Perineal pain and inferior cluneal nerves: anatomy and surgery

Origin, course, and distribution of the posterior femoral cutaneous nerve and the spatial relationship among its branches

This study aimed to elucidate the origin, course, and distribution of the branches of the posterior femoral cutaneous nerve, considering the segmental and dorsoventral compositions of the sacral plexus, including the pudendal nerve. The buttocks and thighs of five cadavers were analyzed bilaterally. The branches emerged from the sacral plexus, which was divided dorsally to ventrally into the superior gluteal, inferior gluteal, common peroneal, tibial, and pudendal nerves. It descended lateral to the ischial tuberosity and comprised the thigh, gluteal, and perineal branches. As for the thigh and gluteal branches, the dorsoventral order of those originating from the sacral plexus corresponded to the lateromedial order of their distribution. However, the dorsoventral boundary was displaced at the inferior margin of the gluteus maximus between the thigh and gluteal branches. The perineal branch originated from the ventral branch of the nerve roots. In addition, the pudendal nerve branches, which ran medially to the ischial tuberosity, were distributed in the medial part of the inferior gluteal region. These branches should be distinguished from the gluteal branches; the former should be classified as the medial inferior cluneal nerves and the latter as the lateral ones. Finally, the medial part of the inferior gluteal region was distributed by branches of the dorsal sacral rami, which may correspond to the medial cluneal nerves. Thus, the composition of the posterior femoral cutaneous nerve is considered necessary when considering the dorsoventral relationships of the sacral plexus and boundaries of the dorsal and ventral rami.

Cluneal neuropathy: Background, diagnosis, and treatment

BACKGROUND AND AIMS

Cluneal neuropathy is encompassed by three distinct clinical entities. Superior, middle, and inferior cluneal neuralgia make up the constellation of symptoms associated with cluneal neuropathy. Each has its own variable anatomy.

MATERIALS AND METHODS

We compiled a narrative review including a review of available literature. We conducted searches on PubMed/MEDLINE, Embase and Google Scholar on the topics of cluneal neuropathy and treatment therein.

RESULTS

We collected source articles regarding original descriptions of the disease entities in addition to articles focused on treatment.

DISCUSSION

Adjusted incidence rates of superior cluneal neuropathy are 1.6%-11.7%. Accurate diagnosis remains challenging due to the lack of standardized criteria and the aforementioned variability. Treatment may include therapeutic nerve blocks, ablative techniques, neuromodulation, and surgical decompression. Gaps including those related to true incidence and work up exist. Outcomes from interventional studies are limited and mixed due to significant population heterogeneity and non-standardized treatment approaches coupled with very small sample sizes.

Simultaneous Posterior Femoral Cutaneous Nerve and Sciatic Nerve Variations: A Case Report

During the routine dissection of a formalin fixed Caucasian cadaver, a previously unreported variation of the sacral plexus was found in the right gluteal region. The posterior femoral cutaneous nerve was found to pierce the piriformis muscle as opposed to running along its more common course below the muscle. At the same level of the posterior femoral cutaneous nerve, the common fibular nerve also pierced the piriformis muscle, while the tibial nerve passed inferior to the piriformis muscle. No other anatomical variations were found.

Diagnosis and treatment of pudendal and inferior cluneal nerve entrapment syndrome: a narrative review

AIM

Pudendal and inferior cluneal nerve entrapment can cause a neuropathic pain syndrome in the sensitive areas innervated by these nerves. Diagnosis is challenging and patients often suffer several years before diagnosis is made. The purpose of the review was to inform healthcare workers about this disease and to provide a basis of anatomy and physiopathology, to inform about diagnostic tools and invasive or non-invasive treatment modalities and outcome.

METHODS

A description of pudendal and inferior cluneal nerve anatomy is given. Physiopathology for entrapment is explained. Diagnostic criteria are described, and all non-invasive and invasive treatment options are discussed.

RESULTS

The Nantes criteria offer a solid basis for diagnosing this rare condition. Treatment should be offered in a pluri-disciplinary setting and consists of avoidance of painful stimuli, physiotherapy, psychotherapy, pharmacological treatment led by tricyclic antidepressants and anticonvulsants. Nerve blocks are efficient at short term and serve mainly as a diagnostic tool. Pulsed radiofrequency (PRF) is described as a successful treatment option for pudendal neuralgia in patients non-responding to non-invasive treatment. If all other treatments fail, surgery can be offered. Different surgical procedures exist but only the open transgluteal approach has proven its efficacy compared to medical treatment. The minimal-invasive ENTRAMI technique offers the possibility to combine nerve release with pudendal neuromodulation.

CONCLUSIONS

Pudendal and inferior cluneal nerve entrapment syndrome are a challenge not only for diagnosis but also for treatment. Different non-invasive and invasive treatment options exist and should be offered in a pluri-disciplinary setting.

Easy to treat when the diagnosis is made: Three cases of clunealgia and the advantage of ultrasonography

In this article, we present three cases of clunealgia admitted with low back pain. Their pain relieved with superior cluneal nerve block. The posterior side of the iliac crest, which is the location where the superior cluneal nerve passes, was identified using a high-frequency linear transducer. The drug injected separates the erector spinae muscle and thoracolumbar fascia and accumulates between these two structures. All patients were discharged with a complete pain relief. This report highlights the fact that superior cluneal nerve entrapment should be kept in mind in patients with low back pain and that ultrasound guidance can correctly identify the infiltration and eliminate anesthetization of other surrounding structures.

Inferior gluteal pain with sitting, unrelated to ischial bursitis

A 64-year-old woman presented to an academic medical centre with postoperative left ischial pain following a left total hip replacement. Her pain was exacerbated by sitting down and with forward flexion of the spine, and the pain radiated from the left ischial tuberosity to the left perineum, groin and medial thigh. An ischial bursa injection was performed, but only resulted in 1 day of excellent pain relief. A diagnosis of inferior cluneal neuralgia was then made. Subsequent inferior cluneal nerve radiofrequency ablation was performed, and provided sustained 50% relief in pain. The patient had a concomitant sensation of 'ball like' pressure at her rectum which was determined to be due to levator ani syndrome. She was prescribed pelvic floor physical therapy and botulinum toxin injection, which resulted in further notable improvement of her symptoms.

Expanded Perineal Coverage With Combined Pudendal and Inferior Cluneal Nerve Blocks: A Case Report

The pudendal nerve (PN) block is an effective regional technique for providing analgesia to the perineum. However, when the surgical site involves dermatomal areas lateral to the PN dermatome, additional blocks are necessitated. We present a case report of a 6-year-old female who presented for surgical resection of widespread condylomata accuminata involving the perineum and buttocks. Analgesia was achieved using a combined PN and inferior cluneal nerve block. To our knowledge, this is the first report of this combined technique used for perioperative analgesia.

Pain Syndromes Secondary to Cluneal Nerve Entrapment

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the cluneal nerves, present a summary of pain syndromes secondary to clunealgia, and evaluate current literature for diagnostic and treatment modalities.

RECENT FINDINGS

Multiple trials and studies have reported success with numerous modalities ranging from nerve blocks, neuroablation, and even peripheral neuromodulation with varying degrees of clinical benefit. Cluneal nerve entrapment or chronic impingement can cause buttock pain or referred pain to nearby areas including the lower back, pelvic area, or even the lower extremities. Clunealgias and associated pain syndromes can often be challenging to diagnose and differentiate. An appreciation of the pathophysiology of clunealgias can assist with patient selection for interventional pain strategies targeted towards the cluneal nerves, including nerve blocks, neuroablation, and peripheral neuromodulation. More research is needed to better delineate the efficacy of these procedures for clunealgias.

The Feasibility of a Sensate Profunda Artery Perforator Flap in Autologous Breast Reconstruction: An Anatomic Study for Clinical Application

BACKGROUND

The profunda artery perforator (PAP) flap has been demonstrated to be an effective method of autologous breast reconstruction, particularly when the abdominal donor site is contraindicated. However, there are no current reports regarding the use of a sensate PAP flap in this type of reconstruction. The objective of this study is to describe the feasibility and anatomic location of the sensory nerves supplying the PAP flap in relation to surface landmarks for use in autologous breast reconstruction.

METHODS

In this anatomic study, 10 cadaver lower limbs were microsurgically dissected. We investigated the posterior femoral cutaneous nerve (PFCN), which supplies sensation to the skin of the posterior thigh and distribution of the PAP flap. The midline of the posterior thigh and gluteal crease were used for surface landmarks. The diameter and length of the nerve branches were documented.

RESULTS

There were between 2 and 5 PFCN branches, with an average of 3 branches, that were found within the distribution of the PAP flap. Measurements were taken from the gluteal crease and midline to the nerve branches. The average distance caudal to the gluteal crease was 2.4 cm (0 to 7 cm). The average distance medial to the midline was 4.3 cm (0.2 to 8.1 cm). The average diameter of the nerve branches was 1.8 mm (1 to 2.5 mm). The average length of nerve branches from the flap to the fascia was 2.0 cm (1.5 to 2.4 cm). The maximum length of the nerve branches from the flap to the main trunk of the PFCN was 7.8 cm when tracing the nerve branches intramuscularly.

CONCLUSIONS

The findings from this study provide an anatomic basis for the sensate PAP flap that would potentially provide an additional dimension to the use of this perforator flap in autologous breast reconstruction. These preliminary results are promising, and further physiological studies are warranted to validate the use of this sensate flap.

A new endoscopic minimal invasive approach for pudendal nerve and inferior cluneal nerve neurolysis: An anatomical study

AIM

To describe a new minimal invasive approach of the gluteal region which will permit to perform neurolysis of the pudendal and cluneal nerves in case of perineal neuralgia due to an entrapment of these nerve trunks.

METHOD

Ten transgluteal approaches were performed on five cadavers. Relevant anatomic structures were dissected and further described. Neurolysis of the pudendal nerve or cluneal nerves were performed. Landmarks for secure intraoperative navigation were indicated.

RESULTS

The first operative trocar for the camera was inserted with regards to the iliac crest in the deep gluteal space. With the aid of pneumodissection, the infragluteal plane was dissected. The piriformis muscle was identified as well as the sciatic and the posterior femoral cutaneous nerve. Consequently, the sciatic tuberosity was visualized together with the cluneal nerves. Hereafter, the second trocar was introduced caudal to the first one and placed on an horizontal line passing at the level of the coccyx, allowing access to the ischial spine and the visualization of the pudendal nerve and vessels. A third 5 mm trocar was then inserted medial from the first one, permitting to dissect and transsect the sacrospinous ligament. The pudendal nerve was subsequently transposed and followed on its course in the pudendal channel.

CONCLUSIONS

A reliable exploration of the gluteal region including identification of the sciatic, pudendal, and posterior femoral cutaneous nerves is feasible using a minimal invasive transgluteal procedure. Consequently, the transposition of the pudendal nerve and the liberation of the cluneal nerves can be performed.

High-resolution ultrasound of the posterior femoral cutaneous nerve: visualization and initial experience with patients

OBJECTIVE

The posterior femoral cutaneous nerve (PFCN) is a sensory nerve originating from the sacral plexus. PFCN neuropathy leads to pain within the inferior gluteal region and the posterior aspect of the thigh. As electrophysiological assessment is challenging, diagnosis of PFCN neuropathy has been, thus far, primarily based on clinical findings, which can result in misdiagnosis. Therefore, alternative confirmatory assessments such as an imaging modality that could aid in the diagnosis of PFCN neuropathy would be desirable. The purpose of this study was to determine the feasibility of visualization of the PFCN with high-resolution ultrasound (HRUS) and to test this technique in our clinical routine.

MATERIALS AND METHODS

The study consisted of two parts. In the first part, HRUS-guided perineural ink injections along the course of the PFCN were performed at the posterior aspect of the thigh in 26 lower limbs of 14 fresh non-embalmed cadavers. Subsequent dissection confirmed correct identification of the nerve. In the second part, patients with a suspected PFCN neuropathy were examined and a selective HRUS-guided nerve block was performed to verify the suspected diagnosis.

RESULTS

The PFCN was correctly identified with HRUS in 96.2% (25/26) of cadavers. Further, six patients with a suspected lesion of the PFCN were examined, and the diagnosis was proven by successful HRUS-guided block in all cases.

CONCLUSION

We confirmed the reliable visualization of the PFCN using HRUS. This offers a new technique for the assessment of the PFCN, which could also be demonstrated with the case series presented.

Pelvic pain: a pathway for care developed for both men and women by the British Pain Society

This paper aims to explain the key points and highlight some of the controversies in the development of the British Pain Society's pelvic pain patient pathway map. Many clinicians lack experience and confidence with this group of patients, and this issue is highlighted. Additionally, the difficulties of classification and definitions in this area are discussed in detail. These are historical causes of disagreement among specialists which can lead to confused clinical care. This group of patients have multiple issues that cross many professional boundaries; they are best managed by the co-ordinated involvement of multiple teams. Patients suffer from significant distress and disability that often needs specialist assessment and intervention (interdisciplinary). This suggests that an integrated approach is required across the historic boundaries of primary and secondary care. A variety of interventions, including opioids and neuromodulation are recommended in the pathway and the controversies surrounding these inclusions are aired in detail.

Percutaneous retrograde posterior column acetabular fixation: is the sciatic nerve safe? A cadaveric study

OBJECTIVES

The purpose of this cadaveric study was to determine the proximity of the neurologic structures to the path of the screw inserted percutaneously into the ischial tuberosity.

DESIGN

Cadaver study.

INTERVENTION

Ten screws were inserted in 10 limbs (5 cadavers) under fluoroscopic guidance. Dissection was then performed to expose the head of the screw and was extended laterally to expose the sciatic nerve, the posterior cutaneous nerve of the thigh, and its inferior cluneal branches.

MAIN OUTCOME MEASURE

The distance from the screw head to the sciatic nerve, posterior cutaneous nerve of the thigh, and the inferior cluneal nerves.

RESULTS

The distance from the center of the screw head to the sciatic nerve averaged 58 mm (range, 40-70 mm). The average distance between the screw head and the posterior cutaneous nerve of the thigh was 42 mm (range, 30-60 mm). The inferior cluneal branches were the closest to the path of the screw with an average distance of 3.5 mm in 6 specimens (range, 1-6 mm) and were injured by the screw in 3 and could not be located in another specimen.

CONCLUSIONS

The sciatic nerve and the posterior cutaneous nerve of the thigh appear to be safe during retrograde percutaneous screw fixation of a posterior column acetabular fracture through a central entry point in the ischial tuberosity. However, the inferior cluneal nerves that are responsible for the cutaneous sensitivity of the lower half of the gluteal region are at risk of injury.

Magnetic resonance neurography-guided nerve blocks for the diagnosis and treatment of chronic pelvic pain syndrome

Magnetic resonance (MR) neurography - guided nerve blocks and injections describe a techniques for selective percutaneous drug delivery, in which limited MR neurography and interventional MR imaging are used jointly to map and target specific pelvic nerves or muscles, navigate needles to the target, visualize the injected drug and detect spread to confounding structures. The procedures described, specifically include nerve blocks of the obturator nerve, lateral femoral cutaneous nerve, pudendal nerve, posterior femoral cutaneous nerve, sciatic nerve, ganglion impar, sacral spinal nerve, and injection into the piriformis muscle.

High-resolution magnetic resonance-guided posterior femoral cutaneous nerve blocks

OBJECTIVE

To assess the feasibility, technical success, and effectiveness of high-resolution magnetic resonance (MR)-guided posterior femoral cutaneous nerve (PFCN) blocks.

MATERIALS AND METHODS

A retrospective analysis of 12 posterior femoral cutaneous nerve blocks in 8 patients [6 (75%) female, 2 (25%) male; mean age, 47 years; range, 42-84 years] with chronic perineal pain suggesting PFCN neuropathy was performed. Procedures were performed with a clinical wide-bore 1.5-T MR imaging system. High-resolution MR imaging was utilized for visualization and targeting of the PFCN. Commercially available, MR-compatible 20-G needles were used for drug delivery. Variables assessed were technical success (defined as injectant surrounding the targeted PFCN on post-intervention MR images) effectiveness, (defined as post-interventional regional anesthesia of the target area innervation downstream from the posterior femoral cutaneous nerve block), rate of complications, and length of procedure time.

RESULTS

MR-guided PFCN injections were technically successful in 12/12 cases (100%) with uniform perineural distribution of the injectant. All blocks were effective and resulted in post-interventional regional anesthesia of the expected areas (12/12, 100%). No complications occurred during the procedure or during follow-up. The average total procedure time was 45 min (30-70) min.

CONCLUSIONS

Our initial results demonstrate that this technique of selective MR-guided PFCN blocks is feasible and suggest high technical success and effectiveness. Larger studies are needed to confirm our initial results.

[Somatic nerve block in the management of chronic pelvic and perineal pain]

INTRODUCTION

Chronic pelvic and perineal pain can be related to a nerve lesion caused by direct or indirect trauma or by an entrapment syndrome, which must then be demonstrated by a test block. The purpose of this article is to review the techniques and modalities of somatic nerve block in the management of chronic pelvic and perineal pain.

MATERIAL AND METHODS

A review of the literature was performed by searching PubMed for articles on somatic nerve infiltrations in the management of chronic pelvic and perineal pain.

RESULTS

Nerves involved in pelvic and perineal pain are: thoracolumbar nerves (obturator, ilioinguinal, iliohypogastric and genitofemoral) and sacral nerves (pudendal and inferior cluneal branches of the posterior cutaneous nerve of the thigh). Infiltration has a dual objective: to confirm the diagnostic hypothesis by anaesthetic block and to try to relieve pain. Evaluation of the severity and site of the pain before and immediately after the test block is essential for interpretation of the block. The various infiltration techniques for each nerve are described together with their respective advantages, disadvantages and risk of complications.

CONCLUSION

Somatic nerve blocks are an integral part of the management of chronic pelvic and perineal pain and are predominantly performed under CT guidance in order to be as selective as possible. Once the diagnosis and the level of the nerve lesion have been defined, more specific therapeutic procedures can then be proposed.

[Symptomatic approach to chronic neuropathic somatic pelvic and perineal pain]

OBJECTIVES

To determine the characteristics of neuropathic pain and the somatic nerve lesions most frequently encountered in the context of chronic pelvic and perineal pain.

MATERIAL AND METHODS

Review of the literature devoted to pelvic and perineal neuralgia.

RESULTS

The diagnosis of pelvic and perineal pain related to a somatic nerve lesion is essentially clinical. The topography of the pain and its characteristics (burning, paraesthesia, etc.) can help to link the pain to the neurological territory involved. Complementary investigations are poorly contributive. Two main systems are involved in this region: sacral nerve roots that give rise to the pudendal nerve and the posterior cutaneous nerve of the thigh, thoracolumbar nerve roots that give rise to the ilioinguinal, iliohypogastric, genitofemoral and obturator nerves. The first system is essentially perineal and the second is essentially anterior inguinoperineal.

DISCUSSION

Pudendal neuralgia is the most common and most disabling form of pelvic pain. It presents as unilateral or bilateral burning pain of the anterior or posterior perineum that is worse on sitting and relieved by standing, not usually associated with night pain. It is related to a ligamentous nerve compression mechanism. Inferior cluneal neuralgia tends to be experienced as ischial and lateroperineal pain, and is sometimes accompanied by pain in a truncated sciatic territory, corresponding to projections of the posterior cutaneous nerve of the thigh. This neuralgia can be related to a piriformis syndrome or an ischial lesion. Sacral nerve root lesions do not cause acute pain, but are accompanied by sacral sensory loss and urinary, anorectal or sexual disorders. Pain related to ilioinguinal, iliohypogastric and genitofemoral nerves is generally secondary to surgical trauma and scars. Although these various lesions are sometimes difficult to distinguish from each other, an essential part of management consists of performing a local anesthetic block at the trigger point detected in the scar. Referred pain derived from the spinal cord due to thoracolumbar painful minor intervertebral dysfunction is experienced in the inguinal region, pubis, labium majorum and sometimes the trochanter, and only a complete clinical examination of the thoracolumbar region can demonstrate local signs (posterior facet joint pain at several levels, fibromyalgia).

Identification of perineal sensory neurons activated by innocuous heat

C-fiber sensory neurons comprise nociceptors and smaller populations of cells detecting innocuous thermal and light tactile stimuli. Markers identify subpopulations of these cells, aiding our understanding of their physiological roles. The transient receptor potential vanilloid 1 (TRPV1) cation channel is characteristic of polymodal C-fiber nociceptors and is sensitive to noxious heat, irritant vanilloids, and protons. By using immunohistochemistry, in situ hybridization, and retrograde tracing, we anatomically characterize a small subpopulation of C-fiber cells that express high levels of TRPV1 (HE TRPV1 cells). These cells do not express molecular markers normally associated with C-fiber nociceptors. Furthermore, they express a unique complement of neurotrophic factor receptors, namely, the trkC receptor for neurotrophin 3, as well as receptors for neurturin and glial cell line-derived neurotrophic factor. HE TRPV1 cells are distributed in sensory ganglia throughout the neuraxis, with higher numbers noted in the sixth lumbar ganglion. In this ganglion and others of the lumbar and sacral regions, 75% or more of such HE TRPV1 cells express estrogen receptor alpha, suggestive of their regulation by estrogen and a role in afferent sensation related to reproduction. Afferents from these cells provide innervation to the hairy skin of the perineal region and can be activated by thermal stimuli from 38 degrees C, with a maximal response at 42 degrees C, as indicated by induction of extracellular signal-regulated kinase phosphorylation. We hypothesize that apart from participating in normal thermal sensation relevant to thermoregulation and reproductive functions, HE TRPV1 cells may mediate burning pain in chronic pain syndromes with perineal localization.

[Somatic perineal pain other than pudendal neuralgia]

In addition to the well-established syndrome of pudendal compression, and given the rich nerve trunk innervation of the perineum, pain originating in other nerve trunks can occur and must be remembered. Nerves originating high in the thoracolumbar area (ilioinguinal nerve, iliohypogastric nerve, genitor femoral nerve) can be the seat of traumatic lesions occurring during surgical approaches through the abdominal wall or can undergo compressions when crossing the fascia of the large abdominal muscles. Misleading perineal irradiations do not resemble pudendal neuralgia and should suggest pain in these trunks whose cutaneous territories are not solely perineal and whose clinical expression as pain is does not occur in the seated position. Similarly, painful minor intervertebral dysfunction of the thoracolumbar junction is not simply in the mind and should be considered, searched for, and treated. Related more to pudendal neuralgia, pain in the inferior cluneal nerve, triggered by the seated position, should be considered when the pain reaches the lateral anal region, the scrotum, or the labia majora but not involving the glans penis or the clitoris. Specific treatments (physical therapy, infiltrations, surgery) have proven effective.