Diffusion‐weighted imaging and diagnosis of transient ischemic attack

Abstract

ObjectiveMagnetic resonance (MR) diffusion-weighted imaging (DWI) is sensitive to small acute ischemic lesions and might help diagnose transient ischemic attack (TIA). Reclassification of patients with TIA and a DWI lesion as “stroke” is under consideration. We assessed DWI positivity in TIA and implications for reclassification as stroke.MethodsWe searched multiple sources, without language restriction, from January 1995 to July 2012. We used PRISMA guidelines, and included studies that provided data on patients presenting with suspected TIA who underwent MR DWI and reported the proportion with an acute DWI lesion. We performed univariate random effects meta-analysis to determine DWI positive rates and influencing factors.ResultsWe included 47 papers and 9,078 patients (range = 18–1,693). Diagnosis was by a stroke specialist in 26 of 47 studies (55%); all studies excluded TIA mimics. The pooled proportion of TIA patients with an acute DWI lesion was 34.3% (95% confidence interval [CI] = 30.5–38.4, range = 9–67%; I2 = 89.3%). Larger studies (n > 200) had lower DWI-positive rates (29%; 95% CI = 23.2–34.6) than smaller (n < 50) studies (40.1%; 95% CI = 33.5–46.6%; p = 0.035), but no other testable factors, including clinician speciality and time to scanning, reduced or explained the 7-fold DWI-positive variation.InterpretationThe commonest DWI finding in patients with definite TIA is a negative scan. Available data do not explain why ⅔ of patients with definite specialist-confirmed TIA have negative DWI findings. Until these factors are better understood, reclassifying DWI-positive TIAs as strokes is likely to increase variance in estimates of global stroke and TIA burden of disease. ANN NEUROL 2014;75:67–76

Cognitive Impairment in Transient Ischemic Attack Patients: A Systematic Review

“…Even when cognitive function after minor stroke (defined as National Institute of Health Stroke Scale ≤3) is compared to TIA, the prevalence of impairment after the latter is lower [31]. However, signs of acute infarction are present on DWI in up to 30% of TIA patients [4]. Whether these patients or those with longer symptom duration have worse cognitive performance afterward is unknown.…”

“…A TIA could, despite the transient nature of the focal symptoms, cause permanent brain damage, thereby disrupting networks involved in cognitive processes and leading to cognitive impairment [46]. This theory is however only partly supported by DWI studies, in which signs of recent infarction are found in about 30% of clinically defined TIA patients [4]. Furthermore, we recently showed that the clinical diagnosis of TIA may be inadequate, as more than 20% of patients not fulfilling the clinical criteria for TIA were found to have DWI lesions compatible with recent infarction [47].…”

“…Only one-third of the patients have signs of acute infarction on diffusion weighted imaging (DWI) [4]. Despite the transient nature of focal symptoms associated with TIA and the absence of visible brain lesions in most patients, many experience persistent cognitive problems afterward [5].…”

“…Whether these characteristics also apply to TIA is to date unknown. A persistent ischemic lesion after TIA might be the substrate for cognitive impairment, but the severity of TIA symptoms only weakly corresponds to the presence of vascular lesions on neuroimaging [4]. New cerebrovascular events that occur after a TIA might also have cognitive consequences, even though they often pass without recognized acute clinical symptoms [10,11].…”

Патогенез Транзиторных Ишемических Атак: Проблема Подтипов

“…Отже, тривалість та оборотність неврологічного дефіциту -це єдина ознака, за якою диференціюють TIA та ішемічний ін-сульт [26,27]. Слід враховувати, що транзиторність при ТІА стосується лише осередкових неврологічних по-рушень і меншою мірою церебральних циркуляторно-метаболічних порушень та структурно-морфологічних змін тканини мозку [28][29][30][31].…”