The hyperdense middle cerebral artery sign

Abstract

The Hyperdense Middle Cerebral Artery Sign (HMCAS) is a specific finding on non-enhanced computed tomography (NECT) that correlates with acute ischaemic stroke affecting the middle cerebral artery (MCA). It is one of the first investigation findings that may be apparent to a clinician and has potential implications for management. Given that the HMCAS is seen on the routinely performed NECT brain scan and that its presence has significant time-critical clinical implications, a clear understanding of the sign is essential. A number of investigators have looked at characteristics associated with the sign including its reliability, sensitivity, specificity, association with stroke severity, comorbid associations, treatment response in patients who present with the sign and overall prognosis. The sign appears to be a consistent marker of severe stroke. Overall, the patient group presenting with the sign has been shown to have a poor short-term prognosis without thrombolytic therapy and poorer intermediate-long term outcome with thrombolytic therapy when compared to patients without the sign. Chapter 1 presents a literature review on the topic of the HMCAS, detailing and summarising the significant findings to date. Chapter 2 reports a prospective observational study that has confirmed previous results relating to the low sensitivity and high specificity of the sign. It looked carefully at comorbid associations with the sign as well as the intermediate-long term prognosis of patients not treated with thrombolytic therapy. The results showed that the sign was associated with a more severe initial neurological deficit, as well as atrial fibrillation (AF). The 3-6 month outcome of patients in this group was poor, with the majority being fully dependent or deceased on follow-up. Inter-observer agreement between the two reporting neuroradiologists was good, however, the study generated some doubt on the reliability and accuracy of HMCAS reporting in general. Chapter 3 presents a study that assessed the reliability of HMCAS reporting amongst clinicians with varying levels of experience. It also examined how accurately and consistently clinicians of similar experience report on the presence or absence of an HMCAS when reporting NECT scans. The results showed that if a scan was reported not to show an HMCAS, then this was highly likely to be the case regardless of the level of experience of the reporting clinician. However, true positive scans were far more difficult to report accurately. Chapter 4 outlines the key conclusions that can be derived from literature to date and the two studies. It further offers recommendations for clinicians dealing with HMCAS-positive patients in the setting of acute ischaemic stroke. Show more