CDE Detailed Report

Choose one. These terms are defined differently in the clinical, radiologic, and pathologic arenas, and have evolved in the radiologic sphere concurrent with advances in detection, particularly using MRI. The term DAI was initially coined to describe the pathologic findings in primates subjected to experimental, high magnitude, non-impact angular deceleration ("inertial") forces, which resulted in prolonged unconsciousness and widespread injury to axons in the hemispheric white matter and brainstem 17. The injury was modeled to explain prolonged coma in human patients with high-energy injury mechanisms and prolonged unconsciousness with minimal CT findings, but widespread axonal damage in a similar distribution to that seen in animal models on histopathology 18. As CT spatial resolution improved and specialized MR sequences evolved, lesions similar to those described in autopsy studies have been identified in patients with clinically less severe injuries, in whom the length of unconsciousness is shorter and the outcome better than those for whom the term was originally employed. Currently, there exists a spectrum of animal models of inertial white matter injuries which do not necessarily follow the specific anatomic distribution of the original descriptions. Similarly, radiologic techniques demonstrate lesions in more limited distributions in human patients. Therefore, many authors use the term "traumatic axonal injury" to refer to more limited axonal injury which appears to result from traumatic inertial forces and tissue strains in the white matter. While these injuries occur in a continuum, for purposes of classification they are operationally defined as described below.