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Neurosurgery:
doi: 10.1227/NEU.0000000000000087
Research-Human-Clinical Studies

Is Intraoperative Diffusion Tensor Imaging at 3.0T Comparable to Subcortical Corticospinal Tract Mapping?

Ostrý, Svatopluk MD, PhD*; Belšan, Tomáš MD, PhD; Otáhal, Jakub MD, PhD§; Beneš, Vladimír MD, PhD*; Netuka, David MD, PhD*

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Abstract

BACKGROUND: Primary brain tumors in motor eloquent areas are associated with high-risk surgical procedures because of potentially permanent and often disabling motor deficits. 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: Twenty-five patients (13 males, 12 females, median 47 years) were enrolled prospectively from June 2010 to June 2012. Patients were included if they had a solitary supratentorial intracerebral lesion compressing or infiltrating the CST according to preoperative MRI. Subcortical CST mapping was performed by monopolar (cathodal) stimulation (500 Hz, 400 μs, 5 pulses). CST DTT was made both at preoperative and intraoperative 3.0T MRI. Subcortical motor-evoked potential 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 = 0.470 (P < .001); post-iMRI, the correlation coefficient was R = 0.338 (P < .001). MRI radical resection was achieved in 17 patients (68%), subtotal in 5 (24%), and partial in 3 (12%). Postoperative paresis developed in 8 patients (32%); the paresis was permanent in 1 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 2 methods in selected cases can help increase the safety of tumor resection close to the CST.

ABBREVIATIONS: cont-MEP, continuous motor-evoked potentials

CRDT, complete resection of detectable tumor

CRET, complete resection of enhancing tumor

CS, central sulcus

CST, corticospinal tract

DTI, diffusion tensor imaging

DTT, diffusion tensor tractography

FOV, field of view

FSPGR, fast spoiled gradient-recall-echo

iDTT, intraoperative diffusion tensor tractography

iMRI, intraoperative magnetic resonance imaging

iPT, intraoperative pyramidal tract

iUS, intraoperative ultrasound

MEP, motor-evoked potential

NEX, number of excitations

PMC, primary motor cortex

Post-Dist, distances measured after iMRI

Pre-Dist, distances measured before iMRI

PT, pyramidal tract

scMEP, subcortical motor-evoked potential

SEP, somatosensory-evoked potential

SNR, signal-to-noise ratio

WHO, World Health Organization

Copyright © by the Congress of Neurological Surgeons

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