Fluid-Attenuated Inversion Recovery and Diffusion- and Perfusion-Weighted MRI Abnormalities in 117 Consecutive Patients With Stroke Symptoms

Abstract

Background and Purpose-Diffusion-weighted MRI (DWI) is highly sensitive to early cerebral ischemia, but its dependence on lesion location, acuity, and etiology remains unknown. Furthermore, although a marked perfusionweighted MRI (PWI)-DWI mismatch may exist in a subset of acute strokes, the frequency and distribution of these mismatches have never been methodically characterized in an unselected population. To address these 2 issues, we evaluated echo-planar imaging in 117 consecutive patients with signs and symptoms of acute stroke. Methods-Clinical diagnoses were determined by chart review. Fluid-attenuated inversion recovery (FLAIR), DWI, and PWI sequences were scored for lesion acuity, neuroanatomy, and vascular territory. Lesion and PWI-DWI mismatch volumes were determined by image analysis. Results-DWI was more sensitive than was FLAIR for the detection of stroke for all subtypes in all anatomic distributions and at all tested time intervals. Although DWI exhibited its greatest benefit over FLAIR during the first 6 hours, it was still superior to FLAIR even after 24 hours. PWI abnormalities were detected in 49% of patients with DWI abnormalities. In the majority of these cases, the PWI-DWI mismatch was substantially larger than the DWI lesion itself. Both the largest DWI lesion volumes and the largest mismatch volumes occurred in patients with carotid disease. Conclusions-DWI nearly doubles the likelihood of detecting acute ischemic stroke lesions compared with FLAIR for all etiologies and in all anatomic locations. In the hyperacute period (0 to 6 hours), DWI more than triples the likelihood of acute-stroke detection over FLAIR. PWI reveals a measurable mismatch compared with DWI nearly 50% of the time; and in more than half of these patients, the ratio of the volume of the PWI lesion to the DWI lesion is several times larger than the core ischemic lesion itself. In the final analysis, approximately one fourth of all stroke patients present with a large volume of potentially salvageable tissue at risk for infarction. (Stroke. 2001;32:2774-2781.)

Fluid–attenuated inversion recovery (FLAIR) sequences for the assessment of acute stroke

“…Only a few studies have compared DWI and FLAIR at the early ischemic stage and no studies evaluated inter- [14], DWI was more accurate than FLAIR sequences for the detection of acute stroke with a detection rate (DWI/FLAIR) of 46.3 %. In these series, DWI was more sensitive than FLAIR imaging for the acute detection of all stroke subtypes; however, there was a relationship between the size of the infarct measured on FLAIR images and that measured on DWI with a linear regression between FLAIR and DWI lesion volumes.…”

“…However, only a few studies have assessed the sensitivity of FLAIR sequences versus T2 weighted imaging or DWI for the detection of brain ischemia within the first 12 hours after symptom onset [3,[13][14][15]. In the acute phase of brain ischemia, DWI is theoretically the best examination to demonstrate restricted water motion related to the cytotoxic oedema [2,11] whereas conventional MR imaging including FLAIR sequences are mainly sensitive to vasogenic edema observed in the subacute phase of stroke [1].…”

Guidelines for the Early Management of Patients With Acute Ischemic Stroke

“…DWI can detect relatively small cortical lesions and small deep or subcortical lesions, including those in the brain stem or cerebellum, areas often poorly or not visualized with standard MRI sequences and NECT scan techniques. [182][183][184][185] DWI can identify subclinical satellite ischemic lesions that provide information on stroke mechanism. 173,176,179,[186][187][188][189][190][191][192][193][194][195][196][197] There are a few articles describing negative DWI studies when cerebral perfusion is decreased enough to produce infarction 198,199 and the reversal, partial or complete, of DWI abnormalities with restoration of perfusion.…”

Quantitative T2 Values Predict Time From Symptom Onset in Acute Stroke Patients

“…However, the sensitivity of FLAIR imaging within the first 6 hours of stroke onset was also reported to be time-dependent, and its relation to time from symptom onset is not well-defined. 8,9 In addition, visual interpretation of FLAIR images only provides binary information on lesion visibility and reveals an interobserver variability.…”