Cerebral blood flow and metabolism in patients with cognitive impairments after minor traumatic brain injury: PET study in a chronic state

Abstract

In order to clarify the pathophysiology of cognitive impairments after mild traumatic brain injury (TBI), we studied cerebral blood flow and metabolism using positron emission computed tomography (PET). Fifty-two patients with mild TBI were divided into three groups based on magnetic resonance images (MRI) findings: normal (group N), diffuse axonal injury (DAI) (group D), and DAI with brain atrophy (group V). PET data were obtained by the steady state method using 15O labeled gases. Regional cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2) were measured for each brain area. Higher cortical dysfunction was evaluated using Wechsler Adult Intelligence Scale-Revised (WAIS-R). WAIS-R scores for group V were significantly lower than for group N. In almost all patients, CBF and OEF were within normal ranges, however, CMRO 2 was decreased slightly. CMRO 2 in all regions of group V except for the bilateral parietal lobes was significantly lower than in group N. We conclude that the severity of higher cortical dysfunction in these cases correlated with a decrease of CMRO 2 and the severity of DAI.