Ischemic Stroke Without Corresponding Brain Lesion in Magnetic Resonance Imaging

Keimyung Medical Journal 1998;17(4):504-513.

뇌자기공명영상촬영술상 병변을 관찰 할 수 없는 허혈성 뇌경색

김진석; 김태완; 임정근

Abstract

Background ‘ Brain magnetic resonance imaging (MRI) is more sensitive than computed tomography in the diagnosis of acute ischemic stroke; but may not visualize all acute ischemic stroke. For deeper understanding of MRI negative strokes; we reviewed case histories; abnormal neurological findings; and localized ischemic lesions presumedly which were not present in brain MRI scans. Methods : Patients with a clinically definite first ischemic stroke and absence of corresponding lesion in brain MRI scans were studied retrospectively with hospital records dating from January 1994 to November 1996 and prospectively from December 1996 to August 1997. Patient with transient ischemic stroke; postictal paralysis; central nervous system infection; demyelinating disease; hemiplegic migraine; functional or hysterical cause; multiple cerebral infarction; scans within 24 hours and equivocal findings were excluded. Brain MRI was scanned with T2WI; T1WI and FLAIR sequence. Results： We studied 722 patients with clinically diagnosed definite acute ischemic stroke during the study period and identified 22 patients (3.1%) with the absence of corresponding lesion in brain MRI scan. The ischemic strokes without brain lesions on MRI scan were clinically localized to the brain stem (n=13; 59%); subcortex (n = 8; 36%) and in the cortex (n = l; 4.5%). Perforating arterial and thrombotic ischemic lesions seemed to be more common than large arterial & embolic lesions. Risk factors was not different between MRI positive and MRI negative ischemic stroke. Summary: Acute ischemic stroke with absence of brain lesion in MRI scans is more common in brain stem and subcortex than in the cortex. There is some potential limitation of standard MRI scan for diagnosis of acute ischemic stroke; therefore further scans with new imaging studies such as perfusion/diffusion weighted magnetic resonance imaging are required in selected cases.

Key Words: Ischemic stroke, Brain MRI, FLAIR sequence