SOMATOSENSORY EVOKED-POTENTIALS AFTER POSTERIOR TIBIAL NERVE-STIMULATION IN FOCAL SPINAL-CORD DISEASES

We investigated the somatosensory evoked potentials (SEPs) produced by posterior tibial nerve (PTN) stimulation in 8 infants and children with focal spinal cord disorders. The spinal responses of the PTN-SEPs were considered to assist in the localization of spinal lesions because their abnormalities were consistent with the neurologic and/or radiologic findings in all 6 examinations that revealed abnormal spinal SEPs. The cortical responses correlated significantly with proprioception in the lower limbs because proprioception was only disturbed when the cortical SEPs were absent (3 examinations). When both the spinal and cortical responses were abnormal, the spinal lesion probably involved the dorsal column so extensively that it completely interrupted the afferent impulses. In contrast, when SEP studies demonstrated abnormal spinal and normal cortical SEPs (3 examinations), the dorsal column involvement was probably less severe; therefore, both the spinal and cortical responses provided useful information regarding afferent conduction in the dorsal column. PTN-SEPs appear to have the potential to be of value in the diagnosis of focal spinal disease, especially in infants and young children who cannot cooperate with detailed neurologic examinations.