Chronic aphasias after left-hemisphere resective surgery

Background. Surgical resection of brain tumours is associated with an increased risk of aphasia. However, relatively little is known about outcomes in the chronic phase (i.e., > 6 months). The aim of this study was to document the incidence of chronic post-surgical aphasia and characterise the neuroanatomical mechanism(s) responsible for poor outcomes. Methods. 46 patients who underwent surgical resection of a primary left-hemisphere tumour were assessed with the Comprehensive Aphasia Test (CAT) between 6- and 24-months post-surgery (mean 10 months). Using voxel-based lesion symptom mapping (VLSM), we investigated whether chronic language impairments are related to the location of surgical resection, residual tumour characteristics (e.g., progressive infiltration, oedema) or both. Results. Approximately 72% of patients scored below the cut-off for aphasia. Action naming and spoken sentence comprehension deficits were significantly associated with lesions in the left anterior temporal and inferior parietal lobes, respectively. Voxel-wise analyses of white matter disconnection severity revealed significant associations between ventral language pathways and action naming deficits. Reading impairments were also associated with increasing disconnection of cerebellar pathways. No significant results were observable for writing deficits. Only lesions comprising both the resection site and residual tumour characteristics were significantly associated with language impairments. Conclusions. Our findings indicate chronic post-surgical aphasias are common. In addition, the nature of the aphasia reflects a combination of resected tissue and tumour infiltration of language-related white matter tracts, implicating progressive disconnection as the critical mechanism of impairment. This information may prove useful for predicting language outcomes and planning appropriate language therapies following surgery.