EFFECTS OF REGIONAL ANESTHESIA ON PHANTOM LIMB PAIN ARE MIRRORED IN CHANGES IN CORTICAL REORGANIZATION

The causes underlying phantom limb pain are still unknown. Recent stud ies on the consequences of nervous system damage in animals and humans reported substantial reorganization of primary somatosensory cortex s ubsequent to amputation, and one study showed that cortical reorganiza tion is positively correlated with phantom limb pain. This paper exami ned the hypothesis of a functional relationship between cortical reorg anization and phantom limb pain. Neuroelectric source imaging was used to determine changes in cortical reorganization in somatosensory cort ex after anesthesia of an amputation stump produced by brachial plexus blockade in six phantom limb pain patients and four pain-free amputee s. Three of six phantom limb subjects experienced a virtual eliminatio n 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 ver y 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 a mputees 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 rel ationship. Methods designed to alter cortical reorganization should be examined for their efficacy in the treatment of phantom limb pain.