Which neurologic findings are commonly associated with vitamin B12 deficiency?

• A. Severe headache and photophobia
• B. Seizures and focal deficits
• C. Tremor and chorea
• D. Paresthesias, diminished vibration and position sense, ataxia, and cognitive changes

Answer: (D)

Vitamin B12 deficiency causes demyelination in the dorsal columns and lateral corticospinal tracts, leading to a sensory‑neural pattern of neurologic injury. This produces paresthesias and a loss of vibration and position sense, which manifests as ataxia when walking and a positive Romberg test. Neuropsychiatric or cognitive changes are also common as the deficiency affects brain function. Taken together, the combination of paresthesias, diminished vibration and position sense, ataxia, and cognitive changes is the classic neurologic presentation of B12 deficiency.

Other neurologic symptoms listed—severe headache with photophobia, seizures with focal deficits, or tremor and chorea—aren’t the typical pattern seen with B12 deficiency and don’t reflect the predominant dorsal column–predominant demyelination that characterizes subacute combined degeneration.