Sensitivity of diffusion-weighted magnetic resonance imaging in the diagnosis of acute lacunar infarcts

Background and purpose: Heightened interest in the early diagnosis and trea tment of acute stroke challenges neuroimaging specialists to optimize avail able modalities and to develop new techniques for the evaluation of cerebro vascular disease. The purpose of this study was to evaluate the sensitivity of diffusion-weighted (DW) magnetic resonance (MR) imaging in detecting ea rly small infarcts and in differentiating acute from nonacute small infarct s when conventional MR imaging demonstrates multiple small infarcts. Methods: Thirty-eight consecutive patients with a clinical diagnosis of lac unar infarcts (20 men and 18 women, aged 50-79 yr) who under-went DW MR ima ging within 3 days of symptom onset were enrolled in this study. All patien ts underwent both conventional fast spin-echo (FSE) MR imaging and DW MR im aging. Apparent diffusion coefficient (ADC) maps were also acquired, All pa tients had at least one of the following classic lacunar syndromes: pure mo tor hemiparesis, ataxic hemiparesis, dysarthria-clumsy hand, pure sensory s troke, and sensorimotor stroke. Results: Thirty-six patients (40 acute lesions) had focal areas of high int ensity on DW MR imaging associated with their clinical symptoms. Acute lacu nar infarcts were seen on DW MR imaging as bright areas of decreased ADC ra tio (range 0.31-0.85, mean 0.64). Lesion conspicuity with DW MR imaging was superior to that with FSE in 33 acute lesions. In four patients with small hyperacute (within 6 hours) infarcts, DW MR imaging was particularly sensi tive for infarcts that were not visible on FSE sequence. The sensitivity of DW MR imaging and ADC map for acute lacunar infarcts was 95%, specificity 94%, positive predictive value 97%, negative predictive value 90%, and accu racy 95%. In 15 patients with both acute and nonacute old small infarcts, D W MR imaging and ADC map could easily distinguish the new infarct from adja cent old ones, although this distinction was difficult to make with FSE. Conclusions: DW MR imaging accompanied by ADC map is a sensitive diagnostic modality for hyperacute and acute lacunar infarcts. It is also sensitive i n distinguishing fresh small infarcts from adjacent multiple old infarcts.