Introduction

Peripheral nerve tumors can occur anywhere in the body. Most of them aren't cancerous (malignant), but they can lead to pain, nerve damage and loss of function in the affected area. Mots peripheral nerve tumors are growths in or near the strands of tissue (axon) that transmit signals from your brain to the rest of your body. However some pelvic bone tumors may also involve the pelvic nerves.

• Schwannoma are benign nerve sheath tumors composed of Schwann cells, that can start anywhere in the body. These tumors rarely arise within bones, among which mandible and sacrum are the most common sites of involvement. The cause of schwannomas is unknown, but they sometimes occur in individuals with certain disorders, such as some types of neurofibromatosis. Because of originating in the nerve sheath, schwannomas may theoretically not induce major disturbance to nerve functions, but may induce neuropathic pain by distortion or compression of nerves fascicles. Surgical exploration and removal of schwannomas is always mandatory at last for histological confirmation, since malignant transformations are rare but do exist. Surgical management of sacral schwannomas is challenging because of difficulties in accessing the lesion, risk for massive intra- and postoperative blood loss due to an extensive vascularity of the pelvis, and because of risk for surgical nerve damages.

• Presacral dermoid tumors are usually present in the female adult population. These are benign tumors with high risk for recurrence when resection is incomplete. Malignant teratomatous lesions are the most common presacral lesions in the paediatric population. Presacral tumors are rare and originate anterior to the sacrum and coccyx. Dermoid cysts are the most common congenital presacral lesions and arise from totipotent cells, which are ectodermal in origin. They are usually found near the midline anterior to the sacrum or in the ischiorectal and perirectal areas. Some may be associated with coexistent spina bifida. Dermoid cysts can be differentiated from epidermoid cysts because they are not only composed of stratified squamous epithelium, but also have skin appendages like sweat glands, hair follicles or sebaceous cysts. Dermoid cysts can be unilocular or multilocular with the contents varying from clear fluid to blood and mucus.

• Tarlov cysts are fluid-filled nerve root cysts found most commonly at the sacral level of the spine – the vertebrae at the base of the spine. These cysts typically occur along the sacral nerve roots. The main feature that distinguishes Tarlov cysts from other spinal lesions is the presence of spinal nerve root fibers within the cyst wall or in the cyst cavity itself. Small, asymptomatic Tarlov cysts are actually present in an estimated 5 to 9 percent of the general population, while large cysts that cause symptoms are relatively rare. An increase in pressure in or on the cysts may increase symptoms and cause nerve damage. However, most of Tarlov cyst are asymptomatic and do not necessities any treatment.

• Osteochondromsarcoma are primary malignant bone tumor with cartilaginous differentiation. In terms of incidence, it represents the second most frequent bone tumor in adults, and is preferentially located in the pelvis in 22 to 39% of cases. Osteocondrosarcoma of the pelvic girdle remain asymptomatic in the long-term and may thus be large at the time of diagnosis. The only available treatment is carcinological surgical resection since the usual adjuvant treatments are ineffective. The pelvic location creates specific technical difficulties both for exeresis and reconstruction.

Symptoms

The symptoms and signs of a peripheral nerve tumor develop from direct effects on the main nerve or from the tumor pressing on nearby nerves, blood vessels or tissues. As the tumor grows, it may be more likely to cause signs and symptoms, although tumor size doesn't always determine effects. In case of pelvic nerve tumors, irritation, compression or even destruction of the the sacral plexus or the sciatic nerve will produce pain on the affected nerve's dermatomes, with symptoms such as:

• Sharp burning pain (allodynia),
• Tingling, shooting, aching
• Electric shock–like pain, with more sensitivity
• Numbness or a pins-and-needles feeling, like when your leg falls asleep
• A swollen feeling
• Muscles weakness
• bladder irritation with sudden or frequent need to go to the bathroom (urgency, frequency) of painful urination (dysuria) – why this pain condition is too often labeled as a “interstitial Cystitis”
• Trouble or pain during sex
• Sexual problems with for men, problems getting an erection, pain during sex, painful erection or trouble of libido

The location of the pain can be highly variable, depending on the nerve(s) affected:

• the clitoris, vulva (vulvodynia), labia, vagina (penis in men), urethra, perineum, anus or rectum (= pudendal pain)
• the buttocks, legs (dorsal areas) and feet and even under the sole of the foot
• Coccyx or tailbone area (coccygodynia)
• Deep pelvis which explains which such pain is too often labeled as a “chronic prostatitis” in men

All symptoms usually have something in common: as long as the diagnosis has not been made, the diagnosis remains unknown, the pain is usually labeled as refractory and the treatment is limited to pain control using often disabling medical treatments. If the tumor is not palpable on transvaginal or transrectal examination, MRI will be the first test to evoke a pelvic mass, while confirmation of the nature of the tumor can only be obtained on histopathological examination. Indeed, even if the vast majority of these tumors are benign, the possibility of a malignant tumor should never be ruled out. The MRI examination is therefore essential, but also the neuropelveological examination is very useful: tumor size, duration of symptoms and presence of sensory disturbance possesses little value in differential diagnosis whether the tumor is benign or malignant, but severe motor weakness confirmed by neuropelveological examination is of great diagnostic importance and of high suspicion for malignancy.

Classical treatments

In case of isolated tumors of the pelvic nerves, simple resection is usually sufficient. In bone tumors of the pelvis reaching the pelvic nerves (tumor of the pelvic bone or of the sacrum..), however, resection requires tumor free margins, which implies a large and en bloc resection of the bone and the affected nerves.

• Primary therapy for sacral bone tumor often involves en bloc surgical resection with tumor-free margins and functional reconstruction challenges, especially important in cases where the lesion is high in the sacrum. Such a management is challenging because of difficulties in accessing the lesion, risks for damages of neighboring organs, and risks for massive blood loss due to an extensive vascularity. Preoperative angiography should be performed to characterize the vascular anatomy and to determine if the lesion would be amenable to embolization. Percutaneous intralesional injections of alcohol embolizing emulsions has been proposed, but exposes the patients for ischemic neuropathy that can result in motor and sensory deficits in the pelvis and lower extremities.

• Many studies in surgical treatment for sacral schwannoma and dermoid cysts have been reported. Most of the cases were treated by curettage and overall results were favorable due to preservation of sacral nerve roots [5-18]. Abernathey et al. reported on 13 cases of schwannoma of the sacrum. 54% of the patients in this study who were treated by intralesional curettage, experienced tumor recurrence and underwent additional surgery. This study suggested that schwannoma originating in the sacrum should be aggressively resected with sacral amputation, lumbopelvic fixation and sacrifice of all or peritumoral nerve roots. Such procedures might cause extensive blood loss, greater chance of having postoperative bowel and bladder dysfunction, and sensor-motor troubles in the lower extremities. In contrast, Dominguez et al. reassured that a conservative approach with intracapsular enucleation alone produced a favorable result of only 16 percent recurrence rate. The treatment by high-dose postoperative radiation must be judged with regard to risks and benefits especially in women of reproductive age.

Laparoscopic management

At the Possover International Medical Center, our management is based on laparoscopic exploration of the pelvis with resection of the tumor. The procedure is performed under general anesthesia avoiding drugs that reduce muscle contractility in the administration of anesthesia. The interventions is usually started by opening the retroperitoneal space and exposure of all vessels surrounding the tumor.

Primary identification of the pelvic nerves using the LANN technique

It is well known that radical pelvic surgery can be accompanied by postoperative morbidity. This functional urinary and intestinal tracts morbidity varies, depending on the approach to the pelvis. The perineal or perianal surgical approach causes functional morbidity problems with bladder or rectum continence; the abdominal approach causes problems with hypercontinent bladder retention, chronic constipation, or both.

For this reason, nerve-sparing techniques were developed in different speciality areas and consist mainly of identifying and respecting, as far as possible, the different nerves during resection of anatomical structures. Because of the magnification effect and the possibility of blood-free dissection, even in the depth of the pelvis, laparoscopic surgery became one of the most useful and important instruments in learning the pelvic retroperitoneal anatomy. The combination of a good knowledge of pelvic neuroanatomy and the technique of laparoscopic dissection of the pelvic nerves aided by the magnification of the endoscope allows a very gentle dissection of all structures deep into the pelvis. To gain intraoperative information about the motoric function of the exposed nerves, we developed for many years the technique of laparoscopic neuronavigation, also called the LANN technique. Using anodin electrical stimulation of the nerves, the surgeon is able to gain direct information on the functionality of all exposed nerves making this way intraoperative an individual functional cartography of the all pelvic nerves in each patient. While the sciatic nerve – the biggest nerve of the entire body - is easy to be identified, identification of the different sacral nerves root is not always that easy. In case of doubt, differentiation of the pelvic nerves is obtained by intraoperative electrical stimulation with a laparoscopic probe. While s #4 stimulation does not produce any motor reaction in the lower extremities, stimulation of Sacral Nerve Root #3 is confirmed visually by a deepening and flattening of the buttock groove as well as a plantar flexion of the large toe and to a lesser extent of the smaller toes. Stimulation of Sacral Nerve Root #2 produces an outward rotation of the leg and plantar flexion of the foot as well as a clamp-like squeeze of the anal sphincter from anterior/posterior. Stimulation of Sacral Nerve Root #1 induces a motion of the leg with interne rotation while stimulation of the lumbal root #5 induces a flexion/extension of the foot. Stimulation of the obturator nerve induces an adduction of the leg, while stimulation of the femoral nerve induces an extension of the knee.

Sources

Possover M. "Laparoscopic exposure and electrostimulation of the somatic and autonomous pelvic nerves: a new method for implantation of neuroprosthesis in paralysed patients?" J Gynecol Surg – Endoscopy, Imaging, and Allied Techniques 2004;1:87–90

Possover M et al "The Laparoscopic Neuro-Navigation“ - LANN: from a functionnal cartography of the pelvic autonomous neurosystem to a new field of laparoscopic surgery. Min Invas Ther & Allied Technol, 2004;13: 362-367.

Possover M et al. "Anatomy of the sacral roots and the pelvic splanchnic nerves in women using the LANN technique". Surg Lap Endosc Percutan Tech, 2007; 17: 508-510.

Laparoscopic resection of pelvic nerve tumors – schwannoma / dermoide cyste/teratoma

Because the laparoscopic approach allows a sufficient and necessary magnification to make microsurgery of the nerves possible, laparoscopy enables the integrity of the nerves to be respected as much as possible. With an open abdomen, because it is not possible to see these nerves placed so profound in the pelvis behind the pelvic vessels, laparotomy does not allow such precision in the dissection of the nerves. Similarly, the rear approach is far too destructive because it requires the resection of a part of the sacral bone.

The laparoscopic exploration not only permits resection with tumor-free margins of the lesions, but also histological confirmations. Primary exposure of the rectum, the ureter and the pelvic nerves make the procedure safe and much easier than classical neurosurgical approaches, and with less risk for postoperative functional morbidities. All vessels surrounding the tumor have to be secured. Primary exposure of the pelvic artery - the internal iliac artery - is strongly recommended, so that in case of hemorrhage, this artery can be directly closed (temporarily or permanently) in order to make bleeding control easier and faster. In case of young women, because desire of pregnancy, the vessels of the uterus have to preserved as much as possible.

Because schwannomas are as their name suggests, a tumor of the Schwann sheath of the nerves, as long as the tumor is benign, the enucleation of the tumor with preservation of the nerves themselves - and therefore with preservation as much as possible the functional integrity of the nerve - can be obtained by laparoscopy. For this purpose, the surgeon must make maximum use of the magnification effect of the endoscope, in order to be able to follow the rules of micro-neurosurgery. Because schwannoma can be malignant tumors, the tumor is dissected keeping the capsules intact and morcellated only within an endobag avoiding strictly any contamination of the abdominal cavity.

Nevertheless, this surgery is not easy. It requires a lot of experience in laparoscopic surgery of pelvic nerves - ISoN-level 3 certified neuropelveologist- within particular an absolute knowledge of the anatomy of pelvic nerves to avoid surgical lesions of them, as well as an absolute knowledge of the anatomy of pelvic vessels to avoid bleeding during the operation. The surgeon must remain calm throughout the operation and dissect the tumor as if it was cancer, i.e. with as little contact with the tumor as possible in order to avoid at all costs a rupture of the capsule with possible spread of tumor cells in the pelvic cavity. The resection of the tumor must be complete in order to avoid a recurrence.

Sources

Possover M. "Laparoscopic management of sacral nerve root schwannoma with intractable vulvococcygodynia: report of three cases and review of literature". J Minim Invasive Gynecol. 2013 May-Jun;20(3):394-7.

Paravginal tumor 12cm in diameter

Laparoscopic Treatment of Pelvic Schwannoma

Laparoscopic assisted resection of pelvic bone tumors (osteocondrosarcoma)

Operative treatment of tumors in the sacroiliac area is among the most challenging muscloskeletal tumor surgeries. Because almost all the deaths from chondromas result from local recurrence, greater effort to obtain adequate surgical excision has been made over the last decades. Most used common surgical approaches are the posterior, posterolateral, anterior and posterior, anterior and lateral combined approach. The anterior and lateral combined approach is used in the resection of large iliac tumors, and the abdominoinguinal approach is selected for large retroperitoneal tumors. In tumor of the sacrum, exposition is mostly obtained by a posterior midline incision; lateral osteotomies are usually performed through the sacralforamina using a threadwire saw and Kerrison rongeurs. Although various reports analyzed "en-bloc" excision of sacral tumors, there are still technical problems to improve protection of nerve roots, preserve surrounding structures and reduce intraoperative bleeding, maintaining the oncologic result. In posterior approach, because first elevation of the sacrum allows dissection of presacral structures, risk for damages intrapelvic structures is high. Wound infections, neurologic deficits, pelvic instability, and cerebrospinal fluid leakage are the main complications of sacrectomy. Among these complications, extensive hemorrhage is the most serious complication since it may threaten the life of the patient and jeopardize the outcome of surgery. Angelini reported about sacral resection by posterior approach with a mean blood loss by 2961 ml (range; 1000 to 8000 ml) [8]. In a further retrospective study on 173 patients who underwent sacral tumor resection, sixty-nine (39.88%) patients had blood loss greater than 3000 ml. It is obvious that primary control on blood supply of the sacrum and of the parametries may reduce such intraoperative blood loss. The results of several studies suggest preoperative arterial embolization and aortic balloon occlusion. However, indications for performing embolization still remain uncertain. Because of numerous anastomoses between the sacral (medial and lateral), gluteal (inferior and superior) and pudendal vessels, single closure of the internal iliac artery does not protect from hemorrhage. We opted for a primary closure of all parametric vessels including the internal iliac artery, the gluteal and the sacral vessels by laparoscopy before starting with bone resection. Open surgery should have had expose the patient for a greater and unnecessary morbidity. In contrary, control of the pelvic blood supply by laparoscopy do not present major difficulties for pelvic surgeons trained in laparoscopic retroperitoneal surgery. In our patient, primary laparoscopic closure of the pelvic blood supply decrease considerably blood loss despite the massive postgravid pelvic varicosis.

Primary laparoscopic dissection of the ureter and of the bowel had not only protected the patient from severe visceral complications, but also had permitted an adequate exploration of the pelvis for possible retroperitoneal, intraabdominal or even visceral tumor infiltration. The laparoscopic dissection of the tissue surrounding the tumor permits a precise selection of the level of sacral resection with macroscopic tumor-free margins. The introduction of the Gigly saw through the different sacral foramens had also contributed to a precise transaction of the bone under laparoscopic control.

Pelvic bone amputation may also result in pelvic nerves damages. High amputation of the sacrum inevitably results in damages of the sacral nerve roots, the pudendal nerve and the coccygeal plexus. It is well-known that simultaneous abdominosacral resection circumvents many of problems for such advanced procedures since it provides good exposure of the intraabdominal structures, and avoids damage to the sacral nerve roots. Laparoscopic exposure of the sacral plexus and other pelvic somatic nerves, enabled the exploration of their relation to the tumor that had a direct impact on the radicality of the procedure. Laparoscopic dissection of the femoral nerve before psoas muscle resection permit preservation of locomotion while preservation of the sacral nerves roots S3/4 reduce risk for bladder and rectum dysfunctions.

Sources

Possover M, Uehlinger K, Exner U. "Laparoscopic assisted resection of a ilio-sacral chondrosarcoma: A single case report".Int J Surg Case Rep. 2014;5(7):381-4.

Laparoscopically Assisted Resection of a Sacro-Iliac Osteochondrosarcoma