"With the nerve stimulation data, Dr. McCormack then cuts only those nerves that innervate sweat glands in the areas affected with hyperhydrosis. For example, a patient with palmar hyperhydrosis, T2 and T3 ganglion may individually, or both be involved. The intraoperative nerve testing precisely defines which ganglion has to be cut and avoids injury to the ganglion not involved. This is important because post-operative compensatory sweating problems increase with the number of ganglion cut."
http://www.nosweatsurgery.com/hyperhyd.htm