Surgical Management of Intradural Extramedullary Tumors

Introduction

Tumors arising from the intradural extramedullary (IDEM) spinal canal reflect a wide variety of histopathologies. With few exceptions, however, these tumors are histologically benign and amenable to complete surgical resection. Long-term tumor control or cure with preservation or improvement in neurologic function can be achieved with surgery alone for most patients. This chapter focuses on direct surgical techniques and strategies for these largely benign tumors.

Histology

IDEM tumors arise outside the spinal cord and inside its dural coverings. They may originate from tissues within that anatomic space, such as dorsal or ventral nerve roots (neurofibromas, schwannomas), dura (meningiomas), blood vessels (hemangioblastomas), filum terminale (myxopapillary ependymoma, paraganglioma), and ectopic inclusion tumors from disordered embryogenesis (dermoids, epidermoids, lipomas, teratomas). Secondary metastatic involvement usually occurs as a drop metastasis from the intracranial space.

In adults, the vast majority of IDEM tumors are nerve sheath tumors, meningiomas, or ependymomas of the filum terminale. Most are solitary and sporadic in occurrence. Multiple tumors are rare except in patients with syndromes such as neurofibromatosis or von Hippel-Lindau syndrome, although primary benign myxopapillary ependymomas may occasionally disseminate through the subarachnoid space.

Indications

Presence of symptoms constitutes the main indication for surgery. Depending on tumor location and biology, symptoms are variable and may range from back and radicular pain to neurologic deficits such as weakness, sensory changes, or bowel/bladder dysfunction. Asymptomatic tumors present a management dilemma owing to their biologically indolent behavior. They may be managed with serial imaging and, in case of radiographic progression, with the consideration of surgical intervention.

One potential exception is the patient with a midline tumor of the cauda equina, since benign myxopapillary ependymomas can exhibit cerebrospinal fluid (CSF) dissemination. Early surgery to avoid this complication should be reasonably considered. Prophylactic surgery is rarely recommended in syndromic patients with multiple lesions.