Diagnostic performance of magnetic resonance imaging in suspected stroke: Strengths, weaknesses, and clinical correlates.
BACKGROUND Stroke and transient ischemic attack (TIA) are clinical diagnoses; however, magnetic resonance imaging (MRI) with diffusion weighted imaging (DWI) is frequently used as a supplement in the diagnostic process and may also assist in differentiating stroke from stroke mimics. We aimed to test strengths and weaknesses of applying MRI as first scan in patients with suspected stroke, using clinical diagnoses as a reference. METHODS Patients consecutively admitted with suspected stroke to a non-comprehensive stroke emergency medical unit with a concomitant MRI were included. A neuroradiologist and a neurology resident collected imaging and clinical data, respectively. We calculated sensitivity and specificity between clinical diagnosis and radiological findings, and tested associations between bedside characteristics and disagreement in diagnoses. RESULTS We included 627 patients (mean age 68 years, 56% female) and found 137 (22%) had ischemic stroke, 102 (16%) TIA, and 5 (0.8%) hemorrhagic strokes at discharge. On the MRI, 155 (25%) had ischemic lesions, 8 (1.3%) hemorrhagic lesions. For all ischemic strokes or TIAs there was 58% sensitivity and 96% specificity with MRI where sensitivity increased to 93% when excluding TIA-patients. Persistent symptoms at admission in the Emergency Department and unilateral motor symptoms associated with DWI-positive stroke/TIA whereas decreased level of consciousness associated with DWI-positive stroke/TIA mimics. CONCLUSIONS In non-comprehensive stroke care with an MRI-first approach, MRI is moderately sensitive and highly specific for stroke and TIA, and its performance varies depending on the clinical context.