Eye movement disorders in vitamin B12 deficiency: two new cases and a review of the literature.

Eye movement disorders are rarely reported in vitamin B12 deficiency. We describe two cases with eye movement disorder and vitamin B12 deficiency; one with bilateral internuclear ophthalmoplegia and the other with downbeat nystagmus. Both of the patients received replacement therapy but their eye movement disorders did not respond to treatment. We also review the nine previously reported cases.