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Peripheral nerve stimulation (PNS) was the first application of neuromodulation. Widespread application of PNS was limited by technical concerns. Recent advances now allow the percutaneous placement of leads with ultrasound or fluoroscopic guidance, while the transcutaneous powering of these leads removes the need for leads to cross major joints. This systematic review was written to assess the current status of high-quality evidence supporting the use of PNS for pain conditions treated by interventional pain physicians. The available literature on PNS, limited to conditions treated by interventional pain physicians, was reviewed and the quality assessed. Literature from 1966 to June 2021 was reviewed. The outcome measures were pain relief and functional improvement. One hundred and two studies were identified. Five randomized controlled trials (RCT) and four observational studies, all case series, met the inclusion criteria. One RCT was of high quality and four were of moderate quality; all four case series were of moderate quality. Three of the RCTs and all four case series evaluated peripheral nerve neuropathic pain. Based upon these studies, there is level II evidence supporting the use of PNS to treat refractory peripheral nerve injury. One moderate-quality RCT evaluated tibial nerve stimulation for pelvic pain, providing level III evidence for this indication. One moderate-quality RCT evaluated surgically placed cylindrical leads for cluster headaches, providing level III evidence for this indication. The evidence suggests that approximately two-thirds of patients with peripheral neuropathic pain will have at least 50% sustained pain relief. Adverse events from PNS are generally minor. A major advantage of PNS over spinal cord stimulation is the absence of any risk of central cord injury. The study was limited by the paucity of literature for some indications. No studies dealt with joint-related osteoarthritic pain. Supplementary Information The online version contains supplementary material available at 10.1007/s40122-021-00306-4.

Supplemental Digital Content is Available in the Text., Spinal cord stimulation (SCS) is an interventional nonpharmacologic treatment used for chronic pain and other indications. Methods for evaluating the safety and efficacy of SCS have evolved from uncontrolled and retrospective studies to prospective randomized controlled trials (RCTs). Although randomization overcomes certain types of bias, additional challenges to the validity of RCTs of SCS include blinding, choice of control groups, nonspecific effects of treatment variables (eg, paresthesia, device programming and recharging, psychological support, and rehabilitative techniques), and safety considerations. To address these challenges, 3 professional societies (Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials, Institute of Neuromodulation, and International Neuromodulation Society) convened a meeting to develop consensus recommendations on the design, conduct, analysis, and interpretation of RCTs of SCS for chronic pain. This article summarizes the results of this meeting. Highlights of our recommendations include disclosing all funding source and potential conflicts; incorporating mechanistic objectives when possible; avoiding noninferiority designs without internal demonstration of assay sensitivity; achieving and documenting double-blinding whenever possible; documenting investigator and site experience; keeping all information provided to patients balanced with respect to expectation of benefit; disclosing all information provided to patients, including verbal scripts; using placebo/sham controls when possible; capturing a complete set of outcome assessments; accounting for ancillary pharmacologic and nonpharmacologic treatments in a clear manner; providing a complete description of intended and actual programming interactions; making a prospective ascertainment of SCS-specific safety outcomes; training patients and researchers on appropriate expectations, outcome assessments, and other key aspects of study performance; and providing transparent and complete reporting of results according to applicable reporting guidelines.

Introduction Intercostal cryo nerve block has been shown to enhance pulmonary function recovery and pain management in post-thoracotomy procedures. However, its benefit have never been demonstrated in minimal invasive thoracotomy heart valve surgery (Mini-HVS). The purpose of the study was to determine whether intraoperative intercostal cryo nerve block in conjunction with standard of care (collectively referred to hereafter as CryoNB) provided superior analgesic efficacy in patients undergoing Mini-HVS compared to standard-of-care (SOC). Methods FROST was a prospective, 3:1 randomized (CryoNB vs. SOC), multicenter trial in patients undergoing Mini-HVS. The primary endpoint was the 48-h postoperative forced expiratory volume in 1 s (FEV1) result. Secondary endpoints were visual analog scale (VAS) scores for pain at the surgical site and general pain, intensive care unit and hospital length-of-stay, total opioid consumption, and allodynia at 6 months postoperatively. Results A total of 84 patients were randomized to the two arms of the trial CryoNB (n = 65) and SOC (n = 19). Baseline Society of Thoracic Surgeons Predictive Risk of Mortality (STS PROM) score, ejection fraction, and FEV1 were similar between cohorts. A higher 48-h postoperative FEV1 result was demonstrated in the CryoNB cohort versus the SOC cohort (1.20 ± 0.46 vs. 0.93 ± 0.43 L; P = 0.02, one-sided two-sample t test). Surgical site VAS scores were similar between the CryoNB and SOC cohorts at all postoperative timepoints evaluated, but VAS scores not related to the surgical site were lower in the SOC group at 72, 94, and 120 h postoperatively. The SOC cohort had a 13% higher opioid consumption than the CryoNB cohort. One of 64 CryoNB patients reported allodynia that did not require pain medication at 10 months. Conclusions The results of FROST demonstrated that intercostal CryoNB provided enhanced FEV1 score at 48 h postoperatively with optimized analgesic effectiveness versus SOC. Future larger prospective randomized trials are warranted to determine whether intercostal CryoNB has an opioid-sparing effect in patients undergoing Mini-HVS. Trial Registration Clinicaltrials.gov identifier: NCT02922153.

Peripheral nerve entrapments can occur anywhere in the head and body and can cause significant pain. Cancer pain can be caused by these entrapments, triggered by a variety of etiologies, including tumor invasion, surgical trauma, chemotherapy, or scarring. Knowing the cause of pain can help the physician treat the problem effectively, and will decrease unnecessary and potentially worsening surgeries and high dose opioid therapies, as well as unnecessary pain. A knowledgeable interventional pain physician can diagnose and treat these nerves entrapments in the most effective manner, providing improved pain relief and quality of life.Key points Nerve entrapments can occur throughout the body in cancer patients due to multiple etiologies such as tumor invasion, surgical trauma, or cancer therapy. The problem of nerve entrapments in cancer pain is under-recognized. Patients with nerve entrapment syndromes frequently complain of a burning tingling sensation and other paresthesias in the nerve distribution which can progress to a complete loss of sensory and motor function. Diagnostic tools include history and physical exam, imaging, nerve conduction studies as well as diagnostic nerve injections/blocks. Treatment of nerve entrapments can range from neuropathic pain medications to nerve blocks and nerve ablations to surgical decompression.

Although opioids are potent central acting broad-spectrum analgesics, their effectiveness is diminished by various factors pertaining to their metabolism, drug interactions, genetic issues, adverse/side effects, and potential for abuse. All these factors present potential barriers to effective analgesia requiring specific considerations in clinical practice, which include monitoring and case-based intervention.

There are multiple peripheral nerve problems that can mimic or co-exist with thoracic outlet syndrome (TOS), including primary or secondary pathology related to the suprascapular, axillary, dorsal scapular, long thoracic, and spinal accessory nerves. Failure to recognize these problems can lead to inadequate or failed TOS treatment. This chapter discusses the anatomy, entrapment, diagnosis, and types of treatment of the suprascapular, axillary, dorsal scapular, long thoracic, and spinal accessory nerves. It should be noted that this chapter deals with the diagnosis and treatment of primary entrapment syndromes encountered during the workup of patients with cervicobrachial syndrome.

Author(s): Gabriel, Rodney A; Finneran, John J; Swisher, Matthew W; Said, Engy T; Sztain, Jacklynn F; Khatibi, Bahareh; Wallace, Anne M; Hosseini, Ava; Trescot, Andrea M; Ilfeld, Brian M | Abstract: BackgroundAcute post-mastectomy pain is frequently challenging to adequately treat with local anesthetic-based regional anesthesia techniques due to its relatively long duration measured in multiple weeks.CaseWe report three cases in which preoperative ultrasound-guided percutaneous intercostal nerve cryoneurolysis was performed to treat pain following mastectomy. Across all postoperative days and all three patients, the mean pain score on the numeric rating scale was 0 for each day. Similarly, no patient required any supplemental opioid analgesics during the entire postoperative period; and, no patient reported insomnia or awakenings due to pain at any time point. This was a significant improvement over historic cohorts.ConclusionsUltrasound-guided percutaneous cryoanalgesia is a potential novel analgesic modality for acute pain management which has a duration that better-matches mastectomy than other currently-described techniques. Appropriately powered randomized, controlled clinical trials are required to demonstrate and quantify both potential benefits and risks.

Cervicogenic headaches are a significant cause of head and neck pain, and occipital neuralgia is a common component of these cervicogenic headaches. Occipital injections are commonly performed at the occipital ridge, but this site does not address more proximal entrapments of the nerve in the suboccipital region. Because of the potentially dangerous structures in this region, clinicians have tended to avoid the suboccipital region, despite the pathologies seen in this region. This article discusses the pathology of the region, the alternative techniques, and the novel interventional approach developed for this region, specifically the “Stealth” approach of occipital decompression.

Radiofrequency (RF) lesioning, developed in 1965, has been very useful in pain medicine, providing long-term relief for many chronic pain problems by denervating the regions involved in the generation of pain. The technique involves the use of a probe placed into the targeted tissue to be ablated. An electrical current is then passed from the machine to the tip of the probe, ionically heating up the tissues, which destroys the nerve tissue. The circuit is completed when the electrons are collected by a distal dispersing electrode that carries the current back to the generator. The potential sites for RF lesioning are expanding, and this has led to an expansion of the use of RF in a variety of medical fields, including cardiology, gastroenterology, otolaryngology, neurosurgery, and pain medicine. The size of the probes is increasing as well, as is the length of time used in lesioning, which increases the power and therefore the electrical field generated by the ablating system. By the nature of the electrical field created, the RF technique creates a risk of superficial (and potentially deep) burns at the dispersive electrode. This small but significant risk of burns has been reported after cardiac and gastrointestinal ablation, but has not been emphasized to practicing pain physicians. We present here the case report of a significant burn at the dispersive electrode site after a denervation procedure of the sacroiliac joint. We describe the mechanism of injury and propose potential methods of prevention. Key words: Radiofrequency lesioning, sacroiliac denervation, complications, sacroiliac joint treatment

Patients see their primary care physicians (PCPs) for a variety of medical conditions, chronic pain being one of the most common. An increased use of prescription medications (especially opioids) has led to an increase in adverse drug reactions and has heightened our awareness of the variability in response to medications. Opioids and other pain adjuvants are widely used, and drug–drug interactions involving these analgesics can be problematic and potentially lethal. Pharmacogenetics has improved our understanding of drug efficacy and response, opened doors to individual tailoring of medical management, and created a series of ethical and economic considerations. Since it is a relatively new field, genetic testing has not been fully integrated into the primary care setting. The purpose of this paper is to review the metabolism of commonly prescribed opioids, discuss the economic and ethical issues, and provide PCPs with an understanding of how to incorporate genetic testing into routine use to improve clinical practice and patient management.

Chronic pain management techniques have evolved in recent years. With regard to this, ultrasound (US) technology has become a standard for most acute pain procedures and essential for postsurgical pain relief and enhanced recovery after surgery protocols. This manuscript summarizes clinical studies evaluating US use for chronic pain management and compares efficacy with standard techniques including fluoroscopy (FL). US possesses several unique benefits when compared with FL, including elimination of radiation exposure while providing similar clinical outcomes. In summary, US use for chronic pain procedures is emerging as a viable, safe, and effective modality. Additional studies are needed to best appreciate US and its role in chronic pain management.

Pain after limb amputation is frequently challenging to adequately treat with local anesthetic-based regional anesthesia techniques due to its relatively long duration. Furthermore, uncontrolled pain in the immediate postoperative period is associated with persistent postsurgical pain, and frequently phantom limb pain. Cryoneurolysis is an alternative regional analgesic method to local anesthesia-based techniques. We report 3 cases in which ultrasound-guided percutaneous cryoneurolysis was performed in the perioperative period of limb amputation. All reported profound analgesia in the postoperative period without persistent postsurgical residual limb or phantom pain in the following months. No adverse events associated with the cryoneurolysis procedure occurred.

Myofascial pain syndrome (MPS) is a common pain condition and one of a spectrum of soft tissue pain syndromes (Mense and Gerwin, Muscle pain: understanding the mechanisms. Springer, New York, 2010). Patients can demonstrate pain in one or more body regions associated with referred pain to a site not associated with the pain source. Taut muscle bands and especially myofascial trigger points (MTrPs) are the key components of the diagnosis, which is mostly clinical. MPS can be acute or chronic and can be associated with additional pain syndromes such as cervical facet joint syndrome and headaches. An excessive release of acetylcholine (ACh) plays a role in the pathophysiology, triggering more muscle spasms and the release of biologically active molecules, leading to peripheral and central sensitization. Therapy is usually multimodal with physical modalities including stretching exercises and trigger point injection therapy.

IntroductionCryoneurolysis is the direct application of low temperatures to reversibly ablate peripheral nerves to provide pain relief. Recent development of a handheld cryoneurolysis device with small gauge probes and an integrated skin warmer broadens the clinical applications to include treatment of superficial nerves, further enabling treatments for pre-operative pain, post-surgical pain, chronic pain, and muscle movement disorders.Areas coveredCryoneurolysis is the direct application of cold temperatures to a peripheral nerve, resulting in reversible ablation due to Wallerian degeneration and nerve regeneration. Use over the last 50 years attests to a very low incidence of complications and adverse effects. Cryoprobes have traditionally been applied through a surgical incision; but, recent technical advances allow percutaneous administration. A new hand-held device is now approved for use within the United States. Cryoneurolysis has been used to treat postoperative and chronic pain states as well as spasticity. Expert commentary: Changes in the US healthcare system such as a push for the reduction of opioid use and the incorporation of Diagnostic Related Group codes, as well as recent technological advances including a handheld unit that allows for treatment of superficial nerves while protecting the skin from damage, may contribute to the resurgence of cryoneurolysis for the treatment of peripheral nerves.

Study design Description of a new technique. Objectives To describe a safe ultrasound (US)-guided cryoneuroablation technique of the proximal greater occipital nerve (GON). Background Cryoneuroablation is a treatment option for occipital neuralgia, providing more sustained relief when steroid injections fail. US can identify the proximal GON between the C2 spinous and C1 transverse process over the inferior oblique capitis muscle (IOCM), where the GON is clearly visualized. US-guided GON injections are often performed with an out-of-plane approach; however, that approach is difficult with cryoneuroablation, because the probe has no opening (prohibiting hydrodissection), and the size and dullness of the probe hinders easy manipulation. Setting University-based outpatient pain clinic. Methods We provide a description of the procedure based on experience in the authors' clinic. With the patient in the prone position, the US probe is placed parallel to the IOCM. The GON is seen on top of the IOCM; a midline 2-mm incision allows access to the bilateral GONs with a single skin entry. Using an in-plane approach, the cryo probe is advanced to the nerve in a medial-to-lateral direction, with constant US visualization, staying far away from the spinal cord and vertebral artery, which increases safety. Conclusions Based on anecdotal evidence from the authors' clinic, cryoneuroablation of the proximal GON can be performed safely at the level of the IOCM. Limitations The procedure described is based on anecdotal evidence from a small number of patients; however, the procedure is promising and formal study is warranted.

Complex regional pain syndrome (CRPS) is a chronic debilitating pain condition of the extremities; it can affect, less commonly, other areas of the body (face, pelvis, abdomen). Its early presentation—pain disproportionate to the injury, skin temperature changes, hyperalgesia, allodynia—is often not recognized, delaying treatment. In later phases, with sympathetic nervous system involvement, it presents with skin and muscle atrophy, hair loss, allodynia, loss of function, and decreased range of motion. In severe cases, it can spread from one area to the other. Imaging findings (X-ray, MRI, bone scintigraphy) are nonspecific. They are used to support the diagnosis, and to exclude conditions that can present similarly. Treatment is challenging and includes physical therapy, psychologic support, medication management, and minimally invasive interventions to decrease pain, to positively influence the sympathetic nervous system, and to preserve function. A multidisciplinary approach is likely to be the most beneficial.

Neurogenic thoracic outlet syndrome (nTOS) is caused by compression of the brachial plexus as it travels from the exiting nerve roots to the axilla. Its presentation, with varying degrees and distributions of arm and hand pain, paresthesias, and numbness, is often either not recognized or is confused with other conditions. Delay in diagnosis causes ongoing suffering for patients, with a concomitant increased use of healthcare services. Imaging and electrodiagnostic studies are often unremarkable, and therefore the diagnosis is based on a detailed medical history, a thorough physical exam, and diagnostic injections. Treatment options are available and can lead to significantly improved quality of life for the patient. Increased awareness of nTOS will likely contribute to its proper diagnosis and treatment.

Tendinopathy is characterized by failure of the normal tendon repair mechanism, and is a common malady that leads to chronic pain. Although pain relief is an important goal in treating the patient with tendinopathy, modalities that are intended to decrease pain in the short term do not address the underlying tissue disorder. As no current gold standard exists in the treatment of tendinopathy, physicians face a unique challenge in treating this common pathology. Regenerative medicine applications in pain medicine aim to address this unique challenge.

Peripheral nerve entrapments are an underrecognized cause of pain and disability. Hydrodissection (perineural deep injections) is one of the techniques that can release the entrapped nerve. Futhermore, discussed are the techniques of neural therapy, neural prolotherapy (perineural injection therapy), and autologous platelet lysate, as well as the use of adipose-derived stem cells.

Prolotherapy, or fibroproliferative therapy, is a regenerative injection therapy, first popularized in the 1940s and 1950s. Unfortunately, the combination of “better” surgical techniques and a series of high-profile medical catastrophes by poorly trained providers relegated the technique into the “fringe” arena. However, recent recognition of the failure of surgical interventions, combined with better technology and a burgeoning interest in the continuum of regenerative injection options, has renewed the interest and research into this “old” technique.

We report 3 different cases in which ultrasound-guided percutaneous cryoneurolysis was performed to treat acute pain: 1 patient with refractory incisional pain after percutaneous nephrolithotomy; 1 patient with burns to the foot; and 1 patient with pain from iliac crest grafting. Acute pain associated with surgery or injury is a challenge to treat with local anesthetic-based regional anesthesia techniques when the anticipated pain duration exceeds a few days. Cryoneurolysis is an alternative analgesic method that utilizes extremely cold temperatures to reversibly ablate peripheral nerves and is potentially a novel method for acute pain management.

Background: Pain clinicians have always been challenged by the variability of response to pain treatment. Differences in the degree of pain stimulation and pain sensitivity, weight and age differences, prior opioid use and tolerance, as well as the differences in bioavailability of various opioid formulations have been cited as causes for the wide variability in analgesia seen with opioids. Genetics may explain the variability of responses and help to predict more effective (or less dangerous) medication choices and doses. Genetics may also help to predict the response to specific opioids and antidepressants. Objectives: In this review article, we discuss the genetic influence of nociception, analgesia, and hyoanalgesia. The CYP450 enzymes involved in the metabolism and activity of opioids and adjuvant analgesics are genetically controlled, as are the opioid receptors and a variety of brain chemistries. Methods: This article discusses the specific pain implications of genetic variations in CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, CYP3A7, OPRM1, OPRK1, OPRD1, COMT, GABA, UGT, MC1R, GCH1, ABCB1, P-glycoprotein, 5HTR1A, 5HTR2A, MTHFR, CACNA2D2, and 5-HTTLPR. Results: Recent research findings suggest the relationship between genetic predisposition and clinical behavior, including the risk of opioid misuse and addiction. While urine drug testing may hint at genetic issues regarding opioid metabolism, cheek swab DNA testing has become economically viable, and we review the current and future genetic pain issues that may influence the decisions that pain clinicians make every day. Conclusion: Genetic testing may explain and predict many of the clinical responses seen with opioids and adjuvant medications, and may help the clinician identify those patients at genetic risk of opioid misuse and addiction. Key words: Genetics, genetic testing, opioid metabolism, drug interactions, urine drug testing, opioid risk evaluation, opioid receptors

Cryoneurolysis entails using low temperatures to reversibly ablate nerves, with a subsequent analgesia duration measured in weeks or months. Previously, clinical applications for acute pain were limited because treatment originally required exposing the target nerve surgically. However, three developments have now made it possible to provide prolonged postoperative analgesia by cryoneurolysis: 1) new portable, hand-held cryoneurolysis devices, 2) ultrasound machine proliferation, and, 3) anesthesiologists trained in ultrasound-guided peripheral nerve block administration. This report is the first to describe the use of a single preoperative administration of ultrasound-guided percutaneous cryoneurolysis to provide multiple weeks of analgesia following shoulder rotator cuff repair and total knee arthroplasty. Considering the significant benefits of cryoanalgesia relative to continuous peripheral nerve blocks (e.g., lack of catheter/pump care, extremely long duration), this analgesic modality may be a practical alternative for the treatment of prolonged post-surgical pain in a select group of surgical patients.

Persistent anterior knee pain, especially after surgery, can be very frustrating for the patient and the clinician. Injury to the infrapatellar branch of the saphenous nerve (IPS) is not uncommon after knee surgeries and trauma, yet the diagnosis and treatment of IPS neuralgia is not usually taught in pain training programs. In this case report, we describe the anatomy of the saphenous nerve and specifically the infrapatellar saphenous nerve branch; we also discuss the types of surgical trauma, the clinical presentation, the diagnostic modalities, the diagnostic injection technique, and the treatment options. As early as 1945, surgeons were cautioned regarding the potential surgical trauma to the IPS. Although many authors dismissed the nerve damage as unavoidable, the IPS is now recognized as a potential cause of persistent anterior and anteriomedial knee pain. Even more concerning, damage to peripheral nerves such as the IPS has been identified as the cause and potential perpetuating factor for conditions such as complex regional pain syndromes (CRPS). Because the clinical presentation may be vague, it has often been misdiagnosed and underdiagnosed. There is a documented vasomotor instability, but, unfortunately, sympathetic blocks will not address the underlying pathology, and therefore patients often will not respond to this modality, although the correct diagnosis can lead to rapid and gratifying resolution of the pathology. An entity unknown to the clinician is never diagnosed, and so it is important to familiarize pain physicians with IPS neuropathy so that they may be able to offer assistance when this painful condition arises. Key words: infrapatellar saphenous nerve, saphenous neuralgia, nerve injury, knee pain, postoperative pain, peripheral nerve entrapment, diagnostic nerve blocks, complex regional pain syndrome, cryoneuroablation

The pathophysiology of phantom limb pain (PLP) is multifactorial. It probably starts in the periphery and is amplified and modified in the central nervous system. A small group of patients with PLP were questioned as to the portion of the phantom limb affected by pain (e.g., "great toe," "thumb"). In the stump, the corresponding amputated nerve was located with a nerve stimulator. With correct placement and stimulation, the PLP could then be reproduced or exacerbated. A small dose of local anesthesia was then injected, resulting in the disappearance of the PLP. If a peripheral nerve injection gave temporary relief, our final treatment was cryoanalgesia at this location. Evaluation of 5 patients, followed for at least 2.5 years, yielded the following results: 3 patients had excellent results (100%, 95%, and 90% decrease in complaints, respectively), 1 patient had an acceptable result (40% decrease), and 1 patient had only a 20% decrease in pain. Although both central and peripheral components are likely involved in PLP, treatment of a peripheral pain locus with cryoanalgesia should be considered. We propose the identification of a peripheral etiology may help match patients to an appropriate therapy, and cryoanalgesia may result in long-term relief of PLP.

Ankle sprains are a very common injury, suffered by approximately 25,000 patients per year, and affect all age groups, including children, athletes, and the elderly. The recognition of the type of ankle sprain (medial, lateral, syndesmotic) affects early and late management of ankle sprains. Also discussed are the acute diagnosis and treatment of ankle sprains, as well as the consequences of chronic ankle instability, which may include serious conditions such as complex regional pain syndrome and chronic ankle instability. Surgical and nonsurgical treatment, evaluation, prognosis, and prevention are also discussed. Key words: ankle pain, ankle sprain, chronic ankle instability, complex regional pain syndrome, cryoneuroablation, high ankle sprain, lateral ankle sprain, medial ankle sprain

Injections have a unique role in the management of peripheral nerve entrapments. Injections with local anesthetic help localize and confirm nerve entrapment diagnoses. Injections can also treat the nerve entrapment, with putative mechanisms including hydrodissection, the anti-inflammatory effect of injected corticosteroids, and the dilution and flushing out of inflammatory mediators. Precise and atraumatic injection techniques are essential to maximize the informational and treatment value of any nerve injection for peripheral nerve entrapment.

Ilioinguinal nerve entrapment is a common cause of groin or inguinal area pain. The ilioinguinal nerve can become entrapped after pelvic or hernia surgery, which can result in disabling pain in the inguinal area, lateral genitalia, or abdominal wall. The distribution and features of this pain can vary between patients, depending on anatomic variations in the course of the ilioinguinal nerve and the location of the entrapment. The pain can be diagnosed with nerve blocks and treated with neurolysis or neurectomy. Ilioinguinal entrapment causing abdominal pain is discussed in Chap. 40; this chapter discusses ilioinguinal entrapment causing groin and pelvic pain.

Entrapment of the distal saphenous nerve is the least common of the entrapment syndromes in the ankle and foot. However, the nerve can be injured by inappropriate footwear or as a complication of a variety of procedures.

Superficial radial neuralgia is an under-recognized cause of radial wrist and thumb pain. It is misdiagnosed as wrist tendonitis, DJD of the thumb, carpal tunnel syndrome, lateral epicondylitis, and cervical radiculopathy. Careful attention to the presentation and physical exam will reveal the etiology, which will lead to a variety of treatment options.

Peripheral nerve entrapments are common and treatable sources of pain. These conditions are a significant cause of morbidity and disability in the general population. The epidemiology and pathophysiology of peripheral nerve entrapment are reviewed, highlighting the most important risk factors and mechanisms leading to peripheral nerve entrapment.

Inferior gluteal nerve entrapment is a rare (or under-recognized) cause of low back and buttock pain. When the piriformis muscle entraps it, the resulting pain is often misdiagnosed as myofascial pain. The inferior gluteal nerve may also be injured during surgery (especially hip surgery) and poorly placed intramuscular injections. Entrapment of this nerve is commonly seen with (and probably masked by) sciatic, superior gluteal, and posterior femoral cutaneous pathologies.

The greater occipital nerve (GON) entrapment commonly causes occipital and cervicogenic headaches and can sometimes cause headaches with similar characteristics to migraine headaches. Diagnosis is made by physical examination of the neck and injection of local anesthetic. Treatment for GON includes medications, nerve injections, cryoneuroablation, radiofrequency lesioning, neuromodulation, and surgical decompression.

Intercostal nerve entrapment is rarely considered as a cause of chest wall pain, even though the pain is usually dermatomal in nature and therefore should be readily apparent. A history of chest wall injury (trauma, surgery, or infection) should alert the clinician to the possibility of intercostal neuralgia.

The posterior tibial nerve is a portion of the sciatic nerve that runs down the posterior leg into the foot. It can be entrapped at two major sites: behind the knee at the proximal edge of the soleus muscle and at the ankle in the tarsal tunnel. The small terminal branches of the tibial nerve can be entrapped in the distal ankle and foot and are discussed in other chapters. Posterior tibial nerve entrapment can lead to pain and dysesthesias in the calf and sole of the foot, as well as dysfunction of the foot flexors and intrinsic muscles.

Auriculotemporal nerve (ATN) entrapment commonly causes pain around the ear and jaw and can have overlapping characteristics to migraine headaches. Diagnosis is made by physical examination of the temporal fossa and the temporomandibular joint and by injection of local anesthetic over the nerve. Treatment of ATN entrapment includes medications, nerve injections, cryoneuroablation, chemical neurolysis, neuromodulation, and surgical decompression.

The neurosurgical management of nerve entrapment syndromes, beyond the options of decompression, transfer, and grafting, also includes the modality of neuromodulation. Neuromodulation techniques involve interrupting signals from entrapped nerves anywhere along the signal’s pathway, from just proximal to the nerve lesion up to the central nervous system.

The third occipital nerve (TON) is an under-recognized cause of occipital headaches and can sometimes cause headaches with similar characteristics to migraine headaches. Diagnosis is made by fluoroscopic injections of local anesthetic. Treatment for TON includes medications, nerve injections, cryoneuroablation, radiofrequency lesioning, neuromodulation, and surgical decompression.

Entrapment of the lumbar plexus is an under-recognized cause of pelvic, low back, abdominal, and leg pain. Due to the wide variety of entrapments, there can be a large variety of potentially confusing clinical presentations. The clinician needs to have a high index of suspicion to diagnose and therefore treat psoas entrapment of the lumbar plexus.

The lesser occipital nerve (LON) entrapment is an under-recognized cause of cervicogenic and occipital headaches and can sometimes cause headaches with similar characteristics to migraine headaches. Diagnosis is made by physical examination of the neck and injection of local anesthetic. Treatment for LON entrapment includes medications, injections, radiofrequency lesioning, neuromodulation, and surgical decompression.

Heel pain is common in clinical practice. Medial calcaneal nerve entrapment in the superficial posterior foot can mimic more common conditions such as plantar fasciitis or pain referred from the back or proximal leg, which can present with similar pain but are treated differently. A patient with a previous diagnosis of “plantar fasciitis” who has failed all conservative management may have an entrapment neuropathy of the medial calcaneal nerve and may respond to nerve injections and neurolytic techniques.

Ulnar nerve entrapment can be a cause of elbow, wrist, and hand pain. The ulnar nerve travels through several canals or tunnels, and, like the better-known carpal tunnel syndrome, these tunnels can cause entrapment. It is commonly seen in patients participating in throwing sports, such as baseball. Two primary sites are seen in ulnar nerve entrapments – cubital tunnel and Guyon’s canal. Appropriate diagnosis is necessary for appropriate treatment, and ulnar entrapment should be considered in patients with weakness or clumsiness of the hand.

Ilioinguinal and iliohypogastric nerve entrapment is an under-recognized cause of abdominal and groin pain. These nerves can become entrapped after abdominal or hernia surgery and can result in disabling pain in the inguinal area or abdominal wall. The distribution and features of this pain can vary between patients, depending on anatomic variations in the course of the ilioinguinal and iliohypogastric nerves and the location of the entrapment. The pain can be diagnosed with nerve blocks and treated with neurolysis, neurectomy, or stimulation.

Because of the potentially dangerous structures in the suboccipital region (such as the foramen magnum and vertebral artery), clinicians have tended to avoid this area, despite the pathology often seen there. This chapter discusses the regional pathology, the alternative techniques, and a novel interventional approach, the “Stealth” approach, for occipital decompression.

The posterior femoral cutaneous nerve is an under-recognized cause of posterior thigh and buttocks pain. There are many overlapping pain patterns in this region, and the etiology of posterior femoral cutaneous nerve entrapment must be actively sought out in order to be diagnosed.

The appropriate prescribing of opioids requires an in-depth understanding of the pharmacology and pharmacokinetics of these broad-spectrum analgesics. This chapter discusses opioid receptors, opioid mechanism of action, routes of administration, pharmacogenetics, side effects, and future directions of opioid analgesics.

The lateral plantar nerve is a cause of pain in the lateral sole and toes. Since this nerve can be entrapped as part of the tarsal tunnel syndrome as well as entrapped separately, it is important to carefully assess the site of entrapment; proximal treatment will not address distal pathology. Lateral plantar nerve entrapment may be treated with injection, neurolytic or surgical techniques.

Knee pain is a common reason for people to seek medical care. Its causes are many and varied; accurate diagnosis is central to appropriate therapy. Entrapment or injury of the proximal saphenous nerve or its major infrapatellar branch should be considered as a possibility.