Ischemic stroke: Effects of etiology and patient age on the time course ofthe core apparent diffusion coefficient

PURPOSE: To determine whether the evolution of the core apparent diffusion coefficient (ADC) of water in ischemic stroke varies with patient age or in farct etiology. MATERIALS AND METHODS: One hundred forty-seven patients with stroke underwe nt 236 diffusion-weighted magnetic resonance imaging examinations. Etiologi es of lesions were classified according to predefined criteria; in 224 imag es, the diagnosis of lacune could be firmly established or excluded. ADC wa s measured in the center of each lesion and in contralateral normal-appeari ng brain. A model was used to describe the time course of relative ADC (rAD C), which is calculated by dividing the lesion ADC by the contralateral ADC , and to test for age- or etiology-related differences in this time course. RESULTS: Transition from decreasing to increasing rADC was estimated at 18. 5 hours after stroke onset. In subgroup analysis, transition was earlier in nonlacunes than in lacunes (P =.02). There was a trend toward earlier tran sition in patients older than the median age of 66.0 years, compared with y ounger patients (P =.06). Pseudonormalization was estimated at 216 hours. A mong nonlacunes, the rate of subsequent rADC increase was more rapid in you nger patients than in older patients (P =.001). Within the smaller sample o f lacunes, however, no significant age-related difference in this rate was found. CONCLUSION: Differences in ADC depending on the patient's age and infarct e tiology suggest differing rates of ADC progression.