Introduction: The objective of this study was to prospectively assess the evolution of traumatic axonal injury (TAI) / diffuse axonal injury lesions detected by structural magnetic resonance imaging (MRI) in patients with moderate to severe head injury during the first year post-injury and relate the findings with outcome.
Methods: Sixty-one patients with traumatic brain injury (Glasgow Coma Scale score 3-13) were examined with MRI at median 8 days, 3 and 12 months post-injury. TAI lesions were evaluated blinded for patient information and categorized into three stages based on location; hemispheres, corpus callosum and brainstem. The number of T2*-weighted gradient echo (GRE) and fluid-attenuated inversion recovery (FLAIR) lesions were counted and FLAIR lesion volumes were segmented and an inter-rater reliability calculated. Outcome was assessed 12 months post-injury by Glasgow Outcome Scale Extended.
Results: In the first MRI, 33% had brainstem lesions compared with 18% at 3 months (p=0.008). In the FLAIR sequences number and volumes of lesions were reduced at 3 months compared with early MRI (p<0.001). In T2*GRE sequences the number of lesions persisted at 3 months, but was reduced at 12 months (p=0.004). Number of T2*GRE lesions and FLAIR lesion volume predicted worse outcome in adjusted analyses (p<0.01). The inter-rater reliability was excellent for FLAIR volume and number of T2*GRE lesions.
Conclusions: This is the first study to demonstrate and quantify the attenuation of non-hemorrhagic TAI lesions during the first year post-injury, most importantly the disappearance of brainstem lesions during the initial 3 months. Hemorrhagic TAI lesions attenuate first after 3 months. Both number of T2*GRE lesions and FLAIR lesion volumes predict clinical outcome even after adjustment for other known prognostic factors.
Patient Care: It is an important finding that non-hemorrhagic lesions, especially in the brain stem, attenauate shortly post-injury. Thus, early MRI is important both for outcome prediction and determination of rehabilition needs.
Learning Objectives: By the conclusion of this session, participants should understand the clinical implication of MRI preferably beeing performed during the first few weeks post-injury in severe TBI patients to improve outcome prediction. Because of the prominent attenuation of non-hemorrhagic lesion, we believe early MR imaging also applies for the moderate TBI patients despite the less prognostic importance.