Ahead of Print: Tractography Versus Motor Tract Mapping

Screen Shot 2013-07-30 at 2.07.11 PMBackground: Primary brain tumors in motor eloquent area are associated with high-risk surgical procedures because of potentially permanent and often disabling motor deficit. Intraoperative primary motor cortex mapping and corticospinal tract (CST) monitoring are well-developed and reliable techniques. Imaging of the CST by diffusion tensor tractography (DTT) is also feasible.

Objective: To evaluate the practical value of 3.0T intraoperative MRI (iMRI) with intraoperative DTT (iDTT) in surgery close to the CST, and to compare high-field iDTT with intraoperative neurophysiological CST mapping during glioma and metastasis resection in a routine setting.

Methods: 25 patients (13 males, 12 females, median 47 years) were enrolled prospectively from June 2010 to 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 (500Hz, 400us, 5 pulses). CST DTT was made both at preoperative and intraoperative 3.0T MRI. Subcortical motor evoked potential (scMEP) threshold current and probe-CST distance were recorded at 155 points before, and at 103 points after iMRI. Current-distance correlations were performed both for pre-iMRI and for post-iMRI data.

Results: The correlation coefficient pre-iMRI was R = .470 (p < .001); post-iMRI was R = .338 (p < .001). MRI radical resection was achieved in 17 patients (68%), subtotal in 5 (24%), and partial in 3 (12%). Postoperative paresis developed in eight patients (32%), permanent remained in one case (4%).

Conclusion: The linear current-distance correlation was found both in pre-iMRI and in post-iMRI data. Intraoperative image distortion appeared in 36%. Neurophysiological subcortical mapping remains superior to DTT. Combining these two methods in selected cases can help increase the safety of tumor resection close to the CST.

From: Is Intraoperative Diffusion Tensor Imaging at 3.0T Comparable to Subcortical Corticospinal Tract Mapping? by Svatopluk et al.

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