Involuntary movements due to vitamin B12 deficiency

Abstract

Deficiency of vitamin B₁₂ produces protean effects on the nervous system, most commonly neuropathy, myelopathy, cognitive and behavioural symptoms, and optic atrophy. Involuntary movements comprise a relatively rare manifestation of this readily treatable disorder. Both adults and infants deficient in vitamin B₁₂ may present with chorea, tremor, myoclonus, Parkinsonism, dystonia, or a combination of these, which may precede diagnosis or become apparent only a few days after parenteral replacement therapy has begun. The pathogenesis of these movement disorders shows interesting parallels to certain neurodegenerative conditions. The clinical syndrome responds well to vitamin B₁₂ supplementation in most cases, and an early diagnosis is essential to reverse the haematological and neurological dysfunction characteristic of this disorder. In this article, we elucidate the association of vitamin B₁₂ deficiency with movement disorders in adults and in infants, discuss the pathogenesis of this association, review previously reported cases, and present a young adult male with severe generalized chorea that showed a salutary response to vitamin B₁₂ supplementation.