Subacute Combined Degeneration of the Spinal Cord Due to Nitrous Oxide Use

A previously healthy 30-year-old man was admitted with one week of progressive bilateral limbs weakness and numbness. Neurological examination revealed a power of 4/5 in all limbs and impaired pain sensation in a glove-and-stocking distribution. There was an absence of vibration sense in the lower extremities. He had a positive Romberg test and displayed unsteady gait. His full blood count showed mild anemia but a normal level of vitamin B12 (352 pg/mL). Upon further questioning, he admitted to using nitrous oxide (N2O) recreationally for the past 4–5 months. MRI of the cervical spine demonstrated abnormal bilateral symmetrical T2 hyperintense signals in the dorsal column, extending from C3 to C5 level [Figure 1]. This finding was suggestive of subacute combined degeneration of the spinal cord.[1] Specific clinical guidelines for the treatment of subacute combined degeneration of the spinal cord secondary to nitrous oxide abuse are scarce, largely due to under-recognition of the widespread and damaging nature of nitrous oxide use. Abstinence from nitrous oxide and vitamin B12 replacement seem to be effective treatments.[2] The patient received a 14- day course of 1000 ug daily intramuscular B12 and physical therapy, followed by a plan for 1000 ug/day of oral vitamin B12. His numbness and gait have improved by the time of discharge.Figure 1: Cervical spinal cord MRI imaging findings. (a) T2 hyperintensity (white arrow) of the dorsal columns in the cervical cord visualised on sagittal MRI. (b) T2 hyperintensity of the dorsal columns (black arrow) visualised in the axial plane, demonstrating the classical ‘inverted V’ signResaerch ethics and informed consent The patient provided written informed consent, and the Institutional Review Board at the Third People’s Hospital of Hubei Province approved this case report. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.