Nerve Root, Sacral, and Pelvic Stimulation

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Chapter 13 Nerve Root, Sacral, and Pelvic Stimulation

Erich O. Richter, Marina V. Abramova, Durga Sure, Kenneth M. Alò

Chapter Overview

Chapter Synopsis: Electrical stimulation of the spinal cord (SCS) can be used to relieve pain that arises from many sources. Conditions that are classified as pelvic pain affect a diverse array of organs and structures and feature primarily neuropathic pain. This chapter covers the anatomical and physiological considerations for implantation of SCS hardware for the treatment of these pelvic conditions. For the most part these pelvic pain conditions are best addressed by stimulation of the sacral nerve roots. SCS may be used as treatment for interstitial cystitis, a painful inflammatory bladder condition, and other conditions of urinary dysfunction. The genitals and reproductive organs are affected in both sexes. Women may suffer from vulvodynia, a chronic neuroinflammatory stinging or burning pain of the external genitalia; whereas men are subject to chronic testicular pain and prostadynia. Coccygodynia is a painful syndrome arising from the coccyx. In addition to alleviating the pain associated with these indications for SCS, treatment can improve the underlying pathophysiology in the periphery, particularly improving bladder function. As in all indications for SCS, proper patient selection can increase the chances of a successful treatment.

Important Points:

Stimulation of sacral nerve roots from within the spinal canal is an important technique to consider for the treatment of many forms of chronic pelvic pain, including epididymoorchialgia, vulvodynia, and interstitial cystitis; urinary control problems; and other forms of pelvic floor dysfunction and bilateral foot pain.

A transforaminal placement from a cranial to caudal orientation is often the best way to obtain the stimulation pattern desired with a low migration rate.

A “laterograde” approach to gain cephalad access is easier to perform and improves the learning curve.

Clinical Pearls:

The entry site is best at L2-L3. The angle of the thecal sac to the skin is most favorable there.

The more lateral the entry site, the more shallow is the angle of the needle to the dura, and the easier the access.

The needle is perpendicular to the skin in craniocaudal orientation—the entire angle is mediolateral.

When placing bilateral electrodes, allow the needle tips to nearly “kiss” in the midline, then turn the bevels caudally to pass the electrodes.

For transforaminal placement keep the electrode in the midline until the last minute; then roll laterally into the foramen only about a vertebral level from target.

Clinical Pitfalls:

In patients with prior lumbar surgery, the epidural space may be obliterated. Get appropriate imaging.

Many practitioners are less familiar with sacral radiographs. Make use of lateral films to verify level.

Avoid the tendency to aim the needle caudally at the entry site. The shingling of the laminae makes it difficult to gain entrance this way.

When placing electrodes transforaminally, do not “wedge” the electrode distally in the foramen. Leave it loosely in the proximal foramen to avoid painful low threshold stimulation.

Introduction

Brindley ¹ performed the first implantation of a sacral anterior root stimulator in a patient with multiple sclerosis who suffered from impaired bladder emptying and incontinence in 1976. Since then, sacral neuromodulation has evolved rapidly, with the development of several different anatomic approaches and Food and Drug Administration (FDA) approval of a specific device in 1997 for the treatment of urge incontinence and frequency-urgency syndrome and nonobstructive urinary retention in 1999.²^–⁶ Sacral neuromodulation has also been shown to be efficacious in the treatment of chronic pelvic pain syndromes such as interstitial cystitis (IC), vulvodynia, prostadynia/epididymoorchialgia, sacroiliac pain, and coccygodynia.

Establishing the Diagnosis

Interstitial Cystitis

Interstitial cystitis (IC) is a chronic, often debilitating condition with symptoms of urinary urgency and frequency associated with suprapubic or pelvic pain with bladder filling in the absence of urinary tract infection (UTI) or other obvious pathology.⁷^–¹² The diagnosis of IC can be made in patients with characteristic cystoscopic findings of glomerulation or Hunner ulcers (10%) along with clinical findings.^12,¹³ The histological findings are consistent with neurogenic inflammation.¹³ The prevalence varies across studies least in part because of differing diagnostic criteria, but it is in the range of 45 to 197 per 100,000 women and 8 to 41 per 100,000 men^14,¹⁵ The pathogenesis and natural history are not completely understood but appear to be multifactorial,^12,¹⁵ including infection, allergic, immunological, and genetic processes.^12,¹⁵ The most popular theory is that a sequence of toxic reactions follows damage to the bladder epithelium, resulting in a severe inflammatory reaction that induces neurogenic pain and bladder irritation.^9,^12,^16,¹⁷ Other chronic pelvic conditions may mimic this process with minimal differences. The European Society for the Study of Interstitial Cystitis (ESSIC) has proposed a new nomenclature and classification system with the name of painful bladder syndrome.¹⁸ Patients without classic cystoscopic or histological findings were included in these criteria.

IC is typically associated with other chronic debilitating conditions such as irritable bowel syndrome (IBS), systemic lupus erythematosus (SLE), migraine, fibromyalgia, asthma, incontinence, or vulvodynia, and is commonly associated with a history of abuse.^12,^14,^19,²⁰ The differential diagnosis includes a variety of similar conditions such as overactive bladder (OAB), chronic pelvic pain (CPP), vulvodynia, UTI, or even endometriosis.¹⁵

Vulvodynia

Vulvodynia is a chronic stinging, burning, itching, or irritating pain in the vaginal region without evidence of infectious, inflammatory, or neoplastic causes or any underlying neurologic disorder.²¹^–²³ The estimated prevalence is more than 2 million women in the United States.²⁴ This chronic condition has debilitating effects on both physical and psychological aspects of the patient’s life.²² The pathology is not well understood. Hormonal and immunologic factors that stimulate nociceptive nerve endings directly or lead to local inflammatory signals can cause neuropathic pain of this kind.²² Clinical symptoms occur in episodes with irregular intervals. The diagnosis is one of exclusion. Both a gynecologist and urologist should evaluate the patient to make this diagnosis. The mainstays of therapy are dietary changes, physical therapy, psychological and sexual counseling, and oral or local medications under the guidance of pain specialists.^22,^23,²⁵

Chronic Testicular Pain

Chronic testicular pain is pain in the scrotal or testicular area lasting for more than 3 months and interfering with daily activities and quality of life. It is also called chronic orchialgia, orchiodynia or chronic scrotal pain syndrome.^26,²⁷ It typically occurs in patients with infectious, inflammatory, vascular, postsurgical, or neoplastic conditions. Detailed examination by a urologist with proper investigations to rule out treatable causes is the primary initial focus in patient evaluation.

Prostadynia

Prostadynia is defined as chronic genital or perineal pain associated with urinary urgency and dysuria. It is seen in 5 of every 10,000 outpatient visits. National Institutes of Health (NIH) criteria differentiate this from CPP syndrome based on the presence or absence of leukocytes in expressed prostatic secretions, postprostatic massage urine, or seminal fluid analysis.¹³ Some authors suggest that this pathological process in males is similar to IC in females.²⁸

Coccygodynia

Coccygodynia is a painful syndrome limited to the coccyx; it may be aggravated by sitting or standing up. The process is commonly attributed to fractures or soft tissue injuries, but many cases are idiopathic.²⁹ Coccygodynia is extremely challenging to treat. Options include rubber ring cushions, sacrococcygeal rhizotomy, physiotherapy, local injections, coccygectomy, and neuromodulation.¹³

Anatomy

Fibers from the thoracic, lumbar, and sacral segments of the spinal cord all contribute to the formation of the pelvic and sacral plexuses. These fibers include sympathetic (T12-L2 via the superior hypogastric plexus), parasympathetic (S2-S4 via the preganglionic pelvic splanchnic nerves), and somatic components (S2-S4). Afferent fibers in the parasympathetic system (S2-S4) primarily carry sensation from the pelvic viscera. The anterior pelvic floor musculature is primarily controlled by the S3 segment roots. Therefore the S2-S4 nerve roots are the primary targets in nerve root stimulation (NRS).

Basic Science

Spinal cord or nerve root neuromodulation for pain was initially explored based on the gate control theory introduced by Melzack and Wall,³⁰ which suggested that activation of large-diameter afferent fibers (Aβ) suppressed pain signals travelling to the brain (Fig. 13-1). Since its adoption for widespread clinical use, it has become clear that for electrical neuromodulation to be successful, the following criteria must be met:

The stimulation-induced paresthesia should cover the entire painful area.

The anatomical distribution of the paresthesia is primarily determined by the location of the cathode, or negative contact, often referred to as the active contact.

Alternative positions of the anode, or positive contact, can “pull” the perceived stimulation in a desired direction or “shield” other areas by hyperpolarizing them.

Fig. 13-1 The Aα and Aβ fibers are represented by the thick blue lines running from the dorsal root and traveling to substantia gelatinosa. The Aδ and C fibers are represented by fine pink lines running from the dorsal root to substantia gelatinosa. The fibers synapse with the cells of the substantia gelatinosa (G). G cells modulate the activity of transmission cells (T) located in the spinothalamic tract. Aα, Aβ, Aδ, and C fibers are excitatory to T cells. Large myelinated fibers (Aα and Aβ) are excitatory to G cells, whereas small myelinated and unmyelinated fibers (Aδ and C fibers) inhibit G cell activity. The G cell in turn inhibits T cell activity.

Shaker and colleagues ³¹ suggested that neuromodulation acts by inhibiting signal transmission to the central nervous system (CNS) via C fibers, but chronic neuropathic pain conditions can also induce new neural activity in second-order neurons in the CNS, shifting the focus of activity.¹³ Matharu and associates³² showed that successful stimulation may change thalamic metabolism and remodel the intrinsic pain circuits. Thus neuromodulation can be applied to many neuropathic pain conditions.

Pelvic pain syndromes appear to be neuropathic in nature, with characteristics of hyperpathia and allodynia.¹³ Histological findings in both IC and vulvodynia suggest neurogenic inflammation.³³^–³⁵ In addition, 40% of women with IC have a history of hysterectomy, suggesting that injury may lead to transient inflammation, which resembles reflex sympathetic dystrophy.¹³

Imaging

No specific imaging techniques are available that demonstrate the pathological changes that cause neuropathic pain disorders such as CPP and coccygodynia. Imaging is directed at ruling out other causes of the symptoms such as infection or spinal pathology and for delineating anatomical difficulties in applying neuromodulation techniques such as spina bifida, previous surgical sites where the epidural space is obliterated, severe spondylolisthesis, or severe stenosis, which would make placing epidural electrodes more difficult or impossible (Fig. 13-2).

Fig. 13-2 This myelogram demonstrates vacuum changes in multiple discs, indicating that mechanical pain is likely a major issue in this patient. The large disc herniations at multiple levels also raise concerns regarding the safety of passing electrodes over the cord in the epidural space.

Voiding cystourethrogram and cystometrogram are usually performed to assess bladder function in patients with voiding dysfunction. Urodynamic evaluation may also include uroflowmetry and detrusor pressure-flow studies aimed to determine the presence of detrusor overactivity.

Indications/Contraindications

General Indications

Sacral intraspinal NRS is commonly used for ³⁶:

CPP

Epididymoorchialgia

Vulvodynia

Urinary urge incontinence

Detrusor dysfunction

Bilateral foot pain

Postlaminectomy syndrome

The transforaminal approach is commonly used for ³⁶:

Ilioinguinal neuralgia

Failed back surgery syndrome

Discogenic back pain

The extraforaminal approach is commonly used for ³⁶:

Urinary urge incontinence

Urgency-frequency syndromes

Fowler syndrome

Pelvic floor muscle overactivity

Fecal incontinence

Careful patient selection and accurate diagnosis are essential for effective treatment. A multidisciplinary approach, including urology, gynecology, and psychiatry is needed to develop an optimal treatment plan. Careful and thorough investigation based on symptomatology is needed to rule out treatable causes of pain. Psychiatric evaluation is particularly useful in the management of these disorders since there is frequently some psychogenic component of the pain. Neuromodulation is an important consideration when conservative methods are ineffective in controlling the pain or improving quality of life. The optimal treatment modality and surgical approach is tailored to each patient based on pain distribution, patient anatomy, and the surgeon’s experience with particular techniques.

Absolute Contraindications

Significant systemic infection

Any process that obliterates the epidural space is a contraindication to epidural placement over that location (e.g., previous laminectomy at that level). Computed tomography (CT) scan best shows bony removal from previous operation; magnetic resonance imaging (MRI) with gadolinium is the best test to show scar formation.

Ongoing intravenous drug abuse

Severe psychiatric disease such as personality disorders, severe depression and other mood disorders, somatoform disorders, or somatization

Equipment

In principle nearly any stimulator could be used to deliver sacral NRS. In practice many centers prefer a cephalocaudal intraspinal approach using standard spinal cord stimulators with percutaneous leads.³⁷^–³⁹ Two devices have received FDA approval for sacral NRS.

In 1997 the Medtronic InterStim (Medtronic, Inc., Minneapolis, Minn) (Fig. 13-3) received the Food and Drug Administration (FDA) approval for the treatment of urge incontinence.

In 1999 the FDA approved Medtronic InterStim (Medtronic, Inc., Minneapolis, Minn) for the treatment of urinary retention and urgency-frequency.

In 2002 the FDA approved the revised Medtronic InterStim (Medtronic, Inc., Minneapolis, Minn) to include the term overactive bladder.

The FDA approved Renew radiofrequency (RF)-powered generator (St. Jude Medical, Inc., Plano, Tex) (Fig. 13-4) in 1999 for the treatment of chronic pain of the trunk and limbs.

Fig. 13-3 Neurostimulation system for sacral nerve root stimulation.

With permission of Medtronic, Inc. 2010.

Fig. 13-4 Radio frequency–powered generator with an external power source.

With permission of St. Jude Medical, Inc., Plano, Tex.

Brief summary of equipment:

Tuohy needle—used to access epidural space

The C-arm portable fluoroscopy machine—used to guide needle placement and electrode steering to the desired final location

Electrodes, most commonly dual percutaneous quadripolar electrodes (St. Jude Medical, Inc., Plano, Tex)

Subcutaneous tunneller—used to externalize percutaneous trial lead extensions or to connect the lead to the permanent pulse generator

Trial stimulator—external generator used during trial stimulation period

Anchors—to anchor the leads as they exit the fascia or the skin; also prevent migration

Lead extension—used to connect the epidural leads to the internal pulse generator (IPG) or to extend out to the trial stimulator when the leads are intended to be permanent if the trial is successful

IPG—implanted programmable power source

Technique

Several techniques for stimulation of lower lumbar and sacral nerve roots have been described in the literature. These include intraspinal, typically transforaminal, NRS; extraforaminal NRS; and trans-spinal NRS. Each may have advantages or disadvantages in various situations.

Intraspinal Nerve Root Stimulation

In these techniques the desired roots are stimulated from the intraspinal epidural space. This can be accomplished via an anterograde or retrograde placement. Anterograde placement is usually used for thoracic and cervical roots, with a traditional entry point in the upper lumbar spine, keeping the electrode in the midline as for a traditional dorsal column stimulator; and then rolling laterally to cover the nerve root in the lateral gutter as it approaches the foramen. This approach is not feasible for the lower lumbar or sacral roots, but entry at the sacral hiatus can be used for anterograde access to these lower roots.³⁹ Widespread adoption of this technique has been limited by the extremely caudal area of the incision and the personal hygiene issues that are associated with it. The concern for infection with any contamination of the wound in permanent implant situations is considerable, and it is often difficult to place the connections and anchors in this region in such a way that they are not uncomfortable in a seated position when the permanent system is fully implanted. Selective NRS via the retrograde (aka cephalocaudad) percutaneous placement of electrode is also a well-established technique. It has been described by two techniques. Under fluoroscopic guidance the epidural Tuohy needle can be placed in a paramedian fashion and advanced caudally until it reaches the desired interspace. The shingling of the laminae (Fig. 13-5) can make access to the epidural space quite difficult from this approach; but, if the electrode can be introduced to the epidural space in this fashion, it can be directed retrograde from this point without difficulty. Because of the technical difficulty of this approach and the steep learning curve, several centers have moved to what is often termed the laterograde approach.^40,⁴¹ In this technique the Tuohy needle begins initial approach to eventual S2-3 placement more laterally at the L2-L3 interspace, with an entry angle nearly perpendicular to the skin (Fig. 13-6). The bevel is then rotated caudally, and the electrode introduced and passed caudally in the midline (Fig. 13-7).⁴²

Fig. 13-5 Schematic showing anatomic relationships important in understanding the laterograde approach for craniocaudal electrode placement. Note the “shingled” laminae (blue ovals) and spinous processes. The black line represents the dura, and the black arrows depict trajectories a physician can use to access the epidural space for electrode placement. A, In a traditional anterograde electrode placement, the orientation of the laminae allows a wide variety of trajectories and a very shallow angle of approach, which minimizes the risk of dural penetration. B, In the sagittal plane the orientation of the laminae limits the ability to obtain a shallow angle of approach to the dura in a craniocaudal approach. C, Approaching “straight on” in the sagittal plane provides a wide corridor of entry, but the angle of approach to the dura must be controlled in the axial plane. D, In the axial plane with a midline site of entry, the dura (blue line) is beginning to slope away; and as the needle approach is brought more steeply from lateral to medial, the angle of approach to the dura becomes more shallow.

Reprinted with permission from Neuromodulation—Technology at the Neural Interface, 2010.

Fig. 13-6 Placement of dual S2-S3 “retrograde” electrodes: the needle placement is bilateral with the needle tips nearly “kissing” in the midline.

Reprinted with permission from Deer T: Atlas of implantable therapies for pain management, New York: Springer, 2011.

Fig. 13-7 Placement of S2-S3 “retrograde” electrodes: the electrode is directed caudally in the midline.

Reprinted with permission from Deer T: Atlas of implantable therapies for pain management, New York: Springer, 2011.

Retrograde Transforaminal Nerve Root Stimulation

To address limited spinal segment pathology, the transforaminal approach for spinal NRS may be used. This can be done through an open laminectomy or through a minimally invasive technique. The electrode is introduced by a retrograde technique; and, when the foramen of interest is approached, the electrode is rotated laterally and passed to just inside the foramen.^42,⁴³

Extraforaminal Nerve Root Stimulation

This technique is used primarily for isolated S3 stimulation, but it can be applied with modifications at higher levels when dictated by the presence of significant spinal stenosis. Two landmarks are visualized: the spinous processes and the inferior point of the sacroiliac joints. The S3 foramen is located lateral to the intersection of these two lines (Fig. 13-8). The needle is inserted under the fluoroscopic guidance 1 to 4 cm above the foramen. A small paramedian incision is made over the S3 foramen, and a finder needle is inserted. Next, an Angiocath or introducer sheath is advanced over the finder needle. The beveled end of it should not go beyond the S3 foramen. The finder needle is removed, and the permanent electrode (typically the tined Medtronic InterStim (Medtronic, Inc., Minneapolis, Minn) is inserted through the sheath, which is removed.⁴⁴ This technique becomes more invasive when surgical exposure is necessary to identify the foramen.³⁶ Retrograde lead placements have a lower rate of lead migration.¹³

Fig. 13-8 Anatomic landmarks for needle placement at the S3 foramen. The vertical line denotes the midline; the horizontal line connects the inferior limit of the sacroiliac joints. The S3 foramen is generally slightly lateral to the intersection of these two lines. SI, Sacroiliac.

Sacral Nerve Root Stimulation for the Treatment of Coccygodynia or Sacroiliac Joint Pain

To implant the leads over the S4 and S5 roots, a retrograde technique or the approach through the sacral hiatus is required. With a retrograde technique the needle is advanced caudally in the midline until it crosses S3. However, a transforaminal technique is not used, leaving the electrode in the midline caudally. Care must be taken to avoid placing the tip close to the sacral hiatus since undesired stimulation may result in pain (Fig. 13-9).

Fig. 13-9 Midline S4-S5 electrode placed by caudal technique for coccygodynia. The entry point is at the sacral hiatus.

An alternative technique is to place an electrode in a retrograde fashion over the posterior surface of the sacrum to provide peripheral nerve stimulation as depicted in Fig. 13-10. Generally this technique is used after mapping the pain generators with RF stimulation via a needle probe, confirmed with a stimulation-guided local anesthetic block. For coccygodynia this is treated with placement of quadripolar electrodes where stimulation leads to coccygeal paresthesia. This activates the S4-S5 roots and lateral transverse branches but avoids the potential discomfort of stimulation at the sacral hiatus. An identical technique with treatment of the lateral transverse branches of L5 to S3 is often effective in the treatment of sacroiliac joint pain. This represents a fairly simple and stable approach to sacroiliac joint pain, which is extraordinarily difficult to cover from the epidural space.

Fig. 13-10 Electrode placement for peripheral nerve stimulation for the treatment of sacroiliac joint pain and coccygodynia. Placement is guided by needle radiofrequency stimulation, followed by confirmation of the pain generator by local anesthetic injection. A, AP diagram of placement of a peripheral stimulator for the transverse branches of S4 and S5 to treat coccygodynia. B, Lateral diagram of electrode from A. C, AP diagram of placement to treat the lateral transverse branches from L5 to S3 for sacroiliac pain. D, Lateral view of electrode in C. AP, Anteroposterior.

Courtesy of Krista Runge.

Patient Management/Evaluation

Evaluation begins with a complete history and examination, followed by appropriate preoperative laboratory evaluation and imaging as discussed previously. All patients should undergo psychological screening before trial stimulation and receive appropriate psychiatric care as indicated. The trial period varies from center to center, but most commonly lasts for the better part of a week. The programming of stimulation electrodes has evolved from the “simple C-stim” program (continuous stimulation) that gave the patient only a single program, to modern devices, which can often offer multiple independent programs across 16 independently programmed electrodes. This programming flexibility, although often critical in dorsal column stimulation, is often not as critical in selective nerve root applications, where the precise position of the electrode over the foramen is of greatest importance. Criteria for a successful trial generally include a greater than 50% relief of pain, reduced use of narcotic pain medications, and improvement in functional daily activity.

Success of the trial must be gauged sequentially by the answers to two questions. Was the trial technically successful? In other words, when the stimulator is activated, does it produce paresthesias that “map” to the areas of pain? If the paresthesias do not cover the painful areas, the trial is a technical failure, and the second question cannot be asked appropriately. If the paresthesia covers the area of pain, the second question is, “Does it help the pain?” The first question is answered immediately after the trial implantation with the first few programming sessions. The remainder of the trial period is devoted to answering the second question, determining the effect of stimulation on the visual analog scale pain score, the quality of life indices, the use of narcotics, and function in activities of daily living.

Outcome Evidence

Treatment of Interstitial Cystitis

Treatment is tailored to each individual patient. First-line treatment includes diet modifications, oral pentosan polysulfate sodium (PPS), hydroxyzine, amitriptyline, gabapentin, prednisone, and cyclosporine A. Intravesical dimethylsulfoxide (DMSO), cystoscopic bladder hydrodistention, and resection of Hunner ulcers are more aggressive options. Intramural botulinum toxin injections and hyperbaric oxygen have been shown beneficial in some patients.^10,^15,⁴⁵ Major reconstructive surgery has been performed as well.^12,⁴⁵

In 1997 the FDA approved the Medtronic InterStim (Medtronic, Inc., Minneapolis, Minn) device for urinary urge incontinence, urinary urgency-frequency, and unobstructive urinary retention.⁴⁶ Many reports in the literature document the efficacy of neuromodulation in IC.^13,^38,^42,⁴⁷^–⁵² These studies have shown significant decreases in urinary urgency-frequency and pelvic pain and decreased antiproliferative factor activity. These findings were established in a multicenter trial.⁵³ Improvements in muscular activity are clearly seen in these patients.⁴⁷ These patients can experience an initial worsening of their typical symptoms with subsequent improvement,^47,⁴⁹ which can be treated effectively with caudal epidural block or prevented by giving the block before stimulator placement.⁴⁷ It is postulated that, if administered early before the muscularis fibrosis phase, caudal block might prevent or reverse the neurogenic inflammation.⁴⁷

Other centers have found that S2-S4 stimulation from an intraspinal approach, either unilateral or bilateral,^47,^54,⁵⁵ may be more effective than isolated S3 stimulation. Alternatively Peters, Feber, and Bennett⁴⁶ in a randomized, cross-over trial demonstrated that pudendal nerve stimulation leads to better improvement than S3 root stimulation.

Treatment of Vulvodynia

Because of the excellent results in patients with IC, the treatment of vulvodynia has also been explored. Nair and associates ²² reported a patient with vulvodynia treated with bilateral S4 NRS with 90% improvement in symptomatology and overall quality of life.²² Ramsey, Wright, and Fischer²³ demonstrated an excellent clinical outcome after S3 NRS in a patient with vulvar vestibulitis. The literature for this indication suffers from variable selection of patients, target nerve roots, stimulation systems, and surgical approaches.^13,^22,²³ Because the disorder is uncommon and difficult to distinguish clearly from other pelvic pain conditions, prospective trials with good outcome scales are very difficult to conduct.

Treatment of Chronic Testicular Pain

Treatment with antibiotics, nonsteroidal antiinflammatory drugs, tricyclic antidepressants, and pudendal nerve blocks is considered first line for pain management.²⁶ More invasive methods such as microsurgical denervation of the spermatic cord, epididymectomy, and vasovasostomy have been advocated as the next level of care.²⁶ When these treatments have failed, the inguinal orchiectomy can be considered. However, sacral nerve stimulation is considered by many to be a less morbid alternative. In a single case McJunkin, Wuollet, and Lynch²⁷ reported 80% improvement after unilateral S2, S3, and S4 NRS. Feler, Whitworth, and Fernandez¹³ demonstrated 75% improvement with sacral NRS at S2-S4 performed via an anterograde approach.

Results Summary

There is a paucity of level I evidence literature on pelvic and sacral NRS for the treatment of CPP and coccygodynia. A review of the literature is summarized in Table 13-1.^37,^{47–49,56–60}

Table 13-1: Literature Review of Outcomes after Sacral Nerve Root Stimulation

Risk and Complication Avoidance

Establishing and practicing strict patient selection criteria are perhaps the most important factors for obtaining positive long-term results. Significant contraindications should be actively searched for, and poor risk patients should not be offered the therapy.

The primary complications are neurological injury, infection, lead migration, and cerebrospinal fluid (CSF) leakage with spinal headache.

The nature of neurological injury is determined by the spinal level of the procedure and the nature of access to the perineural space. As discussed in the section on contraindications, some patients have anatomical abnormalities that increase the risk of complication. For example, spina bifida involves abnormalities of the lamina, and usually of the dura, which makes accurate access of the epidural space and safe steering of the electrodes more difficult. Significant spondylolisthesis changes the alignment of the spinal canal. Large disc herniations or other masses in the spinal canal may be completely asymptomatic but may reduce the volume of the canal to the point that it is no longer possible to place an electrode in the epidural space without neural compromise. The introduction of the Tuohy needle may be traumatic to the neural elements in the setting of severe spinal stenosis or if the needle is passed too deeply by using poor technique in accessing the epidural space.

Meticulous attention to sterile technique and wound closure are the best defenses against infection. It is critical that preoperative antibiotics are administered in such a way that tissue levels are therapeutic at the time of skin incision. The risk of infection is higher at the site of the IPG implantation and is often related to seroma formation. Avoid making the pocket any larger than necessary since this encourages seroma formation. Wearing an elastic abdominal binder for up to 2 weeks after surgery has been found helpful by many. Women may prefer to find a comfortable girdle with very similar results. If patients find the binder too uncomfortable, any form of gentle pressure after surgery may help to prevent this problem. If a seroma forms and develops significant pressure, it is important to aggressively manage the wound complication quickly, before leakage begins that can lead to infection. Drainage of a seroma and resumption of pressure is one method of addressing this. If the system becomes infected, it must be removed until all evidence of infection is completely resolved, evaluated by imaging and inflammatory markers such as C-reactive protein and erythrocyte sedimentation rate. Some centers routinely keep patients on oral antibiotics for the duration of their externalized trial, but there is no evidence base to support this.

Lead migration, which is a common problem with percutaneous electrodes in general, seems to be somewhat less problematic with intraspinal cephalocaudal placement than with direct extraforaminal techniques, which rely on “tines” on the electrode to prevent backing out (see Fig. 13-3) since they pass directly through a significant amount of muscle tissue just before reaching the target. A loss of coverage that is not associated with extremely high impedance (which would indicate a broken lead) is usually caused by migration of the lead. Careful attention to anchoring and formation of a relaxing loop at the midline incision are the technique points to help prevent this complication.^61,⁶² Particularly with bending and twisting motions of the lower lumbar area, a tension is exerted on the lead or lead extension as it traverses the distance between the entry point to the epidural space and the pulse generator. If this tension is applied repetitively, it can cause lead migration. The mechanics of this process are best avoided by careful attention to the relaxing loop and meticulous attention to anchoring technique. A tension relief loop of at least several centimeters should always be left at the spinal incision. The anchor should attach the lead to the fascia just as it exits the fascia and directly in line with this exit site. When the spine moves in flexion and extension, the distance between the target space and the exit from the fascia changes. When there is a substantial gap between the exit site and the anchor, the electrode may be slightly withdrawn during such movements, but it is quite unlikely to be pushed back through the fascia into position when the movement reverses. This ratcheting phenomenon can lead to electrode migration; but, if the anchor is placed perfectly in line with the exit site and just at the point of fascial exit, these factors are minimized. Some newer anchors have flexible extensions that can be passed through the fascial defect to further minimize this risk.

It is advisable to undermine a small pocket for the relaxing loop above the lumbar fascia to allow the loop to lie flat across the wound. This avoids the tendency for the loop to push up through the wound and risk erosion through the skin.

Most “wet taps,” or attempted epidural placement with return of CSF, do not go on to become symptomatic. It is generally not recommended to continue attempting to place the lead in that particular location. Placing two trocars on the same side at a given level or using an adjacent level (typically the level above, to avoid traversing the area) usually allows placement of the electrode and does not aggravate the problem. If the leak becomes symptomatic, a blood patch typically resolves the condition but may slightly increase the risk of infection.

These devices can generally be used safely but cautiously in conjunction with cardiac pacemakers. When used with a cardiac device, they should generally be programmed in bipolar mode, with a frequency of at least 20 Hz. Using caution, with electrocardiogram monitoring during stimulator programming, is advised.⁶³