In g u i n a l hernia surgery is one of the most common. Long-term outcome following ilioinguinal neurectomy for chronic pain.

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1 J Neurosurg 112: , 2010 Long-term outcome following ilioinguinal neurectomy for chronic pain Clinical article And r e w C. Za c e s t, M.D., St e p h e n T. Ma g i l l, B.S., Va l e r i e C. And e r s o n, Ph.D., a n d Kim J. Bu r c h i e l, M.D. Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon Object. Ilioinguinal neuralgia is one cause of chronic groin pain following inguinal hernia repair, and it affects ~ 10% of patients. Selective ilioinguinal neurectomy is one proposed treatment option for carefully selected patients. The goal of this study was to determine the long-term outcome of patients who underwent selective ilioinguinal neurectomy for chronic post-hernia pain. Methods. The authors retrospectively reviewed the clinical assessment, surgical treatment, and long-term outcome in 26 patients with ilioinguinal neuralgia who underwent selective ilioinguinal neurectomy performed by the senior author (K.J.B.) at Oregon Health & Science University between 1998 and Data were collected from patient charts and a follow-up telephone questionnaire. Results. Twenty-six patients (14 men and 12 women) had a clinical diagnosis of ilioinguinal neuralgia based on a history of radiating neuropathic groin, medial thigh, and genitalia pain. One patient had bilateral disease (therefore there were 27 surgical cases). A selective nerve block was performed in 21 (81%) of 26 patients and was positive in 20 (77%) of the 26. In all but 2 patients, pain onset followed abdominal surgery (for hernia repair in 18 patients), and was immediate in 16 (67%) of 24 patients. The mean patient age was 48.7 years, and the mean duration of pain prior to neurosurgical consultation was 3.9 years. Surgery was performed after induction of local or general anesthesia in 17 and 10 cases, respectively. The ilioinguinal nerve was identified in 25 cases, and the genitofemoral nerve in 2, either entrapped in mesh, scar, or with obvious neuroma (22 of 27 cases). The identified nerve was doubly ligated, cut, and buried in muscle at its most proximal point. At the 2-week follow-up evaluations, 14 (74%) of 19 patients noted definite pain improvement. Nineteen (73%) of the 26 patients were contacted by telephone and agreed to participate in completing longterm follow-up questionnaires. The mean follow-up duration was months. Return of pain was reported by 13 (68%) of 19 patients. Using a verbal numerical rating scale (0 10), pain was completely relieved in 27.8%, better in 38.9%, no better in 16.7%, and worse in 16.7% of patients. Conclusions. Ilioinguinal neurectomy is an effective and appropriate treatment for selected patients with iatrogenic ilioinguinal neuralgia following abdominal surgery. Although a high proportion of patients reported some longterm recurrence of pain, complete or partial pain relief was achieved in 66.7% of the patients observed. (DOI: / JNS09533) Ke y Wo r d s ilioinguinal nerve neurectomy neuropathic pain hernia repair In g u i n a l hernia surgery is one of the most common surgeries performed, and persistent postoperative pain is uncommon. 1,7,8,10,11,17,19 However, up to 10% of patients after 1 year 4,8,10 and 6% at 6 years 3 report severe pain with functional impairment. Patients with these symptoms may be treated by their primary surgeon, referred to a pain clinic, or, infrequently, referred to a neurosurgeon. There are several potential causes of persistent postoperative inguinal hernia surgery pain. During surgery the ilioinguinal, iliohypogastric, and genitofemoral nerves may be injured, or a delayed injury may lead to neuropathic pain. 6,20,23 Clinically, neuropathic pain is typically characterized as burning or lancinating in the distribution of the injured nerve, is usually associated with an area of sensory disturbance, and may be relieved by infiltration of local anesthetic in the area of the nerve. Neuropathic pain is usually unresponsive to conventional analgesics and can be difficult to manage with anticonvulsants or neuromodulation, and therefore targeted nerve section may be appropriate and effective. Treatment options for postsurgical neuralgia include the following: anticonvulsants, 9 local anesthetic blocks, 23 percutaneous radiofrequency nerve root lesioning, 22 neurostimulation, and peripheral surgical neurectomy. 5,15 The majority of these medical treatments are performed in pain clinics, and long-term outcomes are unclear. Selective ilioinguinal neurectomy performed either at the time of hernia repair or following hernia repair in those patients with ilioinguinal neuralgia would seem to be a This article contains some figures that are displayed in color on line but in black and white in the print edition. 784

2 Long-term outcome after ilioinguinal neurectomy for chronic pain promising and potentially simple treatment in the short term; however, the long-term outcome of this treatment is also unclear. Although techniques to identify and protect regional nerves during hernia repair 7,10,12,16,18,21 are under investigation, postoperative neuralgia remains a significant problem. A better understanding of patient selection criteria and the efficacy and limitations of current surgical treatments for neuropathic pain are needed to guide surgeons now and in the future. Methods Patient Population Following institutional review board approval, patients who had undergone ilioinguinal neurectomy for ilioinguinal neuralgia were identified from clinic charts. Selection criteria included the following: a history of probable iatrogenic nerve injury (if applicable); symptoms of radiating neuralgia pain in the distribution of the ilioinguinal nerve (medial groin, testicle, or labia); pain triggerability; a positive Tinel sign; allodynia or sensory loss on examination; and relief of pain following a proximal block of the ilioinguinal nerve. Twenty-six patients who fit the selection criteria underwent ilioinguinal neurectomy performed by the senior author (K.J.B.) between 1998 and 2008 at Oregon Health & Science University. Patient Data Collection Patient charts were reviewed retrospectively. Demographic details (age, sex); details of prior surgery; and history, location, character, and duration of the pain complaint were recorded, as was response to prior pain treatment(s). Examination findings including Tinel sign, sensory loss, and response to preoperative diagnostic nerve block were documented. Operative findings were noted and postoperative outcome was determined. The patients were mailed an invitation to participate in a postsurgery follow-up telephone questionnaire (the telephone questionnaire is presented in Table 1). Patients were asked to recall the character, location, and response to treatment of their preoperative pain. Patients were asked to score their pain retrospectively preoperatively, 2 weeks postoperatively, and at the present time by using a 0 10 verbal numerical rating scale (0 being no pain and 10 the worst pain imaginable). Medication use and physical activity pre- and postoperatively were recorded, as well as whether there was a Workers Compensation claim or prior history of chronic pain, defined as pain lasting > 3 months. Surgical Approach and Technique Procedures were performed after induction of general anesthesia or with local anesthetic and sedation. The latter had the advantage of allowing direct localization of the painful lesion with the patient s cooperation, thus minimizing the need for extensive dissection. After induction of general anesthesia, the ilioinguinal nerve was located using anatomical principles. The inguinal incision was generally extended laterally as required, up to the anterior superior iliac spine. At this point the ilioinguinal nerve pierces the transversus abdominis muscle and crosses the internal oblique muscle. From here the nerve travels toward the pubic tubercle under the aponeurosis of the external oblique along the spermatic cord or round ligament. Finally, it exits through the superficial abdominal ring with the spermatic cord to supply the skin of the anteromedial thigh, root of the penis (or labia majora in women). If the nerve was identified medially within scar tissue or hernia mesh, it was followed proximally toward the superficial ring, doubly ligated, and the stump buried in muscle. If not identified medially, the nerve was located proximally and followed into the scar or mesh and distally ligated (Fig. 1). Results Twenty-six patients (14 men and 12 women) with ilioinguinal neuralgia were identified. The mean age was 48.7 ± 10.4 years (range years). One patient had bilateral disease and underwent a bilateral procedure (for a total of 27 surgical cases). The mean pain duration prior to neurosurgical consultation was 46 ± 54 months. As reported by the patient, neuropathic pain was either constant (52.63%) or lancinating (74.68%). On examination, a positive Tinel sign was observed in 44%, anticonvulsants were used in 42.3%, and opioids in 27% of patients. A selective nerve block was performed in 21 (81%) of 26 patients and was positive, as defined by distal relief of neuralgic pain, in 20 (77%) of 26 patients, or 20 (74%) of 27 procedures. The block was usually performed by the surgical team as part of the preoperative evaluation and was an important factor in selection for surgery. A summary of retrospective patient chart data is presented in Table 2, and data collected via the telephone questionnaire are presented in Table 3. In all but 2 patients, pain onset was noted after abdominal surgery (for hernia repair in 18 patients) and was immediate in 16 (67%) of 24 patients. The total number of prior surgeries ranged from 1 to 4 per patient, and 27% of patients had already undergone prior surgery for pain relief, procedures which included wound revisions and attempted neurectomy. All were reportedly uniformly unsuccessful in the long term. Surgery was performed after induction of local anesthesia in 17 cases and general anesthesia in 10 cases. The ilioinguinal nerve was identified in 25 cases and the genitofemoral in 2 patients, either entrapped in mesh, scar, or with an obvious neuroma in 22 of 27 cases. The identified nerve was doubly ligated, cut, and buried in muscle at its most proximal point. There were 2 surgery-related complications, 1 a wound hematoma and 1 a testicular infarction, which required orchiectomy. Histological confirmation of neuroma was obtained in 6 of 19 cases in which specimens were sent for histopathological examination. Nineteen (73%) of 26 patients contacted agreed to participate in the long-term telephone questionnaire. Two patients were deceased, and 2 declined to participate. The remaining 3 patients could not be reached. In the telephone interview, 74% of patients recalled that their pain was better at 2 weeks, with 53% reporting improvement of lancinating pain or a reduction in medication, as recorded in their charts. 785

3 A. C. Zacest et al. TABLE 1: Retrospective telephone questionnaire conducted in 19 of 26 patients who had undergone ilioinguinal neurectomy for chronic pain Questions Response Options preoperative questions Was your pain predominantly in your groin? Did your pain consist of unpredictable sensations (electrical, shocking, stabbing, shooting) either entirely or briefly? Did you have any constant background pain (aching, burning, throbbing, stinging)? Could your pain be triggered by touching the wound? Did the pain radiate to the genitalia or inner thigh? Did you notice an area of numbness in the area of the pain? When did you first experience this pain after the original operation? Did you ever take medications like Tegretol (carbamazepine), Neurontin (gabapentin), Lioresal (baclofen), Treleptal (oxcarbamazepine), Topamax (topiramate), or Lyrica (pregabalin) for your pain? Did you experience any reduction in your pain from taking any of these medications? Have you ever had a nerve block for relief of this pain? Did you notice any reduction in your pain from that blockade? If zero (0) is no pain and ten (10) is the worst pain imaginable, what score would best describe your pain level before the operation by Dr. B.? Did your pain significantly affect your activities of daily living? Did your pain interfere with your capacity to work? Are you involved in Workers Compensation or litigation related to your pain? Have you ever had or do you have another pain complaint that has lasted more than 3 months? postoperative questions Two weeks after the operation by Dr. B., was your pain better? If zero (0) is no pain and ten (10) is the worst pain imaginable, what score would best describe your pain level 2 weeks after the operation by Dr. B.? If your pain was better following surgery, what type of pain was improved intermittent/sharp/shooting pain? constant, aching/burning pain? Since the operation have you experienced periods of weeks, months, or years when you were pain free? Has your medication use for pain declined following the surgery by Dr. B.? Have your activities of daily living improved following the surgery by Dr. B.? Does your pain interfere with your capacity to work? Have you had any return of the original pain since the surgery by Dr. B.? How long is it now since the surgery by Dr. B.? If zero (0) is no pain and ten (10) is the worst pain imaginable, what score would best describe your pain level now? months _ /10 _ /10 months _ /10 Fig. 1. Photographs showing exploration of left inguinal hernia wound. A: Lateral extension toward anterior superior iliac spine. B: Full opening of wound with exposure of lateral mesh wall and ilioinguinal nerve exiting the transversus muscle and surrounded by scar going under mesh. C: The distal ilioinguinal nerve has been cut and the proximal end is about to be doubly ligated and cut as it exits the transversus muscle. 786

4 Long-term outcome after ilioinguinal neurectomy for chronic pain TABLE 2: Preoperative and operative data obtained in 26 patients who underwent surgery for ilioinguinal neuralgia Patient Data Value demographic data no. of patients 26 no. of op cases 27 age (yrs) 48.7 ± 10.4, range no. of each sex 14 M, 12 F pain history pain duration (mos) 46.3 ± 54.7, range positive Tinel sign 12 of 27 (44.44%) nerve block performed 21 of 27 (77.77%) nerve block positive 20 of 27 (74.07%) prior pain ops 7 of 26 (26.9%) medications anticonvulsants 11 of 26 (42.3%) opioids 7 of 26 (26.9%) prior tx (no. of) general surgery 18 gynecology 5 urology 2 no surgery 2 no. of previous ops 1 15 of 26 (57.69%) 2 5 of 26 (19.23%) 3 5 of 26 (19.23%) 4 2 of 26 (7.69%) neurectomy local anesthesia 17 of 27 (62.96%) general anesthesia 10 of 27 (37.04%) mesh in wound (yes) 15 of 27 (55.55%) nerve identified 27 of 27 (100%) pathology 6 of 19 (32% identified as neuroma) complications 2 of 27 (7.4%: wound hematoma & testicular infarction) postop tx further pain surgery 5 of 26 (19.23%) Return of some pain was reported by 68% of patients. Based on a 0 10 verbal numerical rating scale (0 being no pain and 10 the worst pain imaginable), pain was reported by the patient as completely relieved in 27.8% (Score 0 of 10); partially reduced in 38.9% (a reduced verbal numerical rating scale); no better in 16.7%; and worse in 16.7% in long-term follow-up. At 2 weeks, as determined by the verbal numerical pain rating scale, 72% (14/18) of patients recalled obtaining either complete or partial relief, compared with 66.7% at long-term follow-up (Table 3). The mean follow-up duration for patients who participated in the telephone questionnaire was 35 ± 28 months (range months), and 18% of patients had undergone further pain procedures to help manage their pain, including spinal cord stimulation or intrathecal pumps, only 1 of which treatments led to any improvement in pain relief. The median age and sex distribution were not significantly different in the telephone questionnaire population (19 of 26 of the patients) compared with the entire study cohort. Most patients had either constant or lancinating pain (74%), which was triggerable in 68.4%. Thirty-two percent were involved in a Workers Compensation claim, and 37% had a history of other pain problems lasting > 3 months. Discussion The chief finding from the study we present is that, in agreement with other surgical series, 2,5,6,15,23 a subset of patients with chronic inguinal pain have neuropathic pain secondary to injury to the ilioinguinal nerve or nearby nerves (that is, the genitofemoral nerve), and may potentially achieve pain relief from selective neurectomy, provided that the preoperative assessment is suggestive of nerve injury. In this study, those features included a clear history of neuropathic pain in the distribution of the ilioinguinal or genitofemoral nerve, a positive Tinel sign, and a clear response from a targeted nerve block (that is, distal and concordant pain relief in the distribution of the nerve). In such cases, in our opinion, nerve exploration and proximal section may be offered to the patient as a therapeutic option to relieve the neuropathic component of the pain. Chronic pain is a common and, until relatively recently, an often underestimated problem following surgery. Following inguinal hernia surgery, the frequency of pain lasting > 3 months has been reported to range from 0 to 53%, 19 but is probably closer to 10 12%. 1 Although it is not known what happens to the majority of these patients, in one study 1% of all patients who had undergone hernia repair were referred to a regional pain clinic. 14 Some are referred to neurosurgeons. The pathophysiological origin of pain following surgery in the ilioinguinal region is incompletely understood and is probably multifactorial in origin. Theoretically, pain could arise from somatic structures; for example, the inguinal ligament and its attachments to the pubic tubercle, visceral structures, and also neural structures, particularly the ilioinguinal, iliohypogastric, and genitofemoral nerves, which are clearly at risk during surgery. 1 The potential contribution of mesh toward post-herniorrhaphy pain has been raised, 13 but has not been shown overall to increase the chance of pain. 1 In addition, risk factors for chronic postoperative pain including the severity of preoperative and early postoperative pain; repeat surgery; psychological factors (anxiety, depression, and a history of chronic pain); and Workers Compensation status often color the clinical assessment and need to be considered. The current surgical management of chronic pain following inguinal hernia repair has consisted largely of neurectomy and mesh removal. This has been based on the premise that nerve injury is a prerequisite for development of neuropathic pain, although clearly many patients have sensory loss but do not develop pain. In reviewing the outcome following surgical neurectomy for this condition, Aasvang and Kehlet 2 reviewed 14 peer-reviewed manuscripts and noted an overall favorable outcome, 787

5 A. C. Zacest et al. TABLE 3: Long-term follow-up as determined based on a postoperative telephone questionnaire (see Table 1) in 19 patients who underwent ilioinguinal neurectomy Patient Data Value demographic data no. of patients 19 age (yrs) 48 ± 10.1, range no. of each sex 11 M, 8 F preop pain described as* lancinating constant triggerable 14 of 19 (73.68%) 10 of 19 (52.63%) 10 of 19 (52.63%) postop pain details (follow-up ± 28.2 mos [range mos])* two weeks after the operation was your pain better? 14 of 19 (73.68%) following surgery was intermittent/sharp/shooting pain improved? 10 of 19 (52.63%) has your medication use for pain declined following the surgery? 10 of 19 (52.63%) have you had any return of the original pain since the surgery? 13 of 19 (72.22%) verbal numerical pain rating scale (0 10) recalled at 2 wks at ± 28.2 mos complete pain relief 3 of 18 (16.7%) 5 of 18 (27.8%) partial pain reduction on reduced numerical scale 10 of 18 (55.6%) 7 of 18 (38.9%) same no pain relief; no change in numerical scale 4 of 18 (22.2%) 3 of 18 (16.7%) worse increased pain; increased numerical scale 1 of 18 (5.5%) 3 of 18 (16.7%) * Based on a yes response. Pain relief recorded as a verbal numerical rating on a scale of 0 10 (0 being no pain and 10 the worst pain imaginable). Data were complete for 18 of 19 patients. Patients could be taking pain medication or using other pain-reducing therapies. with pain relief ranging from 0 to 80%. On superficial inspection these results look attractive; however, in criticism it was noted that almost all were retrospective, that the diagnostic criteria (including blocks and neurophysiological and neuropsychological assessment) were unclear; and that none of the studies reported long-term follow-up or quantitated pain pre- or postoperatively. How effective is selective neurectomy in selected patients? We found that 74% of patients reported definite improvement of their pain at the 2-week clinical follow-up evaluation, with improvements in the lancinating component and a reduction in medication use. In the long term, however, only 28% of patients had complete pain relief, although another 39% had some improvement. The remainder (33%) were either no better or their pain was worse. Factors that were associated with a significant chance of pain relief or improvement included a history of lancinating pain and operation in which local anesthesia was used. These results are sobering but hardly surprising when dealing with pain that may have been due to multiple causes, including neuropathic, and that was often chronic in duration. To our knowledge, no long-term follow-up data for patients with ilioinguinal neuralgia treated by neurectomy has been reported in the literature to date. Additionally, in the data we present, a high proportion of patients reported recurrent pain (68%). This is consistent with anecdotal experience of surgical treatment with neurectomy, in which pain has a tendency to recur, presumably due to regrowth of nerve fibers, which may again become mechanosensitive. Various surgical approaches have been used to address the problem of neuropathic pain in the inguinal region. The more traditional approach has been the attempted discrete localization of the affected nerve preoperatively based on nerve blockade and classic descriptions of nerve anatomy and distribution. A problem with this is that significant anatomical variability of the skin supply exists between the ilioinguinal and genitofemoral nerve; Rab et al. 20 describe 4 variants. Therefore, differentiation between the 2 nerves may prove difficult, and isolated nerve section may fail to eliminate the pain generator adequately. This could account for our identification of the genitofemoral nerve in 2 cases. Nerve blockade may help differentiate the 2, but not always. A second surgical strategy is to perform a triple neurectomy, as advocated by Amid, 5 accepting that the only sure way to eliminate all causes of neuropathic pain is to section all nerves. Unfortunately, the lack of long-term follow-up data from surgical series makes it difficult to compare the relative merits of each approach. The method we describe represents a targeted approach based on a preoperative assessment of the probable injured nerve, based on the results of proximal nerve blockade in conjunction with wound exploration, guided ideally by patient input (local anesthesia and sedation). In patients in whom general anesthesia is induced, an anatomical exploration for the ilioinguinal and genitofemoral nerves was conducted, with resection and burying of obviously injured nerves. No attempt was made to perform neurolysis. The presence of mesh and scar clearly made normal dissection and identification more difficult. In this 788

6 Long-term outcome after ilioinguinal neurectomy for chronic pain situation, extending the incision laterally to the level of the anterior superior iliac spine allowed us to identify the emergence of the ilioinguinal nerve from the transversus abdominis muscle and follow it into the inguinal region. The genitofemoral nerve was more likely to be found distally, close to the spermatic cord and vessels. The one complication of testicular infarction in this series highlights the dangers of dissection close to these structures. In agreement with other authors, 5 we found the ilioinguinal nerve most likely to be entrapped. Limitations of this study include the small number of cases, a single surgeon and single institution, 70% followup rate, the absence of controls, and lack of functional scales. However, given the unlikelihood of a prospective or randomized trial for chronic pain following hernia repair, the retrospective data we present may represent the best available that detail long-term pain relief outcome. Conclusions Ilioinguinal neuralgia is one cause of chronic pain following abdominal surgery, and patients may be referred to a neurosurgeon. The results we present parallel other surgical neurectomy studies for pain relief, which suggest potential benefit but a high likelihood of pain recurrence. In spite of this, up to 65% of carefully selected patients may benefit, either fully or partially, from selective proximal neurectomy. Patients with a history of a lancinating component to their pain appear to have an increased chance of improvement from surgery. Careful preoperative discussion should emphasize the surgical objective of solely targeting the neuropathic pain component, with the potential of pain return and the possibility of pain exacerbation in some patients. Disclaimer There are no conflicts of interest or financial disclosures in relation to this manuscript. Acknowledgments We express our appreciation and thanks to Shirley McCartney, Ph.D., for editorial assistance, and to Andy Rekito, M.S., for illustrative assistance. References 1. Aasvang E, Kehlet H: Chronic postoperative pain: the case of inguinal herniorrhaphy. Br J Anaesth 95:69 76, Aasvang E, Kehlet H: Surgical management of chronic pain after inguinal hernia repair. Br J Surg 92: , Aasvang EK, Bay-Nielsen M, Kehlet H: Pain and functional impairment 6 years after inguinal herniorrhaphy. Hernia 10: , Alfieri S, Rotondi F, Di Miceli D, Di Giorgio A, Ridolfini MP, Fumagalli U, et al: [Chronic pain after inguinal hernia mesh repair: possible role of surgical manipulation of the inguinal nerves. A prospective multicentre study of 973 cases.] Chir Ital 58:23 31, 2006 (Italian) 5. 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Mt Sinai J Med 73: , Starling JR, Harms BA: Diagnosis and treatment of genitofem oral and ilioinguinal neuralgia. World J Surg 13: , 1989 Manuscript submitted April 2, Accepted August 6, Please include this information when citing this paper: published online September 25, 2009; DOI: / JNS Address correspondence to: Kim J. Burchiel, M.D., Department of Neurological Surgery, Mail Code: CH8N, Oregon Health & Science University, 3303 SW Bond Avenue, Portland, Oregon burchiek@ohsu.edu. 789