Tag: voxel-based lesion-symptom mapping

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Dissociation of Broca’s area from Broca’s aphasia in patients undergoing neurosurgical resections

J Neurosurg 138:847–857, 2023

Broca’s aphasia is a syndrome of impaired fluency with retained comprehension. The authors used an unbiased algorithm to examine which neuroanatomical areas are most likely to result in Broca’s aphasia following surgical lesions.

METHODS Patients were prospectively evaluated with standardized language batteries before and after surgery. Broca’s area was defined anatomically as the pars opercularis and triangularis of the inferior frontal gyrus. Broca’s aphasia was defined by the Western Aphasia Battery language assessment. Resections were outlined from MRI scans to construct 3D volumes of interest. These were aligned using a nonlinear transformation to Montreal Neurological Institute brain space. A voxel-based lesion-symptom mapping (VLSM) algorithm was used to test for areas statistically associated with Broca’s aphasia when incorporated into a resection, as well as areas associated with deficits in fluency independent of Western Aphasia Battery classification. Postoperative MRI scans were reviewed in blinded fashion to estimate the percentage resection of Broca’s area compared to areas identified using the VLSM algorithm.

RESULTS A total of 289 patients had early language evaluations, of whom 19 had postoperative Broca’s aphasia. VLSM analysis revealed an area that was highly correlated (p < 0.001) with Broca’s aphasia, spanning ventral sensorimotor cortex and supramarginal gyri, as well as extending into subcortical white matter tracts. Reduced fluency scores were significantly associated with an overlapping region of interest. The fluency score was negatively correlated with fraction of resected precentral, postcentral, and supramarginal components of the VLSM area.

CONCLUSIONS Broca’s aphasia does not typically arise from neurosurgical resections in Broca’s area. When Broca’s aphasia does occur after surgery, it is typically in the early postoperative period, improves by 1 month, and is associated with resections of ventral sensorimotor cortex and supramarginal gyri.

 

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Transient aphasias after left hemisphere resective surgery

Transient aphasias after left hemisphere resective surgery

J Neurosurg 123:581–593, 2015

Transient aphasias are often observed in the first few days after a patient has undergone resection in the language- dominant hemisphere. The aims of this prospective study were to characterize the incidence and nature of these aphasias and to determine whether there are relationships between location of the surgical site and deficits in specific language domains.

Methods One hundred ten patients undergoing resection to the language-dominant hemisphere participated in the study. Language was evaluated prior to surgery and 2–3 days and 1 month postsurgery using the Western Aphasia Battery and the Boston Naming Test. Voxel-based lesion-symptom mapping was used to identify relationships between the surgical site location assessed on MRI and deficits in fluency, information content, comprehension, repetition, and naming.

Results Seventy-one percent of patients were classified as aphasic based on the Western Aphasia Battery 2–3 days postsurgery, with deficits observed in each of the language domains examined. Fluency deficits were associated with resection of the precentral gyrus and adjacent inferior frontal cortex. Reduced information content of spoken output was associated with resection of the ventral precentral gyrus and posterior inferior frontal gyrus (pars opercularis). Repetition deficits were associated with resection of the posterior superior temporal gyrus. Naming deficits were associated with resection of the ventral temporal cortex, with midtemporal and posterior temporal damage more predictive of naming deficits than anterior temporal damage. By 1 month postsurgery, nearly all language deficits were resolved, and no language measure except for naming differed significantly from its presurgical level.

Conclusions These findings show that transient aphasias are very common after left hemisphere resective surgery and that the precise nature of the aphasia depends on the specific location of the surgical site. The patient cohort in this study provides a unique window into the neural basis of language because resections are discrete, their locations are not limited by vascular distribution or patterns of neurodegeneration, and language can be studied prior to substantial reorganization.

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