High-definition fiber tractography for the evaluation of perilesional white matter tracts in high-grade glioma surgery

Abstract

Conventional white matter (WM) imaging approaches, such as diffusion tensor imaging (DTI), have been used to preoperatively identify the location of affected WM tracts in patients with intracranial tumors in order to maximize the extent of resection and potentially reduce postoperative morbidity. DTI, however, has limitations that include its inability to resolve multiple crossing fibers and its susceptibility to partial volume effects. Therefore, recent focus has shifted to more advanced WM imaging techniques such as high-definition fiber tractography (HDFT). In this paper, we illustrate the application of HDFT, which in our preliminary experience has enabled accurate depiction of perilesional tracts in a 3-dimensional manner in multiple anatomical compartments including edematous zones around high-grade gliomas. This has facilitated accurate surgical planning. This is illustrated by using case examples of patients with glioblastoma multiforme. We also discuss future directions in the role of these techniques in surgery for gliomas.

Keywords: Diffusion tensor imaging; edema; glioblastoma multiforme; intracranial mass lesions.

Fig. 1.

(A) MRI of the brain in Case 1 demonstrated a contrast-enhancing lesion in the left postcentral gyrus with associated perilesional edema. (B) Preoperative high-definition fiber tractography (HDFT) revealed an anteriorly displaced corticospinal (Cort-sp.) tract compared with the contralateral side as demonstrated by the cortical end points of the tract. (C) Preoperative HDFT was used to demonstrate the corticospinal and supplementary motor area (SMA) fibers coursing adjacent to the lesion in the edematous zone. (D) Early postoperative MRI of the brain with contrast demonstrated a resection cavity in the postcentral gyrus, limited anteriorly due to the location of the precentral gyrus and preoperatively identified displaced corticospinal tracts. (E) A delayed follow-up MRI after chemoradiotherapy shows evidence of resolution of some of the postoperative residual tumor.

Fig. 2.

(A) MRI of the brain in Case 2 demonstrated a left-sided contrast-enhancing basal ganglia mass with evidence of a previous middle cerebral artery territory infarction. (B) Preoperative high-definition fiber tractography revealed a displaced corticospinal tract (Cort-sp.) in the perilesional area. (C) T2-weighted MRI of the brain further delineated the tumor. (D) Postoperative contrast-enhanced MRI showed a residual cuff of tumor along the margin adjacent to the corticospinal tract and thalamus.

Fig. 3.

(A) MRI of the brain in Case 3 demonstrated a right-sided contrast enhancing parieto-occipital lesion leading to left-sided homonymous hemianopia (panel below). (B) Preoperative high-definition fiber tractography (HDFT) showed medially and inferiorly displaced optic radiation (Optic Rad.) in the perilesional edematous area. (C) Postoperative MRI with contrast confirmed an adequate resection with a small residual on the medial margin adjacent to the optic radiation. (D) Postoperative HDFT confirmed the improvement in the configuration of the displaced optic radiation (red: preoperative; green: postoperative). This was accompanied by an improvement in the visual field deficit (panel above).

Fig. 4.

(A, axial) and (B, coronal) Preoperative MRI with contrast in Case 4 demonstrated an enhancing left insular lesion with extension into the fronto-orbital operculum and the temporal lobe. (C) Preoperative high-definition fiber tractography (HDFT) demonstrated the course of the arcuate fasciculus (Arc. Fas.) through the perilesional edematous area. Arrow (yellow) represents the site of the corticotomy in the frontal operculum. (D) Frontal termination of the arcuate fibers was identified in the pars opercularis, precentral gyrus, and middle frontal gyrus using HDFT and to help with the decision-making regarding the site of corticotomy in the frontal operculum. (E) A representative anatomical view in a cadaveric specimen shows the insula with overlying M2 branches of the middle cerebral artery and the location of the pars triangularis (Pars triang.) and the superior temporal gyrus (STG). (F) A comparable intraoperative view is presented after debulking of the tumor in between the M2 branches. The location of the pars triangularis is demonstrated.

Fig. 5.

(A, sagittal); (D, axial), and (G, coronal) Preoperative MRI with contrast revealed a right-sided enhancing posterior cingulate lesion with an encysted atrium (G). (B, sagittal) and (E, axial) Preoperative high-definition fiber tractography (HDFT) characterized the qualitative changes in the perilesional white matter (cingulum, forceps major [Forceps Maj.] and optic radiations [Optic Rad.]). (H) Postoperative HDFT demonstrated disruption in the forceps major (Forceps Maj.) due to the surgical trajectory through this potentially infiltrated fiber bundle. (C, sagittal); (F, axial) and (I, coronal) Postoperative MRI with contrast demonstrated the resection cavity in the posterior cingulum with resolution of the tumor cyst.