Role of Magnetic Resonance Imaging in Patients With Suspected Stroke and Nondiagnostic Computed Tomography

Stroke is the second most common cause of death and a major cause of disability. Most EDs use CT imaging (non-contrast and CT angiography) as their only diagnostic modality, while others use MRI. Many of our patients receive both CT and MRI. We determined how often adding MRI detected new findings or led to a significant change in clinical management.

We performed a retrospective chart review of 200 consecutive patients presenting to a primary stroke center in 2024 with a suspected stroke which led to a stroke activation. Data collected included patient demographics, comorbidities, presenting symptoms, time from symptom onset, NIH Stroke Scale score (NIHSS), imaging findings, diagnosis, and disposition. The primary outcome was the percentage of patients in whom the MRI found an acute ischemic stroke (AIS) not found on CT. A secondary outcome with the percentage of cases where MRI led to a significant change in patient management such as administration of thrombolytics, thrombectomy, or craniotomy.

There were 200 patients, 2 were excluded since imaging was performed at an outside institution prior to transfer. Mean (SD) age was 65.7 (17.6) years, 62% were greater than age 60. Of all patients, 51.3% were females, 77.5% were white, 9.8% were Hispanic, 8.4% were Black, 1.0% were Asian. Time from symptom onset was 0-3 hours (44%), 3-6 hours (22%), 6-24 hours (15.5%), greater than 24 hours (4.5%) and unknown (14%). Mean (SD) NIHSS was 6 (8), median (IQR) score was 2 (0-9). Imaging included non-contrast head CT (NCCT) (99%), CT angiography (94.5%), CT perfusion (93.5%), and MRI (45.2%). NCCT findings included no abnormalities (83.7%), hemorrhage (8.2%), and AIS (8%). CT angiography was abnormal in 32.6%. Occluded vessels included left MCA (24%), right ICA (20%), right MCA (16%), right PCA (12%), right ACA (9%), right vertebral (8%) and basilar (4%). CT perfusion was abnormal in 21.2%. Of 90 patients (45.5%) who had MRI in addition to CT, 23.6% were abnormal. MRI identified an AIS in 14 of 87 cases in which CT was normal (16%, 95%CI 9.8-25.2) including 4 cortical, 8 subcortical, and 2 cerebellar strokes. None of these patients received thrombolytics or thrombectomy.

Nearly half of all patients presenting with suspected stroke had an MRI in addition to CT. AIS was identified on 16% of MRIs where CT was normal. MRI should be considered in addition to CT, especially with persistent symptoms despite negative CT.