Stroke with negative brain magnetic resonance imaging.

Magnetic resonance imaging (MRI) of the brain is replacing computed tomography in the diagnostic evaluation of acute ischemic strokes. Past studies have suggested that MRI may not visualize all acute strokes, but few clinical details were included. To better understand the clinical characteristics of strokes not detected by MRI, we collected and reviewed case histories of several patients with acute stroke who had negative MRI scans. Patients with a clinical diagnosis of stroke and negative brain MRI scans were ascertained from hospital records dating from 1989 to mid-1991. Patients with transient ischemic attacks, postictal paralysis, functional examinations, central nervous system infections, other nonstroke diagnoses, or equivocal findings were excluded. The MRI scans were performed with a GE Signa 1.5-T magnet in an axial plane (spin-echo repetition time/echo time: 500 msec/20 msec; 2,500 msec, 30 msec/80 msec). One patient received contrast material. We identified seven patients with clinically diagnosed ischemic stroke and negative brain MRI scan. Six of seven patients were scanned within 7 days of symptom onset and two patients within 24 hours. One patient was scanned 3 months after symptom onset. The strokes not detected by MRI were clinically localized to the cortex (n = 3), brain stem (n = 3), and subcortical/lacunar area (n = 1). One patient underwent two MRI scans, one with gadolinium. These cases, while selected, illustrate some potential limitations of MRI for diagnosing stroke.