Intramedullary Spinal Cord Tumors Treatment & Management

Because most of these 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 this treatment 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 reduce 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

This is considered experimental in the treatment of spinal cord tumors. A number of protocols are undergoing examination, primarily with childhood astrocytomas.

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.^[4]

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 exposes 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.

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.

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 rehab (Virtually all patients will have some degree of sensory dysfunction that is a result of dorsal column manipulation during surgery. Most patients benefit from a course of inpatient rehab.)

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 neurological function worsens, immediate re-imaging 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.

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

Histology

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 histological 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 outcomes stems 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.

Severity of preoperative neurologic deficit

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.^[5]

Age

Advancing age (>60 y) is a negative prognostic factor.

Completeness of resection

Total removal of a benign tumor may result in long-term control or cure.

Location of lesion

Higher morbidity is associated with surgical removal of upper thoracic and conus lesions.

Size of lesion

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

These are negative prognostic factors for ependymomas.

Syrinx

The presence of a syrinx suggests a noninfiltrative lesion and carries a better prognosis.

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 slowly 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.^{[6, 7]}

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.

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.

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