Classification of Cause of Motor Weakness in Traumatic Brain Injury Using Diffusion Tensor Imaging

Background: Many studies have attempted to elucidate the causes of motor weakness in patients with traumatic brain injury (TBI). Most of these studies have focused on the specific cause of motor weakness. However, little is known about the classification and elucidation of the causes of motor weakness in consecutive patients with TBI. Objective: To attempt to classify with diffusion tensor imaging the causes of motor weakness in patients with TBI by conducting an analysis of the injury mechanism of the corticospinal tract (CST). Design: Retrospective study. Setting: Rehabilitation department of a university hospital. Patients: We recruited 41 consecutive patients who showed motor weakness among patients with TBI admitted for rehabilitation. Main Outcome Measures: We classified the causes of weakness according to the injury mechanism of the CST on diffusion tensor imaging. Results: Injury mechanisms of the CST were classified as follows, in order: diffuse axonal injury, 24 patients (58.5%); traumatic intracerebral hemorrhage, 9 patients (21.9%); transtentorial herniation, 6 patients (14.6%); and focal cortical contusion, 4 patients (9.8%). In patients with diffuse axonal injury, the mean number of lesions composing CST injury was 3.6 (range, 2-6) and CST injury locations were as follows: the pons (61%), the cerebral peduncle (50%), the medulla (40%), the posterior limb of the internal capsule (17%), and the corona radiata (13%). Conclusion: We found that diffusion tensor imaging was useful in elucidation and classification of the causes of motor weakness resulting from CST injury in patients with TBI.