Cerebral Venous Sinus Thrombosis Following Nitrous Oxide Abuse: A Clinical Reminder of a Growing Trend.

Cerebral venous sinus thrombosis (CVST) is a rare cause of stroke that may mimic other intracranial disorders. A 32-year-old male with bipolar disorder and prior venous thromboembolism presented with severe occipital headache, progressive blurred vision, and a brief sensory episode. He reported recent chronic nitrous oxide use. Imaging revealed extensive thrombosis of the superior sagittal, bilateral transverse, and sigmoid sinuses with venous congestion but no infarction. Laboratory studies showed markedly elevated homocysteine, elevated methylmalonic acid, and low vitamin B12 levels. He was treated with anticoagulation, parenteral vitamin B12, folic acid, and acetazolamide for suspected intracranial hypertension. Symptoms improved, and he was discharged for continued rehabilitation. This case underscores nitrous oxide-induced functional vitamin B12 deficiency and hyperhomocysteinemia as potential contributors to CVST, especially in younger patients without conventional risk factors. Early recognition, targeted metabolic correction, and cessation of exposure are essential to prevent complications and support recovery.