Imaging Predictors of Vasospasm and Delayed Cerebral Ischaemia After Subarachnoid Haemorrhage

Acute spontaneous subarachnoid haemorrhage (SAH) is a severe disease, frequently complicated by vasospasm and delayed cerebral ischaemia (DCI), which have a negative impact on prognosis. Imaging studies are essential in the diagnosis of SAH. In this article, we review the available imaging techniques for prediction, monitoring and diagnosis of these complications of SAH. Non-contrast computed tomography (CT) and transcranial Doppler (TCD) have been so far the mainly used techniques to evaluate SAH patients during the acute stage of disease and to screen for vasospasm and DCI. However, there have been new developments of brain imaging techniques, with the introduction of automated methods to quantify blood volume and cerebral flow velocities, and the use of perfusion studies that could contribute to predict or diagnose such complications. Magnetic resonance (MR) imaging studies are proving useful to evaluate early brain injury and to diagnose DCI. Newer angiography suites have sophisticated post-processing tools that quantify cerebral haemodynamics in SAH and may provide important clues for the diagnosis of vasospasm. Imaging studies are part of the standard management of patients with acute SAH. Blood quantification on CT and the evaluation of cerebral flow velocities on TCD are known to predict and monitor the occurrence of vasospasm. DCI has increasingly been recognized as the most clinically relevant complication of SAH but also the most difficult to predict. MR imaging is the most sensitive tool to diagnose DCI. Future developments in imaging are needed to predict this important complication and help to improve the prognosis of patients with SAH.