What is the diagnostic value of head MRI after negative head CT in ED patients presenting with symptoms atypical of stroke?

The diagnostic value of head magnetic resonance imaging after negative head computed tomography for emergency department patients with vague neurologic symptoms, such as dizziness and altered mental status, remains an ongoing discussion. The objective of this study is to detect the subgroup of patients with such presentations having minor strokes whom may benefit from primary and secondary stroke prevention. We conducted a retrospective analysis and stratified patient risk factors associated with positive findings on subsequent head MRI ordered by the emergency department physician following a normal head CT. Two hundred fifty-two patients presenting with atypical stroke symptoms to the emergency department had a negative head CT followed by head MRI within 24 h ordered by emergency department clinician (123 males and 129 females; mean age of 59.4). Twenty nine of the 252 patients (11.5 %) had findings of acute to subacute infarct on the subsequent MRI. Positive MRI findings were statistically correlated with the following variables: age (p < 0.001), history of hyperlipidemia (p = 0.019), hypertension (p < 0.001), diabetes (p = 0.004), anticoagulation use (p = 0.029), and prior transient ischemic attack or stroke (p < 0.001). The mean age of the MRI-positive group was 74.1 years, with a mean difference of 16.7 ± 2.4 years more than the MRI-negative group (95 % CI, 11.8-21.5 years) (t = 6.8, p < 0.001). Emergency physicians caring for patients with vague neurologic complaints should maintain a lower threshold for ordering a head MRI despite a negative head CT for elderly patients with a history of prior stroke or transient ischemic attack to exclude a CT occult or minor ischemic stroke.