Intramedullary Spinal Cord Tumors 

Updated: Jan 30, 2020
Author: Alfred T Ogden, MD; Chief Editor: Brian H Kopell, MD 

Overview

Practice Essentials

Intramedullary spinal cord tumors (IMSCTs), like the one depicted in the image below, refer to a subgroup of intradural spinal tumors that arise from cells within the spinal cord, as opposed to adjacent structures such as the nerve roots or meninges. They are much less common than brain tumors and are thought to account for 5-10% of all intrinsic tumors of the central nervous system. Their most common initial symptom is generalized back pain, which is very difficult to distinguish clinically from back pain from musculoskeletal conditions. Most intramedullary spinal cord tumors are considered to be glial in origin because they are histologically and immunohistochemically similar to differentiated non-neuronal cell types, such as ependymal cells and astrocytes, which occur in nonpathological spinal cord tissue. Because of the slow-growing nature of many of these tumors, symptoms precede diagnosis by an average of 2 years. Patients with malignant or metastatic spinal cord tumors present in the range of several weeks to a few months after symptoms develop.[1, 2, 3, 4, 5, 6]

The most commonly encountered intramedullary spinal tumors are ependymomas, astrocytomas, and hemangioblastomas. Collectively, spinal ependymomas and astrocytomas account for 80-90% of  intramedullary spinal tumors, with ependymomas occurring roughly twice as frequently as astrocytomas.[7] In adults, ependymomas are the most common tumor type. In children, astrocytomas are the most common tumor type, 

View of a cervical intramedullary ependymoma in si View of a cervical intramedullary ependymoma in situ after midline myelotomy and initial dissection (top left). The tumor was removed en bloc (right), and the postsurgical cavity in the spinal cord is shown (bottom left).

Diagnosis

MRI produces exquisite detail of the spinal cord. Most tumors are isointense or slightly hypointense as compared to the normal cord signal. Tumors generally exhibit some enhancement with gadolinium, and this enhancement may be homogenous or irregular. Contrast-enhanced MRI is very sensitive and may reveal minute lesions.

Plain radiographs of the spine cannot diagnose an intramedullary tumor but may be useful for surgical planning if the tumor is associated with a deformity.

Patients are often diagnosed only after the development of neurologic signs and symptoms that may occur later in the course of the disease. Early diagnosis is important, however, because surgical removal for most tumors is curative, and surgical results are optimized when tumors are smaller. Also, neurologic deficits resulting from intramedullary spinal cord tumors are seldom reversible. As such, functional outcomes after surgery are closely tied to the patient's preoperative neurologic condition.

In the case of a complete spinal block by the tumor, lumbar puncture may precipitate a disastrous shift in the intrathecal contents and, therefore, should not be the first test performed when a spinal cord tumor is suspected. Cerebrospinal fluid (CSF) may show extremely elevated protein levels, and xanthochromia may be present.

Treatment

The first-line treatment for intramedullary tumors is open surgical resection. Surgery is indicated for all symptomatic lesions. Small asymptomatic lesions may be followed clinically and radiographically because the majority of intramedullary tumors are relatively benign and slow growing. However, this approach carries the risk of the development of neurologic deficits that are likely not recoverable and the uncertainty that comes with undetermined diagnosis.

At surgery, aggressiveness with respect to resection depends on the histologic diagnosis of a frozen section and the ability to find and maintain a surgical plane.

Steroids are used in the perioperative period or if a rapid decline in neurologic function occurs. The slow-growing nature of these neoplasms makes proving the benefit of radiation therapy difficult.

In a study of 70 adult cases of intramedullary spinal cord tumors consisting of ependymomas, astrocytomas, carcinoma metastases, hemangioblastomas, cavernomas, and others, the investigators recommended evoked potential-guided microsurgical total resection for ependymomas and other benign lesions; partial resection or biopsy followed by adjuvant therapy for high-grade astrocytomas; and resection or biopsy for metastatic lesions.

A study of 225 patients with 250 intramedullary tumors found that 83.3% of displacing tumors underwent gross total resection (GTR), 22.5% of infiltrating tumors underwent GTR, and none of the nonproliferating tumors underwent GTR. Permanent morbidity (19.5%) was lowest after GTR and correlated significantly with surgical experience and the preoperative neurologic state. Patients with tumors of thoracic levels, tumor hemorrhages, and malignant and recurrent tumors were at a higher risk for permanent morbidity.[8]

A group of patients who underwent spinal surgery with the use of neurophysiologic intraoperative monitoring (NIOM) (N=38) were compared with a group who underwent surgery without NIOM (N=36), before the introduction of NIOM, and the number of neurologic complications was found to be significantly lower in the intramedullary procedure group with NIOM. There was no significant difference in the number of complications in patients undergoing intradural or extradural extramedullary procedures with NIOM versus without NIOM.[9]

Epidemiology

Spinal tumors occur with an incidence of 0.97 per 100,000 persons in the United States.[10]  Spinal cord gliomas account for approximately 80% of intradural intramedullary spinal tumors. Of the spinal cord gliomas, astrocytomas constitute 30-40% and ependymomas 60-70%. However, hemangioblastomas, gangliogliomas, lymphomas, and melanomas also occur.[11, 5, 6]

In adults, intramedullary spinal tumors comprise 5-10% of all spinal tumors and are the most common spinal tumor in children. The most commonly encountered intramedullary spinal tumors are ependymomas, astrocytomas, and hemangioblastomas.. Collectively, spinal ependymomas and astrocytomas account for 80-90% of  intramedullary spinal tumors, with ependymomas occurring roughly twice as frequently as astrocytomas.[7]

Astrocytoma accounts for 6-8% of all spinal cord tumors and is primarily low grade. It occurs in both adult and pediatric populations, with the most common presenting symptoms being back pain, sensory dysfunction, or motor dysfunction.[11, 5, 6]

Ependymoma is a common primary neoplasm of the spinal cord and filum terminale. It is the most common primary glial neoplasm of the spinal cord, constituting 50-60% of intramedullary cord neoplasms. They frequently present in middle age but can occur at any age. Ependymomas are believed to be slow-growing tumors. Because of their tendency to compress adjacent parenchyma, patients with spinal ependymomas usually experience gradual symptoms because of slow progression, making early diagnosis difficult.[12]

Hemangioblastomas are benign, slow-growing, highly vascularized tumors of the central nervous system, with the most common location being the posterior fossa. Hemangioblastomas are often associated with von Hippel-Lindau disease. [13]

In children, astrocytomas are the most common tumor type, accounting for around 60% of all intramedullary spinal tumors, and the mean age of presentation is 5-10 years.

Intramedullary spinal tumors can arise anywhere in the spinal cord, from the cervicomedullary junction to the filum terminale. Spinal ependymomas are found most frequently in the cervical cord, presumably because it contains more neural tissue than the thoracic or lumbar segments.[14, 15]

Hemangioblastomas and astrocytomas most commonly arise in the thoracic cord, followed by the cervical cord.[16]

 

Etiology

The etiology of intramedullary spinal tumors remains obscure but undoubtedly varies according to histology. Most intramedullary spinal cord tumors are considered to be glial in origin because they are histologically and immunohistochemically similar to differentiated non-neuronal cell types, such as ependymal cells and astrocytes, which occur in nonpathologic spinal cord tissue. The traditional thinking is that tumors occur when these differentiated cells, which normally stop propagating after spinal cord development, acquire mutations that cause them to divide again in an uncontrolled fashion.

There is increasing evidence that genes regulating radial glial cell differentiation play a role in molecular pathogenesis. Compared to supratentorial and posterior fossa ependymomas, spinal ependymomas overexpressed homeobox (HOX) family genes and insulinlike growth factor 1 (IGF1). Distinct malignant transformations in regional radial glial cells also can give rise to anatomically and molecularly distinct ependymomas. These findings underscore the notion that cranial and spinal ependymomas should be considered separately, for both clinical management and biological investigation.[7]

Individuals with type I and type II neurofibromatosis (NF1 and NF2) have been recognized for some time as having an increased incidence of intramedullary spinal tumors, as well many other kinds of tumors, compared with the general population. This general predisposition to tumors has been linked to germline mutations in 2 different genes named for their associated diseases. Patients with the NF1 gene are predisposed to spinal astrocytomas, whereas patients with the NF2 gene are predisposed to spinal ependymomas. Genetic analyses of spinal ependymomas from individuals without syndromic neurofibromatosis have shown somatic mutations in the NF2 gene in a subset of cases.

The identification of mitotically active neural stem cells and neural progenitor cells throughout the central nervous system has altered current thinking about how all intrinsic CNS tumors arise. Many lines of evidence point toward neural stem cells as the cells of origin in brain tumors. This line of inquiry is not nearly as advanced in the spinal cord, but some preliminary work has shown similarities between tumor cells from spinal ependymomas and neural stem cells from the spinal cord.

The other relatively common type of intramedullary spinal tumor is hemangioblastoma. Hemangioblastomas are thought to arise from red blood cell precursors and are not intrinsic spinal cord tumors, but they are often anatomically intramedullary because of their association with the blood vessels that penetrate and nourish the spinal cord. Hemangioblastomas occur as a result of mutations in a tumor suppressor gene called vhl, which was found to be altered in patients with the neurocutaneous disorder von Hippel-Lindau disease (VHL). Patients are predisposed to form hemangioblastomas in the brain and spinal cord, and somatic mutations in the vhl gene have been found in tumors from patients without syndromic VHL.

Pathophysiology

The pathophysiology of intramedullary spinal cord tumors varies according to tumor type. Ependymomas are usually indolent, encapsulated tumors that are histologically benign. Pain and neurologic deficits arise as a result of a progressive stretching and distortion of nerve fibers. Usually a clear anatomic plane is present at surgery, and a gross visual anatomic resection results in a cure. Rare anaplastic subtypes can be invasive, however, and are more likely to recur or spread through CSF spaces. Even histologically benign–appearing spinal ependymomas can metastasize in this way.

Although malignant forms do exist, most spinal astrocytomas are low grade (WHO grade II) and less aggressive than astrocytomas in the brain. Pain and neurologic defects arise from a combination of nerve fiber stretching and the invasion of cord parenchyma. Because they are infiltrative tumors, complete surgical removal without damage to functional tissue is usually not possible. Exceptions to this general rule may include some pilocytic astrocytomas of the spinal cord (WHO grade I) that are more common in children.

Hemangioblastomas are highly vascular tumors with capillaries that display an increased permeability thought to be related to a hypersensitivity to vascular endothelial growth factor (VEGF). Lesions usually become symptomatic because this capillary hyperpermeability leads to fluid collections or syringes, which are often larger than the tumor itself, causing mass effect in addition to stretching of neural pathways. These fluid spaces are not lined with tumor cells, however, and only the tumor nidus needs to be removed at surgery.

Presentation

Symptoms

The clinical features of intramedullary spinal cord tumors are variable. Symptoms are not specific to spinal cord tumors and may be present in any myelopathic process.

Because of the slow-growing nature of many of these tumors, symptoms precede diagnosis by an average of 2 years. Patients with malignant or metastatic spinal cord tumors present in the range of several weeks to a few months after symptoms develop.

Pain and weakness are the most common presenting symptoms of intramedullary spinal cord tumors. Pain is often the earliest symptom, classically occurring at night when the patient is supine. The pain is typically local over the level of the tumor but may radiate.

Progressive weakness may occur in the arms (cervical tumors) or legs (cervical, thoracic, conus tumors). Impaired bowel, bladder, or sexual function often occurs early. Patients may have poor balance. Rarely, symptoms of subarachnoid hemorrhage may be present.

Intratumoral hemorrhage can cause an abrupt deterioration, a presentation most often associated with ependymomas.

Examination

Examination may reveal a combination of upper and lower motor neuron signs. Lower motor signs may be at the level of the lesion and may aid in localization. Other signs evident upon physical examination may include spine tenderness, stiffening of gait, trophic changes of extremity, sensory loss, hyperreflexia, clonus, and scoliosis or torticollis (generally in children).

Indications

The first-line treatment for intramedullary tumors is open surgical resection. Surgery is indicated for all symptomatic lesions. Small asymptomatic lesions may be followed clinically and radiographically because the majority of intramedullary tumors are relatively benign and slow growing. However, this approach carries the risk of the development of neurologic deficits that are likely not recoverable and the uncertainty that comes with undetermined diagnosis.

At surgery, aggressiveness with respect to resection depends on the histologic diagnosis of a frozen section and the ability to find and maintain a surgical plane. Given the difficulty in determining many ependymomas from astrocytomas on frozen section, the presence or absence of a clear surgical plane is usually the key determining factor in defining the surgical goal. If, after analysis of all available data, including imaging characteristics, frozen section, and intraoperative appearance, a diagnosis of ependymoma is perceived, a complete surgical resection should be attempted. If a diagnosis of astrocytoma is perceived, most clinicians advocate a more limited debulking of only the tissue that is clearly abnormal.

External beam radiation is generally reserved for disseminated ependymomas and infiltrative astrocytomas but remains an option whenever radiographic residual or recurrent ependymoma is found. Stereotactic radiosurgery for intramedullary tumors remains untested.

Relevant Anatomy

The spinal cord originates at the foramen magnum and extends to the conus medullaris, which terminates at the L1-L2 vertebral body junction in adults. The pia matter condenses caudally to this area, extending to the sacrum as the filum terminale. It is an ovoid structure, most narrow in the anterior-posterior direction. At every vertebral level paired ventral and dorsal nerve roots exit the lateral aspect of the cord and coalesce to form 31 pairs of spinal nerves.

In contrast to the brain, the white matter of the spinal cord surrounds the interior gray matter. The spinal cord is covered by a supporting connective tissue layer called the pia matter that acts as a trellis for the vascular supply. A vestigial extension of the ventricular system, the central canal runs the length of the spinal cord. Dilation of the central canal may be pathologic in some instances. In general, ventral portion of the spinal cord parenchyma subserves motor function, whereas the dorsal portion subserves sensation. The spinal cord contains the same cell types as the brain, but these are highly specialized to their niche in the spinal cord.

The vascular supply for the spinal cord comes from the anterior spinal artery, the paired posterior spinal arteries, and the 31 radicular arteries. The anterior and posterior spinal arteries form off branches of the vertebral arteries at the cervicomedullary junction and course inferiorly along the length of the spinal cord. The anterior spinal artery is relatively constant and runs in the middle of the ventral surface of the cord, sending deep penetrating branches into the anterior median sulcus. These branches then send arterial twigs radially to the deepest portions of the spinal cord.

The paired posterior spinal arteries are relatively inconstant, course along the posterolateral surface of the cord, medial to the dorsal root entry zones, and send short penetrating end arterioles into the dorsal cord parenchyma. Thus, the anterior spinal artery supplies the ventral two thirds of the cord, whereas the posterior spinal artery supplies the dorsal third.

The spinal arteries form the nexus of an arterial network that is replenished by the radicular arteries that enter the spinal canal through the spinal nerve root sleeves. The radicular supply to the spinal cord is highly variable, but a few vital feeding arteries are usually present. The most important of these is the artery of Adamkiewicz, which is usually found on the left side, from T9 to L2.

Contraindications

Absolute contraindications to surgical intervention include uncorrected coagulopathy and systemic infection.

Relative contraindications to surgical intervention include complete neurologic deficit over 24 hours and short life expectancy.

 

Workup

Imaging Studies

MRI produces exquisite detail of the spinal cord. Most tumors are isointense or slightly hypointense compared with the normal cord signal. Tumors generally exhibit some enhancement with gadolinium, and this enhancement may be homogeneous or irregular, as depicted in the images below. Contrast-enhanced MRI, shown in the images below, is very sensitive for tumors and may disclose minute lesions.

Plain radiographs of the spine cannot diagnose an intramedullary tumor but may be useful for surgical planning if the tumor is associated with a deformity.

Myelography has now been surpassed by MRI and is used mainly when MRI is not available.

Spinal angiography and embolization can be useful in cases of hemangioblastoma.

The first panel shows a cervical syrinx. The diffe The first panel shows a cervical syrinx. The differential diagnosis for syrinx includes trauma, Chiari malformation, and dysmerogenesis. A syrinx can also be the by product of a tumor, which may be distant anatomically from the associated syrinx. The second panel shows a small enhancing ependymoma of the thoracic spine that was found during the workup for the cervical syrinx.
This is a sagittal image of an enhancing conus med This is a sagittal image of an enhancing conus medullaris lesion in a 45-year-old man who presented with midline back pain. This hemangioblastoma was removed completely. The patient remains neurologically intact, and imaging of his neuroaxis did not reveal other lesions.
Axial image of hemangioblastoma. Axial image of hemangioblastoma.

Determining whether an abnormal MRI definitively indicates the presence of a tumor can be problematic. MRI alone does not guarantee an accurate diagnosis in every case, and the clinical history and neurologic examination help avoid unnecessary surgery on multiple sclerosis plaques or vascular or inflammatory myelitis. The spinal cord appears enlarged when a tumor is present, while inflammatory lesions result in a normal or minimal increase in cord size appearance. In cases where a syrinx is noted, as depicted in the first image above, one must distinguish a primary syrinx from a tumor-associated syrinx. Therefore, a search for a Chiari malformation or abnormal contrast enhancement must be undertaken.

Some tumors have a tendency to occur in multiple areas, and imaging the entire neuroaxis may be indicated (eg, hemangioblastoma).

The differential diagnosis of a patient presenting only with back pain is legion and most commonly is the result of degenerative spine disease. The contrast-enhanced MRI characteristics of the spinal cord have greatly simplified the diagnosis of intrinsic spinal cord tumors. However, diagnosis still can be problematic, as follows:

  • Syrinx - Multiple causes, including tumor

  • Multiple sclerosis - May show multiple lesions of neuraxis

  • Transverse myelitis

  • Cord infarction

  • Abscess

  • Tuberculosis

  • Hematoma

  • Herniated disk

  • Spondylosis

  • Cord contusion

  • Extradural neoplasm

  • Intradural extramedullary neoplasm

  • Arteriovenous malformation and fistulae

  • Arachnoid cyst

  • Sarcoidosis and other granulomatous diseases, as depicted in the images below

    This is a sagittal image of an enhancing cord lesi This is a sagittal image of an enhancing cord lesion in a 41-year-old man with a rapidly progressing severe quadriparesis. A biopsy showed this to be sarcoidosis. Following treatment with steroids, he is now ambulatory with assistance.
    Axial image. Axial image.

 

Histologic Findings

Ependymomas

Ependymoma is a common primary neoplasm of the spinal cord and filum terminale. It is the most common primary glial neoplasm of the spinal cord, constituting 50-60% of intramedullary cord neoplasms. They frequently present in middle age but can occur at any age. Ependymomas are believed to be slow-growing tumors. Because of their tendency to compress adjacent parenchyma, patients with spinal ependymomas usually experience gradual symptoms because of slow progression, making early diagnosis difficult.[12]

Ependymomas occur anywhere in the cord and are commonly in the conus medullaris, where an exophytic component may be present. They rarely change growth characteristics and metastasize.

Lesions are characteristically hypovascular, well circumscribed, and noninfiltrative of the surrounding cord. Sometimes they are associated with a cystic "capping” of the tumor poles. Symptoms are due to a chronic dilation of neural tissue rather than infiltration. Complete resection often results in cure.

The first panel shows a cervical syrinx. The diffe The first panel shows a cervical syrinx. The differential diagnosis for syrinx includes trauma, Chiari malformation, and dysmerogenesis. A syrinx can also be the by product of a tumor, which may be distant anatomically from the associated syrinx. The second panel shows a small enhancing ependymoma of the thoracic spine that was found during the workup for the cervical syrinx.

Astrocytoma

Astrocytoma accounts for 6-8% of all spinal cord tumors and is primarily low grade. It occurs in both adult and pediatric populations, with the most common presenting symptoms being back pain, sensory dysfunction, or motor dysfunction.[11, 5, 6]  In children, astrocytomas are the most common tumor type, accounting for around 60% of all intramedullary spinal tumors, and the mean age of presentation is 5-10 years. Sometimes they are associated with microcysts or syringes. The pilocytic varieties are well differentiated and tend to be indolent, with a definable surgical plane.

The remainder of low-grade astrocytomas are infiltrative and impossible to resect completely. Residual tumor often has an indolent course, and controversy exists in the management of such tumors.

Fortunately, anaplastic astrocytoma or glioblastoma is rare. These malignant tumors exhibit rapid growth, are locally invasive, and may seed the CSF. Distinguishing between tumor and normal cord is difficult. Aggressive surgical resection has a controversial role with such tumors.

Hemangioblastomas

Hemangioblastomas are benign, slow-growing, highly vascularized tumors of the central nervous system, with the most common location being the posterior fossa. Hemangioblastomas are often associated with von Hippel-Lindau disease.[13]  Hemangioblastomas often have an associated syrinx and occur in multiple locations. These should not be removed in a piecemeal fashion because significant bleeding may ensue, increasing the risk of the procedure. Removal of the lesion is considered curative.

Developmental tumors

Dermoid, epidermoid, and teratoma are slow-growing neoplasms with a thoracolumbar predominance. Some dermoids of the conus medullaris have been attributed to lumbar punctures that carry in cutaneous tissue.

These tumors may have a dense capsule, precluding complete removal, although this may be compatible with prolonged symptom-free survival. When complete removal is unobtainable, debris produced by the tumor may cause an early recurrence of symptoms.

Lipoma

Not true neoplasms, lipomas present in the first 3 decades of life when fat is being deposited. They may be associated with cutaneous abnormalities. Loss of total body fat may be necessary to reduce the mass of the tumor.

Fibrous adhesions to the cord make total removal difficult. Removal is not the goal of surgery. The carbon dioxide laser is particularly useful for this lesion.[17]

Other tumors

Unusual lesions include subependymoma, ganglioglioma and intramedullary schwannoma, and neurofibroma. Management of low-grade lesions parallels other indolent lesions. Metastatic lesions to the spinal cord are unusual. 

 

Treatment

Medical Therapy

Because most of the intramedullary spinal cord tumors are slow growing and locally contained, surgical extirpation, where possible, is the treatment of choice. In selected situations, watchful waiting can be considered. Steroids are used in the perioperative period or if a rapid decline in neurologic function occurs, but steroids are not considered tumoricidal.

Radiation therapy

The slow-growing nature of these neoplasms makes proving the benefit of radiation therapy difficult. Conclusions regarding the efficacy of radiation therapy as a primary therapy are not available for all tumor types. Series have shown poor control of local disease in ependymomas.

Data are available that suggest surgically excised ependymomas need not undergo subsequent radiation therapy. Evidence of this modality preventing recurrence or halting progression of low-grade astrocytomas is lacking. No lesion should undergo radiotherapy without a tissue diagnosis. This modality may be primary treatment for (1) inoperable tumors and (2) aggressive lesions such as anaplastic astrocytomas and glioblastomas.

Radiotherapy may be useful for (1) residual tumor after surgery and (2) recurrent tumor, but controversy exists. A dose of 50 Gy is delivered to the tumor in daily fractions of 1.5-2 Gy. This dose has not been shown to be curative in most studies. Some series report local failure rates are reduced when more than 50 Gy is administered.

Pitfalls include (1) acute and delayed myelopathy, (2) diminished skeletal growth in young children, and (3) increased difficulty with subsequent surgical tumor removal. This is particularly important if radiotherapy does not control the growth of the lesion.

Chemotherapy

Chemotherapy is considered experimental in the treatment of spinal cord tumors.

The management of spinal cord ependymomas in neurofibromatosis type 2 (NF2) has traditionally been conservative, in contrast to the management of sporadic cases. In a multi-center retrospective review comparing surgical management of NF2-associated spinal ependymomas with bevacizumab, the researchers concluded that while resection may prevent neurologic deterioration, bevacizumab may be beneficial for patients with significant tumor burden that is not amenable to resection.[18]

Intraoperative Details

Surgical positioning

The patient is positioned prone on bolsters or a Wilson frame, freeing the abdomen and thorax from pressure and taking care to pad all pressure points. For cervical and high thoracic lesions, the head is immobilized using a Mayfield head holder or equivalent.

Neurophysiologic monitoring

Intraoperative neurophysiologic monitoring is used by many surgeons to obtain feedback on the effects of positioning and manipulation of neural structures during surgery.[19, 20]  

In a meta-analysis by Rijs and Klimek regarding intraoperative neuromonitoring (IONM) for intramedullary spinal cord tumors, IONM had a high sensitivity and specificity, was found to prevent neurologic damage, but limited the extent of tumor resection.[20]

Anesthesia

General anesthesia is performed using total intravenous anesthesia (TIVA), which entails a combination of intravenous opioids and a continuous administration of propofol. Halogenated volatile anesthetics are avoided because these interfere with sensory evoked potentials (SSEP). Low levels of muscle relaxants are used to minimize spontaneous muscle activity but permit motor evoked potentials and detect elicited EMG activity. The spinal cord is sensitive to decreased perfusion, and an arterial line is needed to ensure that dips in blood pressure are detected and corrected as quickly as possible.

Approach

A standard dorsal midline approach is used. A midline incision and subperiosteal dissection of the paraspinal musculature expose the lamina and spinous processes. The level is confirmed by radiograph. A laminectomy or laminoplasty is performed exposing the dorsal dura. Meticulous hemostasis is obtained. The tumor may be visualized with ultrasound to confirm adequate exposure prior to opening the dura. A durotomy is made in the midline, and the dural edges are tacked to the soft tissues laterally, exposing the arachnoid overlying the swollen spinal cord.

Myelotomy

Using an operating microscope, the arachnoid is opened and tacked laterally to the dural edges. In most cases, the myelotomy is performed in the midline between the dorsal columns. The normal surface anatomy may be distorted by the tumor, and the midline may need to be approximated by visualizing a vertical line running equidistant from both dorsal root entry zones. The line is cauterized, and the pia is sharply incised. Traversing blood vessels are cauterized and divided. The dorsal columns are dissected apart. Occasionally, eccentric lesions may be approached through the dorsal root entry zone.

Tumor excision

If the tumor has an exophytic component, this is the initial area of approach. Otherwise, the tumor is encountered after the dorsal columns are split. Then, gradually, if a clear plane between cord and tumor is identifiable, the spinal cord parenchyma is dissected circumferentially off of the tumor capsule. Pial tacking sutures are useful to maintain exposure. Many tiny bridging vessels need to be cauterized and cut during this process.

Early on in the dissection, a specimen should be sent for frozen section. Eventually, the tumor poles are identified and the tumor is freed of all but its ventral attachments; then, gradually, the ventral portion of the tumor is liberated and disconnected from its major blood supply off of the anterior spinal artery. Although these tumors should optimally be removed en bloc, this is sometimes impossible in cases of very large tumors, tumors with poor internal integrity, and tumors with an unclear surgical plane. An ultrasonic aspirator is often useful either to debulk internally to facilitate capsule dissection or to perform an inside-out resection when no clear plane is identifiable.

(See the image below.)

View of a cervical intramedullary ependymoma in si View of a cervical intramedullary ependymoma in situ after midline myelotomy and initial dissection (top left). The tumor was removed en bloc (right), and the postsurgical cavity in the spinal cord is shown (bottom left).

Dural closure

After tumor resection and hemostasis, the dorsal columns are gently rotated back into position. A primary dural closure is achieved using a running stitch. In cases of subtotal resection, a dural patch may be used to expand the thecal sac. Various dural substitutes and sealants are available to aid closure. A Valsalva confirms a water-tight closure.

Soft tissues

Meticulous hemostasis is achieved. The muscles are loosely approximated with an absorbable stitch, such as a 0 Biosyn. A water-tight fascial closure is achieved with an interrupted absorbable stitch such as a 0 Vicryl. The subcutaneous tissues are closed with interrupted inverted 2.0 Vicryl. The skin is approximated with a running 3.0 Nylon.

Postoperative Details

A typical regimen of postoperative care for patients after surgery for intramedullary tumors entails the following:

  • A level body position for 24-48 hours

  • A 3-7 day steroid taper

  • Foley catheter until out of bed

  • Sequential compression device and subcutaneous heparin for deep venous thrombosis (DVT) prophylaxis until ambulatory

  • Incentive spirometry until ambulatory

  • Careful wound monitoring for cerebrospinal fluid (CSF) leak

  • Physical therapy, occupational therapy, and rehabilitation (virtually all patients will have some degree of sensory dysfunction resulting from dorsal column manipulation during surgery; Most patients benefit from a course of inpatient rehabilitation)

Follow-up

Patients are followed clinically and radiographically. The vast majority of patients will have some degree of new proprioceptive dysfunction that requires intensive physical therapy. Most patients will benefit from a course of in-patient rehabilitation.

Some clinicians obtain immediate postoperative imaging; others delay imaging for a period of months after surgery. Routine interval imaging is required for years, even after gross radiographic resection. If neurologic function worsens, immediate reimaging is of course warranted.

Residual tumor can be considered for repeat resection, radiation therapy, or observation. If tumor recurrence is noted, imaging the entire neuraxis is warranted to rule out distant seeding through CSF spaces.

Complications

The majority of patients have an increased sensory deficit after surgery. This may be due to edema from surgical manipulation or an alteration in blood flow. Most deficits greatly improve within 3-6 months, and patients develop compensating mechanisms with therapy. Complications are as follows:

  • Progressive or delayed neurologic deficit

  • Hematoma

  • CSF leak requiring wound revision, spinal drainage, and or reoperation

  • Wound infection

  • Sepsis

  • Infectious meningitis

  • Chemical meningitis, particularly from epidermoid and dermoid tumors

  • Deep venous thrombosis

  • Pulmonary embolism

  • Spinal instability

  • Arachnoiditis

  • Perforated gastric ulcer

Outcome and Prognosis

Prognosis regarding the likelihood of a surgical cure is dependent upon histology. Surgical series of ependymomas report recurrence rates of 0-9%, with anywhere from 2-10 years of follow-up. Factors associated with recurrence include histologic anaplasia and piece-meal resection. For hemangioblastomas, complete surgical resection of sporadic cases is usually curative. Patients with VHL are of course always at risk of developing new lesions and must have their entire neuroaxis imaged periodically.

Regarding astrocytoma, the literature is confused and often contradictory regarding the role of surgery, radiation, and prognosis in general. Undoubtedly, some of the differences in outcome stem from differences in patient populations, specifically pediatric cases versus adult ones. Clearly, the prognosis for astrocytoma is worse than for ependymoma because many astrocytomas are infiltrative and impossible to resect completely. For high-grade lesions such as anaplastic astrocytoma and glioblastoma, the prognosis is clearly poor, with aggressive surgical resection having a debatable role in prolonging survival.

Neurologic morbidity is associated with preoperative functional status. Individuals with mild-to-moderate deficits may improve following surgical removal, while those with advanced neurologic compromise generally have no worthwhile improvement. This emphasizes the need for early intervention and close follow-up.[21]  Advancing age (>60 y) is a negative prognostic factor.

Total removal of a benign tumor may result in long-term control or cure. Higher morbidity is associated with surgical removal of upper thoracic and conus lesions. Tumors spanning several levels may produce a corkscrew growth pattern that requires extensive dissection of the spinal cord in order to expose the tumor. Arachnoid scarring and cord atrophy are negative prognostic factors for ependymomas. The presence of a syrinx suggests a noninfiltrative lesion and carries a better prognosis.

Future and Controversies

Whereas the value of total excision of ependymomas is clear, the value of radical resection of astrocytomas is less certain. If an easily defined plane around the tumor can be followed and complete removal achieved, management is rather straightforward. However, if an ill-defined plane is present, the risk-to-benefit ratio for aggressive removal is unclear.

The role of radiotherapy in the management of slow-growing tumors is also controversial. Total excision of ependymomas does not warrant further treatment. This also may be true of many astrocytomas, particularly pilocytic astrocytomas. In cases of residual or recurrent tumor, clear clinical indications have not been established. Reoperation, radiation, and watchful waiting with serial examinations and imaging are all viable options.[22, 23]

Intraoperative electrophysiologic monitoring is thought to be useful, but its efficacy is unproven. Although MRI greatly facilitates diagnosis of these lesions, pressure to control health care costs may delay diagnostic testing of mildly symptomatic patients.

Currently, no satisfactory modality is available to affect the relentless course of malignant astrocytomas. Novel therapies need to be developed. Stereotaxic radiosurgery has found a place in the management of intracranial tumors. With anticipated future developments, spinal radiosurgery may have a role in management. Developmental tumors can be quite adherent to the spinal cord. Given the slow growth rates of these tumors, the role of radical surgery to remove all traces of the tumor is not advocated by most clinicians.

Fluorescence-guided resection of malignant cerebral gliomas utilizing 5-aminolevulinic acid (5-ALA) and protoporphyrin IX (PpIX) accumulation in tumors has become a well-established technique to facilitate greater extent of resection resulting in improved progression-free survival. The utility of 5-ALA-guided resection of spinal neoplasms has not been determined, but there is a growing body of literature describing its use.[10]

Development of neuroprotective agents for use during surgery warrants further study.

Management of these potentially debilitating and treacherous lesions has come a long way in the last 100 years. Advances in imaging and surgical technique have led to removal of many tumors, with high success and low morbidity. However, the relative rarity of the tumor, along with its slow growth characteristics, makes the accumulation of large patient series difficult.

Currently, in many situations, the clinician can only care for patients harboring intramedullary spinal cord tumors using an incomplete knowledge base regarding the optimal management.