Trauma-Specific Brain Abnormalities in Suspected Mild Traumatic Brain Injury Patients Identified in the First 48 Hours after Injury: A Blinded Magnetic Resonance Imaging Comparative Study Including Suspected Acute Minor Stroke Patients

Abstract

We assessed the utility of a brief MRI protocol, appropriate for the acute setting, to detect acute traumatic brain injury (TBI) in patients with suspected mild TBI (mTBI) and distinguish traumatic from nontraumatic brain injury by comparing trauma with nontrauma patients. Twenty-two patients with suspected mTBI were included in this exploratory study over a period of 9 months. Median time from injury to MR scanning was 5.4 h (interquartile range 3.6-15.3). To determine the specificity of certain findings for TBI, 61 patients presenting with suspected minor acute stroke were included as a comparative group using the same MRI methods. A selected series of MRI sequences (diffusion-weighted imaging, fluid attenuated inversion recovery [FLAIR], and T2* weighted) were independently evaluated by two neuroradiologists blinded to clinical diagnosis, for presence of specific findings. In a separate session, all cases in which at least one MRI sequence above was positive were classified as TBI, stroke, or indeterminate. Intracranial MRI abnormalities were observed in 47 (57%) of the 83 studied patients. Based on findings on MRI, 12 (55%) of 22 suspected mTBI patients were classified as having traumatic injury. Nine (47%) of the 19 suspected mTBI patients with a negative CT had findings on MRI. Abnormalities on MRI consistent with trauma were observed most frequently on postcontrast FLAIR (83%) and T2*-weighted (58%) sequences. We demonstrated the ability of a fast MRI protocol to identify trauma-related abnormalities not seen on CT, and differentiate acute trauma from nonspecific chronic disease in a blinded cohort of mTBI patients.

Keywords: CT scanning; MRI; TBI.

FIG. 1.

Examples of meningeal enhancement of both frontal convexity and falx (A) and falx cerebri alone (B) determined by comparison of pre- and postcontrast fluid attenuated inversion recovery (FLAIR) in two mild traumatic brain injury (mTBI) patients whose trauma was caused by different mechanisms of injury. (C) Negative noncontrast CT of a 47-year-old male mTBI patient on admission to the emergency department (ED) (1 h after injury); 1.5 T MR T2*-weighted image showed linear microbleeds at 12 h after injury (circle). (D) Images of a 40-year-old male patient who underwent noncontrast CT on ED admission showed no extra-axial hemorrhage; however, the T2-FLAIR-weighted images on MRI depicted a small amount of subdural hematoma (SDH) along the right temporal and the left occipital lobes (arrows). (E) A 47-year-old male patient involved in a high-speed motor vehicle accident. CT scan was negative on ED admission; however, MRI showed blood in parenchyma on T2*-weighted, and cytotoxic edema on diffusion-weighted imaging (DWI) (circle).

FIG. 2.

(A) Flow diagram of the enrolled patients, final clinical diagnosis, and number of patients with MRI abnormalities for each diagnosis. Of the 22 patients with suspected mild traumatic brain injury (TBI), 3 had complicated mild TBI, showing evidence of brain injury on early CT scan. Sixty-one suspected minor stroke patients were included as a comparative nontrauma group. (B) MRI interpretation: of the 83 MRI examinations, 47 were read as positive. MRI abnormalities consistent with a diagnosis of trauma occurred in 12 in the group of suspected TBI patients and in 32 in the group of patients with suspected stroke-like symptoms. None of the suspected stroke patients were incorrectly classified as a TBI patient and none of the TBI patients were incorrectly classified as a stroke patient. Final diagnosis of ischemic stroke was confirmed in 28 of the 32 patients with positive MRI scans.