Spinal tumors are classified as extradural, intradural and extramedullary, or intradural intramedullary based upon their anatomic location. Nerve sheath tumors (NSTs) constitute about 25 percent of tumors arising in the intradural extramedullary space [1,2].
Although the majority of NSTs are confined to the intradural extramedullary space, some of these tumors extend into either the extradural compartment or the spinal cord. In addition, occasional spinal NSTs are confined to either the extradural or intramedullary spaces .
NSTs are derived from the Schwann cells and perineurial cells of the peripheral nervous system. Approximately 65 percent of intradural nerve sheath tumors are schwannomas, and most of the remainder are neurofibromas . Malignant NSTs are rare, constituting about 5 percent of such tumors.
The clinical presentation, diagnosis, and treatment of NSTs will be reviewed here. Peripheral extradural nerve sheath tumors, intramedullary spinal tumors, and meningiomas of the spinal cord are discussed separately. (See "Spinal cord tumors", section on 'Intramedullary tumors' and "Spinal cord tumors", section on 'Meningioma' and "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma", section on 'Introduction'.)
EPIDEMIOLOGY AND ETIOLOGY
Intradural, extramedullary nerve sheath tumors (NSTs) may be either sporadic or associated with an inherited disorder. Sporadic NSTs are most common in the fifth to seventh decades and have a similar incidence in men and women . In addition, spinal NSTs are a manifestation of neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis: