Physical exam maneuvers, such as bending, extension, and rotation of the back, aggravate the pain and aid in diagnosis. The patient usually exhibits tenderness to palpation surrounding the paraspinal region [5]. The mainstay of diagnosis lies in the diagnostic medial branch block, in which local anesthetic, alone or in combination with steroid, is injected around the medial branch portion of the spinal nerves which innervate the facet joints. A positive response occurs when the patient experiences significant but temporary pain relief and suggests that facet disease is the cause of the patient’s pain. In patients with successful medial branch blocks, longer-term radiofrequency ablation of the medial branch nerves can be considered and will be discussed later in this chapter [2].
Mechanical Compression
Occasionally, tumors or masses can arise in various areas of the spine and cause radicular-like symptoms that involve the urogenital dermatomes. These can include benign tumors such as bone cysts or hemangiomas, as well as primary malignancies like osteosarcomas [14]. In addition, a variety of cancers preferentially metastasize to the spine, such as prostate, breast, lung, and multiple myeloma. These bony metastases can cause bone pain or have the potential to cause neural and vascular compression, thus resulting in radiculopathy. The location of the pain, that is, pelvis, low back, sacral, depends on where the tumor is situated and what structures surround it [1]. The exact sacral innervation was determined during past radiofrequency ablation procedures of sacral nerve roots. The S2 dermatome reflects the innervation of the groin, buttocks, genitals, and posterior thigh, while the S3 dermatome covers the genitals, rectum, and perianal region. S4 and S5 dermatomes include the vagina and anus [15].
Cysts are another form of physical occurrence that can affect the pelvis and sacral nerves to cause urogenital symptoms. Sacral cysts, also known as Tarlov cysts, have been described as occurring in 4.6–9 % of the adult population [16] and are irregular protrusions of the meninges that occur in close proximity to the sacral nerve roots. These perineural cysts contain cerebrospinal fluid and at times have a connection with the general subarachnoid space, although that does not always occur. Past surgical examination of these cysts has shown that the walls contain sacral nerve roots that have lengthened and elongated over time as the cysts increased in size. Patients with sacral cysts often describe atypical and persistent pain, tingling, and dysesthesias in the region of the buttocks, perineum, rectum, and vagina [15] and even bowel and bladder dysfunction, sacral pain, and impotence [16].
In imaging Tarlov cysts, MRI is utilized first line to show the specific location of the cyst and its relationship to surrounding structures, as well as to quantify the amount of CSF contained. CT myelography can be used afterwards to better evaluate its features. Treatment of sacral cysts include conservative forms, such as NSAIDs, physical therapy, caudal ESIs [17], lumbar CSF drainage or cyst drainage, and surgical options, such as cyst excision, although surgery is typically reserved for patients who show no response to medical management [16].
There have been reports in the literature of schwannomas occurring in sacral nerve roots and causing pelvic pain and lumbosacral radicular symptoms. Schwannomas are nerve sheath tumors that can occur throughout the body and can cause compression of the nerve roots leading to pain and other symptoms. Possover and Kostov discussed three women who presented with long-standing pelvic pain unresponsive to various medications. Physical exam revealed S2–S4 radiculopathy and imaging, both transvaginal ultrasound and MRI, showed a sacral mass. Each of these patients underwent laparoscopy for tumor resection and recovered with complete resolution of vulvar and coccyx pain postoperatively. The reasoning for the varied symptoms experienced by the patients, from urogenital discomfort to lumbosacral radiculopathy, stems from the combined involvement of the S2–S4 nerve roots and compression of them by the schwannoma [18].
Coccygodynia
Coccygodynia is a disease process described as pain in the area of the coccyx that usually presents when a person is sitting. It can be idiopathic in patients with normal coccygeal mobility or it can arise with atypical mobility of the coccyx, such as after trauma, fractures, or childbirth. It occurs more commonly in women than in men and presents with sacrococcygeal pain that is usually exacerbated by sitting on the buttocks. Physical exam can show tenderness to palpation of the coccyx or on rectal examination.
Dynamic X-ray imaging can commonly display hypermobility or subluxation of the coccyx. Treatment includes conservative management with NSAIDs, heat, physical therapy, massage, and local anesthetic/steroid injection at the ganglion impar, or can be more aggressive with coccygectomy for severe intractable pain [19].
Other Radiculopathies
Diabetic radiculopathy is a phenomenon that has been described, occasionally with features clinically indistinguishable from lumbar disc herniation. It can produce symptoms of lumbar and/or sacral radiculopathy, including pelvic and urogenital discomfort. Naftulin et al. discussed several case reports in which diabetic patients presented with lower extremity pain, pelvic and groin pain, weakness, decreased sensation, and decreased reflexes. They underwent thorough work-ups with EMGs that showed denervation and were treated conservatively with NSAIDs, adjuvant medications, physical therapy, bed rest, and tighter glucose control. These patients have the potential for spontaneous improvement of some, if not all, of their symptomatology [20].
Another unique pathology is herpes zoster-related radiculopathy. Helfgott et al. described the case report of a patient with buttock and lower extremity pain upon presentation, with physical exam showing motor weakness, decreased reflexes, and positive straight leg raise. After several days, the patient had new cutaneous lesions of the knee, thigh, and gluteal region diagnostic of herpes zoster, which later progressed to bladder dysfunction. EMG and nerve conduction studies showed denervation in the left-sided L3–L5 nerve roots, and the patient improved progressively over the next several months. In this form of radiculopathy, diagnosis can be difficult as the radicular symptoms can often predate the skin findings [21].
Treatment
Lumbar Epidural Steroid Injections
ESIs performed under fluoroscopy are a nonsurgical intervention used to treat symptoms of radiculopathy caused by inflammation in the area of disc herniation or similar pathology in the lumbar spine [1]. The theory behind the mechanism of action of these injections states that during disc herniation, the nucleus pulposus releases multiple inflammatory factors into the spine, such as phospholipase A-2, prostaglandins, leukotrienes, IL-6, IL-8, and TNF-α. The epidural steroids serve to moderate this inflammatory process and thus reduce the pain and other radicular symptoms that patients can feel. The various corticosteroids currently in use consist of triamcinolone, methylprednisone, betamethasone, and dexamethasone. Additionally, the mixture includes a local anesthetic such as bupivacaine and a contrast agent [2]. The local anesthetic alleviates the patient’s pain initially after injection and the steroid takes action several days later [1].
There are numerous indications for lumbar ESIs (LESIs), including disc herniation, spinal stenosis, and nerve root compression and/or inflammation. Contraindications include sepsis, local infection at the site to be injected, coagulopathy including increased international normalized ratio (INR) or thrombocytopenia, elevated intracranial pressure, and allergy to any of the injected substances [2].
The epidural space, the target of these injections, extends from foramen magnum down to the sacrococcygeal membrane. When starting at the skin, the planes traversed by the epidural needle include the subcutaneous tissue and fat, supraspinous ligament, interspinous ligament, the ligamentum flavum, and then finally the epidural space. The ligamentum flavum is very dense and lends a feeling of increased resistance on the needle as one is performing an epidural. Once the ligamentum is passed, there is an immediate and characteristic “loss of resistance” which signifies entry into the epidural space [22].
There are several approaches to performing a LESI: interlaminar, transforaminal, and caudal. The interlaminar approach is usually attempted with the patient in the prone position and a pillow or blanket under the abdomen to aid in opening the interlaminar space. The fluoroscope is used initially to determine the target, after which the back is prepped and draped in sterile fashion. Lidocaine or similar local anesthetic is infiltrated to numb the skin, and then, the epidural Tuohy needle is inserted. Typically, the loss of resistance technique is utilized in combination with fluoroscopy to identify the epidural space and contrast is injected. Following epidurography, the steroid/local anesthetic mixture is administered. After this procedure, the patient is then routinely monitored in a recovery area to ensure that no neurologic deficits or pain has developed [2].
The transforaminal approach to LESIs (TFLESI) focuses on application of the steroid medication anteriorly close to the nerve root, and thus, the source of the patient’s pain and other symptoms [2]. This injection is performed through the intervertebral foramen of the spine, as opposed to interlaminar injections, which are performed between the laminae [23]. The theory behind this technique is based on the belief that interlaminar LESIs can be too dispersed and that concentrating the medication close to the affected nerve can increase pain relief [24]. TFLESIs are accomplished exclusively under fluoroscopic guidance with similar equipment and preparation as for an interlaminar epidural.
Another variation of ESI to treat radicular pain is the caudal injection (Fig. 6.2). Caudal epidural injections are performed under fluoroscopy, using the sacral hiatus as an initial landmark. Once the steroid mixture is injected, it moves upward within the epidural space to approximately the L4 level [2]. Caudals typically require a greater volume of injectate than LESIs and TFLESIs, varying from 10 to 64 mL [24].
