ReportsBRAIN INJURY

Local changes in network structure contribute to late communication recovery after severe brain injury

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Science Translational Medicine  07 Dec 2016:
Vol. 8, Issue 368, pp. 368re5
DOI: 10.1126/scitranslmed.aaf6113

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Establishing communication after severe brain injury

Recovery of communication after severe brain injury can occur over long time scales, yet the biological underpinnings of this uncertain process remain unknown. Thengone et al. longitudinally captured the 2.75-year evolution of the recovery of communication in a severely brain-injured patient by repeatedly measuring brain structure and function using multimodal imaging. Concordant findings of structural and functional reorganization of expressive language networks in both hemispheres suggested that recovery of communication involved both local changes within the language-dominant hemisphere and increased connections between hemispheres. These findings support a specific mechanism underlying the recovery of communication after severe brain injury.

Abstract

Spontaneous recovery of brain function after severe brain injury may evolve over a long time period and is likely to involve both structural and functional reorganization of brain networks. We longitudinally tracked the recovery of communication in a patient with severe brain injury using multimodal brain imaging techniques and quantitative behavioral assessments measured at the bedside over a period of 2 years and 9 months (21 months after initial injury). Structural diffusion tensor imaging revealed changes in brain structure across interhemispheric connections and in local brain regions that support language and visuomotor function. These findings correlated with functional brain imaging using functional magnetic resonance imaging and positron emission tomography, which demonstrated increased language network recruitment in response to natural speech stimuli, graded increases in interhemispheric interactions of language-related frontal cortices, and increased cerebral metabolic activity in the language-dominant hemisphere. In addition, electrophysiological studies showed recovery of synchronization of sleep spindling activity. The observed changes suggest a specific mechanism for late recovery of communication after severe brain injury and provide support for the potential of activity-dependent structural and functional remodeling over long time periods.

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