Reemergence of the language network during recovery from severe traumatic brain injury: A pilot functional MRI study

Primary objective: We hypothesized that, in patients with acute severe traumatic brain injury (TBI) who recover basic language function, speech-evoked blood-oxygen-level-dependent (BOLD) functional MRI (fMRI) responses within the canonical language network increase over the first 6 months post-injury.

Research design: We conducted a prospective, longitudinal fMRI pilot study of adults with acute severe TBI admitted to the intensive care unit. We also enrolled age- and sex-matched healthy subjects.

Methods and procedures: We evaluated BOLD signal in bilateral superior temporal gyrus (STG) and inferior frontal gyrus (IFG) regions of interest acutely and approximately 6 months post-injury. Given evidence that regions outside the canonical language network contribute to language processing, we also performed exploratory whole-brain analyses.

Main outcomes and results: Of the 16 patients enrolled, eight returned for follow-up fMRI, all of whom recovered basic language function. We observed speech-evoked longitudinal BOLD increases in the left STG, but not in the right STG, right IFG, or left IFG. Whole-brain analysis revealed increases in the right supramarginal and middle temporal gyri but no differences between patients and healthy subjects (n = 16).

Conclusion: This pilot study suggests that, in patients with severe TBI who recover llanguage function, speech-evoked responses in bihemispheric language-processing cortex reemerge by 6 months post-injury.