Functional anatomy of neuropsychological deficits after severe traumatic brain injury

Background: Neurobehavioral disorders after Severe traumatic brain injury (TBI) are poorly correlated with focal lesions detected by structural neuroimaging techniques such as CT scan or MRI. Objective: To explore the relationships between regional cerebral glucose metabolism at rest, as measured by PET, and neurobehavioral status after severe TBI at the subacute stage. Methods: Thirteen patients without focal structural lesion on MRI were studied. Neuropsychological assessment included tests of memory, attention and speed of information processing, and executive functions, and a global neurobehavioral assessment. Regional cerebral glucose metabolism at rest was measured with (F-18)-fluorodeoxyglucose and PET. Results: A close link was found between cognitive and behavioral disorders and decreased cortical metabolism in prefrontal and cingulate cortex. Tests of memory and executive functions significantly correlated with regional metabolism in the mesial and lateral prefrontal cortex and the cingulate gyrus. Behavioral disorders correlated significantly with mesial prefrontal and cingulate metabolisms. Conclusion: These results suggest a predominant role of prefrontal and cingulate dysfunction in cognitive and behavioral disorders of patients with severe traumatic brain injury, even in the absence of focal structural lesion of the brain. Further cognitive functional activation research using PET or functional MRI might help clarify the relative contributions of both areas to dysfunction.