DWI reversal is associated with small infarct volume in patients with TIA and minor stroke.

BACKGROUND AND PURPOSE More than half of patients with TIA/minor stroke have ischemic lesions on early DWI, which represent irreversibly damaged tissue. The presence and volume of DWI lesions predict early deterioration in this population. We aimed to study the rate and implications of DWI reversal in patients with TIA/minor stroke. MATERIALS AND METHODS Patients with TIA/minor stroke were prospectively enrolled and imaged within 24 hours of onset. Patients were followed for 3 months with repeat MR imaging either at day 30 or 90. Baseline DWI/PWI and follow-up FLAIR final infarct volumes were measured. RESULTS Of 418 patients included, 55.5% had DWI and 37% had PWI (time-to-peak of the impulse response ≥2 seconds' delay) lesions at baseline. The median time from symptom onset to baseline and follow-up imaging was 13.4 (interquartile range, 12.7) and 78.73 hours (interquartile range, 60.2), respectively. DWI reversal occurred in 5.7% of patients. The median DWI lesion volume was significantly smaller in those with reversal (0.26 mL, interquartile range = 0.58 mL) compared with those without (1.29 mL, interquartile range = 3.6 mL, P = .002); 72.7% of DWI reversal occurred in cortically based lesions. Concurrent tissue hypoperfusion (time-to-peak of the impulse response ≥2 seconds) was seen in 36.4% of those with DWI reversal versus 62.4% without (P = .08). DWI reversal occurred in 3.3% of patients with penumbral patterns (time-to-peak of the impulse response ≥6 seconds - DWI) > 0 and in 6.8% of those without penumbral patterns (P = .3). The severity of hypoperfusion, defined as greater prolongation of time-to-peak of the impulse response (≥2, ≥4, ≥6, ≥8 seconds), did not affect the likelihood of DWI reversal (linear trend, P = .147). No patient with DWI reversal had an mRS score of ≥2 at 90 days versus 18.2% of those without reversal (P = .02). CONCLUSIONS DWI reversal is uncommon in patients with TIA/minor stroke and is more likely to occur in those with smaller baseline lesions. DWI reversal should not have a significant effect on the accuracy of penumbra definition.