455 - No Laughing Matter: Myelopathy in the Setting of Nitrous Oxide Induced Vitamin B12 Deficiency

Case Diagnosis: Myelopathy in the setting of nitrous oxide induced vitamin B₁₂ deficiency

Case Description: 46 year old _male_ presented with several months of bilateral lower extremity paresthesias which progressed to involve the mid-abdomen accompanied by sensory ataxia, paraparesis, urinary retention and neurogenic bowel. Neuraxis magnetic resonance imaging (MRI) with and without contrast revealed abnormal spinal cord signal and enhancement throughout the cervical and thoracic spine. Laboratory
studies revealed reduced vitamin B₁₂ levels, elevated homocysteine and markedly elevated methylmalonic acid levels. Lumbar puncture with analysis was unremarkable. Further history determined symptoms were secondary to prolonged whippet use resulting in cervical and thoracic myelopathy. Patient’s functional status was grossly dependent to maximal assistance with mobility and activities of daily living.

Discussions: Nitrous oxide is increasingly being used as a recreational drug which may cause disabling neurological sequelae with prolonged use due to functional inactivation of vitamin B₁₂. Nitrous oxide is commonly abused through the inhalation of whipped cream canisters. As in our patient, cases of nitrous oxide abuse have resulted in myelopathy with both sensory and motor symptoms. Prognosis in patients with subacute combined degeneration (SCD) depends on several factors; presence of sensory deficits, longer symptom duration and greater than seven spinal segments involved indicate a poor prognosis. In our patient, T2 hyperintensities were seen throughout the cervical and thoracic cord, and symptoms persisted for a few months prior to presentation. However, treatment with high dose parenteral vitamin B₁₂ and an intensive rehabilitation program resulted in nearly complete recovery of sensory and motor symptoms.

Conclusions: This case report highlights the deleterious effects of nitrous oxide abuse. Healthcare professionals should suspect possible nitrous oxide abuse in young adults with neurologic manifestations of SCD. Additionally, judicious management with aggressive B₁₂ supplementation, intensive rehabilitation along with addressing psychosocial factors is imperative for a favorable prognosis.