Abstract Details

Title Axonal Neuropathy, Myelopathy and Hypercoagulable State Secondary to Chronic Nitrous Oxide Abuse Despite Combined B12 Supplementation

Topic General Neurology

Presentation(s) P3 - Poster Session 3 (5:30 PM-6:30 PM)

Poster/Presentation
Number 4-040

Objective Chronic nitrous oxide inhalant use produces a myeloneuropathy syndrome resembling subacute combined degeneration of the spinal cord with features of peripheral nerve disease despite normal-appearing vitamin B12 levels. We present a case, where a patient presented with chronic nitrous oxide (whippet) use along with oral B12 supplementation and how the diagnosis was made despite patient denying any drug use.

Background A 30-year-old male presented to the emergency department with bilateral lower extremity paresthesia and gait instability. Physical examination was significant for diminished vibration and position senses up to the knees, normal strength with mild spasticity and fasciculations in the lower extremities, and hyperreflexia of the patellar tendon. Romberg’s test was positive and he exhibited a wide-based, ataxic gait. Magnetic resonance imaging was unremarkable and lumbar puncture was also negative. The patient was self-supplementing with vitamin B12 for the past 4-5 months, therefore his vitamin B12 levels were normal and elevated about a week ago when he presented to another ER with similar complaints. Methylmalonic acid was severely elevated. The patient was also identified to have a DVT and was found to have elevated homocysteine levels.

Design/Methods NA

Results NA

Conclusions Vitamin B12 is a cofactor for two important enzymes involved in methylation reactions and DNA synthesis, methionine synthase and methylmalonyl-coenzyme A mutase. Nitrous oxide converts the active monovalent form of vitamin B12 to its inactive bivalent form, rendering B12 unable to play its role in myelin synthesis and maintenance. Without functioning methionine synthase, homocysteine cannot be converted to methionine. After identification of elevated methylmalonic acid levels and fluctuating B12 levels from his previous ER visits, the patient had finally admitted to whippet use. Treatment included folic acid-B6-B12 and warfarin for the next several months. The patient had complete improvement of symptoms except for rare, mild fasciculations that are still present.

Authors/Disclosures
Amanda Olney PRESENTER	No disclosure on file
Geetha Kanakeswaran, MD	No disclosure on file
Mangala Venkatesh, MD (Premier Health- Clinical Neuroscience Institute)	No disclosure on file
Praveen Venkatachalam, MD (The Youngstown Stroke Institute)	No disclosure on file

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