INTRODUCTION 　　Postherpetic neuralgia (PHN) is defined as pain per- sisting for more than 1-6 months after the rash has healed [1-3]. Disseminated herpes zoster occurs primarily in im- munocompromised patients including patients with chronic kidney disease (CKD) undergoing a regular schedule of he- mo-dialysis [4,5]. 　　Doses of anticonvulsants need to be adjusted in these patients according to the glomerular filtration rate and their scheduled dialysis [3,6]. However, it is difficult for them to adjust to the doses of neuropathic medications. If the neural blockade and pulsed radiofrequency ablation provide only short-term amelioration of pain [7], spinal cord stimulation (SCS) with a low level of evidence may be used only as a last resort. 　　SCS is well known to be effective in some patients with failed back surgery syndrome, peripheral vascular dis- orders, and complex regional pain syndrome [8-11]. However, it is rare to find the studies with good results in patients with PHN. 　　The aim of study was to evaluate the efficacy of spinal cord stimulation in the treatment of PHN in patients with chronic kidney disease. MATERIALS AND METHODS 　　This retrospective study was done at a pain clinic of Pusan National University Hospital in Korea. The recruit- ment period was from January 2003 to December 2007. The protocol was approved by the Policy of the Ethical Committee at Pusan National University Hospital Institu- tional Review Board. The patients eligible were informed about the procedure of the study and agreed to participate in this study and gave their written consent. 　　The PHN patients with CKD who needed hemo-dialysis who received insufficient relief from pain with a visual an- alogue scale score of over 8 for at least 6 months regard- less of neuropathic medications were eligible for percuta- neous SCS test trial. A permanent SCS implant was im- planted after patients had experienced at least 50% reduc- tion in the pain score. The follow-up period was at least 2 years after permanent SCS implantation. The successful cases of permanent SCS implantation were defined as the patients who had experienced at least 50% reduction in pain score continuously with tolerable neuropathic medi- IY Beak, et al / SCS for PHN in Patients with CKD 155 cations till the end of study. 　　The efficacy of the permanent SCS implant was eval- uated using the pain score and daily doses of neuropathic medications at the final visit day for the successful cases of the permanent SCS implants. The complications related to SCS were also recorded.  RESULTS 　　All postherpetic neuralgia pain patients with chronic renal failure who had received trial spinal cord stimulation were male. Mean age was 66.1 ± 4.5 years old. Mean du- ration of pain was 24.5 ± 5.2 months. Dermatomal dis- tributions of pain were 1 cervical, 8 thoracic, and 2 thor- acolumbar areas. Mean duration after diagnosis of chronic renal failure was 8.3 ± 1.8 years. Mean duration of he- mo-dialysis was 6.6 ± 1.2 years. Their stages of renal failure were from 3B to 4. Four patients had comorbid dia- betes mellitus. All patients had received hemo-dialysis 3 times a week regularly (Table 1). 　　Eleven patients received the SCS test trial during the study period. Four patients had the permanent SCS im- planted successfully with their pain being tolerable with a VAS score of less than 3 along with small doses of neuro- pathic medication at the final visit. Mean follow-up period was 34.5 months (range, 28 to 41 months) (Table 2). There were no complications related to the SCS implant including lead migration, infection, or bleeding. DISCUSSION 　　Although it was a small number of PHN patients with CKD, 4 of the 11 patients showed considerable relief of pain and experienced mild pain intensity of less than VAS 3 with tolerable neuropathic medications. 　　It seemed that factors including age, dermatomal dis- tribution and duration of pain, duration of hemo-dialysis and CKD, stages of CKD, and comorbidity between the success or failure group of permanent SCS did not show any differences in the effectiveness of SCS in this study. Randomized clinical studies showed the efficacy of antiviral agents in the prevention of PHN and the use of anti- convulsants, antidepressants, opioids, and lidocaine patch in the treatment of PHN (level A evidence). The role of epi- dural local anesthetic and steroid injections in preventing PHN has not been completely established (level B evidence).