Plasticity in language cortex and white matter tracts after resection of dominant inferior parietal lobule arteriovenous malformations: a combined fMRI and DTI study

Abstract

OBJECTIVEThe dominant inferior parietal lobe (IPL) contains cortical and subcortical structures that serve language processing. A high incidence of postoperative short-term aphasia and good potential for language reorganization have been observed. The authors’ goal was to study the plasticity of the language cortex and language-related fibers in patients with brain arteriovenous malformations (BAVMs) located in the IPL.METHODSA total of 6 patients who underwent microsurgical treatment of an IPL BAVM were prospectively recruited between September 2016 and May 2018. Blood oxygen level–dependent functional MRI (BOLD-fMRI) and diffusion tensor imaging (DTI) were performed within 1 week before and 6 months after microsurgery. Language-related white matter (WM) eloquent fiber tracts and their contralateral homologous fiber tracts were tracked. The Western Aphasia Battery was administered to assess language function. The authors determined the total number of fibers and mean fractional anisotropy (FA) indices for each individual tract. In addition, they calculated the laterality index (LI) between the activated language cortex voxels in the lesional and contralesional hemispheres and compared these indices between the preoperative and postoperative fMR and DT images.RESULTSOf the 6 patients with IPL BAVMs, all experienced postoperative short-term language deficits, and 5 (83.3%) recovered completely at 6 months after surgery. Five patients (83.3%) had right homologous reorganization of BOLD signal activations in both Broca’s and Wernicke’s areas. More fibers were observed in the arcuate fasciculus (AF) in the lesional hemisphere than in the contralesional hemisphere (1905 vs 254 fibers, p = 0.035). Six months after surgery, a significantly increased number of fibers was seen in the right hemispheric AF (249 fibers preoperatively vs 485 postoperatively, p = 0.026). There were significantly more nerve fibers in the postoperative left inferior frontooccipital fasciculus (IFOF) (874 fibers preoperatively vs 1186 postoperatively, p = 0.010). A statistically significant increase in right hemispheric dominance of Wernicke’s area was observed. The overall functional LI showed functional lateralization of Wernicke’s area in the right hemisphere (LI ≤ −0.20) in all patients.CONCLUSIONSThe authors’ findings provide evidence for the functional reorganization by recruiting the right hemispheric homologous region of Broca’s and Wernicke’s areas, right hemispheric AFs, and left hemispheric IFOFs following resection of IPL BAVMs.Clinical trial registration no.: NCT02868008 (clinicaltrials.gov)