Subacute Combined Degeneration Secondary to Nitrous Oxide Toxicity.

Subacute combined degeneration (SCD) of the spinal cord is a neurological condition caused by vitamin B12 deficiency and is most associated with cases of malabsorption, nitrous oxide exposure, or pernicious anemia. The lateral corticospinal tracts and dorsal columns are classically affected, leading to neurologic symptoms including gait disturbance, sensory deficits, and weakness. We report the case of a 35-year-old man who presented with paraesthesia and weakness of the upper and lower extremities bilaterally, along with urinary incontinence. Examination revealed a long segment of signal abnormality and enhancement involving the cervical and thoracic spinal cord, predominantly along the bilateral dorsal column. Upon further investigation, the patient reported a chronic history of recreational nitrous oxide abuse resulting in vitamin B12 deficiency inevitably leading to the development of SCD of the spinal cord.