40% affirmed they would ask for the operation if it were to be redone, 53% recurrence

At an average 12 years after surgery, 47% of patients were satisfied with the treatment results, 40% were disappointed. 
53% complaining about a decent to moderate recurrence of hand sweating and compensatory and gustatory sweating were observed in 9 (60%) and 5 (33%) patients, respectively. 
Interact CardioVasc Thorac Surg(2009) 8 (1): 54-57.

Only 56% would recommend thoracoscopic sympathectomy to others with hyperhydrosis

http://www.ncbi.nlm.nih.gov/pubmed/21539945

post-sympathectomy hyperalgesia

Behavioral test of tolerance for aversive mechanical stimuli in sympathectomized cats.

C Van Petten

 , 

W J Roberts

  and 

D L Rhodes

Cats were studied behaviorally to determine their suitability as an animal model for the post-sympathectomy hyperalgesia reported to occur in humans. For this study a device and methodology were developed which allow humane testing of tolerance for intense mechanical stimulation of the hindlegs. Behavioral tolerance was measured quantitatively before and after unilateral sympathectomy. The results from this preliminary study of 6 cats are remarkably similar to those reported for humans; 1 of the 6 cats showed a decreased tolerance on the sympathectomized side which was delayed in onset and of limited duration. The new methodology appears to provide relatively stable, quantitative measures of tolerance for aversive stimulation, and the cat shows promise as an animal model for post-sympathectomy hyperalgesia.

Pain. 1983; 15(2)

"return of sweating in the hands is common occurrence in patients followed up for sufficient length of time"

Annals of the Royal College of Surgeons of England (1989) vol. 7.1

significant number of primary hyperhidrosis patients (more than 70%) were so pleased with the results that they decided to forgo the surgery

At the beginning of our study, thoracic sympathectomy was indicated indiscriminately to all primary hyperhidrosis patients. The authors observed a number of patients who were dissatisfied with the results obtained from this technique, particularly due to the undesirable but frequent side effect of compensatory hyperhidrosis. Hyperhidrosis is a condition that deeply affects the individual's emotional component, and many of them, despite being warned previously, are not psychologically prepared to address this new situation. The authors then included a psychologist in the study and directed the patients for routine psychological evaluations to prepare and better select them for surgery. In addition, the authors began to study a pharmacological formula to medicate these patients for the same purpose. Oxybutynin is an anticholinergic drug that has been used safely at high doses (up to 15 mg/day) to treat micturition disorders, and a side effect observed in these patients has been diminished sudoresis. Studies conducted by our group have documented the clinical benefits of a low dose of oxybutynin (10 mg/day). The authors found that a significant number of primary hyperhidrosis patients (more than 70%) were so pleased with the results that they decided to forgo the surgery [50-53].

Expert Review of Dermatology7.6 (Dec 2012): 529-538.

Neuralgia due to sympathectomy

Depending on the skill of the surgeon and difficulty encountered performing various intraoperative maneuvers, the incidence of complications following sympathectomy should be the same as that following any other extraperitoneal or extrapleural operation. However, a frequent complication following sympathectomy, and one which is apparently unrelated to operative technique, is that of postsympathectomy neuralgia.

This neuralgia is characterized by aching thigh pain after lumbar sympathectomy or aching shoulder and arm pain after cervical sympathectomy. The pain is intense in severity, sudden in onset and disappearance, and not related to any major neurologic manifestations.

Recently we have reviewed the files of the Vascular Surgical Service at the West Roxbury Veteran's Hospital and the literature on this condition. This report is a presentation of our findings.

Incidence  Pain following sympathectomy has been described as "an all too common complaint."⁸ Reports have varied in incidence from 2.1% to "practically every case."

http://archsurg.jamanetwork.com/article.aspx?articleid=560162

Autonomic neuropathy in the skin following sympathectomy

In diabetics with the anhidrotic syndrome, autonomic nerve fibres were studied in skin biopsies using argentic techniques and light microscopy. The Minor test was used to differentiate normal from anhidrotic skin areas. In the anhidrotic areas, histology of the nerve fibres showed beading, spindle-shaped thickening and fragmentation adjacent to the sweat glands. These changes were similar to those observed in two patients who had previously undergone lumbar sympathectomy. No abnormalities of the sympathetic nerve endings could be found in biopsies taken from normal areas of the forearm of the same patients. We conclude that the diabetic anhidrotic syndrome, a form of diabetic autonomic neuropathy, is due to a lesion of the sympathetic nerve supply to the skin.

I. Faerman¹, E. Faccio³, I. Calb², J. Razumny¹, N. Franco², A. Dominguez² and H. A. Podestá¹

Diabetologia

Volume 22, Number 2 / February, 1982