Posterior reversible encephalopathy syndrome complicating hyperosmolar hyperglycemic syndrome.

Hyperosmolar hyperglycemic syndrome is a life-threatening diabetic emergency that manifests as altered mental status. An otherwise healthy 40-year-old man presented to our emergency department with headache and severe hypertension. Brain magnetic resonance imaging showed evidence of posterior reversible encephalopathy syndrome, a usually reversible neurological syndrome characterized by subcortical vasogenic oedema.