SHM Converge Scientific Abstract ePoster Gallery-N2o Laughing Matter: Nitrous Oxide-Induced Vitamin B12 Myelopathy

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This case describes a 50-year-old woman with alcohol use disorder who presented with acute unsteady gait, decreased lower extremity sensation, and slurred speech after heavy recreational nitrous oxide (“whippits”) use. Her exam showed impaired vibration, proprioception, and fine touch in the distal legs, reduced reflexes, upper extremity dysmetria, a positive Romberg sign, and a wide-based ataxic gait, consistent with dorsal column dysfunction.<br /><br />Although her serum vitamin B12 level was within the normal range, she had marked elevations in homocysteine and methylmalonic acid, supporting functional B12 deficiency. MRI findings were consistent with nitrous oxide-related myelopathy. She was diagnosed with nitrous oxide-induced vitamin B12 myelopathy and treated with high-dose vitamin B12 and thiamine, along with cessation of nitrous oxide use. Her biochemical markers normalized and lower extremity function improved, but she continued to have persistent ataxia and sensory deficits requiring inpatient rehabilitation and a rollator walker.<br /><br />The document emphasizes that nitrous oxide misuse is an increasing public health problem. N2O irreversibly inactivates vitamin B12, leading to impaired myelin synthesis and demyelination of the dorsal columns, corticospinal tracts, and spinocerebellar tracts. Neurologic manifestations include paresthesias, weakness, sensory loss, impaired proprioception/vibration, ataxia, and upper motor neuron signs. Psychiatric effects can include delirium and delusions. Autonomic instability may also occur, including orthostatic hypotension, bradycardia, urinary retention, and delirium.<br /><br />Key teaching points are that serum B12 may appear normal, so homocysteine and methylmalonic acid are important diagnostic tests. Early recognition and treatment with B12 replacement can improve outcomes, but recovery may be incomplete.

Asset Subtitle

Lindsey Phillips

Meta Tag

Author List Ann Marie Kumfer, Elizabeth Cole, Evan Raff, Lindsey Phillips, Nicholas Piazza, Robert W. Lampman

Category Clinical Vignettes

Concept Vitamin B12 Myelopathy

Concept Nitrous Oxide Misuse

Concept Sensory Loss

Concept Gait Instability

Concept Ataxia

Distinguished Non-Finalist

Presenter Organization University of North Carolina School of Medicine

Presenting Author Lindsey Phillips

Track Adult

Keywords

nitrous oxide

vitamin B12 deficiency

myelopathy

dorsal column dysfunction

ataxia

methylmalonic acid

homocysteine

sensory loss

alcohol use disorder

demyelination

Vitamin B12 Myelopathy

Nitrous Oxide Misuse

Sensory Loss

Gait Instability

Ataxia