Recovery patterns of motor and somatosensory evoked potentials following treatment of vitamin B12 deficiency.

Motor and somatosensory pathway functions were studied using motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs) and F-wave responses in a woman with vitamin B12 deficiency. Initial evaluation before treatment revealed: 1) prolongation of central motor conduction to both the upper and lower limbs, and prolongation of peripheral conduction to the lower limbs; 2) prolongation of central conduction time to median nerve stimulation and absence of cortical SEPs to tibial nerve stimulation; and 3) prolongation of F-wave responses to tibial and peroneal nerve stimulation. After 11 months of treatment with hydroxocobalamin, follow-up studies disclosed: 1) normalization of central motor conduction to the upper limbs, peripheral motor conduction to the lower limbs and improvement of central motor conduction to the lower limbs; 2) normalization of central conduction time to median nerve stimulation but persistent absence of cortical SEPs to tibial nerve stimulation; and 3) normalization of F-wave responses. These data suggest that both central and peripheral conductions of motor and somatosensory pathways may respond to hydroxocobalamin therapy, and that MEPs are useful in the early detection of central and peripheral motor pathway function recovery following treatment with vitamin B12 deficiency.