Diffusivity of Normal-Appearing Tissue in Acute Traumatic Brain Injury

Abstract

Apparent diffusion coefficient (ADC) values derived from diffusion-weighted magnetic resonance imaging (MRI) can provide information about traumatic changes not visible in conventional MRI. The ADC values in acute traumatic brain injury (TBI) were measured and correlated with initial severity and outcome scores. In this study 22 unselected patients were studied 1week (mean 7 ± 2days) after TBI of variable severity. In conventional MRI 7patients were without visible findings, 15 showed cortical contusions or traumatic axonal injury and 14 healthy subjects served as controls. The ADC values were measured from 46 brain regions away from the visible traumatic changes and compared between the groups. Regional ADC values and the number of abnormal regions were correlated with the Glasgow coma scale (GCS) on arrival in hospital and the Glasgow outcome scale (extended version, GOS-E) at 1 year after injury. The ADC values of TBI patients with and without visible lesions did not show any differences but both groups differed significantly from the controls in several cortical and deep brain regions. Increased ADC values were common in TBI groups but decreased ADC values were relatively uncommon. The regional ADC values and the number of abnormal regions did not correlate with either GCS or GOS-E scores. Increased diffusion in normal appearing brain tissue is a common finding 1 week after TBI in patients with and without visible lesions in conventional MRI. More investigations are needed to evaluate how these findings could be used for clinical applications.