A reliable new method to estimate >1/3 middle cerebral artery infarction on early computed tomography scan
Objectives: To develop a reliable method of estimation of >1/3 involvement of the middle cerebral artery territory (MCAT) on early CT scan. Background: The European Cooperative Acute Stroke Study (ECASS) suggested that > 1/3 involvement of the MCAT on early CT scan was a risk factor for symptomatic intracerebral hemorrhage (SICH) following treatment with tissue plasminogen activator (tPA) for acute ischemic stroke (AIS). There are no published guidelines on how to perform such an evaluation. The ICE method was developed for the purpose of standardizing the approach of infarct size estimation. This method requires the observer of the CT scan to mentally: 1) Idealize the MCAT into an area approximating a trapezoid, 2) Close a geometric figure around the area(s) of hypodensity(ies), and 3) Estimate the ratio of the two geometric figures (C/I). Methods: Five stroke fellows (observers) were tested with 40 CT scans which had been performed within the first few hours of an acute neurological event. Observers were blinded to patient history. They were asked whether to treat the patient on the basis of the CT scan. The decision not to treat was predicated on the presence of hemorrhage or > 1/3 MCAT involvement. Results: Five scans showed evidence of hemorrhage. All observers detected the hemorrhages. The remaining scans were of patients with presumed ischemia. Six scans were thought to show > 1/3 MCAT involvement by all observers. For all scans, median interobserver agreement among 10 paired comparisons was 86% (range 73–93%). Median kappa was 0.72 (range 0.44–0.85, p<0.001). Conclusion: The ICE method has very good interobserver reliability. The method merits further investigation among non-stroke physicians.