Teaching NeuroImages: Myelopathy due to B12 deficiency in long-term colchicine treatment and nitrous oxide misuse

A 35-year-old man with colchicine-treated gout presented with 4 weeks of progressive paresthesias and wide-based gait after several months of recreational nitrous oxide (N2O) inhalation. Examination revealed distal weakness, diminished vibration and proprioception sense, and Romberg sign. Babinski and Lhermitte signs were absent. Spinal cord MRI (figure, A and B) demonstrated dorsal column abnormalities. Serum vitamin B12 level was 145 pg/mL; methylmalonic acid was 5,640 nmol/L. Intrinsic factor and parietal cell antibodies were absent. Complete blood …