Reactions Weekly | 2021
Nitrous-oxide
Abstract
Myelopathy secondary to vitamin B12 deficiency following recreational nitrous oxide use: case report A 42-year-old woman developed myelopathy secondary to vitamin B12 deficiency following recreational nitrous oxide use. The woman, who had a medical history of restless leg syndrome, depression, hepatitis C and anxiety, presented to the emergency department with headache, speech difficulty, neck pain and ataxia for 6 weeks. Her neck pain was primarily paracervical and radiated just posterior to her ears bilaterally. She complained of primarily imbalance associated with numbness and difficulty with ambulation. She described feeling as if her legs gave way beneath her, and it resulted in multiple falls and injuries to her knees. A few days after admission, she admitted to using nitrous oxide recreationally for over 2 years. At the time of investigation on hospital admission, she was alert and oriented. Her speech was fluent and non dysarthric. Naming, attention, insight and repetition were intact. Her cranial nerves II-XII were found to be intact. All four extremities showed good muscle bulk and tone with 5/5 strength. Light touch sensation was intact in all extremities, though there was diminished vibratory sensation in the lower extremities was noted. She was unstable upon standing and was found to have an ataxic gait. A brain MRI without contrast demonstrated a large right mastoid effusion, which was consistent with mastoiditis. Thus, she received vancomycin and cefepime. Polymorphonuclear cells were increased at 75%. After admitting to recreational nitrous oxide use [route and amount of substance not stated], she was evaluated for vitamin B12 deficiency. Her serum vitamin B12 level was found to be low at 105 pg/mL with a significantly increased methylmalonic acid of 31000 nmol/L and homocysteine of 38.6 umol/L. Her intrinsic factor antibody was positive. An MRI of the spine reveled focal central cord T2 signal hyperintensity at C4-C5. Later, it was confirmed that her myelopathy secondary to vitamin B12 deficiency was associated with recreational nitrous oxide use. Subsequently, the woman was treated with cyanocobalamin. Eventually, an improvement was noted.