Visual and somotosensory evoked potentials in asymptomatic patients with vitamin B12 deficiency

Vitamin B12 deficiency may be asymptomatic or present with a wide range of neurological and hematological disorders. Our aim in this study is to evaluate visual (VEP) and somatosensory evoked potential (SEP) parameters in patients with vitamin B12 deficiency who had no clinical evidence of visual impairment or neurological syndrome findings and compare the findings with healthy controls to determine whether there is a correlation between VEP and SEP parameters and serum vitamin B12 levels.

30 patients (6 females [20%], 24 males [80%]; mean age, 52 years [range 17-80 years]), and 15 healthy subjects with vitamin B12 deficiency (3 females [20%], 12 [80%] male; mean age, 49 years [range 17-78 years]) were included in the study. P100 wave latencies and amplitudes were recorded as VEP parameters, and P40 wave latencies and amplitudes were recorded as tibial SEP parameters.

Comparison of VEP and SEP parameters in the patient and control groups revealed significantly prolonged SEP latencies and lower SEP amplitudes in the patient group. VEP latencies did not significantly differ between the patient and the control groups while VEP amplitudes were found to be lower in the patient group than in controls. A significant correlation was obtained between serum vitamin B12 levels and tibial SEP latencies (r > 0.5).

These findings suggest that asymptomatic patients with vitamin B12 deficiency may have SEP and VEP abnormalities indicating the subclinical optic nerve and spinal cord involvement.