179 - Nitrous Oxide-Induced Subacute Combined Degeneration of the Spinal Cord: A Case Report

Case Diagnosis: Subacute combined degeneration (SCD)

Case Description: A 32-year-old male presented to the Emergency Department with bilateral lower extremity weakness, numbness/tingling, and difficulty walking. His history was notable for a two-month history of daily recreational nitrous oxide use. One week after acute care admission, he was admitted to the inpatient rehabilitation unit. Upon admission, examination demonstrated 4/5 hip flexion and knee extension strength, with 5/5 strength elsewhere. Sensory assessment revealed that pinprick sensation was absent from T2-T10 and light touch diminished from C3 to S5. Neurological testing revealed a positive Romberg test but normal coordination. Laboratory results revealed elevated vitamin B12, homocysteine, and methylmalonic acid (MMA) levels.

Discussions: Prolonged nitrous oxide use disrupts homocysteine metabolism, leading to inactivation of vitamin B12, an essential coenzyme for myelin synthesis. Impaired myelination causes degeneration primarily in the dorsal and lateral columns of the spinal cord, which are responsible for sensory and motor signal transmission, leading to SCD.

During our patient’s inpatient rehabilitation program, therapies targeted gait, stair climbing, balance, lower extremity strength, and safe performance of activities of daily living. Additionally, high-dose vitamin B12 supplementation was initiated. There was gradual improvement in sensory deficits and motor function over the rehabilitation stay. At discharge, the patient achieved modified independence for mobility, with intermittent supervision required for most activities of daily living.

Conclusions: Prolonged nitrous oxide use poses a significant risk for serious and possibly permanent spinal cord damage. Early diagnosis and intervention are important for SCD management and improving the patient’s quality of life. This case emphasizes the need for raising public awareness and caution regarding recreational nitrous oxide use.