MRI-based selection for intra-arterial stroke therapy: value of pretreatment diffusion-weighted imaging lesion volume in selecting patients with acute stroke who will benefit from early recanalization.

BACKGROUND AND
PURPOSE: Recent studies demonstrate that an acute diffusion-weighted imaging lesion volume >70 cm(3) predicts poor outcome in patients with stroke. We sought to determine if this threshold could identify patients treated with intra-arterial therapy who would do poorly despite reperfusion. In patients with initial infarcts <70 cm(3), we sought to determine what effect recanalization and time to recanalization had on infarct growth and functional outcome.
METHODS: We retrospectively studied 34 consecutive patients with anterior circulation stroke who underwent pretreatment diffusion-weighted imaging and perfusion-weighted imaging and subsequent intra-arterial therapy. Recanalization success and time to recanalization were recorded. Initial diffusion-weighted imaging and mean transit time lesion and final infarct volumes were determined. Patients were stratified based on initial infarct volume, recanalization status, and time to recanalization. Statistical tests were performed to assess differences in clinical and imaging outcomes. Good clinical outcome was defined as a 3-month modified Rankin Scale score <or=2.
RESULTS: Among patients with initial infarcts >70 cm(3), all had poor outcomes despite a 50% recanalization rate with mean infarct growth of 114 cm(3). These patients also had the largest mean transit time volumes (P<0.04). Patients with initial infarct volumes <70 cm(3) who recanalized early had the best clinical outcomes (P<0.008) with a 64% rate of modified Rankin Scale score <or=2 and the least infarct growth (P<0.03) with mean growth of 18 cm(3).
CONCLUSIONS: This study supports the use of an acute diffusion-weighted imaging lesion volume threshold as an imaging selection criterion for intra-arterial therapy. It also confirms the importance of early reperfusion in selected patients.