2. Subcortical mapping and intraoperative DTT 3.0 T of the corticospinal tract in supratentorial intrinsic tumour surgery. What should we rely on?

Abstract

Intraoperative subcortical mapping of the corticospinal tract (CST) using the threshold technique (sc-MEPs) is considered to be helpful during tumour resection adjacent to the CST. Diffusion tensor tractography (DTT) of the CST is feasible. Intraoperative DTT and sc-MEP correlation is thought to be more precise because of brainshift elimination. The goal of the study was to evaluate intraoperative DTT 3.0 T reliability compared with CST mapping in a nonselected series. 25 patients were enrolled consecutively and prospectively between June 2010 and June 2012. Inclusion criteria: solitary supratentorial intracerebral lesion compressing or infiltrating the CST according to preoperative MRI. Subcortical CST mapping was performed by monopolar (cathodal) stimulation (500 Hz, 400Î1/4s, 5 pulses) with a navigated probe. CST DTT was performedon both preoperative and intraoperative 3.0 T MRI. sc-MEP threshold current and probe-CST distance were recorded at 155 points before iMRI (intraoperative MRI) (preoperative scans) and at 103 points after iMRI (intraoperative scans). Current-distance correlations were performed both for pre-iMRI and for post-iMRI data separately. The correlation coefficient between pre-iMRI data was R = 0.470 (p < 0.001), post-iMRI data was R = 0.338 (p < 0.001). MRI radical resection was achieved in 17 (68%), subtotal in 5 (24%) and partial in 3 (12%). Postoperative paresis developed in 8 (32%), but was permanent in only one case (4%). The lowest sc-MEP threshold was ⩽ 5.0 mA in 10 (40%); 5–10.0 mA in 9 (36%); > 10.0 mA in 6 patients (24%). Intraoperative DTT became unreliable because of severe image distortion in 9 (36%). The linear current-distance correlation was found both in pre-iMRI and in post-iMRI data. Correlation of post-iMRI data was weaker. Neurophysiological subcortical mapping was more reliable intraoperatively than DTT. Combining these two methods can help increase the safety of tumour resection close to the CST only in selected cases. Supported by IGAMZCR12253-5.