You are in: eMedicine Specialties > Neurosurgery > MEDICAL TOPICS Tumors of the Conus and Cauda EquinaArticle Last Updated: May 12, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Amiram Shneiderman, MD, PhD, Assistant Program Director, Co-Director of Quality Assurance, Department of Emergency Medicine, Martin Luther King-Charles Drew Medical Center Amiram Shneiderman is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, and Society for Neuroscience Coauthor(s): Joseph T Alexander, MD, FACS, Director of Spine Research, Assistant Professor, Department of Neurosurgery, Division of Surgical Science, Wake Forest University School of Medicine Editors: Paul L Penar, MD, Professor, Department of Surgery, Division of Neurosurgery, University of Vermont School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Ryszard M Pluta, MD, PhD, Associate Professor, Neurosurgical Department Medical Research Center, Polish Academy of Sciences at Warsaw, Poland; Senior Researcher, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, NIH; Herbert H Engelhard III, MD, PhD, Director, UIC Neuro-Oncology Program, Chief, Division of Neuro-Oncology, Associate Professor, Department of Neurosurgery, University of Illinois at Chicago; Allen R Wyler, MD, Former Medical Director, Northstar Neuroscience, Inc Author and Editor Disclosure Synonyms and related keywords: tumors of the conus and cauda equina, cauda equina syndrome, CES, conus medullaris syndrome, spinal cord tumors, spinal cord neoplasms, spinal cord mass, spine mass, spine tumor, spine neoplasm, ependymoma, astrocytoma, intradural-extramedullary tumor, intramedullary tumor, extradural tumor, intra-axial tumors, intraaxial tumors, glioma, schwannoma, neurofibroma, meningioma, lipoma, erectile dysfunction, impotence, sexual dysfunction INTRODUCTIONSection 2 of 12
  The conus medullaris is the cone-shaped caudal ending of the spinal cord. In adults, the spinal cord terminates at approximately the level of L1 because of the differential growth of the vertebral column compared to the spinal cord. The cauda equina ("tail of a horse") is the collection of lumbar and sacral spinal nerve roots that course in a caudal direction to emerge from their respective foramina. Tumors of the cauda equina and the conus medullaris manifest with progressive symptoms, including pain, motor weakness, sensory deficit, and bowel and bladder symptoms. These symptoms are collectively known as the cauda equina syndrome (see Cauda Equina Syndrome). Tumors, disk herniations, fractures, and infection (epidural abscesses) are possible causes of this syndrome. Determining the precise nature of the lesion (eg, intradural-extramedullary vs intramedullary) and the exact type of tumor (eg, ependymoma vs astrocytoma) based on clinical findings is difficult. With the ubiquitous use of magnetic resonance imaging (MRI) for the definitive workup of persistent low back problems or evolving neurological deficits, some of the diagnostic challenge has been eliminated. Other diagnostic studies complement MRI and help in confirming the diagnosis. For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center; Cancer and Tumors Center; and Brain and Nervous System Center. Also, see eMedicine's patient education articles Back Pain, Lumbar Laminectomy, and Cauda Equina Syndrome. History of the ProcedureIn 1887, Horsley performed the first successful removal of a spinal cord tumor in a British Army major, William Gowers. He had an extramedullary-intradural fibromyxoma removed after general anesthesia and a laminectomy, with subsequent regain of his gait. The first successful intramedullary tumor removal was an ependymoma removed by Harvey Cushing in 1905. In 1963, Greenwood reported one of the first modern series on removal of intramedullary tumors with good success. The conclusion was reached that because of the relatively direct surgical approach to the lumbar spinal canal, tumors in that area are amenable to successful surgical resection. ProblemTumors of the spinal cord have a general classification, according to the tissue compartment in which they are located. This classification is based on their relationship to the meninges that enclose the central nervous system. Extradural tumors arise outside the cord and the meninges in the vertebral bodies and the epidural tissue. Intradural-extramedullary tumors arise inside the dural sac, from the leptomeninges or the nerve root, but outside the substance of the cord. Intramedullary tumors arise within the substance of the spinal cord. FrequencyTumors of the spinal cord comprise approximately 15% of all central nervous system tumors. They are rare tumors, with an estimated incidence of 0.5-2.5 cases per 100,000 population. Extradural spinal cord tumors comprise 55% of all tumors and include metastatic tumors. Intradural extramedullary tumors account for 40% of all tumors, and intradural-intramedullary tumors account for approximately 5% of all tumors. Ependymomas are the most common intra-axial tumors of the conus medullaris and filum terminale. They comprise more than one third of the tumors in the region. They comprise approximately 60% of all gliomas of the entire spinal cord and are the most common glioma below the midthoracic region. The average age at detection of conus medullaris tumors is in the third to fourth decade of life, with a slight male predominance. Tumors of the conus medullaris are also observed in the pediatric population. Myxopapillary ependymomas tend to affect the filum terminale exclusively, with cystic degeneration in approximately half the cases. Ependymomas are relatively rare intracranial gliomas and comprise only 5-6% of tumors. Intracranially, the tumor tends to occur mostly in children. Astrocytomas occur less frequently in the region of the conus medullaris and the filum terminale (just less than one third of cases) compared to ependymomas. In contrast to ependymomas, astrocytomas are the most common intra-axial brain tumor. Astrocytoma also has a slight male predominance and tends to occur in the third to fifth decade of life. Other tumors of the spinal cord comprise less than one third of intramedullary spinal cord tumors. This includes dermoid and epidermoid tumors, vascular tumors, and, rarely, lymphomas and oligodendrogliomas. Other rare tumors have been reported periodically. Intradural-extramedullary tumors are predominantly (more than two thirds) schwannomas, neurofibromas, or meningiomas. Their incidence is approximately the same. Lipomas have also been described. The exophytic forms of ependymoma and astrocytoma can be found in the intradural-extramedullary compartment. EtiologyTumors of the nervous system and spinal cord are classified according to their cells of origin. The following is a modified classification by the World Health Organization:
PathophysiologyThe nerve roots of the cauda equina can be considered peripheral nerves. An isolated lesion causes symptoms of a lower motor neuron lesion. This lesion affects lumbar and sacral segments. The patient presents with flaccid paralysis or paresis of the lower extremities. Early on, the symptoms may be unilateral and localized to a specific muscle group. The sensory deficit, at least initially, can be localized to a unilateral dermatomal distribution. As lesions progress in size, symptoms progress and become bilateral. The numbness and paresthesia progress to a saddle distribution and extend into the lower extremity. The lower back pain that is experienced is usually radicular in nature and extends into the lower extremity. Lesions of the conus medullaris manifest as sensory dysfunction of the perineum in a saddle distribution and as bowel and bladder dysfunction. Patients present with back pain that is primarily midline and less radicular in nature. Lesions that are truly isolated to the conus medullaris demonstrate sparing of the lower extremities. If the lesion is large enough to include some lumbar cord segments, symptoms extend into the lower extremities. If the lumbar cord is affected, the lesions have the characteristics of upper motor neuron lesions with hyperreflexic motor weakness. Genitourinary (GU) dysfunction is present in persons with either conus medullaris lesions or cauda equina lesions. No distinct signs or symptoms differentiate one type of lesion from the other. Because the conus medullaris includes most of the sacral cord that controls GU function, a lesion frequently results in GU deficits. By comparison, the cauda equina has roots of both lumbar and sacral origin, and GU sparing may occur. Both types of lesions are associated with urinary retention and incontinence and fecal incontinence or constipation. Both types of lesions are associated with sexual dysfunction, including erectile dysfunction and impotence. ClinicalThe manifestations of spinal cord tumors may include myriad neurologic symptoms. Findings from a careful history and physical examination can help guide the clinician to the diagnosis of a spinal cord tumor. The evolution of symptoms may be slow and progressive, or it may be abrupt with rapid progression. Neurologic symptoms are known as the cauda equina syndrome symptoms (see Cauda Equina Syndrome). The following are the main elements of the neurologic presentation:
Differential diagnosis The differential diagnosis for lumbosacral cord dysfunction includes nonneoplastic causes of myelopathy. An expanded differential diagnosis is presented in Cauda Equina Syndrome. The following are some of the major groupings:
INDICATIONSSection 3 of 12
Surgical considerations Surgical excision is the primary modality of treatment for spinal tumors. In general, the earlier the detection of the tumor and the more minor the neurological deficit, the better the prognosis for treatment and recovery. Advanced age and severe neurologic deficit are associated with a poor prognosis. The correlation of the American Spinal Injury Association (ASIA) score and prognosis are presented in Cauda Equina Syndrome. When preparing for surgery, pay special attention to the cardiopulmonary status and the correction of any coagulation, electrolyte, or metabolic disorders. Informed consent should be obtained from patients or their guardians. A realistic portrayal of the results should be presented, and the expectations of the patient should be addressed. Neurologic deficits may not improve, and a risk of worsening exists, including pain, paralysis, paresthesia, bowel or bladder problems, and sexual dysfunction. Indications for surgery The management of spinal cord tumors is primarily surgical. Urgent or emergent surgery should be performed in patients with rapidly progressing neurologic deficits. Radiation therapy and intrathecal chemotherapy are reasonable adjuvants for the treatment of these tumors. RELEVANT ANATOMYSection 4 of 12
The conus medullaris, or cone-shaped caudal ending of the spinal cord, contains part of the sacral cord and the vestigial coccygeal cord. The nerve roots form the cauda equina, the collection of nerve roots caudal to spinal level L1 that supply the lower part of the body. Extending distally from the conus medullaris is a delicate filament, the filum terminale. The first 15 cm are contained within the dural sac, the filum terminale internum. The filum terminale consists of fibrous tissue that is continuous with the pia mater. The central canal of the spinal cord continues down into the filum terminale for the first 5-6 cm, an area that also contains neural and ependymal cells. The extension beyond the apex of the dural sac is the filum terminale externum, which extends to attach to the first coccygeal vertebra. The filum terminale externum actually has a closely adherent dural layer around it. CONTRAINDICATIONSSection 5 of 12
Contraindications for surgery relate to the overall health and condition of the patient. Patients with significant comorbidity are poor candidates for any surgery, including spinal surgery. A relative contraindication for surgery is tumors that are in a difficult anatomical location, especially on the ventral aspect of the cord. However, experienced surgeons using microsurgical techniques can obtain the appropriate exposure. Fortunately, the roots of the cauda equina may be retracted gently to provide for exposure of most tumors in this area. WORKUPSection 6 of 12
Lab Studies
Imaging Studies
Other Tests
Diagnostic Procedures
Histologic FindingsThe histologic findings of the major tumor types are presented in Ependymoma by Ghosh and Jichici, Low-Grade Astrocytoma by Benardete and Jallo, Meningioma by Haddad and Hatoum, Dermoid, Limbal by Sherman, Neurofibromatosis by Kam and Helm, and Lipomas by Moraru. TREATMENTSection 7 of 12
Medical therapyThe treatment for tumors of the cauda equina or conus medullaris is primarily surgical resection. Medical treatment of the patient is focused on optimizing the treatment of any chronic medical condition that may limit functional status. Surgical therapyThe definitive treatment for intradural spinal cord tumors is surgical resection. Adjuvant radiation therapy or intrathecal chemotherapy is used in some centers. Preoperative detailsAs part of the preoperative preparation, a careful neurological examination is required. The objective is to have a baseline assessment against which to detect any postoperative neurologic deterioration. Some surgeons routinely pretreat patients with one or several doses of steroids such as dexamethasone. Steroids may help with perioperative edema or may improve the tolerance of neurologic tissue, and patients may have improved outcomes. Patients on anticoagulation therapy or aspirin prophylaxis should stop their medications prior to surgery. Obtain laboratory confirmation to demonstrate that the coagulation profile and bleeding time or in vitro platelet function analysis are acceptable. Intraoperative detailsA single dose of prophylactic antibiotic is usually administered intraoperatively. A laminectomy is performed over the appropriate lumbar region. An intraoperative ultrasound study is performed if a question remains about the extent or precise localization of the tumor. For delicate debulking of the tumor, an operating microscope and microsurgical instruments are used. A surgical laser is most helpful with intramedullary lesions. Ultrasonic aspirators can be used; however, concern exists about disrupting certain types of tumors because of possible seeding at distant sites. Meticulous attention to hemostasis is crucial. Some intradural-intramedullary tumors separate out readily, while others need to be removed in a piecemeal manner. When operating on intradural-intramedullary tumors of the conus medullaris, the filum terminale should probably also be removed. Tumors of the cauda equina are usually easier to remove completely compared to those of the conus. Special care should be taken with removal of dermoid and epidermoid tumors. Spilling their irritating content into the subarachnoid space may cause adhesions, arachnoiditis, and inflammation. The area around the tumor may have increased vascularity with enlarged veins. Special care should be taken when performing a myelotomy. Ependymomas tend to be located dorsally. Stay sutures in the pia may be used to help with the exposure. Although a cavity is left after the procedure, the defect in the neural tissue does not need to be closed. The dura is closed in the usual watertight manner. If indicated, an epidural drain may be left in place. Concerns exist regarding infection or tracking spinal fluid along a drain. Postoperative detailsTypically, ambulation is recommended after bedrest for approximately 1-3 days. Attention should be given to any potential cardiovascular or pulmonary problems. Postoperatively, patients should be given prophylaxis for deep vein thrombosis. Some surgeons use a brief course of postoperative steroids and antibiotics. Attention should also be given to the development of any neurologic complications. A hemorrhage may require prompt reexploration. In addition, resumption of normal bowel and bladder function should be monitored carefully. Follow-upProvide patients appropriate follow-up care and instructions. Provide discharge instructions from the hospital, with explicit instructions about wound infection and any neurologic deterioration. Follow-up visits for wound care should be conducted in a timely fashion. Secure appointments for possible adjuvant chemotherapy or radiation therapy. The patient should be observed periodically for a period of several years to monitor for recurrence. COMPLICATIONSSection 8 of 12
General complications Complications of spinal surgery are similar to those for any other major surgery, including the risks of anesthesia, acute myocardial infarction, deep venous thrombosis, pulmonary embolism, pneumonia, and other pulmonary complications. Careful preoperative screening and preparation of patients, attention to details, and aggressive postsurgical rehabilitation can help minimize the risk of these complications. Postsurgical pain Postsurgical pain resulting from manipulation of neural tissue has been categorized as either somatic or central. Somatic or acute pain results from manipulation of nerves and nerve roots. One example is the ligation of the dorsal nerve root during surgery, especially when bleeding occurs from a radicular vessel. A better approach is a sharp incision of the nerve roots with focal cauterization of any bleeding. Steroids (eg, dexamethasone) are very helpful for easing the pain, presumably by minimizing inflammation. Prolonged use of narcotics should be avoided, but they can be used short-term. Central or chronic pain results from resection of intramedullary tumors and is a chronic, persistent pain that is difficult to control. The pain is described as gnawing, sometimes burning, which can be triggered by light touch and may extend well beyond the area of stimulation. The mechanisms are not well understood, and the pain does not respond well to drugs or stimulators. Worsening of neurologic deficits The exposure and manipulation of the cord and the dural sac, the spinal cord, or the nerve roots can cause a worsening of neurological deficits. The trauma from rongeuring of the bone, also known as laminectomy trauma, even without opening of the dural sac, can result in temporary or permanent deficits. Great care must be taken, especially with tumors that are large and occupy most of the spinal canal. Infection Patients are at risk for wound infection or meningitis. With sterile technique and routine use of antibiotic prophylaxis, the risk is minimal. Postoperative hematoma A hematoma in the surgical area is recognized by immediate progressive deterioration of spinal cord or nerve root function. Radiologic confirmation can be obtained by performing a CT scan of the area. If radiographic studies are not available, the surgeon should consider reexploring the surgical site. Aggressive management of a possible hematoma may protect against neural deficits. Postoperative spinal fluid leak This complication occurs as a result of an incompletely closed dura, perhaps discovered after noticing poor healing of the skin and soft tissue over the incision site. In general, a patient who has had prior radiation therapy is more likely to develop this problem. Postoperative instability after extensive laminectomy Small laminectomies of the lumbar region do not usually result in the development of instability; however, more extensive laminectomies and those that are wide and possibly involve the articular facets may result in instability. Younger patients are at a higher risk for developing instability. Flexion/extension films prior to surgery may be compared to postoperative films. If progressive subluxation is identified, a stabilization procedure is indicated. The earlier the intervention, the better the results. Another possibility is a stabilization procedure during the initial surgery; however, stabilization and fusion procedures have associated complications and risks. Residual neurologic complications These may include paresis or paralysis, spasticity, contractures, sensory deficits, bowel and bladder dysfunction, and erectile dysfunction. Preoperative deficits improve in most patients. OUTCOME AND PROGNOSISSection 9 of 12
Series of patients that have been reported suggest a small incidence of recurrence. In general, recurrence depends on the grade of the tumor, the stage at which it was recognized, the completeness of resection, and the use of adjuvant radiation therapy or chemotherapy. Patients with cauda equina tumors fare extremely well, with high rates of survival and recovery of function. Patients with conus medullaris tumors also have a good prognosis. Patients with total or near-total resection have a better outcome. Patients with ependymomas of the conus medullaris have 5-year survival rates of 70-100%. The long-term recurrence rates are reported to be 0-30%. For astrocytoma, the survival rate at 1-5 years is 20-70%. Some small series report a complete cure of astrocytoma. The tumor is infiltrative; therefore, identifying a plane of cleavage and dissection is more difficult. Usually, astrocytomas have a high incidence of recurrence, and mortality is correlated directly with recurrence. Incidences of intra-axial dissemination are also reported. Some series demonstrate that patients receiving adjuvant radiation therapy or chemotherapy tend to fare better. Other series demonstrate excellent results without adjuvant therapy. In children with ependymoma, favorable results have also been achieved without radiation therapy. The risk-to-benefit considerations may justify avoiding postoperative radiation therapy in pediatric patients. The reversal of neurological deficits depends on the extent of the dysfunction at the time of presentation. Patients with severe neurologic impairment are less likely to improve. In some instances of severe deficits, complete or near-complete recovery occurs. Predicting which patients will have significant neurologic improvement is difficult. Patients at advanced ages do not fare as well as younger patients with similar lesions. The correlation of the ASIA score and the prognosis is presented in Cauda Equina Syndrome. FUTURE AND CONTROVERSIESSection 10 of 12
An area of possible progress in the next decade relates to MRI. As MRI becomes more readily available and less costly, physicians may be more likely to order it earlier in the course of the illness. The average time from presentation to diagnosis may be shortened. This will perhaps lead to the discovery of smaller and more readily treatable tumors. Other areas of possible progress include (1) improvements in adjuvant chemotherapy, especially for the treatment of malignant, infiltrative neoplasms such as astrocytoma; (2) progress in tumor markers for diagnostic and prognostic purposes; (3) the resolution of the controversy regarding the role of postoperative adjuvant radiation therapy; and (4) advances in spinal microsurgery and intraoperative imaging. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Tumors of the Conus and Cauda Equina excerpt Article Last Updated: May 12, 2006 | |||||||
