Does the Severity of the Early Perfusion Deficit in Ischemic Stroke Predict the Fate of The PWI/DWI Mismatch?
The degree of expansion of the early DWI lesion into the volume of the baseline PWI lesion is variable. In some patients partial recruitment of the DWI lesion volume occurs, while other patients develop a DWI lesion that equals or exceeds the size of the initial PWI volume. We investigated whether a quantitative analysis of the severity of the early perfusion deficit predicted the evolution of the PWI/DWI mismatch. Methods We studied patients with acute ischemic stroke in whom PWI and DWI MRI were performed within 7 hours after symptom onset and after 4–5 days. Maps of CBF, CBV and Mean Transit Time(MTT)were created after deconvolution of the arterial input function with the time-concentration curve. We compared the lesion volume on DWI at f/u with the baseline MTT volume. Patients in whom the lesion volume on DWI at f/u was smaller than the initial PWI deficit (group 1) were compared with patients in whom the DWI lesion at f/u (group 2) was ≥ than the initial PWI volume. Characteristics analysed included age, NIHSS, time to MRI, initial DWI volume, initial PWI volume, absolute mismatch volume, relative MTT(rMTT), CBF(rCBF) and CBV (rCBV) of the baseline PWI. Results Thirteen patients had an initial PWI>DWI mismatch of >20%. Seven of these patients (group 1) had DWI lesions at f/u that were smaller than the initial PWI lesion (mean 55% of PWI volume), while in 4 patients (group 2) the f/u DWI volume was larger than the PWI volume (mean 121% of initial PWI volume). Only the median rMTT (2.7 [group 1] versus 5.2 [group 2], p=0.006) and the median rCBV (1.4 [group 1] versus 2.7 [group 2], p=0.006) differed between the two groups. The initial rMTT and rCBV correlated significantly with the degree of expansion of the DWI lesion (ρ= 0.918 for rMTT and 0.864 for rCBV, p<0.01). Two patients, who were excluded because of early reperfusion, had no substantial increase in the size of the initial DWI lesion despite severely increased rMTT and rCBV. Conclusion Among acute stroke patients with PWI>DWI, who do not have early reperfusion, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the rMTT and the rCBV.