Identifying preoperative language tracts and predicting postoperative functional recovery using HARDI q-ball fiber tractography in patients with gliomas

Abstract

abbreviatioNs AF = arcuate fasciculus; AFTD = altered fiber tractography density; CD = clinical deficit; CRT set = clinically relevant tract set; DTI = diffusion tensor imaging; FA = fractional anisotropy; GTR = gross-total resection; HARDI = high angular resolution diffusion-weighted imaging; HGG = high-grade glioma; IFOF = inferior frontooccipital fasciculus; ILF = inferior longitudinal fasciculus; IR-SPGR = inversion-recovery spoiled gradient echo; ISM = intraoperative stimulation mapping; LGG = low-grade glioma; MdLF = middle longitudinal fasciculus; MNI = Montreal Neurological Institute; MST set = minimally sufficient tract set; ODF = orientation distribution function; ROI = region of interest; SLF = superior longitudinal fasciculus; SLF-tp = temporoparietal component of SLF; SLF-II&III = SLF components II and III; UF = uncinate fasciculus. obJective Diffusion MRI has uniquely enabled in vivo delineation of white matter tracts, which has been applied to the segmentation of eloquent pathways for intraoperative mapping. The last decade has also seen the development from earlier diffusion tensor models to higher-order models, which take advantage of high angular resolution diffusion-weighted imaging (HARDI) techniques. However, these advanced methods have not been widely implemented for routine preoperative and intraoperative mapping. The authors report on the application of residual bootstrap q-ball fiber tracking for routine mapping of potentially functional language pathways, the development of a system for rating tract injury to evaluate the impact on clinically assessed language function, and initial results predicting long-term language deficits following glioma resection. methods The authors have developed methods for the segmentation of 8 putative language pathways including dorsal phonological pathways and ventral semantic streams using residual bootstrap q-ball fiber tracking. Furthermore, they have implemented clinically feasible preoperative acquisition and processing of HARDI data to delineate these pathways for neurosurgical application. They have also developed a rating scale based on the altered fiber tract density to estimate the degree of pathway injury, applying these ratings to a subset of 35 patients with pre- and postoperative fiber tracking. The relationships between specific pathways and clinical language deficits were assessed to determine which pathways are predictive of long-term language deficits following surgery. results This tracking methodology has been routinely implemented for preoperative mapping in patients with brain gliomas who have undergone awake brain tumor resection at the University of California, San Francisco (more than 300 patients to date). In this particular study the authors investigated the white matter structure status and language correlation in a subcohort of 35 subjects both pre- and postsurgery. The rating scales developed for fiber pathway damage were found to be highly reproducible and provided significant correlations with language performance. Preserva...

Brain white matter fibre tracts: a review of functional neuro-oncological relevance

“…An elegant recent study evaluated longitudinal preoperative and postoperative DT against postsurgical language outcomes. All patients with preserved arcuate and temporo-parietal fibres showed preserved language following surgery, whereas damage to either pathway predicted persistent deficits 6 months postsurgery 21. Similar findings have been reported in smaller case studies and highlight an additional postoperative indication of DT to prognosticate recovery of early postoperative deficits 21…”

“…For example, the majority of DT evaluations are based on minimal (six direction) data, analysed with deterministic approaches, an approach that is particularly susceptible to fail in areas of oedema or crossing fibres (figure 2). Instead, studies comparing basic and advanced algorithms highlight that probabilistic tractography and multifibre models provide results that better represent anatomical complexity in cortical terminations of fibre tracts14 and better predict surgical outcomes21 than deterministic DT results. High variability in acquired data quality, as well as user-defined analysis approaches, fundamentally limits evaluations of DT’s clinical utility.…”

“…In contrast, DES applied near the lateral SLF-III fibres produces dysarthria or anarthria,3 supporting contributions to motor articulatory aspects of speech. After resections up to these tracts, patients tend to exhibit transient speech disorders,21 while infarcts affecting SLF/arcuate fibres disrupt phonological processing22 and reduce speech fluency 23. These clinical data suggest that, in humans, the dominant-hemisphere arcuate and SLF-III may constitute a ‘dorsal phonological route’ of speech monitoring, planning and execution in modern parallel stream models of language 24…”

“…However, retrospective studies identified damage to connections linking the superior temporal and angular gyri as predictive of aphasia after stroke36 and found surgical damage to the SLF-tp or arcuate to result in sustained language deficits 21…”

Cluster-viz: A Tractography QC Tool

“…In-progress developments include patient-specific anatomical reference in both slice and surface representation, and iterative clustering functionality. The connectivity of an ROI placed on the coronal plane over the external/extreme capsules at the level of the anterior commissure is shown (tractography method: Caverzasi et al 2015). Each color is a cluster, as generated by the Quickbundles algorithm (Garyfallidis et al 2012).…”