A sequential study of visual evoked potential in patients with vitamin B₁₂ deficiency neurological syndrome

Abstract

Objective: Visual pathways are vulnerable to vitamin B₁₂ deficiency but there is paucity of studies evaluating visual evoked potential (VEP) changes following vitamin B₁₂ supplementation. Our aim was to evaluate the visual evoked potential changes in patients with vitamin B₁₂ deficiency neurological syndrome and their changes after vitamin B₁₂ therapy. Methods: Seventeen patients with vitamin B₁₂ deficiency neurological syndromes diagnosed on the basis of megaloblastic bone marrow or low serum vitamin B₁₂ level or both were subjected to testing of visual acuity, field of vision, colour vision and neurological examination. Cranial magnetic resonance imaging was done in 9 patients and pattern reversal VEP was carried out on admission. P₁₀₀ latency and amplitude were measured. Visual function and VEP studies were repeated at 3 and 6 months after vitamin B₁₂ therapy. Results: The patients' age ranged between 17 and 69 years; 7 were females and 16 were lactovegetarians. The duration of symptoms ranged between 10 days and 10 years. Visual acuity, colour vision, field of vision and fundus oculi were normal. VEP revealed prolongation of P₁₀₀ latency in 10 patients (17 eyes) which was mild in 2, moderate in 10 and marked in 5 eyes. Six months after treatment, P₁₀₀ latency improved to normal in all except 4 eyes. VEP abnormality was related to duration of illness and antiparietal cell antibodies. Conclusions: VEP is frequently prolonged in patients with vitamin B₁₂ deficiency neurological syndrome although asymptomatic. It usually returns to normal after treatment.