Somatosensory conduction in vitamin B12 deficiency

We tested the hypothesis that the somatosensory central conduction time (CCT) can reveal central nervous system involvement in vitamin B12-deficient patients when this cannot be established on clinical grounds alone. Three patients with pernicious anemia and without clinical signs of upper motor neuron lesion had a striking increase of CCT. This increase was shown to be reversible in 1 patient who improved over 3 years of treatment. Detailed analysis of the CCT showed that the decrease of conduction velocity occurred in the posterior columns, whereas the conduction was normal at the thalamo-cortical level. We conclude that CCT is a useful parameter to localize and quantify central nervous system disease in vitamin B12 deficiency.