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Intramedullary Spinal Cord Tumors

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.

The most commonly encountered intramedullary spinal tumors are ependymomasastrocytomas, and hemangioblastomas. Collectively, spinal ependymomas and astrocytomas account for 80-90% of  intramedullary spinal tumors, with ependymomas occurring roughly twice as frequently as astrocytomas.
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).

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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.

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.

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