Effects of Regional Anesthesia on Phantom Limb Pain Are Mirrored in Changes in Cortical Reorganization

TLDR

Phantom limb pain’s etiology remains unclear, but studies show that amputation induces substantial reorganization of primary somatosensory cortex, which correlates positively with pain intensity. The study tests whether cortical reorganization functionally relates to phantom limb pain and proposes that targeting reorganization could treat the condition. Neuroelectric source imaging tracked somatosensory cortical reorganization before and after brachial plexus blockade of the stump in six phantom‑pain patients and four pain‑free amputees. Anesthesia eliminated phantom pain in half of the patients and rapidly reduced cortical reorganization, while unchanged pain and reorganization in the others, supporting a causal link and suggesting that interventions modifying reorganization may alleviate phantom limb pain.

Abstract

The causes underlying phantom limb pain are still unknown. Recent studies on the consequences of nervous system damage in animals and humans reported substantial reorganization of primary somatosensory cortex subsequent to amputation, and one study showed that cortical reorganization is positively correlated with phantom limb pain. This paper examined the hypothesis of a functional relationship between cortical reorganization and phantom limb pain. Neuroelectric source imaging was used to determine changes in cortical reorganization in somatosensory cortex after anesthesia of an amputation stump produced by brachial plexus blockade in six phantom limb pain patients and four pain-free amputees. Three of six phantom limb subjects experienced a virtual elimination of current phantom pain attributable to anesthesia (mean change: 3.8 on an 11-point scale; Z = -1.83; p < 0.05) that was mirrored by a very rapid elimination of cortical reorganization in somatosensory cortex (change = 19.8 mm; t(2) = 5.60; p < 0.05). Cortical reorganization remained unchanged (mean change = 1.6 mm) in three phantom limb pain amputees whose pain was not reduced by brachial plexus blockade and in the phantom pain-free amputation controls. These findings suggest that cortical reorganization and phantom limb pain might have a causal relationship. Methods designed to alter cortical reorganization should be examined for their efficacy in the treatment of phantom limb pain.