Study objectives: To investigate the role of cranial magnetic resonance (MR) imaging in evaluating patients discharged from the emergency department after minor head injury.
Design: A prospective blinded cohort study.
Setting: University hospital ED.
Type of participants: Fifty-eight patients with minor head injury who were discharged from the ED with written head injury instructions. Patients admitted to the hospital were excluded.
Interventions: Ultra-low-field cranial MR scans were performed on patients within 24 hours of discharge. Scans were read blindly by two radiologists.
Measurements and main results: Fisher's exact test was used to compare symptoms in patients with abnormal and normal MR scans. There was no significant difference in symptoms between patients with abnormal and those with normal scans (P greater than .10). The proportion of abnormal MR scans was analyzed using the binomial distribution. Six of the 58 patients (10.3%) had traumatic intracranial abnormalities (proportion, 0.103; SD, 0.04; 95% CI, 0.04-0.21). Three had cortical contusions, and three had small subdural hematomas. Two of the six patients with abnormal MR scans, both with small subdural hematomas, had normal computed tomography scans.
Conclusion: Ten percent of patients discharged from the ED after minor head injury had abnormal ultra-low-field cranial MR scans. Additional research is needed to establish the clinical importance of this unexpected observation.