Investigation of Asleep versus Awake Motor Mapping in Resective Brain Surgery

OBJECTIVE

To develop an asleep motor mapping paradigm for accurate detection of the corticospinal tract during glioma surgery and compare outcomes with awake patients undergoing glioma resection.

METHODS

A consecutive cohort of adult patients undergoing craniotomy for suspected diffuse glioma with tumor in a perirolandic location who had awake or asleep cortical and subcortical motor mapping with positive areas of motor stimulation were assessed for postoperative extent of resection (EOR), permanent neurological deficit, and proximity of stimulation to diffusion tensor imaging-based corticospinal tract depiction on preoperative magnetic resonance imaging. Outcome data were compared between asleep and awake groups.

RESULTS

In the asleep group, all 16 patients had improved or no change in motor function at last follow-up (minimum 3 months of follow-up). In the awake group, all 23 patients had improved function or no change at last follow-up. EOR was greater in the asleep group (mean [SD] EOR 88.71% [17.56%]) versus the awake group (mean [SD] EOR 80.62% [24.44%]), although this difference was not statistically significant (P = 0.3802). Linear regression comparing distance from stimulation to corticospinal tract in asleep (n = 14) and awake (n = 4) patients was r = -0.3759, R² = 0.1413, P = 0.1853, and 95% confidence interval = -0.4453 to 0.09611 and r = 0.7326, R² = 0.5367, P = 0.2674, and 95% confidence interval = -7.042 to 14.75, respectively.

CONCLUSION

In this small patient series, asleep motor mapping using commonly available motor evoked potential hardware appears to be safe and efficacious in regard to EOR and functional outcomes.

Principles of Supplemental Motor Area and Cingulate Tumor Resection With Asleep Trimodal Motor Mapping: 2-Dimensional Operative Video

Resection of intra-axial tumors adjacent to the motor pathways can lead to devastating deficits; however, with an appropriate mapping technique, it can be performed safely. We present the case of a 63-yr-old woman with a diffuse glioma centered in the left supplemental motor area (SMA) and extending throughout the cingulate gyrus. In the video, we demonstrate the principles developed by the senior author for trimodal motor mapping under general anesthesia. Trimodal motor mapping includes direct stimulation of the cortex with a strip electrode, use of the bipolar stimulator for cortical and subcortical mapping, and use of the monopolar stimulator for subcortical motor mapping. We highlight technical principles required to safely resect these tumors, including the key anatomic landmarks and approach to SMA/cingulate lesions, techniques for subpial dissection, and preservation of en passage vessels. Patients with SMA tumors will almost always have a deficit after SMA resection, but if motor pathways are preserved and can be stimulated to produce movement at the end of the case, then the deficit will almost always improve, as was the case with this patient. Initially, postoperatively, she was nonverbal and hemiplegic, but by postoperative day 7 she recovered her speech significantly, was naming three of three objects, and was moving her right side. By 6 wk postoperative, she was ambulating independently and had normal speech. This case demonstrates the principles and techniques necessary for achieving maximal safe resection of tumors adjacent to the motor pathways with the patient under general anesthesia. The patient gave written informed consent for the surgical resection of her tumor and for the publication of this video.

Validity and utility of monopolar spinal cord stimulation in pediatric scoliosis surgery

PURPOSE

To assess the validity and utility of monopolar stimulation (between a peridural needle and a large adhesive anode placed in the sternal area) for intraoperative monitoring in scoliosis surgery.

METHODS

This procedure was assessed during 41 operations involving either arthrodesis with posterior instrumentation or a Vertical Expandable Prosthetic Titanium Rib (VEPTR). Responses evoked by monopolar stimulation were compared with those evoked by bipolar stimulation between two epidural needle electrodes. Potentials evoked by monopolar stimulation in the upper limbs were compared with those evoked in the lower limbs during the same stimulation procedure.

RESULTS

Monopolar stimulation yielded equivalent and, if anything, more stable responses in the lower limbs. Recording in the upper limbs was satisfactory and allowed a decrease in responses to be detected in two patients. Acceptable thresholds for changes in amplitude relative to baseline were 40 % for upper limbs and 30 % for lower limbs.

CONCLUSIONS

Monopolar stimulation can be used to monitor the spinal cord during surgery for scoliosis correction. This procedure is more convenient for the surgeon and allows for the combined recording of responses in all four limbs, which can be useful in the case of surgical techniques such as those involving a VEPTR.