Hyperosmolar hyperglycaemic state as a stroke cause or stroke mimic: an illustrative case and review of literature.

Hyperosmolar hyperglycaemic state (HHS) is a life-threatening metabolic complication of type 2 diabetes (T2DM) that often presents with neurological symptoms. A 74-year-old man with known T2DM presented to the emergency department with collapse, left-sided weakness and slurred speech (National Institutes of Health Stroke Scale (NIHSS) 3) and a biochemical profile consistent with HHS. When he further deteriorated (NIHSS 20), he was managed for concurrent ischaemic stroke. All his symptoms fully resolved after 24 hours, which coincided with establishment of normoglycaemia. Subsequent magnetic resonance imaging (MRI) of the head revealed a tiny parietal lobe infarct. Two further cases of HHS mimicking ischaemic stroke have been reported with symptoms and imaging findings resolving with treatment of HHS. Our case demonstrates how HHS can also accentuate symptoms of a minor stroke, highlighting the importance of excluding ischaemic stroke in HHS patients with neurological dysfunction. We recommend consideration of early MRI and/or computed tomography angiography in this cohort, especially in those appropriate for intervention. © Royal College of Physicians 2022. All rights reserved.