A review of monopolar motor mapping and a comprehensive guide to continuous dynamic motor mapping for resection of motor eloquent brain tumors.
Monopolar mapping of motor function differs from the most commonly used method of intraoperative mapping, i.e. bipolar direct electrical stimulation at 50-60Hz (Penfield technique mapping). Most importantly, the monopolar probe emits a radial, homogenous electrical field different to the more focused inter-tip bipolar electrical field. Most users combine monopolar stimulation with the short train technique, also called high frequency stimulation, or train-of-five techniques. It consists of trains of four to nine monopolar rectangular electrical pulses of 200-500μs pulse length with an inter stimulus interval of 2-4msec. High frequency short train stimulation triggers a time-locked motor-evoked potential response, which has a defined latency and an easily quantifiable amplitude. In this way, motor thresholds might be used to evaluate a current-to-distance relation. The homogeneous electrical field and the current-to-distance approximation provide the surgeon with an estimate of the remaining distance to the corticospinal tract, enabling the surgeon to adjust the speed of resection as the corticospinal tract is approached. Furthermore, this stimulation paradigm is associated with a lower incidence of intraoperative seizures, allowing continuous stimulation. Hence, monopolar mapping is increasingly used as part of a strategy of continuous dynamic mapping: ergonomically integrated into the surgeon's tools, the monopolar probe reliably provides continuous/uninterrupted feedback on motor function. As part of this strategy, motor mapping is not any longer a time consuming interruption of resection but rather a radar-like, real-time information system on the spatial relationship of the current resection site to eloquent motor structures.
['Schucht|P|P|', 'Seidel|K|K|', 'Jilch|A|A|', 'Beck|J|J|', 'Raabe|A|A|']
D001931:Brain Mapping D001932:Brain Neoplasms D004558:Electric Stimulation D019054:Evoked Potentials, Motor D006801:Humans D016343:Monitoring, Intraoperative D009044:Motor Cortex
Monopolar motor mapping Motor-evoked potential Continuous dynamic mapping Glioma surgery Intraoperative neuromonitoring