Post"sympathectomy neuralgia is a syndrome of pain in the thigh, often of a burning nature,
which can occur after sympathectomy and typically lasts 2– 3 months. The incidence has
been variously quoted as 12–35% after both open sympathectomy47 49 and percutaneous
phenol sympathectomy.13 50 The fact that the incidence is so similar after open and
percutaneous sympathectomy suggests that the problem is a result of the sympathectomy
itself rather than the technique used to achieve it. In the past, some authors have blamed
the spread of phenol from the sympathetic chain posteriorly to the spinal nerve roots for
this pain syndrome. There has never been any evidence to support this claim, and the fact
that open sympathectomy has the same incidence of post"sympathectomy neuralgia
suggests that spread of phenol is not the cause.
http://bja.oxfordjournals.org/content/87/1/88.full