Absence of an infarct on MRI is not uncommon after clinical diagnosis of ischemic stroke

INTRODUCTION: An infarct on brain MRI is often seen as gold standard when diagnosing ischemic stroke. Although MRI has high sensitivity in detecting a lesion shortly after ischemic stroke, this rapidly declines when time progresses. We assessed the occurrence of a negative MRI 4-6 weeks after a discharge diagnosis of ischemic stroke, and compared the clinical characteristics of patients with a positive or negative MRI.

PATIENTS AND METHODS: The first 125 patients from a prospective longitudinal study of cognitive recovery after ischemic stroke were included in this study. Clinical characteristics were collected during admission. Per protocol, 4-6 weeks after stroke a brain MRI was performed. We operationalized different levels of certainty of the clinical diagnosis of ischemic stroke of a panel of 3 expert vascular neurologists.

RESULTS: Thirty patients (24%) were MRI negative. Patients that were MRI negative had lower stroke severity at admission, shorter duration of hospital-stay, and better functional status at discharge. The panel judged that 18/30 (60%) MRI negative patients and 27/30 (90%) MRI positive patients had a likely diagnosis of ischemic stroke. Compared to MRI negative patients with a less likely diagnosis, those with a likely diagnosis had higher admission stroke severity and more often received an acute intervention.

DISCUSSION AND CONCLUSION: Absence of an infarct on MRI is not uncommon 4-6 weeks after a clinical diagnosis of ischemic stroke. The relatively high proportion of MRI negative strokes with a likely clinical diagnosis of ischemic stroke indicates that neurologists should be cautious ruling out the diagnosis based on MRI beyond the acute stroke stage.