Imaging findings in diffuse axonal injury after closed head trauma

Abstract

Even in patients with closed head trauma, brain parenchyma can be severely injured due to disruption of axonal fibers by shearing forces during acceleration, deceleration, and rotation of the head. In this article we review the spectrum of imaging findings in patients with diffuse axonal injuries (DAI) after closed head trauma. Knowledge of the location and imaging characteristics of DAI is important to radiologists for detection and diagnosis. Common locations of DAI include: cerebral hemispheric gray-white matter interface and subcortical white matter, body and splenium of corpus callosum, basal ganglia, dorsolateral aspect of brainstem, and cerebellum. In the acute phase, CT may show punctate hemorrhages. The true extent of brain involvement is better appreciated with MR imaging, because both hemorrhagic and non-hemorrhagic lesions (gliotic scars) can be detected. The MR appearance of DAI lesions depends on several factors, including age of injury, presence of hemorrhage or blood-breakdown products (e. g., hemosiderin), and type of sequence used. Technical aspects in MR imaging of these patients are discussed. Non-hemorrhagic lesions can be detected with fluid attenuated inversion recovery (FLAIR), proton-density-, or T2-weighted images, whereas gradient echo sequences with long TE increase the visibility of old hemorrhagic lesions.

Diffusion Tensor Imaging Characteristics of the Corpus Callosum in Mild, Moderate, and Severe Traumatic Brain Injury

“…This is somewhat different from the general view that primarily the posterior corpus callosum is affected in TBI. 3,6,7,28 Furthermore, our results show that there are different types of microstructural injuries within the corpus callosum, as indicated by FA and ADC findings in the genu and splenium. A limitation of our study is the absence of neuropsychological correlations and long-term follow-up of our DTI findings.…”

“…Conventional imaging and pathologic-anatomic study have indicated that the posterior corpus callosum is more susceptible to fiber disruption than the anterior corpus callosum. [2][3][4]24 In consequence, it may be hypothesized that the DTI pattern we observed in the splenium is associated with more irreversible traumatic lesions than the DTI pattern in the genu, which in turn may reflect more reversible abnormalities. This should be investigated in a longitudinal study.…”

“…1 The location and severity of traumatic axonal injury is related to various factors, 2,3 including the characteristics of acceleration/deceleration forces during the trauma incident and differences in attenuation and rigidity between adjacent cerebral structures. One of the predilection sites of traumatic axonal injury is the corpus callosum.…”

“…5 CT and MR imaging studies have indicated that the corpus callosum is unevenly affected in TBI in the sense that the splenium more commonly shows traumatic axonal injury than the genu and body. [2][3][4]6,7 However, the frequency of axonal injury is underestimated with CT and various MR imaging techniques, such as fluid-attenuated inversion recovery (FLAIR), T2-weighted fast spin-echo, and T2*-weighted gradient-echo (GE) sequences. 7,8 Diffusion tensor imaging (DTI) has evolved in recent years as a valuable complementary technique to investigate traumatic axonal injury.…”

Abnormal Motor Preparation in Severe Traumatic Brain Injury with Good Recovery

“…This peculiar lesion pattern is characterized by widespread disruption of axons that occurs at the time of an acceleration and deceleration injury. DAI lesions tend to be multiple and small (Parizel et al, 1998). The radiological recognition of DAI can be of critical importance for understanding the clinical syndrome and for predicting TBI patients' outcome.…”