Epileptic or Not? Challenges in Movement Disorders Associated with Vitamin B12 Treatment

Background: Severe vitamin B12 deficiency and subsequent parenteral supplementation have both been associated with a wide range of hyperkinetic movement disorders.

Clinical Course: The patient was hospitalized at the age of 17 months due to severe failure to thrive, global developmental delay, and motor regression. His mother adhered to a vegan diet and he was mostly breastfed when he presented. Laboratory investigations revealed massively increased plasma methyl malonic acid and increased homocysteine levels, decreased plasma vitamin B12, and a hyperchrome, macrocytic anemia. After the second intramuscular vitamin B12 substitution, he presented with perioral dyskinesias, lid and face myoclonus, tongue tremor, and bilateral arm tremor. The movement disorder quickly worsened over the next day and he showed intermittent gaze deviation to the left side. Electrolytes and glucose were normal. Due to clinical suspicion of status epilepticus, he was treated with diazepam, levetiracetam and, when his GCS decreased and gaze deviation persisted, with phenobarbital. The movement disorder gradually decreased thereafter, but re-emerged later to a lesser extent. Duration was 3 weeks in total. EEG analysis showed generalized movement artifacts and single sharp transients on the right frontal side but no concurrent ictal changes, background activity was irregular and slow.

Conclusion: Distinction of vitamin B12 treatment associated movement disorders from seizures can be challenging and requires careful clinical and electroencephalographic evaluation. The exact pathomechanisms are not well understood and several theories have been suggested including “denervation supersensitivity” and transient fibre tract dysfunction due to recovery from demyelination.

Publication History

Article published online:
28 October 2021