Francois Moreau

Cavitation After Acute Symptomatic Lacunar Stroke Depends on Time, Location, and MRI Sequence

Background and Purpose— Definitions for chronic lacunar infarcts vary. Recent retrospective studies suggest that many acute lacunar strokes do not develop a cavitated appearance. We determined the characteristics of acute lacunar infarcts on follow-up MRI in consecutive patients participating in prospective research studies. Methods— Patients with acute lacunar infarction on diffusion-weighted imaging were selected from 3 prospective cohort studies of minor stroke imaged within <24 hours of onset. Follow-up MRI was performed at 30 days (Vascular Imaging of Acute Stroke for Identifying Predictors of Clinical Outcome and Recurrent Ischemic Events [VISION] study, n=21) or 90 days (VISION-2 and CT and MRI in the Triage of TIA and Minor Cerebrovascular Events to Identify High Risk Patients [CATCH] studies, n=34). Evidence of cavitation on MRI was rated separately on fluid-attenuated inversion recovery, T1, and T2 sequences by 2 independent study physicians; discrepant readings were resolved by consensus. Results— Probable or definite cavitation on any sequence was more common at 90 days compared with 30 days (P⩽0.001 for all sequences). At 90 days, evidence of cavitation was seen on at least 1 sequence in 33 of 34 patients (97%). The T1-weighted sequence was most sensitive to the presence of cavitation (94% at 90 days). By contrast, the fluid-attenuated inversion recovery sequence frequently failed to show evidence of cavitation in the brain stem or thalamus (only 10 of 18 [56%] showed cavitation). Conclusions— MRI scanning at 90 days with T1-weighted imaging reveals evidence of cavitation in nearly all cases of acute lacunar infarction. By contrast, reliance on fluid-attenuated inversion recovery alone will miss many cavitated lesions in the thalamus and brain stem. These factors should be taken into account in the development of standardized criteria for lacunar infarction on MRI.

Magnetic Resonance Imaging versus Computed Tomography in Transient Ischemic Attack and Minor Stroke: The More Υou See the More You Know

Background: Magnetic resonance imaging (MRI) is proposed as the preferred imaging modality to investigate patients with transient ischemic attack (TIA). This is mainly based on a higher yield of small acute ischemic lesions; however, direct prospective comparisons are lacking. In this study, we aimed to directly compare the yield of acute ischemic lesions on MRI and computed tomography (CT) in the emergency diagnosis of suspected TIA or minor stroke. Methods: Consecutive patients aged 18 years or older presenting with minor stroke (NIHSS <4) or high-risk TIA and who were examined by a stroke neurologist within 24 h of symptom onset were prospectively enrolled in the CATCH study. Patients who had undergone both a baseline CT and an MRI within 24 h of symptom onset were included in this substudy. Baseline MRI and CT were interpreted independently to identify an acute ischemic lesion. The rates of acute ischemic lesions on CT and MRI were compared, and the volume of acute ischemic lesions was measured on MRI. In addition, the volume of acute ischemic lesions on MRI was compared between patients who had evidence of acute ischemia on CT and in those who did not. Results: A total of 347 patients were included, 168 with TIAs, 147 with minor strokes and 32 with a final diagnosis of a mimic. Acute ischemic lesions were detected in 39% of TIAs by using MRI versus 8% by using CT (p < 0.0001) and in 86% of minor strokes by using MRI versus 18% by using CT (p < 0.0001). Compared to MRI, CT had a sensitivity of 20% and a specificity of 98% in identifying an acute ischemic lesion. The infarct volume on diffusion-weighted MRI was larger in cases where the CT also showed an acute ischemic lesion (median 5.07 ml, IQR 10) as compared to lesions seen only on MRI (median 0.68 ml, IQR 1.31, p < 0.0001). Conclusion: MRI is superior to CT in detecting the small ischemic lesions occurring after TIA and minor stroke. Since these lesions are clinically relevant, MRI should be the preferred imaging modality in this setting.

Early Magnetic Resonance Imaging in Transient Ischemic Attack and Minor Stroke Do it or Lose it

Background and Purpose— The use of magnetic resonance imaging (MRI) after transient ischemic attack (TIA) or minor stroke may be affected by the relative timing of imaging. We measured the impact of scanning an individual patient late versus early after TIA and minor stroke. Methods— Two hundred sixty-three TIA or minor stroke (National Institute of Health Stroke Scale score ⩽3) patients with a baseline MRI completed within 24 hours of symptom onset and a follow-up MRI at 90 days were included. Baseline and 90-day scans were assessed independently for the presence of any stroke lesions that could explain the presenting symptoms. The presence and pattern of any stroke lesions were compared at the 2 time points. Results— The presence of a stroke (acute or chronic) in any location was more common on baseline MRI versus 90-day MRI (68% vs 56%; P=0.005). Thirty percent of subjects with negative scans at 90 days had a clearly identifiable stroke at baseline. When interpreted blinded to the baseline scan, the presumed relevant lesion on the 90-day MR scan was the correct lesion in only 53% patients. One-third (34%) of patients had a different lesion pattern on the baseline scan compared with the 90-day scan. Ninety percent (80/89) of these patients had more lesions on the baseline MRI and 10% (9/89) had new lesions on the 90-day MRI. Conclusions— Delayed MRI after TIA or minor stroke reduces the diagnostic yield and results in missed understanding of the lesion pattern. MRI of minor stroke and TIA patients should occur early after symptom onset, and delayed imaging should be interpreted with caution.

Transient Ischaemic Attack is an Emergency: Think about Best Current Stroke Prevention Options

A medical emergency is a condition that requires immediate action to prevent severe disability or death. Despite the apparent well-being of the patient after the ictus, transient ischaemic attack (TIA) is an emergency. Transient ischemic attack has long been known as a precursortomajorischaemicstroke.Inarecentmeta-analysis,the risk of stroke after TIA was estimated to be 31%, 64% and 87% at 2 days, 1 month and 3 months, respectively. In the same review, using only data from studies using active outcome ascertainment, the risk was estimated at 99%, 134% and 173% for the same time points (1). Half of the 90-day stroke risk occurs in the first 2 days after TIA, and 76% of strokes required hospitalization (2). The FASTER trial provided the first prospective evaluation of early risk of stroke after TIA in a randomized trial, enrolling patients within 24 h of symptom onset. In this selected population of minor stroke or TIA patients with weakness or speech disturbance for more than five minutes as part of their clinical event, the 90-day risk of stroke was 89% across treatment groups and the median time to the event was only 1 day (3). Thus, TIA portends a serious risk of early major stroke and the time window for intervention is short. Immediately after the resolution of neurological deficits, a patient has the whole high risk period before him. For patients with rapidly improving or fully resolved deficits, several reports indicate a high risk of deterioration and permanent deficits, especially for patients with a marked initial improvementon theNationalInstitute ofHealthStrokeScale(NIHSS) (4). Indeed, as a general rule, the risk of stroke and new neurologicaldeficitsishigherinpatientswithTIAthanamong patients with completed stroke, indicating an unstable ongoing process. In parallel, the long-term prognosis after TIA is grave. The combined risk of stroke, MI or death in the first year after TIA has been estimated at 22%, with the composite outcome primarily driven by the high stroke rate (5). A meta-analysis estimated a similar 22% annual rate of MI and a 21% annual rate of non-stroke vascular death after TIA (6). The concept of TIA has evolved, and a new definition has been proposed (7). The current WHO definition states that TIA is a sudden episode of neurological dysfunction, of vascularorigin,lastingo24h.Itissuggestedthatthediagnosis