Weakness and Incontinence in a 24-Year-Old Hiker With Multiple Sex Partners Who Uses Whippets

Hassan Khuram, MS; Scott Goldstein, DO, EMT-PHP


May 18, 2023


The patient in this case had subacute combined degeneration of the spinal cord, which was precipitated by a functional vitamin B12 deficiency secondary to his recreational use of nitrous oxide. He presented with subacute worsening of weakness, numbness, and tingling in the lower extremities, in addition to incontinence.

Laboratory studies revealed megaloblastic anemia and elevated levels of both homocysteine and methylmalonic acid. These findings show that the patient's neurologic symptoms were due to insufficient vitamin B12–dependent fatty acid synthesis, which resulted in inadequate production and maintenance of myelin. Some clues that pointed toward damage to the spinal cord were signs of peripheral neuropathy, autonomic dysfunction, paresthesia, and spinal ataxia in a young patient with a relatively benign family history. The neurologic signs, coupled with the laboratory results, suggested a vitamin deficiency. Thiamine, vitamin E, and folate deficiency can present with similar signs; however, normal serum levels ruled out thiamine and vitamin E deficiency. Elevated levels of methylmalonic acid excluded folate deficiency.

Although multiple sclerosis could have a similar presentation, it is less likely given this patient's gender and age; thus, B12 deficiency is a more probable explanation. Follow-up T2 axial MRI of the cervical spine showed increased signal attenuation of the dorsal columns. A peripheral blood smear revealed hypersegmented neutrophils (Figure 2 shows similar findings in another patient). EMG studies demonstrated length-dependent sensorimotor polyneuropathy without major demyelinating features.

Figure 2.

Vitamin B12 deficiency can affect individuals of all ages, but it is most common among older adults. The causes can be broken down into four categories: malabsorption, malnutrition, increased demand, and use of some drugs.[1] This patient's recreational use of nitrous oxide is the most likely cause of the B12 deficiency.


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