Description of changes in mean diffusivity in magnetic resonance of injuries of the ascending reticular system in patients with traumatic brain injury and impaired consciousness

Abstract

INTRODUCTION:

Patients with severe traumatic brain injury may have severe neurological sequelae that generate disability of different ranges, according to the Barthel scale. The consciousness impairment is the most serious sequela and is a cause of complete dependence of these patients, due to the loss of self-care. The relationship between abnormal findings in neuroimaging and different states of consciousness has been the subject of research in recent years, with the possibility of new options with the post-processing of magnetic resonance imaging (MRI). This study aims to describe the alterations in the mean diffusivity by post-processing of the diffusion weighted imaging (DWI) sequence in 4 patients with severe traumatic brain injury and impairment of consciousness, who were studied with computed tomography (CT) and MRI in the acute phase of the trauma.

MATERIALS AND METHODS:

We describe a series of 4 cases of patients with severe traumatic brain injury and impaired consciousness in whom a non-enhanced brain MRI was performed. The DWI sequence images were post-processed, analyzing different regions through which the fibers of the Ascending Reticular Activating System (ARAS) (including restiform bodies, midbrain, thalamus, sub-insular regions and basal frontal lobes) pass. Likewise, diffusivity values were taken in similar regions, in 5 subjects without any structural brain abnormality, who were taken as controls.

RESULTS:

There was a decrease in mean diffusivity in the different regions established in the study, which had different locations in each patient. Values decreased approximately 50 percent from values in normal patients. After post-processing, some lesions were observed in areas that were not identified in the initial MRI interpretation during the trauma.

CONCLUSIONS:

The post-processing of the DWI sequence shows a decrease in the mean diffusivity values in regions where the ARAS pathways pass through. These changes explaining the different alterations in consciousness were not visualized in the images interpreted under conventional MRI techniques. New studies are required to establish the operative characteristics of this test, that allow to define its potential utility within the algorithms of initial classification of patients with severe traumatic brain injury.