with MER provides better short- or long-term outcomes. Centers using MER do not report a preference of one system over another, but there have not been any studies to compare the relative benefits or risks of using more than 1 electrode simultaneously. Comparison studies of different target structures and targeting techniques in dystonia have not been performed. Additional research, which includes comparative studies, is needed to advance our understanding and optimization of DBS targets, techniques, and approaches along with their relative benefits and risks in dystonia.