SHM Converge Scientific Abstract ePoster Gallery-Subacute Combined Degeneration Secondary to "Whippets" Nitrous Oxide Ingestion

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This case describes a 32-year-old man who developed several months of progressive numbness, paresthesias, gait instability, and falls. His neurologic exam showed severe loss of vibration and proprioception in a stocking-glove distribution, sensory ataxia, hyperreflexia at the knees, absent ankle reflexes, and bilateral upgoing toes, while strength remained intact. MRI of the cervical and thoracic spine showed T2 hyperintensity in the dorsal columns and lateral corticospinal tracts, and his vitamin B12 level was low.<br /><br />Subacute combined degeneration from B12 deficiency was suspected. After further questioning, the patient admitted to heavy inhaled nitrous oxide use (“whippets”). He was treated with parenteral cyanocobalamin, counseled to stop nitrous oxide, and referred for outpatient physical therapy.<br /><br />The discussion explains that nitrous oxide can cause a functional vitamin B12 deficiency by oxidizing and inactivating B12, impairing myelin synthesis. This leads to demyelination of the posterior and lateral spinal cord columns, producing a myeloneuropathy typical of subacute combined degeneration. Common symptoms include paresthesias, unsteadiness, weakness, impaired vibration and joint position sense, and sensory ataxia. MRI often shows dorsal column T2 hyperintensity, especially in the cervical and thoracic cord.<br /><br />Treatment is cessation of nitrous oxide exposure and vitamin B12 replacement. Neurologic recovery is variable, though many patients improve over 4 to 8 weeks.

Asset Subtitle

Arkadiy Finn

Meta Tag

Author List Arkadiy Finn, Sean Smith

Category Clinical Vignettes

Concept Nitrous Oxide

Concept Vitamin B12 Deficiency

Concept Subacute Combined Degeneration

Concept Sensory Ataxia

Concept Dorsal Column

Distinguished Non-Finalist

Presenter Organization The Miriam Hospital, Warren Alpert Medical School at Brown University

Presenting Author Arkadiy Finn

Track Adult

Keywords

subacute combined degeneration

vitamin B12 deficiency

nitrous oxide abuse

dorsal column demyelination

sensory ataxia

paresthesias

gait instability

myeloneuropathy

cervical thoracic MRI

cyanocobalamin treatment

Nitrous Oxide

Vitamin B12 Deficiency

Subacute Combined Degeneration

Sensory Ataxia

Dorsal Column