Histologic Changes in Continuous, Long-Term Electrical Stimulation of a Peripheral Nerve

The chronic stimulation of peripheral nerves has, in the past, usually been of an intermittent or relatively short-term nature. Histologic changes which have taken place have been attributed to the trauma caused by mechanical factors and/or the effects of electrical charges. Investigators, speculating on the effects of electro-stimulation, have designed electrodes specifically to minimize tissue damage. The purpose of the present investigation is to determine which pathologic alterations, if any, are caused specifically by electrical-as distinct from mechanical-factors. Dogs were divided into two groups, differing only in that one group-the controls-had electrodes implanted around the phrenic nerve, but stimulation was never applied. Duration of the test was up to 308 days. The results indicated that no histologic alterations could be attributed specifically to electrical stimulation, as contrasted to mechanical trauma, to the phrenic nerve.