gms | German Medical Science

Surgical treatment of sacral tumors bears a high risk of postoperative neurological deficits. These surgery-related neurological deficits are accompanied by social aspects that reach beyond the functional impairment.

Intraoperative neurophysiological monitoring was applied to 12 patients (18 to 59 years of age) with a sacral tumor (10 chordomas, 1 chondrom, 1 lipoma). The minimum size of the tumors was 3cm. Intraoperative localization of the sacral roots was performed by electromyography of the target muscles and direct electrical stimualtion of the nerve roots (Intensity 3 mA). A pair of needle electrodes placed in the perianal muscles was used for recording. Functional monitoring was performed by intraoperative recording of the bulbocavernosus reflex (BCR). BCR was elicited by stimulating the pudendal nerve (Frequency 2.3 Hz; Intensity 50 mA) and was recorded by electrodes in the perianal muscles. All procedures were performed under general anesthesia without muscle relaxants.

In all cases a macroscopical total tumor removal was achieved. No clinical deterioration was observed postoperatively. Localization of the nerve roots S2 to S5 was achieved by direct electrical stimulation in 11 (11/12) patients. BCR consists of two peaks: the first at 30 ms (P30) and the second at 50 ms (P50). Intraoperative changes of P50 were observed in 9 of the 12 patients. None of these correlated with the postoperative clinical condition. P30 remained unchanged in all cases.

Intraopeative mapping of the sacral nerve roots can be achieved by direct electrical stimulation. Intraoperative recording of the BCR allows functional monitoring of the bladder. However, the P50 component of the BCR is not sensitive for these purpose. Combining EMG and BCR recording reduces morbidity during surgery for sacral tumors.