Spinal ependymomas arise from ependymal lining of the central canal of the spinal cord. The myxopapillary type originates from clusters of ependymal cells in the filum terminale. The myxopapillary ependymoma that originates in the filum terminale causes a special syndrome referable to both lumbar roots (cauda equina) and conus. As commented in Chap. 30, a combination of asymmetric or bilateral sciatic or anterior thigh pain, sphincter difficulty, and upper motor neuron signs is typical. These spinal tumors occur in adults as often as in children, quite different from intracranial ependymomas, which are mainly childhood tumors. Although they are considered to be benign, intraspinal spread can occur and local recurrence after resection occurs in 10 percent of cases, even decades after surgery as described by Rezai and colleagues. Treatment is with surgical removal and selective radiation if there has not been gross total removal and long-term survival is the rule. The main differential diagnosis is a spinal schwannoma (neurofibroma).
Intramedullary growths invade as well as compress and distort fasciculi in the spinal cord white matter. As the cord enlarges from the tumor growing within it or is compressed by a tumor from without, the free space around the cord is eventually consumed, and the CSF below the lesion becomes isolated or loculated from the remainder of the circulating fluid above the lesion. This is marked by Froin syndrome (xanthochromia and clotting of CSF from greatly elevated protein content) and an interruption of flow of contrast medium in the subarachnoid space. The most informative diagnostic procedure is an MRI, which demonstrates both the intramedullary extent of the tumor and the effect on the surrounding subarachnoid space.
Secondary spinal cord tumors can also be subdivided into intramedullary and extramedullary types. Extradural metastases (carcinoma, lymphoma, myeloma) are the most common of all spinal tumors as summarized by Ropper and Ropper. They account for the largest group of patients who develop symptoms of myelopathy while being cared for in hospital and are therefore likely to be encountered in the course of neurologic consultations. Extradural metastases arise from hematogenous deposits or extend from tumors of the vertebral bodies or from a paraspinal tumor extending via the intervertebral foramina (Fig. 42-12). Secondary extramedullary tumor growths are far more often extradural than intradural. The intradural type takes the form of a meningeal carcinomatosis or lymphomatosis and the rare primary melanoma of the meninges, which are considered in Chap. 30.
Intramedullary metastases are not as rare as is generally believed. In a retrospective autopsy study of 627 patients with systemic cancer, Costigan and Winkelman found 153 cases with central nervous system (CNS) metastases, in 13 of which the metastases were located within the cord. In 9 of the 13 cases, the metastasis was deep in the cord, unassociated with leptomeningeal carcinomatosis; in 4 cases, the neoplasm seemed to extend from the pia. Bronchogenic carcinoma was the main source. Diagnosis is difficult but is aided greatly by MRI with gadolinium infusion; there is generally extensive contiguous edema (Fig. 42-13). Differentiation is from meningeal carcinomatosis, radiation myelopathy, and paraneoplastic necrotizing myelopathy, which is the least common of these entities. Treatment is usually ineffective unless radiation therapy is begun before paraplegia supervenes (Winkelman et al).
Patients with spinal cord tumors are likely to present with one of three clinical syndromes: (1) a sensorimotor spinal tract syndrome, (2) a painful radicular-spinal cord syndrome, or (3) least often, an intramedullary syringomyelic syndrome. The sensory features of these syndromes are depicted in Fig. 8-7.