Evolution of the diffusion-weighted signal and the apparent diffusion coefficient in the late phase after minor stroke: a follow-up study.

INTRODUCTION: Diffusion-weighted imaging (DWI) is mainly used in acute stroke, and signal evolution in the acute phase has been studied extensively. However, patients with a minor stroke frequently present late. Recent studies suggest that DWI may be helpful at this stage, but only very few published data exist on the evolution of the DW-signal in the weeks and months after a stroke. We performed a follow-up study of DWI in the late stages after a minor stroke. METHODS: 28 patients who presented 48 hours to 14 days after a minor stroke underwent serial MRI at baseline, 4 weeks, 8 weeks, 12 weeks, 6 months and>or=9 months after their event. Signal intensity within the lesion was determined on T2-weighted images, DW-images and the Apparent Diffusion Coefficient (ADC) map at each time-point, and ratios were calculated with contralateral normal values (T2r, DWIr, ADCr). RESULTS: T2r was increased in all patients from the beginning, and showed no clear temporal evolution. ADCr normalized within 8 weeks in 83% of patients, but still continued to increase for up to 6 months after the event. The DW-signal decreased over time, but was still elevated in 6 patients after>or=6 months. The evolution of ADCr and DWIr showed statistically highly significant inter-individual variation (p<0.0001), which was not accounted for by age, sex, infarct size or infarct location. CONCLUSION: The ADC and the DW-signal may continue to evolve for several months after a minor ischaemic stroke. Signal evolution is highly variable between individuals. Further studies are required to determine which factors influence the evolution of the ADC and the DW-signal.

Heritability of ischemic stroke in relation to age, vascular risk factors, and subtypes of incident stroke in population-based studies.

UNLABELLED: Background- Appropriate design of molecular genetic studies of ischemic stroke requires an understanding of the genetic epidemiology of stroke. However, there are no published population-based data on heritability of aetiological subtypes of ischemic stroke, confounding by heritability of other vascular risk factors, or the relationship between heritability and age of onset. METHODS: We studied family history of stroke (FHx(Stroke)) and of myocardial infarction (FHx(MI)) in first-degree relatives in 2 population-based studies (Oxford Vascular Study [OXVASC]; Oxfordshire Community Stroke Project [OCSP]). We related FHx(Stroke) and FHx(MI) to subtype of ischemic stroke, age, and the presence of vascular risk factors and performed a systematic review of all studies of FHx(Stroke) by stroke subtype. RESULTS: In our population-based studies and in 3 hospital-based studies, FHx(Stroke) was least frequent in cardioembolic stroke (OR=0.74, 95%CI=0.58 to 0.95, P=0.02) but was equally frequent in the other subtypes. In OXVASC and OCSP, FHx(Stroke) (P=0.02), FHx(MI) (P=0.04), and FHx of either (P=0.006) were associated with stroke at a younger age. Only FHx(Stroke) was associated with previous hypertension (OR=1.59, 95%CI=1.08 to 2.35, P=0.02). FHx(MI) was more frequent in large-artery stroke (OR=1.63, 95%CI=0.99 to 2.69, P=0.05). CONCLUSIONS: Consistent results in our population-based studies and previous hospital-based studies suggest that inclusion bias is not a major problem for studies of the genetic epidemiology of stroke. Molecular genetic studies might be best targeted at non-cardioembolic stroke and younger patients. However, genetic susceptibility to hypertension may account for a significant proportion of the heritability of ischemic stroke.

Differences in vascular risk factors between etiological subtypes of ischemic stroke: importance of population-based studies.

BACKGROUND: To understand the mechanisms of stroke and to target prevention, we need to know how risk factors differ between etiological subtypes. Hospital-based studies may be biased because not all stroke patients are admitted. If risk factors differ between patients who are admitted and those who are not, then case-control studies will be biased. If the likelihood of admission also depends on stroke subtype, then case-case comparisons may also be biased. METHODS: We compared risk factors and ischemic stroke subtypes (TOAST classification) in hospitalized and nonhospitalized patients in 2 population-based stroke incidence studies: the Oxford Vascular Study (OXVASC) and Oxfordshire Community Stroke Project (OCSP). We also performed a meta-analysis of risk factor-stroke subtype associations with other published population-based studies. RESULTS: In OXVASC and OCSP, stroke subtypes differed between hospitalized (293 of 647) and nonhospitalized patients (P<0.0001), with more cardioembolic strokes (odds ratio [OR], 1.8; 95% CI, 1.3 to 2.6) and fewer lacunar strokes (OR, 0.4; 95% CI, 0.3 to 0.7). Premorbid blood pressure and cholesterol were higher in hospitalized patients (both P<0.0001). Risk factor-stroke subtype associations in hospitalized patients were consequently biased (P=0.001). Meta-analysis of data from all patients in OXVASC, OCSP, and 2 other studies demonstrated consistent risk factor-stroke subtype associations. However, contrary to previous hospital-based studies, there was only a weak (OR, 1.4; 95% CI, 1.1 to 1.8) and inconsistent (P(heterogeneity)=0.01) association between small-vessel stroke and hypertension and no association with diabetes (OR, 1.0; 95% CI, 0.7 to 1.3). CONCLUSIONS: Prevalences of risk factors and stroke subtypes differ between hospitalized and nonhospitalized patients with ischemic stroke, which may bias hospital-based risk factor studies. Meta-analysis of population-based studies suggests that vascular risk factors differ between stroke subtypes.

Abnormalities on diffusion weighted magnetic resonance imaging performed several weeks after a minor stroke or transient ischaemic attack.

OBJECTIVES: Diffusion weighted brain imaging (DWI) is used in acute stroke, and also shows an acute ischaemic lesion in most transient ischamic attack (TIA) patients scanned acutely. However, it may also be useful in identifying subacute ischaemic lesions in patients with minor stroke or TIA who present several weeks after symptom onset. This study investigated the sensitivity and the observer reproducibility of DWI in cerebral TIA and minor ischaemic stroke patients scanned more than two weeks after the last symptomatic event. METHODS: Consecutive patients underwent magnetic resonance imaging (T2, DWI, ADC). The presence of clinically appropriate lesions was assessed by two independent observers, and related to the type of presenting event, the NIH score, persistence of symptoms and signs, and the time since the presenting event. RESULTS: 101 patients (53 men) were scanned at a median time of 21 days (IQR=17-28) after symptom onset. Reproducibility of the assessment of DWI abnormalities was high: interobserver agreement =97% (kappa=0.94, p<0.0001); intraobserver agreement =94% (kappa=0.88, p<0.0001). DWI showed a clinically appropriate ischaemic lesion in 29 of 51 (57%) minor stroke patients, and in 7 of 50 (14%) TIA patients. The independent predictors of a positive DWI scan were presentation with minor stroke versus TIA (p=0.009) and increasing NIH score (p=0.009), but there was no difference between patients presenting 2-4 weeks compared with >4 weeks after symptom onset. In minor stroke patients, the presence of a clinically appropriate lesion was associated with persistent symptoms (63% versus 36%; p=0.12) and signs (64% versus 33%, p=0.06) at the time of scanning. CONCLUSIONS: DWI shows a clinically appropriate ischaemic lesion in more than half of minor stroke patients presenting more than two weeks after the symptomatic event, but only in a small proportion of patients with TIA. The persistence of lesions on DWI is closely related to markers of severity of the ischaemic event. These results justify larger studies of the clinical usefulness of DWI in subacute minor stroke.

Transient ischaemic attacks mimicking focal motor seizures.

Limb shaking is an under-recognised form of transient ischaemic attack (TIA), which can easily be confused with focal motor seizures. However, it is important to distinguish limb shaking TIAs and focal seizures, as patients with this form of TIA almost invariably have severe carotid occlusive disease and are at high risk of stroke. A patient with limb shaking TIAs is presented in whom the diagnosis was missed.