Both of these patients were left-language-dominant preoperatively. Significance of These Findings in the Context of the Literature on Postlesional Language Plasticityīoth of the patients described above demonstrated changes in language lateralization resulting from new right frontal activation in the postoperative setting. Immediately postoperatively, he exhibited mild expressive aphasia but regained fluent speech within 2 months. More extensive and robust right inferior and middle frontal gyral activation was seen on S3 than on S1 or S2.
We noted a 28.96% increase in LI from S1 to S2, a 562.35% decrease from S2 to S3, and a 696.23% decrease from S1 to S3. No normalization was performed, but instead postoperative functional maps were overlaid on actual postoperative anatomy. After 3 months of therapy, the patient's naming abilities were all within functional limits.įigure 2 displays P task activation maps for patient 2, a 48-year-old man who underwent left frontotemporal anaplastic astrocytoma resection scans were obtained 2 weeks preoperatively and 5.5 and 31 months postoperatively. Three weeks after beginning speech rehabilitation, he demonstrated significant improvement in confrontation naming (90% accuracy). The patient was initially noted to have Broca aphasia based on Western Aphasia Battery testing, with moderate-to-severe anomia and difficulty with phrase repetition. Greater right middle frontal gyrus activation was seen in S2 compared with S1, which was maintained in S3. An 82.4% decrease in LI was noted from S1 to S2, and a 72.92% decrease from S1 to the S3 was observed.
Postoperative BOLD activation maps were normalized to preoperative anatomy. LIs were calculated according to the following formula, which refers to number of activated voxels in each L or R hemispheric region of interest: LI = (L − R) / (L + R).įigure 1 displays NV task activation maps for patient 1, a 33-year old man, who underwent left parietal anaplastic astrocytoma resection scans were obtained 2 weeks preoperatively and 5.5 and 15.5 months postoperatively. Supratentorial (entire frontal and anterior temporal lobe) hemispheric rectangular volume regions of interest were used to compute activated voxel LIs. 001 (without correction for multiple comparisons) with additional 10-voxel clustering (ie, spatial extent threshold) was performed. Images were acquired on a 1.5T MR imaging scanner, with preprocessing and statistical analysis conducted by using SPM (SPM99, Wellcome Department of Cognitive Neurology, London, United Kingdom ) implemented in Matlab 6.0 (MathWorks, Natick, Massachusetts). We will discuss in detail the literature relating to language plasticity following stroke and epilepsy, as well as the more recently described phenomenon of postsurgical cortical reorganization.
This review of the literature pertaining to fMRI investigations of cortical plasticity will begin with a brief illustration of 2 rare cases of brain tumor postsurgical language plasticity as an introduction to the more general phenomenon of postlesional language plasticity. The latter form of language plasticity has been considered rare. Recent emerging evidence has also suggested that in adults, postsurgical plasticity may occur in the setting of resection of diseased but nevertheless partially functional cortex. It has long been thought that the human language cortex loses most of its adaptive capabilities beyond childhood, but evidence during the past decade from BOLD fMRI suggests otherwise. Arguably, some of the most intriguing applications of BOLD fMRI to the study of cortical adaptation have involved the exploration of language plasticity, particularly in adults who have sustained injury to eloquent cortex through neoplastic infiltration, infarction, demyelination, or epilepsy. Abbreviations BOLD blood oxygen level−dependent DECS direct electrical cortical stimulation (intraoperative mapping) fMRI functional MR imaging GABA gamma-aminobutyric acid (neurotransmitter) L left LI laterality index LIFG left inferior frontal gyrus MPRAGE magnetization-prepared rapid acquisition gradient echo NV noun-verb (association) P phonological (rhyming) PET positron-emission tomography R right RIFG right inferior frontal gyrus S1 first (preoperative) fMRI scanning session S2 second (first postoperative) fMRI scanning session S3 third (second postoperative) fMRI scanning session SPM Statistical Parametric Mapping TLE temporal lobe epilepsyīOLD fMRI has provided new insights into brain plasticity with a valuable method for noninvasive in vivo evaluation of longitudinal changes in brain cortical activation.