Presurgical language fMRI: Mapping of six critical regions

Abstract

Language mapping is a key goal in neurosurgical planning. fMRI mapping typically proceeds with a focus on Broca's and Wernicke's areas, although multiple other language‐critical areas are now well‐known. We evaluated whether clinicians could use a novel approach, including clinician‐driven individualized thresholding, to reliably identify six language regions, including Broca's Area, Wernicke's Area (inferior, superior), Exner's Area, Supplementary Speech Area, Angular Gyrus, and Basal Temporal Language Area. We studied 22 epilepsy and tumor patients who received Wada and fMRI (age 36.4[12.5]; Wada language left/right/mixed in 18/3/1). fMRI tasks (two × three tasks) were analyzed by two clinical neuropsychologists who flexibly thresholded and combined these to identify the six regions. The resulting maps were compared to fixed threshold maps. Clinicians generated maps that overlapped significantly, and were highly consistent, when at least one task came from the same set. Cases diverged when clinicians prioritized different language regions or addressed noise differently. Language laterality closely mirrored Wada data (85% accuracy). Activation consistent with all six language regions was consistently identified. In blind review, three external, independent clinicians rated the individualized fMRI language maps as superior to fixed threshold maps; identified the majority of regions significantly more frequently; and judged language laterality to mirror Wada lateralization more often. These data provide initial validation of a novel, clinician‐based approach to localizing language cortex. They also demonstrate clinical fMRI is superior when analyzed by an experienced clinician and that when fMRI data is of low quality judgments of laterality are unreliable and should be withheld. Hum Brain Mapp 38:4239–4255, 2017. © 2017 Wiley Periodicals, Inc.

Presurgical language fMRI: Clinical practices and patient outcomes in epilepsy surgical planning

“…More sophisticated models of language have been suggested for well over a century in the clinical literature [e.g., see Benjamin et al, 2017 for a review] and have been a recent focus in the cognitive literature [e.g. Tremblay & Dick, 2016].…”

“…The analyst's perceived goal will change the activation map. Two overlaid maps (red; yellow) generated independently by two clinicians for the same patient (see Benjamin et al, 2017). [Benjamin et al, 2017] Analysts were blind to case details.…”

“…Two overlaid maps (red; yellow) generated independently by two clinicians for the same patient (see Benjamin et al, 2017). [Benjamin et al, 2017] Analysts were blind to case details. One prioritized frontal (red) and the other temporal (yellow) regions, as when mapping frontal tumor vs temporal lobectomy cases.…”

Presurgical language fMRI: Technical practices in epilepsy surgical planning

“…Historic models emphasizing the role of Broca's and Wernicke's areas in “expressive” and “receptive” speech exclusively are a useful heuristic, but do not reflect all language‐critical areas (Benjamin et al, 2017; Tremblay & Dick, 2016). Expressive and/or receptive deficits can follow either anterior or posterior lesions in at least some instances; this is also true to varying degrees in at least four further regions and almost certainly more (Hamberger et al, 2001).…”

“…For example, software packages often implement different solutions in key analysis steps, and fMRI validation studies have used a range of packages such as AFNI (Sabsevitz et al, 2003), SPM (Bonelli et al, 2012), and custom software (Benjamin et al, 2017). Each step in data preprocessing alters the output; and the literature validating fMRI preprocessing may or may not include explicit realignment of echo‐planar imaging (EPI) data, or involvement of explicit smoothing of 2 mm, 10 mm, or an unspecified amount (Benjamin et al, 2017; Bonelli et al, 2012; Janecek et al, 2013). The approach to identification of task‐related signal also varies, with both general linear modeling and correlation coefficients in use.…”