MR Imaging and Outcome of TBI (Traumatic Brain Injury)

MR Imaging and Outcome of TBI

MR imaging is more sensitive than CT for detecting abnormalities in the brain after TBI .This modality is very sensitive for identifying diffuse axonal injury (DAI) and nonhemorrhagic contusions.In one study MR imaging detected DAI in 30% of patients with a mild head injury whose head CTs appeared normal.

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In recent years, the use of MRI to assess TBI has increased. However, its use in the early posttraumatic period has been limited because scant evidence of its efficacy is available. Most studies have had limited success in correlating late MR imaging findings with neuropsychological outcomes. One explanation for this limited success is that the functional abnormalities that may be associated with mild, moderate, and severe TBI cannot be defined in terms of standard MR imaging sequences. Although more sensitive than CT, MR imaging still may not reflect functional abnormalities. Notwithstanding, an overall increase in the use of MR imaging has increased appreciation for the extent of structural abnormalities associated with TBI. The main problem now facing neurotrauma clinicians is how to interpret these findings in relation to functional outcome.


MR imaging has been used to determine the prognosis of TBI in various studies.These studies, however, have mostly focused on the technical feasibility of using the modality to detect abnormalities in patients with TBIs. Recently, techniques such as fluid-attenuated inversion-recovery (FLAIR), diffusion-weighting, diffusion tensor, and magnetization transfer imaging have been used to define traumatic lesions.MR spectroscopy also has allowed specific cellular metabolites to be measured after TBI. Functional MR imaging has been used to determine that memory deficiencies associated with TBI correlate with lateralization of activation.These advances in imaging technologies have improved the definition of lesions not detected by conventional CT.

Although MR imaging technology has been used extensively with TBI, a comprehensive analysis of the ability of MR imaging to predict outcomes associated with TBIs has not been performed. A recent study from Greece used MR imaging during the acute phase of trauma (within 48 hours) to predict outcomes in a small cohort of patients. They found that severity of DAI loosely correlated with outcome based on the GOS.However, detailed neuropsychological testing was not used to determine subtle changes in outcome not captured by the GOS. Furthermore, only patients with a normal CT scan were included. Thus, patients with known lesions on CT who may have had unseen secondary lesions were excluded.

Another group in Germany used MR imaging to classify TBI and to predict outcomes. They found that the mortality rate significantly increased as the severity of infratentorial lesions increased. Three to 22 months after injury, GOS scores were significantly worse in patients with severe brainstem lesions. However, the neuropsychological effects of these lesions were not studied. Because MR imaging is more sensitive than CT, a thorough investigation of consecutive patients is needed to correlate MR imaging abnormalities associated with TBI with functional (GOS) and cognitive (neuropsychological) endpoints to identify prognostic factors.

In conclusion, the increased use of MR imaging to evaluate head-injured patients has allowed more subtle intracerebral abnormalities to be detected. This heightened sensitivity for detecting abnormalities is beginning to improve the ability to predict long-term outcomes in patients with TBIs.