title: Stereotactic probability and variability of speech arrest and anomia sites during stimulation mapping of the language dominant hemisphere.
abstract: OBJECTIVE Functional mapping using direct cortical stimulation is the gold standard for the prevention of postoperative morbidity during resective surgery in dominant-hemisphere perisylvian regions. Its role is necessitated by the significant interindividual variability that has been observed for essential language sites. The aim in this study was to determine the statistical probability distribution of eliciting aphasic errors for any given stereotactically based cortical position in a patient cohort and to quantify the variability at each cortical site. METHODS Patients undergoing awake craniotomy for dominant-hemisphere primary brain tumor resection between 1999 and 2014 at the authors' institution were included in this study, which included counting and picture-naming tasks during dense speech mapping via cortical stimulation. Positive and negative stimulation sites were collected using an intraoperative frameless stereotactic neuronavigation system and were converted to Montreal Neurological Institute coordinates. Data were iteratively resampled to create mean and standard deviation probability maps for speech arrest and anomia. Patients were divided into groups with a "classic" or an "atypical" location of speech function, based on the resultant probability maps. Patient and clinical factors were then assessed for their association with an atypical location of speech sites by univariate and multivariate analysis. RESULTS Across 102 patients undergoing speech mapping, the overall probabilities of speech arrest and anomia were 0.51 and 0.33, respectively. Speech arrest was most likely to occur with stimulation of the posterior inferior frontal gyrus (maximum probability from individual bin = 0.025), and variance was highest in the dorsal premotor cortex and the posterior superior temporal gyrus. In contrast, stimulation within the posterior perisylvian cortex resulted in the maximum mean probability of anomia (maximum probability = 0.012), with large variance in the regions surrounding the posterior superior temporal gyrus, including the posterior middle temporal, angular, and supramarginal gyri. Patients with atypical speech localization were far more likely to have tumors in canonical Broca's or Wernicke's areas (OR 7.21, 95% CI 1.67-31.09, p < 0.01) or to have multilobar tumors (OR 12.58, 95% CI 2.22-71.42, p < 0.01), than were patients with classic speech localization. CONCLUSIONS This study provides statistical probability distribution maps for aphasic errors during cortical stimulation mapping in a patient cohort. Thus, the authors provide an expected probability of inducing speech arrest and anomia from specific 10-mm2cortical bins in an individual patient. In addition, they highlight key regions of interindividual mapping variability that should be considered preoperatively. They believe these results will aid surgeons in their preoperative planning of eloquent cortex resection.
authors.affiliation: Departments of 1 Neurological Surgery.|Physiology, and.|Center for Integrative Neuroscience, University of California, San Francisco; and.|Center for Neural Engineering and Prostheses, University of California, Berkeley, and University of California, San Francisco, California.
authors.forename: Edward F
authors.initials: EF
authors.lastname: Chang
authors.affiliation: Departments of 1 Neurological Surgery.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Breshears
authors.affiliation: Departments of 1 Neurological Surgery.
authors.forename: Kunal P
authors.initials: KP
authors.lastname: Raygor
authors.affiliation: Departments of 1 Neurological Surgery.
authors.forename: Darryl
authors.initials: D
authors.lastname: Lau
authors.affiliation: Departments of 1 Neurological Surgery.|Epidemiology and Biostatistics.
authors.forename: Annette M
authors.initials: AM
authors.lastname: Molinaro
authors.affiliation: Departments of 1 Neurological Surgery.
authors.forename: Mitchel S
authors.initials: MS
authors.lastname: Berger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000849:Anomia / Q000503:physiopathology*; D001931:Brain Mapping; D001932:Brain Neoplasms / Q000503:physiopathology / Q000601:surgery; D054022:Cerebrum / Q000503:physiopathology* / Q000601:surgery; D003399:Craniotomy; D005260:Female; D007839:Functional Laterality; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D015233:Models, Statistical; D011336:Probability; D013060:Speech / Q000502:physiology*; D013238:Stereotaxic Techniques; D055815:Young Adult
keywords: MNI = Montreal Neurological Institute; anomia; cortical stimulation; functional neurosurgery; language mapping; pSTG = posterior superior temporal gyrus; probability maps; speech arrest; vPMC = ventral premotor cortex