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.