Can MR neurography of the common peroneal nerve predict a residual motor deficit in patients with foot drop?

OBJECTIVE: To determine if MR neurography of the common peroneal nerve (CPN) predicts a residual motor deficit at 12-month clinical follow-up in patients presenting with foot drop. MATERIALS AND METHODS: A retrospective search for MR neurography cases evaluating the CPN at the knee was performed. Patients were included if they had electrodiagnostic testing (EDX) within 3 months of imaging, ankle and/or forefoot dorsiflexion weakness at presentation, and at least 12-month follow-up. Two radiologists individually evaluated nerve size (enlarged/normal), nerve signal (T2 hyperintense/normal), muscle signal (T2 hyperintense/normal), muscle bulk (normal/Goutallier 1/Goutallier > 1), and nerve and muscle enhancement. Discrepancies were resolved via consensus review. Multivariable logistical regression was used to evaluate for association between each imaging finding and a residual motor deficit at 12-month follow-up. RESULTS: Twenty-three 3 T MRIs in 22 patients (1 bilateral, mean age 52 years, 16 male) met inclusion criteria. Eighteen cases demonstrated common peroneal neuropathy on EDX, and median duration of symptoms was 5 months. Six cases demonstrated a residual motor deficit at 12-month follow-up. Fourteen cases underwent CPN decompression (1 bilateral) within 1 year of presentation. Three cases demonstrated Goutallier > 1 anterior compartment muscle bulk. Multivariable logistical regression did not show a statistically significant association between any of the imaging findings and a residual motor deficit at 12-month follow-up. CONCLUSION: MR neurography did not predict a residual motor deficit at 12-month follow-up in patients presenting with foot drop, though few patients demonstrated muscle atrophy in this study.

Brachial plexus anatomy in the miniature swine as compared to human.

Brachial plexus injury (BPI) occurs when the brachial plexus is compressed, stretched, or avulsed. Although rodents are commonly used to study BPI, these models poorly mimic human BPI due to the discrepancy in size. The objective of this study was to compare the brachial plexus between human and Wisconsin Miniature SwineTM (WMSTM ), which are approximately the weight of an average human (68-91 kg), to determine if swine would be a suitable model for studying BPI mechanisms and treatments. To analyze the gross anatomy, WMS brachial plexuses were dissected both anteriorly and posteriorly. For histological analysis, sections from various nerves of human and WMS brachial plexuses were fixed in 2.5% glutaraldehyde, and postfixed with 2% osmium tetroxide. Subsequently paraffin sections were counter-stained with Masson's Trichrome. Gross anatomy revealed that the separation into three trunks and three cords is significantly less developed in the swine than in human. In swine, it takes the form of upper, middle, and lower systems with ventral and dorsal components. Histological evaluation of selected nerves revealed differences in nerve trunk diameters and the number of myelinated axons in the two species. The WMS had significantly fewer myelinated axons than humans in median (p = 0.0049), ulnar (p = 0.0002), and musculocutaneous nerves (p = 0.0454). The higher number of myelinated axons in these nerves for humans is expected because there is a high demand of fine motor and sensory functions in the human hand. Due to the stronger shoulder girdle muscles in WMS, the WMS suprascapular and axillary nerves were larger than in human. Overall, the WMS brachial plexus is similar in size and origin to human making them a very good model to study BPI. Future studies analyzing the effects of BPI in WMS should be conducted.

C6 and not C5 nerve fibers more commonly contribute most to deltoid muscle innervation: anatomical study with application to better diagnosing cervical nerve injuries.

Most anatomical textbooks list both the C5 and C6 spinal nerves as contributing to the deltoid muscle's innervation via the axillary nerve. To our knowledge, no previous study has detailed the exact spinal nerve components of the axillary nerve terminating in the deltoid via cadaveric dissection. Twenty formalin-fixed cadavers (40 sides) underwent dissection of the brachial plexus. The fascicles making up the axillary nerve branch that specifically terminated in the deltoid muscle were traced proximally. The axillary nerve branch to the deltoid muscle was most commonly (70%) made up of three spinal nerve segments and less commonly (30%) by two spinal nerve segments. For all axillary nerve branches to the deltoid muscle, C4 spinal nerves contributed 0-5%, C5 spinal nerves contributed 1-80%, C6 spinal nerve contributed 15-99%, C7 spinal nerves contributed 0-30%, and C8 and T1 spinal nerves were not found to contribute any fibers to any deltoid muscle branches. The nerve to the deltoid muscle was contributed to equally by C5 and C6 nerve fibers on 10% of sides. On 16% of sides, C5 contributed the most nerve fibers to this muscle. On 35% of sides, C6 contributed the majority fibers found in the axillary nerve branches to the deltoid. Based on our anatomical study, C6 is more often than not the main level of innervation. C5 was never the sole component of the axillary nerve branches to the deltoid muscle. Such anatomical data will now need to be reconciled with clinical studies.

Inflammation after spinal cord injury: a review of the critical timeline of signaling cues and cellular infiltration.

Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss of motor and sensory function. Although extensive research to develop treatments for SCI has been performed, to date, none of these treatments have produced a meaningful amount of functional recovery after injury. The primary injury is caused by the initial trauma to the spinal cord and results in ischemia, oxidative damage, edema, and glutamate excitotoxicity. This process initiates a secondary injury cascade, which starts just a few hours post-injury and may continue for more than 6 months, leading to additional cell death and spinal cord damage. Inflammation after SCI is complex and driven by a diverse set of cells and signaling molecules. In this review, we utilize an extensive literature survey to develop the timeline of local immune cell and cytokine behavior after SCI in rodent models. We discuss the precise functional roles of several key cytokines and their effects on a variety of cell types involved in the secondary injury cascade. Furthermore, variations in the inflammatory response between rats and mice are highlighted. Since current SCI treatment options do not successfully initiate functional recovery or axonal regeneration, identifying the specific mechanisms attributed to secondary injury is critical. With a more thorough understanding of the complex SCI pathophysiology, effective therapeutic targets with realistic timelines for intervention may be established to successfully attenuate secondary damage.

Ultrasound-guided microwave ablation in the treatment of inguinal neuralgia.

Chronic groin pain can be due to a variety of causes and is the most common complication of inguinal hernia repair surgery. The etiology of pain after inguinal hernia repair surgery is often multifactorial though injury to or scarring around the nerves in the operative region, namely the ilioinguinal nerve, genital branch of the genitofemoral nerve, and the iliohypogastric nerve, is thought to be a key factor in causing chronic post-operative hernia pain or inguinal neuralgia. Inguinal neuralgia is difficult to treat and requires a multidisciplinary approach. Radiologists play a key role in the management of these patients by providing accurate image-guided injections to alleviate patient symptoms and identify the pain generator. Recently, ultrasound-guided microwave ablation has emerged as a safe technique, capable of providing durable pain relief in the majority of patients with this difficult to treat condition. The objectives of this paper are to review the complex nerve anatomy of the groin, discuss diagnostic ultrasound-guided nerve injection and patient selection for nerve ablation, and illustrate the microwave ablation technique used at our institution.

Intravenous contrast does not improve detection of nerve lesions or active muscle denervation changes in MR neurography of the common peroneal nerve.

OBJECTIVE: To evaluate the effect of intravenous (IV) contrast on sensitivity, specificity, and accuracy of magnetic resonance (MR) neurography of the knee with attention to the common peroneal nerve (CPN) in identifying nerve lesions and active muscle denervation changes. MATERIALS AND METHODS: A retrospective search for contrast-enhanced MR neurography cases evaluating the CPN at the knee was performed. Patients with electrodiagnostic testing (EDX) within 3 months of imaging were included and those with relevant prior surgery were excluded. Two radiologists independently reviewed non-contrast sequences and then 4 weeks later evaluated non-contrast and contrast sequences. McNemar's tests were performed to detect a difference between non-contrast only and combined non-contrast and contrast sequences in identifying nerve lesions and active muscle denervation changes using EDX as the reference standard. RESULTS: Forty-four exams in 42 patients (2 bilateral) were included. Twenty-eight cases had common peroneal neuropathy and 29, 21, and 9 cases had active denervation changes in the anterior, lateral, and posterior compartment/proximal muscles respectively on EDX. Sensitivity, specificity, and accuracy of non-contrast versus combined non-contrast and contrast sequences for common peroneal neuropathy were 50.0%, 56.2%, and 52.3% versus 50.0%, 56.2%, and 52.3% for reader 1 and 57.1%, 50.0%, and 54.5% versus 64.3%, 56.2%, and 61.4% for reader 2. Sensitivity, specificity, and accuracy of non-contrast and combined non-contrast and contrast sequences in identifying active denervation changes for anterior, lateral, and posterior compartment muscles were not significantly different. McNemar's tests were all negative. CONCLUSION: IV contrast does not improve the ability of MR neurography to detect CPN lesions or active muscle denervation changes.

The clinical anatomy of crucifixion.

Crucifixion was a widely used form of execution for capital crimes in antiquity. Civilizations and empires perfected the technique, leading to centuries of discussions, controversies, and questions, many of which concerned the death of Jesus Christ. To this day, much remains to be discovered in both religious and scientific realms. However, the aim of this study is to discuss such facts as are known from the medical perspectives of clinical anatomists. Nails/spikes were driven through the hands/wrists and feet of five adult cadavers, and the cadavers were then dissected to observe the anatomical structures that had been injured or placed at risk for injury. While many historical and archeological facts remain to be discovered, we hope that this cadaveric study will enhance our modern understanding of ancient practices from a medical and anatomical perspective. Clin. Anat. 32:12-21, 2019. © 2019 Wiley Periodicals, Inc.

Sustained interleukin-10 delivery reduces inflammation and improves motor function after spinal cord injury.

BACKGROUND: The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as a treatment method for spinal cord injury (SCI) due to its ability to attenuate pro-inflammatory cytokines and reduce apoptosis. Primary limitations when using systemic injections of IL-10 are that it is rapidly cleared from the injury site and that it does not cross the blood-spinal cord barrier. OBJECTIVE: Here, mineral-coated microparticles (MCMs) were used to obtain a local sustained delivery of IL-10 directly into the injury site after SCI. METHODS: Female Sprague-Dawley rats were contused at T10 and treated with either an intraperitoneal injection of IL-10, an intramedullary injection of IL-10, or MCMs bound with IL-10 (MCMs+IL-10). After treatment, cytokine levels were measured in the spinal cord, functional testing and electrophysiology were performed, axon tracers were injected into the brainstem and motor cortex, macrophage levels were counted using flow cytometry and immunohistochemistry, and lesion size was measured. RESULTS: When treated with MCMs+IL-10, IL-10 was significantly elevated in the injury site and inflammatory cytokines were significantly suppressed, prompting significantly less cells expressing antigens characteristic of inflammatory macrophages and significantly more cells expressing antigens characteristic of earlier stage anti-inflammatory macrophages. Significantly more axons were preserved within the rubrospinal and reticulospinal tracts through the injury site when treated with MCMs+IL-10; however, there was no significant difference in corticospinal tract axons preserved, regardless of treatment group. The rats treated with MCMs+IL-10 were the only group with a significantly higher functional score compared to injured controls 28 days post-contusion. CONCLUSION: These data demonstrate that MCMs can effectively deliver biologically active IL-10 for an extended period of time altering macrophage phenotype and aiding in functional recovery after SCI.

Ultrasound-Guided Microwave Ablation for the Management of Inguinal Neuralgia: A Preliminary Study with 1-Year Follow-up.

PURPOSE: To evaluate the feasibility and efficacy of ultrasound-guided microwave ablation for the treatment of inguinal neuralgia. MATERIALS AND METHODS: A retrospective review of 12 consecutive ultrasound-guided microwave ablation procedures was performed of 10 consecutive patients (8 men, 2 women; mean age, 41 years [range, 15-64 years]), between August 2012 and August 2016. Inclusion criteria for inguinal neuralgia included clinical diagnosis of chronic inguinal pain (average, 17.3 months [range, 6-46 months]) refractory to conservative treatment and a positive nerve block. Pain response-reduction of pain level and duration and percent pain reduction using a 10-point visual analog scale (VAS) at baseline and up to 12 months after the procedure-was measured. Nine patients had pain after the inguinal hernia repair, and 1 patient had pain from the femoral artery bypass procedure. The microwave ablation procedure targeted the ilioinguinal nerve in 7 cases, the genitofemoral nerve in 4 cases, and the iliohypogastric nerve in 1 case. RESULTS: Average baseline VAS pain score was 6.1 (standard deviation, 2.5). Improved pain levels immediately after the procedure and at 1, 6, and 12 months were statistically significant (P = .0037, .0037, .0038, .0058, respectively). Also, 91.7% (11/12) of the procedures resulted in immediate pain relief and at 1 month and 6 months. At 12 months, 83.3% (10/12) of patients had an average of 69% ± 31% pain reduction. Percent maximal pain reduction was 93% ± 14% (60%-100%), and the average duration of clinically significant pain reduction was 10.5 months (range, 0-12 months.). No complications or adverse outcomes occurred. CONCLUSIONS: Ultrasound-guided microwave ablation is an effective technique for the treatment of inguinal neuralgia after herniorrhaphy.

A comparison of midazolam and zolpidem as oral premedication in children, a prospective randomized double-blinded clinical trial.

BACKGROUND: Anxiety associated with pediatric surgery can be stressful. Midazolam is a well-accepted anxiolytic in this setting. However, there are cases in which this medication is not effective. Zolpidem is a short-acting nonbenzodiazepine hypnotic drug that is administered orally and has quick onset of action (~15 minutes), and 2-3 hour duration. AIMS: Based on the theory that impaired perception following oral zolpidem administration would suppress the development of anxiety, we sought to compare zolpidem to midazolam for pediatric preoperative anxiety. METHODS: This prospective randomized double-blinded clinical trial was designed to compare the effectiveness of oral midazolam and zolpidem for anxiety premedication. Eighty ASA class I-II pediatric patients between 2 and 9 years old, surgery >2 hours, and at least 23 hours postoperative admission were included in the study. Randomization was done with 0.5 mg/kg midazolam or 0.25 mg/kg zolpidem administered orally. The primary outcome measure was between group difference in patient anxiety at the time of separation using the Modified Yale Preoperative Anxiety Scale. Secondary outcomes included emergence delirium and mask acceptance at induction. RESULTS: There was no significant difference in Modified Yale Preoperative Anxiety Scale scores at separation between midazolam (median/interquartile range = 26.7/23.3-36.6) and zolpidem (median/interquartile range = 30.0/23.3-56.6) groups, difference 0.01 (95% CI -3E-5 , 3E-2 ; P = 0.07). Mask acceptance score was significantly better in the midazolam group. There was no significant difference in emergence delirium scores between groups. CONCLUSION: This study demonstrates that zolpidem, as dosed, was similar to midazolam with regard to anxiety scoring, and inferior with regard to mask acceptance scores.

Neurofibroma of the peroneal nerve.

Neurofibromas are benign tumors composed of different cell types from the peripheral nervous system. Neurofibromas infiltrate between nerve fascicles and do not have a discrete capsule. On MRI, they are T1 hypointense or isointense, T2 hyperintense, often with a "target sign," and contrast enhancing. The video shows gross-total resection of a peroneal nerve neurofibroma presenting as a painful mass in the popliteal fossa. Incisions across a skin crease can be either oblique or zigzag, but never perpendicular to it. It is also key to expose normal nerve proximal and distal to the tumor. The patient had a good functional outcome. The video can be found here: https://youtu.be/G74Zoa1Y2JM .

Peroneal nerve decompression.

Peroneal neuropathy is a common pathology encountered by neurosurgeons. Symptoms include pain, numbness, and foot drop. When secondary to compression of the nerve at the fibular head, peroneal (fibular) nerve release is a low-risk procedure that can provide excellent results with pain relief and return of function. In this video, the authors highlight key operative techniques to ensure adequate decompression of the nerve while protecting the 3 major branches, including the superficial peroneal nerve, deep peroneal nerve, and recurrent genicular (articular) branches. Key steps include positioning, circumferential nerve dissection, fascial opening, isolation of the major branches, and closure. The video can be found here: https://youtu.be/0y9oE8w1FIU .

Lateral femoral cutaneous nerve transposition: Renaissance of an old concept in the light of new anatomy.

Meralgia paresthetica causes pain in the anterolateral thigh. Most surgical procedures involve nerve transection or decompression. We conducted a cadaveric study to determine the feasibility of lateral femoral cutaneous nerve (LFCN) transposition. In three cadavers, the LFCN was exposed in the thigh and retroperitoneum. The two layers of the LFCN canal superficial and deep to the nerve were opened. The nerve was then mobilized medially away from the ASIS, by cutting the septum medial to sartorius. It was possible to mobilize the nerve for 2 cm medial to the ASIS. The nerve acquired a much straighter course with less tension. A new technique of LFCN transposition is presented here as an anatomical feasibility study. The surgical technique is based on the new understanding of the LFCN canal. Clin. Anat. 30:409-412, 2017. © 2017 Wiley Periodicals, Inc.

Sustained release of neurotrophin-3 via calcium phosphate-coated sutures promotes axonal regeneration after spinal cord injury.

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin-3 (NT-3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT-3 binding and release were characterized in vitro. Then, the NT-3-loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP-coated sutures exhibited a burst release of NT-3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT-3-loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT-3-loaded suture were not significantly different from those of rats treated with PNGs alone. Cholera toxin subunit B (CTB) labeling rostral to the graft was not observed in any controls, but CTB labeling rostral to the graft was observed in almost all rats that had had a PNG. Neurofilament labeling on transverse sections of the graft revealed that the rats treated with the NT-3-loaded sutures had significantly more axons per graft than rats treated with an NT-3 injection and rats without NT-3. These data demonstrate that PNGs serve as scaffolds for axonal growth after SCI and that CaP-coated sutures can efficiently release NT-3 to increase axonal regeneration. © 2016 Wiley Periodicals, Inc.

Intraoperative ultrasound-assisted peripheral nerve surgery.

Historically, peripheral nerve surgery has relied on landmarks and fairly extensive dissection for localization of both normal and pathological anatomy. High-resolution ultrasonography is a radiation-free imaging modality that can be used to directly visualize peripheral nerves and their associated pathologies prior to making an incision. It therefore helps in localization of normal and pathological anatomy, which can minimize the need for extensive exposures. The authors found intraoperative ultrasound (US) to be most useful in the management of peripheral nerve tumors and neuromas of nerve branches that are particularly small or have a deep location. This study presents the use of intraoperative US in 5 cases in an effort to illustrate some of the applications of this useful surgical adjunct.

Clavicular window for brachial plexus schwannoma removal.

Background: Schwannomas are benign nerve sheath tumors that can either be sporadic or part of neurofibromatosis type 2 (NF2). Tumors of the brachial plexus (BP) with both supra- and infraclavicular components are uncommon and represent a challenge to complete surgical resection. There are few reports on single clavicular osteotomies for BP exposure; however, there are currently no reports of utilization of a clavicular window for a large schwannoma resection. Case Description: We report a case of a patient with a schwannoma spanning the BP roots to the cords, with the majority involving the retro clavicular inferior trunk in the setting of NF2. The patient underwent previous subtotal resection and had postoperative enlargement of the residual mass. A gross total resection was made possible by the creation of a clavicular window to expose the BP. A 2 cm segment piece of the mid-clavicle was removed, allowing for roughly 6 cm of mediolateral exposure through clavicular distraction. This clavicular window facilitated complete exposure of the BP schwannoma underneath the clavicle as well as unobstructed exposure of supraclavicular and infraclavicular tumor. The segment was then refixed with a plate after resection of the tumor. Conclusion: The use of a clavicular window allowed for extensive exposure of the trunks and divisions of the BP to achieve a gross total resection in this case. The clavicular window approach may provide a benefit for optimizing exposure in the setting of lesions involving the trunks and divisions that the clavicle would traditionally obstruct.

Preoperative Ultrasound-Guided Localization of the Lateral Femoral Cutaneous Nerve: From Guide Wire to Novel Clip.

BACKGROUND AND OBJECTIVE: Lateral femoral cutaneous nerve (LFCN) decompression and transposition are surgical treatment options for meralgia paresthetica. Identifying the LFCN during surgery may be challenging, and preoperative localization is a valuable adjunct in this case. The objective of this study was to explore a new technique using preoperative ultrasound-guided clip localization (USCL) of the LFCN. METHODS: After Institutional Review Board approval, data were collected on patients who underwent both preoperative ultrasound-guided wire localization (USWL) and USCL over the past 13 years. Skin-to-nerve time was calculated prospectively. RESULTS: Fifty-six patients were identified, 51 had USWL and 5 had USCL; the skin-to-nerve median time was 7.5 and 6 minutes, respectively. Six wires were misplaced, and this was at the beginning of utilization of the USWL technique. There were no nerve injury, infection, or bleeding complications related to either wire or clip placement. CONCLUSION: USWL or USCL is safe and time-efficient in LFCN surgeries.

Compressive median neuropathy caused by brachial artery pseudoaneurysm.

Background: Brachial artery pseudoaneurysms (PSAs) are a rare complication of trauma and medical intervention, estimated to constitute 0.3-0.7% of all PSAs. Although neurologic symptoms are common in patients undergoing hemodialysis, direct nerve compression by large PSAs is rare. Case Description: We report a case of median nerve compression by a brachial artery PSA treated by PSA resection and distal nerve transfer of the extensor carpi radialis brevis nerve to the anterior interosseous nerve. Conclusion: This case illustrates the successful use of distal nerve transfers for the treatment of median neuropathy secondary to brachial PSA. In addition, this case highlights the importance of imaging before any exploratory nerve surgery in the setting of a mass and/or prior vascular procedure. Embarking on a nerve release/ repair surgery in the absence of a vascular surgeon would be disastrous.

Anatomical Relationships of the Sciatic Nerve and Pudendal Nerve to the Ischial Spine as They Exit the Greater Sciatic Foramen.

OBJECTIVE: Deep gluteal syndrome is a clinical condition in which discomfort may arise due to the pathoanatomy of the subgluteal space. We conducted an anatomical exploration to categorize the relationship of the piriformis muscle, sciatic nerve (SN), and pudendal nerve (PN) to the ischial spine (IS) and sacrospinous ligament. METHODS: We analyzed 22 cadavers. The piriformis muscle, SN, and PN were exposed through either a transgluteal approach or a gluteal flap. The relationship of the neural structures to the IS, sacrospinous ligament, and ischial bone as they exit the greater sciatic foramen was observed, and the exit zones were classified as zone A, medial to the IS (entirely on sacrospinous ligament); zone B, on the IS; and zone C, lateral to the IS (entirely on ischial bone). RESULTS: The SN was observed either in zone B or zone C in all specimens. The PN was found to be in either zone A or zone B in 97.6% of specimens. The most common combinations were SN in zone B and PN in zone A (type I), and SN in zone C and PN in zone B (type II). CONCLUSIONS: The results from this study show clear anatomical differences in the SN-PN relationship, which may play a role in pain seen in deep gluteal syndrome. Moreover, classification of the SN-IS and PN-IS relationships described in this article will help describe different pathologies affecting the deep gluteal area.

Anatomical Proximity Between Sciatic Nerve and Ischial Spine and its Relationship to the Development of Deep Gluteal Pain Syndrome.

OBJECTIVE: Deep gluteal syndrome (DGS) is a medical diagnosis in which the pathoanatomy of the subgluteal space contributes to pain. The growing recognition that gluteal neuropathies can be associated with the presence of a bone-neural conflict with irritation or compression may allow us to shed some light on this pathology. This study aims to determine whether the location of the sciatic nerve (SN) in relation to the ischial spine (IS) contributes to the development of DGS. METHODS: The SN - IS relationship was analyzed based on magnetic resonance imaging (MRI) in 15 surgical patients (SPs), who underwent piriformis release, and in 30 control patients who underwent MRI of the pelvis for reasons unrelated to sciatica. The SN exit from the greater sciatic foramen was classified as either zone A (medial to the IS); zone B (on the IS); or zone C (lateral to the IS). RESULTS: The SN was significantly closer to the IS in SPs than in MRI controls (P = 0.014). When analyzing patients of similar age, SNs in SPs were significantly closer (P = 0.0061) to the IS, and located in zone B significantly more (P = 0.0216) as compared to MRI controls. Patients who underwent surgery for piriformis release showed a significant decrease in pain postoperatively (P < 0.0001). CONCLUSIONS: The results from this study suggest that the relationship between the IS and SN may play a role in the development of DGS. This may also help establish which patients would benefit more from surgical intervention.