Insights into Adult Postlesional Language Cortical Plasticity Provided by Cerebral Blood Oxygen Level–Dependent Functional MR Imaging

Abstract

SUMMARY: BOLD fMRI has provided new insights into postlesional brain language plasticity by providing a noninvasive in vivo approach to evaluate longitudinal changes in brain cortical activation during performance of language tasks. Specifically, BOLD fMRI has provided the opportunity to investigate not only changes in eloquent language cortex resulting from different types of brain pathology such as brain tumors, stroke, and epilepsy but also changes in eloquent language cortex occurring as a result of actual surgical resection of diseased but, nevertheless, partially functional tissue. In addition to reviewing the literature relating to stroke and epilepsy-related language plasticity as well as the more intriguing phenomenon of postsurgical plasticity in the setting of brain tumors, 2 unusual cases illustrating this latter manifestation of language plasticity are briefly described in this review article.ABBREVIATIONS: BOLD ϭ blood oxygen levelϪdependent; DECS ϭ direct electrical cortical stimulation (intraoperative mapping); fMRI ϭ functional MR imaging; GABA ϭ gamma-aminobutyric acid (neurotransmitter); L ϭ left; LI ϭ laterality index; LIFG ϭ left inferior frontal gyrus; MPRAGE ϭ magnetization-prepared rapid acquisition gradient echo; NV ϭ noun-verb (association); P ϭ phonological (rhyming); PET ϭ positron-emission tomography; R ϭ right; RIFG ϭ right inferior frontal gyrus; S1 ϭ first (preoperative) fMRI scanning session; S2 ϭ second (first postoperative) fMRI scanning session; S3 ϭ third (second postoperative) fMRI scanning session; SPM ϭ Statistical Parametric Mapping; TLE ϭ temporal lobe epilepsy B

Final Cerebral Infarct Volume Is Predictable by MR Imaging at 1 Week

“…The correlations were not very strong, a point largely reported in the literature [22][23][24] and easy to understand, considering the numerous additional factors that can influence clinical outcomes at the disability/handicap level (On-line Fig 1). [25][26][27] Here, other clinical (initial stroke severity, age) or neuroimaging (recanalization, reperfusion) variables were significantly associated with the outcome, in line with previous studies. 25,28 The relatively weak association between infarct volumes and clinical outcomes does not necessarily discredit volume as a surrogate marker.…”

Effectiveness of four different clinical fMRI paradigms for preoperative regional determination of language lateralization in patients with brain tumors

“…It has been shown indeed that language areas can be found quite remotely from their classical localizations, especially in pathological states such as epilepsy [43]; therefore, we may have incurred the risk of missing intrahemispherically shifted, i.e., reorganized, language activation. However, to date, little is known about the phenomenon of postsurgical language plasticity in brain tumor patients, and for this reason, more studies are needed to investigate this topic [44].…”

Clinical Standardized fMRI Reveals Altered Language Lateralization in Patients with Brain Tumor

“…36 A longitudinal case study comparing pre-and postsurgical language lateralization in 2 patients demonstrated a shift of the dominant hemisphere to the opposite side after neurosurgery. 37 In other studies using different imaging modalities, authors have assumed that cortical reorganization is a step-by-step process, with shortterm recruitment of perilesional areas and long-term recruitment of more distant areas within the dominant or contralateral hemisphere. 22,[38][39][40] Our study supports the hypothesis that cortical reorganization impacts language lateralization, with a possible shift toward the contralateral nondominant hemisphere.…”

“…22,23,52 Those studies led to the hypothesis that neuronal plasticity occurs predominantly in slow-growing neoplasms or after repetitive limited surgical resections. 24,37 However, no study has been performed to evaluate language lateralization in a larger cohort of patients with brain tumor before neurosurgery. Taken together, our results indicate that brain tumors affecting the Broca or Wernicke areas have an impact on language lateralization.…”