230 - Rehabilitating the Invisible Injury: Nitrous Oxide and Spinal Cord Dysfunction

A 45-year-old male with a history of substance use and multiple comorbidities presented with altered mental status, ataxia, and absent deep tendon reflexes. He reported heavy nitrous oxide use in the weeks prior to admission. Laboratory evaluation revealed severely deficient vitamin B12 levels (< 146 pg/mL) and markedly elevated methylmalonic acid (7,615 nmol/L). He was treated with daily intramuscular and subcutaneous vitamin B12. Despite biochemical improvement, neurological deficits persisted, and he was discharged home with outpatient therapy. Three days later, he was readmitted following multiple falls and progressive weakness. Upon admission to inpatient rehabilitation, he required minimal assistance for most activities of daily living (ADLs) and ambulated 60 feet with a walker. After a 7-day rehab course, he demonstrated significant functional gains, achieving independence in bed mobility, transfers, ambulation with a walker (300 feet), and most ADLs. Reflexes normalized, and proprioception improved. He was discharged with recommendations to continue therapy.

Discussions:

This case highlights the growing incidence of subacute combined degeneration (SCD) secondary to nitrous oxide abuse and underscores the critical role of early rehabilitation in functional recovery. Although vitamin B12 repletion corrects the underlying biochemical deficiency, neurologic improvement may lag, necessitating timely initiation of physical and occupational therapy. Balance training and gait re-education were key components of this patient’s rehabilitation plan, addressing deficits in proprioception and lower extremity strength. With focused therapy, the patient demonstrated significant gains in mobility and independence in ADLs within a short inpatient rehabilitation course.

Conclusions:

Given the limited literature on rehabilitation outcomes in nitrous oxide-induced SCD, this case supports early, intensive rehabilitation particularly targeting ambulation and balance as a cornerstone of recovery. Increased awareness of this preventable condition and its rehabilitation potential is essential for optimizing patient outcomes.