Background: Use of MRI with diffusion weighted imaging (DWI) can identify infarcts in 30-50% of patients with transient neurovascular symptoms. Previous guidelines have indicated that MRI-DWI is the preferred imaging modality for patients with TIA symptoms. We assessed the frequency of MRI utilization and predictors of MRI performance in a national integrated health system.
Methods: A review of TIA and minor stroke patients evaluated at Veterans Affairs Hospitals (fiscal year 2011) was conducted. Administrative data was reviewed with regard to demographic factors, past medical history, use of diagnostic imaging within two days of presentation, and in hospital care variables. Detailed chart abstraction was performed in a patient subset of large volume hospitals to assess clinical variables.
Results: 8427 patients with TIA or minor stroke were included in the administrative data cohort. Overall, 6817 patients (80.9%) had cranial imaging (either CT or MRI) within two days of presentation, with 3420 (50.2%) having CT without MRI and 3397 (49.8%) having MRI. 3.6% of patients with CT only had a pacemaker. Specific variables that were associated with CT performance (rather than MRI) in the administrative data cohort included the following: age>80 years, prior stroke, atrial fibrillation, dementia, and congestive heart failure (p<0.0001 for each). On chart review, diplopia as a complaint (87% with diplopia had MRI vs. 13% had CT only, p=0.03), neurological consultation in the Emergency Department (73% had MRI vs. 27% had CT only, p< 0.0001), and symptom duration of >6 hours (74% had MRI vs. 26% had CT only, p=0.0009) were associated with MRI performance.
Conclusions: Within a large national health system, about 40% of patients with TIA or minor stroke had MRI performed within two days. Performance of MRI appears to be influenced by several variables, including age, nature of the symptoms, prior stroke, and neurological consultation in the ED. These data suggest that there has been partial acceptance of the previous guideline which endorsed MRI for patients with TIA.