Plasticity of language networks in patients with brain tumors: A positron emission tomography activation study

Abstract

We investigated plasticity of language networks exposed to slowly evolving brain damage. Single subject 0-15-water language activation positron emission tomography studies were analyzed in 61 right-handed patients with brain tumors of the left hemisphere, and 12 normal controls. In controls, activations were found in left Brodmann's Area (BA)44 and BA45, superior posterior temporal gyrus bilaterally, and right cerebellum. Patients additionally activated left BA46, BA47, anterior insula, and left cerebellum. Superior temporal activation was less frequent, and activations in areas other than posterior temporal gyrus were found bilaterally. Frontolateral activations within the nondominant hemisphere were only seen in patients (63%) with frontal or posterior temporal lesions. Laterality indices of frontolateral cortex showed reversed language dominance in 18% of patients. Laterality indices of the cerebellum were negatively correlated with language performance. Two compensatory mechanisms in patients with slowly evolving brain lesions are described: An intrahemispheric mechanism with recruitment of left frontolateral regions other than classic language areas; and an interhemispheric compensatory mechanism with frontolateral activation in the nondominant hemisphere. The latter one was only found in patients with frontal or posterior temporal lesions, thus supporting the hypothesis that right frontolateral activations are a disinhibition phenomenon.

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

“…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.…”

Right hemisphere structures predict poststroke speech fluency

“…This interpretation would suggest right hemisphere remodeling as a beneficial mechanism rather than a maladaptive one or an epiphenomenon, which is in contrast with interpretations of some previous studies. 13,22,23,40 A principal limitation of our study is that it does not allow us to identify any time points at which these right hemisphere or CC changes may occur or to conclusively determine whether or not these differences are preexisting. In addition, the larger representation of men in our study groups (85% for both patients and controls) may limit the cross-gender generalizability of our findings.…”

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

“…Furthermore, they also suggest that, in addition to short-term recruitment of areas adjacent to the surgical resection cavity, long-term reorganization may occur related to progressive recruitment of more distant areas within the dominant hemisphere or recruitment of contralateral (right) nondominant hemispheric areas via transcallosal disinhibition. 25,46,[56][57][58] This conjecture is intriguing, especially in light of the above-described stroke functional imaging literature, which suggests the opposite phenomenon; this discordance suggests that perhaps the mechanisms of recovery in slow-growing lesions are different from those used in cases of sudden insult such as with stroke (infarction). This observation again highlights the importance of the time course of the cerebral insult in the determination of the most efficient mode of language plasticity.…”