onitoring of spinal cord function during sur- gery of the spine is highly desirable for detect- ing neurological iatrogenic injury before it be- comes irreversible. The goal of balancing complete surgical excision of an intramedullary spinal neo- plasm against the risk of iatrogenic neurologic deficit is nowhere more critical than in a patient with a be- nign tumor and little or no preoperative neurologic dysfunction. Unfortunately, at the time of excision, there is generally little objective feedback available to the surgeon to guide the aggressiveness of the exci- sion. Subjective factors, such as the appearance of the interface between tumor and normal tissue and the amount of manipulation of intact spinal tissue, re- quired during tumor excision can be indirectly sup- plemented by knowledge of the natural history of the disease based on the tissue type reported from frozen sections. Lacking immediate, quantitative physiologic data during resection, however, the correctness of the surgeon's attempt to balance aggressive excision and iatrogenic neurologic deficit remains untestable until the postoperative neurologic examination. We here report a case wherein the use of intraoper- ative monitoring of motor-evoked potentials (MEPs) afforded us immediate feedback on the effect of our excision and had significant influence in guiding the aggressiveness of tumor removal while somatosen- sory evoked potentials CSSEPs) remained unchanged.