Background and purpose: The hyperdense appearance of the main middle cerebral artery (HMCA) is now a familiar early warning of large cerebral infarction, brain edema, and poor prognosis. This article describes the hyperdensity associated with embolic occlusion of branches of the middle cerebral artery in the sylvian fissure (MCA "dot" sign). We define it and determine its incidence, diagnostic value, and reliability.
Methods: CT scans performed on patients with acute ischemic stroke within 3 hours of symptom onset were analyzed for signs of thromboembolic stroke and evidence of early CT ischemia. Two neuroradiologists and 2 stroke neurologists initially blinded to all clinical information and then with knowledge of the affected hemisphere evaluated scans for the presence of the MCA dot sign, the HMCA sign, and early MCA territory ischemic changes.
Results: Of 100 consecutive patients who presented within 3 hours of symptom onset, 91 were considered at symptom onset to have anterior circulation stroke syndromes. Early CT ischemia was seen in 74% of these baseline CT scans. The HMCA sign was seen in 5% of CT scans, whereas the MCA dot sign was seen in 16%. All patients then received intravenous tissue plasminogen activator. All 5 patients with an HMCA sign, including 2 with an associated MCA dot sign, were either dead or dependent at 3 months. The 14 patients with an MCA dot sign alone were independent at 3 months in 64% of cases, compared with 50% without the sign (Fisher's exact test P:=0.79). Balanced kappa statistics for both the HMCA and the MCA dot sign were in the moderate to good range when the stroke symptom side was given.
Conclusions: The MCA dot sign is an early marker of thromboembolic occlusion of the distal MCA branches seen in the sylvian fissure and is associated with better outcome than the HMCA sign.