Assessment of the corticospinal tract alterations before and after resection of brainstem lesions using Diffusion Tensor Imaging (DTI) and tractography at 3 T☆
Introduction
Neurosurgical management of a space occupying lesion in the brainstem includes biopsy for diagnosis and/or possible maximum resection of the lesion for treatment. New developments in microsurgery and radiology, especially along with the experience gained from fiber dissection techniques of the brainstem are important stages in the improvement of brainstem surgery [1], [2]. The presence of major motor and sensory pathways in the brainstem still makes it a challenging area for neurosurgeons. Delineating the status of individual white matter tracts in relation to the lesion is essential for pre-operative evaluation and surgical planning. White matter tracts, gray matter nuclei and sometimes even tumors appear relatively homogeneous and may not be easily differentiated on conventional MRI. DTI from which FA maps and Diffusion Tensor Tractography (DTT) images are generated reveals improved tissue contrast between corticospinal tracts, gray matter nuclei and lesion [3], [4], [5], [6], [7], [8], [9], [10]. DTT has also been found to be very useful in treatment planning of brain and brainstem lesions [3], [11], [12], [13], [14].
DTT was introduced into Neuroradiology practice more than a decade ago, but it has not been widely included in the routine clinical protocols yet. One of the main reasons for this lag is that the technique is user-dependent and often requires extensive manual post-processing.
In addition, there has not yet been a gold standard or in vivo validation method to test its robustness or reliability [15], [16].
Although the color FA maps contain the directionality information of the tracts, DTT has obvious strength by visualization even in 3D movie format of the entire tract prior to surgery to guide the neurosurgeon. While the color in FA maps does change by the changing direction of the tract, the color of DTT can be fixed for the visualization purposes. Also the DTT can be visualized over the clinical MR images to help in the anatomical localization of the tract.
The purpose of this study was to investigate the role of DTI and DTT and to test the reliability and robustness of the technique in brainstem lesions by using it before and after surgical resection.
Section snippets
Methods
The study was approved by the local Institutional Review Board at Yeditepe University Hospital. Fourteen patients with a brainstem lesion (six cavernomas, five glial tumors, one hemangioblastoma, one mixed glial tumor and one metastasis) were included in the study. Table 1 shows the demographic information, diagnosis, location and size of the brainstem lesions.
Results
Neurological exams before surgery revealed MRC Grade 5 (no motor deficits) in 22 CSTs, MRC Grade 4 in five CSTs and MRC Grade 3 in one CST (Table 3). There was no patient with MRC Grade 2 or 1. Some of the patients also had various combinations of sensory and cranial nerve deficits but these symptoms were not discussed in this study's scope.
All patients without motor deficit before surgery also had normal motor neurological exams after surgery. There was no additional motor deficit detected in
Discussion
DTT demonstrating the white matter tracts is needed for pre-surgical planning and favorable post-surgical outcomes in the surgical treatment of supratentorial brain lesions [4], [9], [14], [19], [20], [21]. Wu et al. in their 4-year long prospective study found that DTI-based functional neuro-navigation contributes to maximal safe resection of cerebral gliomas and decreases post-operative motor deficits and increases high-quality survival [22].
However, up to date there have been only a limited
Conclusion
DTT is a promising technique in evaluating patients with brainstem lesions with high sensitivity and negative predictive values although it has relatively high false positive results especially before surgery. Technical improvements and further clinical studies are still needed to increase the accuracy of DTT.
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2021, Journal of NeuroradiologyCitation Excerpt :Previous published literature on DTT in non-hemorrhagic brain stem space-occupying mass lesions reported excellent correlation between the tractography images and patient's neurological status [6,7,11]. Kovanlikaya et al. [6] reported one case of BSCM with interrupted CST but having no motor deficit in a DTT study of 14 patients with brain stem lesions in their study group. DTT provides crucial anatomical information for the preoperative surgical planning about the brain stem entry zone and the surgical trajectory [13].
Neurite orientation dispersion and density imaging in evaluation of high-grade glioma-induced corticospinal tract injury
2021, European Journal of RadiologyCitation Excerpt :However, the underlying assumption of a Gaussian spin displacement distribution in this approach often makes it problematic to interpret the changes of these parameters pathophysiologically. For example, DTI often sensitively predicts a functional injury of the peritumoral white matter in the brain stem, but with a low specificity [8], which sometimes traps the neurosurgeons in a dilemma and may lead to an overestimated destruction of the neural fibers [9]. Additionally, fiber-tracking based on DTI sometimes does not accurately reconstruct the fiber bundle in pathological condition, which may lead to post-surgical sequela like hemiparesis for the patients [10].
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Preliminary version of this study was presented as a scientific paper at RSNA 2007 Chicago, IL.