Piriformis Syndrome With Variant Sciatic Nerve Anatomy: A Case Report

Use of botulinum neurotoxin in the treatment of piriformis syndrome: A systematic review

OBJECTIVE

To determine the pain, functional and adverse outcomes of patients with piriformis syndrome who received botulinum neurotoxin injection, and to determine the optimal dosing of botulinum neurotoxin and choices of modality used during this intervention.

LITERATURE SURVEY

Systematic review of relevant clinical studies published in English language using PubMed/Medline, Embase and CINAHL databases from October 1, 2002 to October 6, 2020.

METHODOLOGY

A comprehensive search was performed to identify all studies addressing the treatment of piriformis syndrome with botulinum toxin. Two reviewers independently screened the titles, abstracts, and full texts and extracted data based on a set of predefined inclusion and exclusion criteria. 23 full-text articles were identified of which consensus was achieved for seven articles for data extraction and quality assessment. The qualities and risk of potential bias of the seven studies were appraised using the National Heart, Lung and Blood Institute (NIH) Study Quality Assessment tools for case controls, cohort studies and randomized trials.

SYNTHESIS

Seven studies (n = 152 patients) were included consisting of three randomized controlled studies (RCTs), two case control studies and two cohort studies. The qualities of these studies were: Two good and one fair for the RCTs, fair for both the case controls and one good and fair for the cohort studies. Most studies reported some reduction in pain using various modalities to guide injection (CT, EMG, US or fluoroscopy). However, the included studies were heterogeneous, making it difficult to quantify pain reduction. There was minimal description of other functional outcomes. Botulinum toxin A doses range from 100 to 300U. Mild adverse effects were reported with no medical intervention needed.

CONCLUSIONS

There is fair quality of evidence to suggest botulinum toxin is safe to reduce pain in piriformis syndrome. There is insufficient data to quantify pain reduction and to describe other functional outcomes. The optimal dose of botulinum toxin A remains unclear. Modalities to guide botulinum injection into the piriformis muscle remain heterogeneous.

Sciatic Nerve Variants in Patients Diagnosed With Sciatica: Is There a Correlation?

PURPOSE

Compression of the sciatic nerve in its path along the piriformis muscle can produce sciatica-like symptoms. There are 6 predominant types of sciatic nerve variations with type 1 being the most common (84.2%), followed by type 2 (13.9%). However, there is scarce literature on the prevalence of sciatic nerve variation in those diagnosed with sciatica.

MATERIALS AND METHODS

The charts of 95 patients clinically diagnosed with sciatica who had a magnetic resonance imaging of the pelvis/hip were retrospectively studied. All patients had T1-weighted axial, coronal, and sagittal images. Magnetic resonance imagings were interpreted separately by 2 board-certified fellowship-trained musculoskeletal radiologists to identify the sciatic nerve variant.

RESULTS

Seven cases were excluded because of inadequate imaging. Of the remaining 88 patients, 5 had bilateral sciatica resulting in a sample size of 93 limbs. Fifty-two (55.9%) had type 1 sciatic nerve anatomy, 39 (41.9%) had type 2, and 2 (2.2%) had type 3. The proportions of type 1 and 2 variations were significantly different from the normal distribution (P < 0.001), whereas type 3, 4, 5, and 6 variants were not (P = 1.00).

CONCLUSIONS

There is strong statistical significance regarding the relationship between sciatic nerve variation and the clinical diagnosis of sciatica. Preoperative magnetic resonance imaging can be considered in sciatica patients to prevent iatrogenic injury in pelvic surgery.

Ultrasound appears to be a reliable technique for the diagnosis of piriformis syndrome

INTRODUCTION

Piriformis muscle syndrome (PS) is a disorder encompassing a constellation of symptoms, including buttock and hip pain. In this study we aimed to assess the value of ultrasound (US) in the diagnosis of PS.

METHODS

Thirty-three clinically diagnosed PS patients and 26 healthy volunteers underwent a clinical PS scoring examination and US and MRI assessment of the bilateral piriformis muscles. The areas under the receiver operating characteristic curves (AUROCs) of the US parameters (i.e., increased thickness [iTh] and increased cross-sectional area [iCSA]) for piriformis muscle were evaluated.

RESULTS

On US and MRI, the thickness and CSA were increased in PS patients. The AUROCs for the iTh and iCSA for discriminating stage 0 (healthy volunteers) from stage 1 through stage 3 (PS patients) were 0.88 and 0.95, respectively.

DISCUSSION

US may be a reliable technique for the clinical diagnosis of PS. Muscle Nerve 59:411-416, 2019.

Diagnosis and Management of Piriformis Syndrome: A Rare Anatomic Variant Analyzed by Magnetic Resonance Imaging

Piriformis syndrome is an uncommon condition that causes significant pain in the posterior lower buttocks and leg due to entrapment of the sciatic nerve at the level of the piriformis muscle. In the typical anatomical presentation, the sciatic nerve exits directly ventral and inferior to the piriformis muscle and continues down the posterior leg. Several causes that have been linked to this condition include trauma, differences in leg length, hip arthroplasty, inflammation, neoplastic mass effect, and anatomic variations. A female presented with left-sided lower back and buttock pain with radiation down the posterior leg. After magnetic resonance imaging was performed, an uncommon sciatic anatomical form was identified. Although research is limited, surgical intervention shows promising results for these conditions. Accurate diagnosis and imaging modalities may help in the appropriate management of these patients.

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.

Detection and prevalence of variant sciatic nerve anatomy in relation to the piriformis muscle on MRI

OBJECTIVE

To determine whether known variant anatomical relationships between the sciatic nerve and piriformis muscle can be identified on routine MRI studies of the hip and to establish their imaging prevalence.

METHODS

Hip MRI studies acquired over a period of 4 years at two medical centers underwent retrospective interpretation. Anatomical relationship between the sciatic nerve and the piriformis muscle was categorized according to the Beaton and Anson classification system. The presence of a split sciatic nerve at the level of the ischial tuberosity was also recorded.

RESULTS

A total of 755 consecutive scans were reviewed. Conventional anatomy (type I), in which an undivided sciatic nerve passes below the piriformis muscle, was identified in 87% of cases. The remaining 13% of cases demonstrated a type II pattern in which one division of the sciatic nerve passes through the piriformis whereas the second passes below. Only two other instances of variant anatomy were identified (both type III). Most variant cases were associated with a split sciatic nerve at the level of the ischial tuberosity (73 out of 111, 65.8%). By contrast, only 6% of cases demonstrated a split sciatic nerve at this level in the context of otherwise conventional anatomy.

CONCLUSION

Anatomical variations of the sciatic nerve course in relation to the piriformis muscle are frequently identified on routine MRI of the hips, occurring in 12-20% of scans reviewed. Almost all variants identified were type II. The ability to recognize variant sciatic nerve courses on MRI may prove useful in optimal treatment planning.

Arthroscopic Piriformis Release-A Technique for Sciatic Nerve Decompression

Various techniques for piriformis muscle release have been published previously. However, it is imperative we continue to improve on existing techniques as well as develop new ones that may further optimize outcomes. Therefore, we aimed to describe an endoscopic technique for the release of the piriformis muscle in those with symptoms of sciatic nerve compression. Using the posterolateral portal, we are able to perform a complete release of the piriformis from the greater trochanter and the piriformis fossa with care to protect the external rotators and the sciatic nerve. It is our belief that this technique can be easily replicated by practitioners who read this technical note.