Relief of Pain and Paraesthesiae by Nerve Block Distal to a Lesion

Lesions of afferent pathways may give rise to a variety of spontaneous sensations. When a lesion affects nerves, nerve roots, the root entry zone, or the spino-thalamic tract, the sensations are usually those of pain and painful pins and needles; when it affects the posterior columns of the cord, the sensation is one of painless pins and needles or of tingling. It is natural to think that the pain and paraesthesiae are due to the discharge of nerve fibres in or near the lesion, and that the lesion on the afferent pathway causes these nerve fibres to fire off. In this paper, evidence will be presented to show that local anaesthetic injections of the afferent pathway, distal to the site of the lesion, may stop the pain or paraesthesiae; further, that this effect may far outlast the duration of the anaesthesia; and further, that blocking a peripheral nerve supply-ing a large part but not the whole of the region where the pain or paraesthesiae are felt may remove these sensations from the entire region. A summary of the cases in which a nerve block distal to the lesion gave these results is presented as Table I. The cases are now briefly described and the experimental protocols are given.