| Summary: | Functional reorganization may explain why. despite a large tumour in eloquent cortex. the patient has no neurological impairment. The aims of the present study were to 1. Investigate the effect of tumour growth on neural circuits for speech production and visual processing and 2. Determine the effect of tumour removal on speech production and visual processing. Three patients with large, left-hemisphere brain tumours had pre- surgery and post-surgery functional neuroimaging (fMRI) and language testing (CAT). In addition, these patients underwent surgery for tumour resection. Pre-operative fMRI demonstrated functional reorganization in the patients. All three patients showed regions of overactivation and underactivation in local and remote regions relative to tumour location. Of particular interest, two patients showed increased activity in the right hemisphere homologue of their left parietal tumour whereas one patient illustrated a decreased activation in the right hemisphere homologue region to her left postcentral tumour. A comparison of pre and post-surgery fMRI results demonstrated that functional reorganization primarily occurs prior to surgery although some changes in activation occur after surgery. This study provides evidence that the right hemisphere homologue region is differentially activated (over and under) across patients. Furthermore, our study suggests that the effect of brain tumour growth is more prominent than tumour resection.
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