Piriformis muscle syndrome in 19 patients treated by tenotomy--a 1- to 16-year follow-up study

Cauda equina, conus medullaris and syndromes mimicking sciatic pain: WFNS spine committee recommendations

Introduction

Cauda equina syndrome (CES), conus medullaris syndrome (CMS), and sciatica-like syndromes or "sciatica mimics" (SM) may present as diagnostic and/or therapeutic dilemmas for the practicing spine surgeon. There is considerable controversy regarding the appropriate definition and diagnosis of these entities, as well as indications for and timing of surgery. Our goal is to formulate the most current, evidence-based recommendations for the definition, diagnosis, and management of CES, CMS, and SM syndromes.

Methods

We performed a systematic literature search in PubMed from 2012 to 2022 using the keywords "cauda equina syndrome", "conus medullaris syndrome", "sciatica", and "sciatica mimics". Standardized screening criteria yielded a total of 43 manuscripts, whose data was summarized and presented at two international consensus meetings of the World Federation of Neurosurgical Societies (WFNS) Spine Committee. Utilizing the Delphi method, we generated seven final consensus statements.

Results and conclusion

s: We provide standardized definitions of cauda equina, cauda equina syndrome, conus medullaris, and conus medullaris syndrome. We advocate for the use of the Lavy et al classification system to categorize different types of CES, and recommend urgent MRI in all patients with suspected CES (CESS), considering the low sensitivity of clinical examination in excluding CES. Surgical decompression for CES and CMS is recommended within 48 h, preferably within less than 24 h. There is no data regarding the role of steroids in acute CES or CMS. The treating physician should be cognizant of a variety of other pathologies that may mimic sciatica, including piriformis syndrome, and how to manage these.

Intrapelvic entrapment of sacral nerve roots by abnormal bundles of the piriformis muscle: description of an extra-spinal cause of sciatica and pudendal neuralgia

Piriformis syndrome is a well-known extra-spinal cause of sciatica characterized by the entrapment of the sciatic nerve by variant bundles of the piriformis muscles in the deep gluteal space. In this case series, we describe the entrapment of intrapelvic portions of the sacral nerve roots by a variant bundle of the piriformis muscle originating medially to the sacral foramina, the surgical technique for the laparoscopic treatment of this condition, and the outcomes of the first eight cases treated with this technique. Five female and three male patients presenting with sciatica, pudendal pain and lower urinary tract symptoms underwent a laparoscopic exploration of the intrapelvic portion of the sacral nerve roots and transection of the abnormal piriformis bundle. Surgical technique is demonstrated in the Supplementary Video. Clinical success was achieved in seven of the eight patients, with a reduction of pain numeric rating scale from 8.5 (±1.2; 7-10) pre-operatively to 2.1 (±2.6; 0-7), 1-year following surgery. In conclusion, entrapment of intrapelvic portions of the sacral nerve roots by variant bundles of the piriformis originating medially to the sacral foramina are an extraspinal cause of sciatica, which can be treated though a laparoscopic approach.

Sciatic Nerve Variants and the Piriformis Muscle: A Systematic Review and Meta-Analysis

The present systematic review and meta-analysis provides a comprehensive assessment of the sciatic nerve (SN) variants relative to the piriformis muscle (PM) and compares those variants’ prevalence among different geographical populations with respect to gender and laterality. A database search was conducted to identify cadaveric studies pertinent to SN variants relative to the PM. A total of 44 articles were included. The typical morphological pattern (type A, with the SN passing undivided below the PM) was found to be the most common variant, with 90% pooled prevalence. SN variants were more common among East Asians, with a 31% pooled prevalence of total variants. No significant differences were established with respect to gender and laterality. In greater than 10% of the population, the SN coursed through or above piriformis. Patients’ epidemiological characteristics may predispose them to certain variants. The common peroneal nerve (CPN) is more susceptible to injury during a total hip arthroplasty or a hip arthroscopy where anomalies are encountered. As anatomical variants are commonly associated with piriformis syndrome, they should always be considered during diagnosis and treatment.

Lower extremity entrapment neuropathies

Entrapment neuropathies are frequently encountered by rheumatologists, not only because they are common but also because of their association with certain rheumatological and systemic disorders. Recognizing entrapment neuropathy early can help avoid progressive neurological deficits, as well as facilitate appropriate treatment measures, which can effectively minimize a patient's symptoms. Entrapment neuropathies may be distinguished from other musculoskeletal causes of lower extremity pain by identifying characteristic patterns of weakness and/or sensory loss, so a focused bedside neurological examination is key for diagnosis. In this chapter, we review the most common entrapment neuropathies that occur in the lower extremities, review the relevant neuroanatomy, outline a diagnostic approach to distinguish them from other mimics, and highlight appropriate management options.

Deep gluteal syndrome as a cause of posterior hip pain and sciatica-like pain

Deep gluteal syndrome is an increasingly recognized disease entity, caused by compression of the sciatic or pudendal nerve due to non-discogenic pelvic lesions. It includes the piriformis syndrome, the gemelli-obturator internus syndrome, the ischiofemoral impingement syndrome, and the proximal hamstring syndrome. The concept of the deep gluteal syndrome extends our understanding of posterior hip pain due to nerve entrapment beyond the traditional model of the piriformis syndrome. Nevertheless, there has been terminological confusion and the deep gluteal syndrome has often been undiagnosed or mistaken for other conditions. Careful history-taking, a physical examination including provocation tests, an electrodiagnostic study, and imaging are necessary for an accurate diagnosis. After excluding spinal lesions, MRI scans of the pelvis are helpful in diagnosing deep gluteal syndrome and identifying pathological conditions entrapping the nerves. It can be conservatively treated with multidisciplinary treatment including rest, the avoidance of provoking activities, medication, injections, and physiotherapy. Endoscopic or open surgical decompression is recommended in patients with persistent or recurrent symptoms after conservative treatment or in those who may have masses compressing the sciatic nerve. Many physicians remain unfamiliar with this syndrome and there is a lack of relevant literature. This comprehensive review aims to provide the latest information about the epidemiology, aetiology, pathology, clinical features, diagnosis, and treatment. Cite this article: Bone Joint J 2020;102-B(5):556-567.

Case report and review of the potential role of the Type A piriformis muscle in dynamic sciatic nerve entrapment variant of piriformis syndrome

Piriformis syndrome (PS) is an underdiagnosed but common cause of chronic buttock pain and sciatica. Anatomical variants of the piriformis muscle and sciatic nerve have not been thought to be significant in the pathophysiology of PS however, recent description of the piriformis musculotendinous junction has identified a common variant that we believe frequently results in dynamic sciatic nerve entrapment at the infra-piriformis fossa. We performed ultrasound guided low-dose Botulinum Toxin-A (BTX-A) injection to the lower piriformis muscle belly in an elite Australian Rules football player with PS and Type A piriformis muscle to relieve symptomatic sciatic nerve compression. Positive response to targeted BTX-A piriformis muscle injections support the hypothesis that sciatic nerve compression by Type A piriformis muscles may contribute to the pathophysiology of neuropathic PS, along with other functional factors. Sciatic nerve compression due to Type A piriformis at the infra-piriformis fossa has not been described previously and is a potentially common cause of neuropathic PS, especially when combined with other functional factors such as piriformis muscle spasm/hypertrophy and sacroiliac joint counternutation.

Piriformis Syndrome: A Narrative Review of the Anatomy, Diagnosis, and Treatment

Piriformis syndrome is a form of sciatica caused by compression of the sciatic nerve by the piriformis muscle. It is a relatively uncommon, but not insignificant, cause of sciatica. The diagnosis of piriformis syndrome is complicated by the large differential diagnosis of low back and buttock pain with many diagnoses having overlapping symptoms. This narrative review highlights the relevant anatomy, history, physical exam maneuvers, electrodiagnostic findings, and imaging findings that are used to diagnose piriformis syndrome. Also discussed are posterior gluteal myofascial pain syndromes that mimic piriformis syndrome. The review then outlines the different treatment options for piriformis syndrome including conservative treatment, injections, and surgical treatment. In addition, it provides the reader with a clinical framework to better understand and treat the complex, and often misunderstood, diagnosis of piriformis syndrome.

Does endoscopic piriformis tenotomy provide safe and complete tendon release? A cadaver study

BACKGROUND

Endoscopic piriformis release (EPR) is among the available treatments for piriformis syndrome. This procedure typically involves dividing the muscle near the sciatic nerve in the sub-gluteal space, which contains numerous blood vessels and nerves. The objectives of this prospective cadaver study were: 1) to assess the reproducibility and quality of endoscopic piriformis tenotomy near the greater trochanter; 2) to detect iatrogenic injuries to the lateral hip rotators, nerves, and vessels; 3) and to define the surgical safety margins relative to the sciatic nerve and inferior gluteal bundle.

HYPOTHESIS

EPR at the greater trochanter ensures full release of the muscle with a limited risk of neuro-vascular injury.

MATERIAL AND METHODS

EPR was performed via two portals on 10 cadaver hips preserved in zinc chloride and placed in the prone position. A third, ancillary portal was required in 7 cases. The area was then dissected with the Kocher-Langenbeck approach to allow an assessment of the tenotomy, detect iatrogenic injuries, and measure the distances separating the tenotomy site from the sciatic nerve and inferior gluteal artery.

RESULTS

Complete tenotomy was achieved in 9 (90%) cases. The tendon adhered to the capsule in 2 (20%) cases and showed acquired avulsion in 1 case. No injuries to the sciatic nerve or inferior gluteal artery occurred. Mean distances from the tenotomy site were 5.21±0.59cm (range, 4.5-6.6cm) for the sciatic nerve and 7.1±0.89cm (range, 5.4-8.5cm) for the inferior gluteal artery.

DISCUSSION

EPR by a tenotomy at the greater trochanter without sciatic nerve release provides full release of the muscle with satisfactory safety margins and a short learning curve.

LEVEL OF EVIDENCE

III, prospective cadaver case-control study.

Endoscopic Release of the Piriformis Tendon and Sciatic Nerve Exploration by the Lateral Decubitus Approach Through an Incision on the Iliotibial Band

Entrapment of the sciatic nerve is considered a challenging problem for orthopaedic surgeons. Many surgical interventions (open or endoscopic) have been described as treatments. We describe an endoscopic technique for release of the piriformis tendon and sciatic nerve exploration by the lateral approach through an incision on the iliotibial band.

Endoscopic release of the piriformis tendon and sciatic nerve exploration

Robinson, in 1947 introduced for the first time the term ‘piriformis syndrome’. More recently, many etiologies of sciatic nerve entrapment around the gluteal region or the non-discogenic area have been identified, resulting in the use of a new term ‘The Deep Gluteal Syndrome’. The purpose of this study was to assess the outcomes following the endoscopic release of sciatic nerve entrapment. Type of study is a consecutive case series. Fifteen patients were diagnosed with sciatic nerve entrapment from January 2012 to December 2015, all of them were treated with endoscopic release of the piriformis tendon and sciatic nerve exploration on lateral decubitus position. Every patient had a minimum follow-up to 2 years. The patient-reported outcome scores used included the modified Harris Hip Score (mHHS), pain was estimated on a visual analog scale (VAS) and the Benson outcomes questionnaire. The patient’s mean age was 40.2 years (range, 28–50 years). The score improvement from pre-operative to 24-month follow-up was 46.8–84.9 for mHHS (P <0.05). The VAS decreased from pre-operative to 24-month follow-up was 7.4–1.86 (P < 0.05). The Benson outcome ratings were excellent for 11 patients, good for 3 and fair for 1. The Endoscopic Release of the Piriformis Tendon and Sciatic Nerve Exploration showed an improvement of functions, diminishing pain and allowing patients to return to daily activities without symptoms (Level of Evidence: IV).

Surgical Management of Deep Gluteal Syndrome Causing Sciatic Nerve Entrapment: A Systematic Review

PURPOSE

To assess the causes, surgical indications, patient-reported clinical outcomes, and complications in patients with deep gluteal syndrome causing sciatic nerve entrapment.

METHODS

Three databases (PubMed, Ovid [MEDLINE], and Embase) were searched by 2 reviewers independently from database inception until September 7, 2016. The inclusion criteria were studies reporting on both arthroscopic and open surgery and those with Level I to IV evidence. Systematic reviews, conference abstracts, book chapters, and technical reports with no outcome data were excluded. The methodologic quality of the studies was assessed with the MINORS (Methodological Index for Non-randomized Studies) tool.

RESULTS

The search identified 1,539 studies, of which 28 (481 patients; mean age, 48 years) were included for assessment. Of the studies, 24 were graded as Level IV, 3 as Level III, and 1 as Level II. The most commonly identified causes were iatrogenic (30%), piriformis syndrome (26%), trauma (15%), and non-piriformis (hamstring, obturator internus) muscle pathology (14%). The decision to pursue surgical management was made based on clinical findings and diagnostic investigations alone in 50% of studies, whereas surgical release was attempted only after failed conservative management in the other 50%. Outcomes were positive, with an improvement in pain at final follow-up (mean, 23 months) reported in all 28 studies. The incidence of complications from these procedures was low: Fewer than 1% and 8% of open surgical procedures and 0% and fewer than 1% of endoscopic procedures resulted in major (deep wound infection) and minor complications, respectively.

CONCLUSIONS

Although most of the studies identified were case series and reports, the results consistently showed improvement in pain and a low incidence of complications, particularly for endoscopic procedures. These findings lend credence to surgical management as a viable option for buttock pain caused by deep gluteal syndrome and warrant further investigation.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II through IV studies.

Exposure of the sciatic nerve in the gluteal region without sectioning the gluteus maximus: Analysis of a series of 18 cases

Background:

Dissecting through the gluteus maximus muscle by splitting its fibers, instead of complete sectioning of the muscle, is faster, involves less damage to tissues, and diminishes recovery time. The objective of the current paper is to present a clinical series of sciatic nerve lesions where the nerve was sufficiently exposed via the transgluteal approach.

Methods:

We retrospectively selected 18 traumatic sciatic nerve lesions within the buttock, operated upon from January 2005 to December 2009, with a minimum follow-up of 2 years. In all patients, a transgluteal approach was employed to explore and reconstruct the nerve.

Results:

Ten males and eight females, with a mean age of 39.7 years, were studied. The etiology of the nerve lesion was previous hip surgery (n = 7), stab wound (n = 4), gunshot wound (n = 3), injection (n = 3), and hip dislocation (n = 1). In 15 (83.3%) cases, a motor deficit was present; in 12 (66.6%) cases neuropathic pain and in 12 (66.6%) cases sensory alterations were present. In all cases, the transgluteal approach was adequate to expose the injury and treat it by neurolysis alone (10 cases), neurolysis and neurorrhaphy (4 cases), and reconstruction with grafts (4 cases; three of these paired with neurolysis). The mean pre- and postoperative grades for the tibial nerve (LSUHSC scale) were 1.6 and 3.6, respectively; meanwhile, for the peroneal division, preoperative grade was 1.2 and postoperative grade was 2.4.

Conclusions:

The transgluteal approach adequately exposes sciatic nerve injuries of traumatic origin in the buttock and allows for adequate nerve reconstruction without sectioning the gluteus maximus muscle.

Soft tissue pathology around the hip

Snapping hip syndromes have been treated with open surgery for many years. Recently, endoscopic techniques have been developed for treatment of snapping hip syndromes with results that are at least comparable if not better than those reported for open procedures. The greater trochanteric pain syndrome is well known by orthopedic surgeons. However, deep understanding of the pathologic conditions generating pain in the greater trochanteric region and endoscopic access to it has only recently been described. Although evidence regarding endoscopic techniques for the treatment of the greater trochanteric pain syndrome is mainly anecdotal, early published reports are encouraging.

Exposure of the sciatic nerve in the gluteal region without sectioning the gluteus maximus: an anatomical and microsurgical study

BACKGROUND

Complete sectioning of the gluteus maximus muscle is an extensive procedure when approaching the sciatic nerve in the buttock, resulting in significant morbidity and a prolonged postoperative recovery period. By contrast, dissecting through the muscle by splitting its fibers is faster, involves less damage to tissues and diminishes recovery time. The objective of the present work was to perform a cadaveric study to obtain measurements of the maximum, minimum and mean exposure that this minimally invasive approach can offer.

METHODS

Both gluteal regions from each of ten fresh cadavers were dissected via a transgluteal approach, using a transverse curvilinear incision. After exposure of the sciatic nerve, the maximum length of exposed nerve was measured. As a final step, a 6 cm long sural graft reconstruction was performed, aided by a surgical microscope and microscopic techniques.

FINDINGS

The mean sciatic nerve exposure obtained was 115.4 ± 17.9 mm, ranging from a maximum of 152 mm to a minimum of 90 mm. In all 20 cases, it was possible to perform microsurgical reconstruction under the microscope. We further illustrate these findings with three live patients in whom the transgluteal approach was employed to successfully expose and repair the sciatic nerve.

CONCLUSIONS

The transgluteal approach is useful in the operative repair of lesions of the proximal sciatic nerve. It is a less invasive technique than classical complete sectioning of the gluteus maximus muscle, and yields better aesthetic results and a faster return to normal daily activities. Complex lesions, like nerve trauma requiring grafts and nerve tumours, can be treated with minimal risk. Nevertheless, it is less comfortable for the surgeon, and the entire extent of the exposed nerve might not be visualized simultaneously during surgery.

The clinical features of the piriformis syndrome: a systematic review

Piriformis syndrome, sciatica caused by compression of the sciatic nerve by the piriformis muscle, has been described for over 70 years; yet, it remains controversial. The literature consists mainly of case series and narrative reviews. The objectives of the study were: first, to make the best use of existing evidence to estimate the frequencies of clinical features in patients reported to have PS; second, to identify future research questions. A systematic review was conducted of any study type that reported extractable data relevant to diagnosis. The search included all studies up to 1 March 2008 in four databases: AMED, CINAHL, Embase and Medline. Screening, data extraction and analysis were all performed independently by two reviewers. A total of 55 studies were included: 51 individual and 3 aggregated data studies, and 1 combined study. The most common features found were: buttock pain, external tenderness over the greater sciatic notch, aggravation of the pain through sitting and augmentation of the pain with manoeuvres that increase piriformis muscle tension. Future research could start with comparing the frequencies of these features in sciatica patients with and without disc herniation or spinal stenosis.

Variations of the piriformis and sciatic nerve with clinical consequence: a review

The deep gluteal region is often encountered when performing injections, when performing surgery such as total hip replacements, or diagnosing problems of this region or lower limbs using clinical or imaging techniques. Previously, the prevalence figures of piriformis and sciatic nerve anomalies have ranged from 1.5 to 35.8% in dissected specimens. This study systematically reviews and meta-analyses the prevalence of piriformis and sciatic nerve anomalies in humans using previously published literature. A further review is conducted regarding the anatomical abnormalities present in surgical case series of procedures for patients suffering from piriformis syndrome. After pooling the results of 18 studies and 6,062 cadavers, the prevalence of the anomaly in cadavers was 16.9%; 95% confidence interval (CI) 16.0-17.9%. The prevalence of the piriformis and sciatic nerve anomaly in the surgical case series was 16.2%, 95% CI: 10.7-23.5%. The difference between the two groups was not found to be significant 0.74%; 95% CI: -5.66 to 7.13; P = 0.824. Because of the high likelihood of an anomaly being present in a patient, clinicians and surgeons should be aware of the potential complications this anomaly may have on medical or surgical interventions. Furthermore, because the prevalence of the anomaly in piriformis syndrome patients is not significantly different from what is thought to be a normal population, it indicates that this anomaly may not be as important in the pathogenesis of piriformis syndrome as previously thought.

[Buttocks sciatic pain]

Confusion between radicular and nerve trunk syndrome is not rare. With sciatic pain, any nerve trunk pain or an atypical nerve course should suggest nerve trunk pain of the sciatic nerve in the buttocks. The usual reflex with sciatic pain is vertebral-radicular conflict. The absence of spinal symptoms and the beginning of pain in the buttocks and not in the lumbar region should reorient the etiologic search. Once a tumor of the nerve trunk has been ruled out (rarely responsible for pain other than that caused by tumor pressure), a myofascial syndrome should be explored searching for clinical, electrophysiological, and radiological evidence of compression of the sciatic trunk by the piriform muscle but also the obturator internus muscle. Hamstring syndrome may be confused with this syndrome. Treatment is first and foremost physical therapy. Failures can be treated with classical CT-guided infiltrations with botulinum toxin. Surgery should only be entertained when all these solutions have failed.

Piriformis and related entrapment syndromes: diagnosis & management

Highly reliable evidence for piriformis syndrome and other pelvic sciatic syndromes arises from three major categories of data: magnetic resonance neurography diagnostic imaging, open magnetic resonance-guided injection studies, and patient treatment outcome studies. This article reviews the evidence in each category. This is part of a Point-Counterpoint discussion with Dr. Robert Tiel's presentation of "Myth and Fallacy".