Review of longitudinal studies of MRI brain volumetry in patients with traumatic brain injury

Introduction: Structural brain imaging in patients with traumatic brain injury (TBI) has progressed remarkably over the years with respect to technology and study design. Methods: Published studies of patients with TBI which used magnetic resonance imaging (MRI), volumetric measures and a longitudinal design-that is, one in which data were collected at more than one point in time-were reviewed. Some of these studies also included analyses using a cross-sectional (one point in time) approach. Results: Ten studies met the review criteria. Although methods varied, these studies showed a consistent pattern of brain atrophy which progressed over the months after injury. Effect sizes (brain size differences) between patients and normal control subjects generally were much larger for comparisons using the longitudinal approach than for those using a cross-sectional approach. Furthermore, atrophy correlated significantly with important clinical variables. Conclusion: In comparison with the cross-sectional design, the longitudinal design may be preferable for understanding the progression of brain atrophy after injury and understanding its association with important clinical variables.