Subacute combined degeneration of the spinal cord in a patient abusing nitrous oxide and self-medicating with cyanocobalamin

Purpose. A case of subacute combined degeneration (SCD) of the spinal cord manifesting as severe ataxia and urinary retention in a patient with a history of heavy nitrous oxide abuse and self-supplementation with cyanocobalamin is reported. Summary. A 27-year-old woman was treated in the emergency department for complaints of abdominal pain and inability to urinate for about 12 hours. The patient also complained of worsening lower-extremity weakness for 10 days and a pins and needles sensation in the lower extremities for approximately I year. She reported nitrous oxide abuse over 3 years (an average of 100-200 whippit cartridges daily on 3 or 4 days per week), as well as long-term self-medication with oral and i.m. cyanocobalamin for the purpose of preventing nitrous oxide-induced neurologic symptoms. Results of magnetic resonance imaging (MRI) were highly suggestive of SCD, which is typically seen in primary vitamin B-12 deficiency but has been reported in the context of chronic nitrous oxide exposure. Treatment was initiated with cyanocobalamin 1000 mu g i.m. daily, to be continued for 5 days and followed by a four-week regimen of 1000 mu g i.m. weekly. The patient was discharged after 3 days, despite continued symptoms, with instructions to obtain ongoing care but was lost to follow-up. Conclusion. A patient who abused nitrous oxide chronically developed ataxia, paresthesia, and urinary retention while self-medicating with cyanocobalamin. A diagnosis of SCD was supported by MRI findings, symptoms, and the known relationship between nitrous oxide exposure and vitamin B-12 deficiency.