Longitudinal evaluation of corticospinal tract in patients with resected brainstem cavernous malformations using high-definition fiber tractography and diffusion connectometry analysis: preliminary experience

Abstract

abbreviatioNs ADL = activities of daily living; CC = corpus callosum; CM = cavernous malformation; CN = cranial nerve; CST = corticospinal tract; DSI = diffusion spectrum imaging; DTI = diffusion tensor imaging; FDR = false discovery rate; HDFT = high-definition fiber tractography; ICH = intracerebral hemorrhage; QA = quantitative anisotropy; ROI = region of interest; SRS = stereotactic radiosurgery. obJect Brainstem cavernous malformations (CMs) are challenging due to a higher symptomatic hemorrhage rate and potential morbidity associated with their resection. The authors aimed to preoperatively define the relationship of CMs to the perilesional corticospinal tracts (CSTs) by obtaining qualitative and quantitative data using high-definition fiber tractography. These data were examined postoperatively by using longitudinal scans and in relation to patients' symptomatology. The extent of involvement of the CST was further evaluated longitudinally using the automated "diffusion connectometry" analysis. methods Fiber tractography was performed with DSI Studio using a quantitative anisotropy (QA)-based generalized deterministic tracking algorithm. Qualitatively, CST was classified as being "disrupted" and/or "displaced." Quantitative analysis involved obtaining mean QA values for the CST and its perilesional and nonperilesional segments. The contralateral CST was used for comparison. Diffusion connectometry analysis included comparison of patients' data with a template from 90 normal subjects. results Three patients (mean age 22 years) with symptomatic pontomesencephalic hemorrhagic CMs and varying degrees of hemiparesis were identified. The mean follow-up period was 37.3 months. Qualitatively, CST was partially disrupted and displaced in all. Direction of the displacement was different in each case and progressively improved corresponding with the patient's neurological status. No patient experienced neurological decline related to the resection. The perilesional mean QA percentage decreases supported tract disruption and decreased further over the follow-up period (Case 1, 26%-49%; Case 2, 35%-66%; and Case 3, 63%-78%). Diffusion connectometry demonstrated rostrocaudal involvement of the CST consistent with the quantitative data. coNclusioNs Hemorrhagic brainstem CMs can disrupt and displace perilesional white matter tracts with the latter occurring in unpredictable directions. This requires the use of tractography to accurately define their orientation to optimize surgical entry point, minimize morbidity, and enhance neurological outcomes. Observed anisotropy decreases in the perilesional segments are consistent with neural injury following hemorrhagic insults. A model using these values in different CST segments can be used to longitudinally monitor its craniocaudal integrity. Diffusion connectometry is a complementary approach providing longitudinal information on the rostrocaudal involvement of the CST.

Endoscopic Endonasal Transclival Approach for Resection of a Pontine Glioma: Surgical Planning, Surgical Anatomy, and Technique

“…36 QA bypasses the limitations of fractional anisotropy (FA) and generalized FA on the areas of crossing fibers, such as the centrum semiovale and the brainstem, and the areas of mass effect originated by a lesion. 12,32 In the case presented here, the quantitative results showed a correlation with the qualitative data of trajectory restoration and tract preservation and with the partial improvement on patient's motor strength.…”

“…In cases involving noninfiltrative lesions (eg cavernous malformations), surgical resection is facilitated by the fact that the white matter tracts are typically displaced to the periphery of the lesion, while no tracts run within the lesion itself. 12,32 In contrast, in cases of diffuse pathology, such as the glioma presented here, important fiber tracts may be infiltrated in addition to displaced, and located within the confines of the lesion instead of the periphery. In such cases, HDFT not only can help defining the anatomy of the displaced fiber tracts around the lesion but can depict the location of infiltrated fiber tracts that could be placed at risk during the resection and therefore can also help defining the boundaries of a safe resection within the lesion.…”

“…As previously reported for brainstem lesions, DTI-based fiber tracking serves as an important tool to preoperatively assess the integrity and status of the white matter tracts. 6,[32][33][34][35] Here we used an advanced diffusion-based fiber tracking technique, HDFT, that has shown to have the best valid connections, with over 90% accuracy as examined in an open competition. 21 As illustrated in our case, HDFT was able to accurately depict the anatomy of important fiber tracts within the brainstem, and helped in constructing a surgical plan.…”

White matter tractography for neurosurgical planning: A topography-based review of the current state of the art

“…For example, in brainstem cavernomas, the classic perilesional hemosiderin deposits can be responsible for susceptibility artifacts that can falsely interrupt nearby tracts (Faraji et al, 2015, Kovanlikaya et al, 2011). The close proximity of large arteries (vertebral and basilar) can also produce pulsation artifacts (Kovanlikaya et al, 2011).…”

Tractography for Surgical Neuro-Oncology Planning: Towards a Gold Standard

“…Each of these factors affects surrounding white matter differently. In general, however, it is observed that benign, non-neuronal lesions such as meningiomas and cavernomas cause tract displacement, whereas diffusely proliferating gliomas produce incremental tract infiltration and destruction with increasing histopathological grade [5,[34][35][36] (Fig. 1).…”