I read this article where they apply electrical stimulation to the nerves. The article was written in 2002, but I can't find any studies on it or any places that do it. It seems much better than cutting the nerves.
Method of treating palmar hyperhydrosis by electrical stimulation of the sympathetic nervous chain - ElectroCore Techniques, LLC
Method of treating palmar hyperhydrosis by electrical stimulation of the sympathetic nervous chain - ElectroCore Techniques, LLC