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James Anstey provides his thoughts on the recent developments in delayed cerebral ischaemia following a subarachnoid haemorrhage (SAH). Unlike TBI, where outcomes have plateaued after 20 years, outcomes have steadily improved for aneurysmal SAH. Early intervention, with an increasing amount of coiling as opposed to clipping as well as ICU all likely playing a part.   However, there is still a subsection of patients who deteriorate three days or more post their event. This is likely due to delayed cerebral ischaemia (as opposed to pure vasospasm). This is a diagnosis of exclusion in a patient who deteriorates after three days post bleed and without hydrocephalus, seizures, infection or another identifiable causal pathology.   There are several pathophysiological factors at play. Firstly, microcirculatory problems, including vasoconstriction in capillary beds and clumping with endothelial damage. This is perhaps why treatments to improve perfusion have had little success. Next, a combination of cortical spreadi