Response to Letter by Sohn et al

Response: We appreciate the comments by Sohn et al concerning our study comparing preperfusion and postperfusion magnetic resonance angiography (MRA) in acute stroke.1 After studying 10 patients with postperfusion MRA and digital subtraction angiography, Sohn et al suggested that most cases of better middle cerebral artery flow after contrast are attributable to collateral flow. We would like to make some observations regarding their findings. The results we reported suggest a rather more complex scenario. All the …