Abstract WP90: Evidence of Acute Ischemic Injury Near Traumatic Vascular Injuryin Patients Following Head Trauma

Introduction: After head trauma, diffusion weighted imaging (DWI) lesions may be interpreted as ischemic stroke. In some patients, multiple traumatic microbleeds are seen on T2* MRI. Post-mortem data following severe injury shows underlying damage to the vessels (traumatic vascular injury (TVI)) with adjacent cell death. Here, in a cohort of patients with predominately mild injury, we investigate whether post-traumatic DWI lesions occur in close proximity to the T2* lesions characteristic of TVI. Methods: Subjects were included in this analysis if they consented, received MRI within 48 hours of injury, were DWI-positive, and had TVI identified by i) linear microbleeds; ii) more than 5 punctate traumatic microbleeds; and/ or iii) evidence of confluent petechial blood (contusion) on baseline T2* MRI. Diffusion and T2* images were reviewed together for TVI, lesions on DWI, and proximity (within 1 mm) to one another. Regions on DWI confounded by extra-axial hemorrhage were excluded. Results: Of 581 patients enrolled over 78-month period, 104 (18%) met criteria. Subjects were 52 (34.5-67) years old, 23 (22%) female, 77 (74%) white, mostly mild with 55 (53%) having GCS=15, 30 (29%) injured in MVA, 55 (53%) by fall, and were imaged 26 (16.9, 37.9) hours from injury. DWI lesions were observed in proximity to TVI in 85 (82%) patients. Linear lesions were detected in 24 (23%), more than 5 punctate in 3 (3%) and confluent petechial blood in 36 (35%) patients. 41 (39%) patients had one or more classifications. There was an association between linear appearing lesions on T2* and lesions on DWI (p=0.001). Discussion: Evidence of ischemic injury to the parenchyma with a hyperintense lesion on DWI and/or low ADC is seen frequently in patients with TVI and in proximity to the vascular lesion (Fig1). While direct injury to the parenchyma cannot be ruled out, the appearance of the lesion on DWI suggests primary injury to the vasculature followed by secondary ischemic injury to the tissue.