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 neuroi maging techniques such as CT scan or MRI. Objective: To explore the relatio nships between regional cerebral glucose metabolism at rest, as measured by PET, and neurobehavioral status after severe TBI at the subacute stage. Me thods: Thirteen patients without focal structural lesion on MRI were studie d. Neuropsychological assessment included tests of memory, attention and sp eed of information processing, and executive functions, and a global neurob ehavioral assessment. Regional cerebral glucose metabolism at rest was meas ured with (F-18)-fluorodeoxyglucose and PET. Results: A close link was foun d between cognitive and behavioral disorders and decreased cortical metabol ism in prefrontal and cingulate cortex. Tests of memory and executive funct ions significantly correlated with regional metabolism in the mesial and la teral prefrontal cortex and the cingulate gyrus. Behavioral disorders corre lated significantly with mesial prefrontal and cingulate metabolisms. Concl usion: 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 t he brain. Further cognitive functional activation research using PET or fun ctional MRI might help clarify the relative contributions of both areas to dysfunction.