Multimodal intraoperative neurophysiological monitoring may better predict postoperative distal upper extremities’ complex-functional outcome than spinal and muscular motor evoked potentials alone in high-cervical intramedullary spinal cord tumor sur

• In high-cervical intramedullary spinal cord tumor surgery, unimpaired D-wave reliably predicts preserved gross-motor function for all covered spinal levels. • D-wave fails to predict the occurrence of mild permanent postoperative deficits affecting the fine-motor and compex hand function. • Only the combination of D-wave, mMEPs, EMG and SSEPs is able to provide a viable power for monitoring the complex hand function. D-wave can safely monitor the corticospinal-tract (CST)-function regarding gross-motor outcome of lower extremities, but it is still unknown whether i)D-wave can also safely monitor the gross-motor outcome of distal upper extremities in those patients undergoing high-cervical intramedullary-spinal-cord-tumor (IMSCT)-resection (enabling epidural D-wave-placement below C5) and ii)multimodal IONM can also predict fine-motor/complex hand function. We prospectively assessed 20 patients undergoing IMSCT-surgery above the C4/5-level with multimodal IONM (D-wave/mMEPs/EMG/SSEPs). Detailed gross-/fine-motor and complex hand function was assessed pre- and postoperatively and during long-term follow-up (mean:29.5 ± 18.8 months) and correlated with IONM-findings. D-wave monitoring was without intraoperative critical changes in all patients and none had any permanent postoperative gross-motor deficits. However, D-wave did not allow to predict the occurrence of mild permanent postoperative deficits affecting fine-motor function which was the case in 8% for distal upper extremities. The complex distal upper extremities’ function assessed by Nine-Hole-Peg-Test (reflecting the complex motor/sensory interaction for hand-usability) was permanently deteriorated in 15% postoperatively and only the combination of D-wave/mMEPs/EMG/SSEPs was able to provide a viable predictive power (specificity:79%/sensitivity:43%). In high-cervical IMSCT-surgery, unimpaired D-wave reliably predicts preserved gross-motor function, but fails to sufficiently cover distal upper extremities’ fine-motor/complex function. Our study underlines the importance of multimodal IONM for fine-motor/complex hand function.