A nerve sheath tumor is a type of tumor of the nervous system (nervous system neoplasm) which is made up primarily of the myelin surrounding nerves. Nerve sheath tumors can be benign or malignant, and may affect both the peripheral and central nervous systems. There are three main types of nerve sheath tumors: schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors.[1]
| Nerve sheath tumors | |
|---|---|
 | |
| Illustration of typical Schwannoma (a.) and Neurofibroma (b.) configurations around nerves. | |
| Specialty | Neuro-oncology |
Classification of nerve sheath tumors
Spinal nerve sheath tumors
Spinal nerve sheath tumors are typically intradural, meaning that they arise inside the dura mater surrounding the spinal cord (thecal sac), but may also be found in other areas of the spine.[2] Spinal nerve sheath tumors generally arise as single lesions.[1] Presence of multiple lesions is associated with genetic conditions including neurofibromatosis type 1, neurofibromatosis type 2, and Schwannomatosis.[1][3][4]
Most spinal schwannomas are intradural-extramedullary, growing inside the thecal sac, but outside the spinal cord itself.[5] Intradural-intramedullary schwannomas have also been reported, but are rare.[5]
Peripheral nerve sheath tumors
A peripheral nerve sheath tumor is a nerve sheath tumor in the peripheral nervous system. Benign peripheral nerve sheath tumors include schwannomas and neurofibromas. A malignant peripheral nerve sheath tumor is a cancerous peripheral nerve sheath tumor, which are frequently resistant to conventional treatments.
Symptoms
Spinal nerve sheath tumors may lead to a variety of symptoms depending on tumor type and severity[1].
Causes
Mechanism
The primary Schwann cell differentiation and neoplastic proliferations are characteristics of peripheral nerve sheath tumors. For instance, the Schwann cell, which is the major neoplastic cell component of neurofibroma,[6] is cytologically distinguished by the expression of S-100 protein and wavy nuclear outlines.[7][8] A variety of peripheral nerve cells, including axons, perineurial cells, fibroblasts, and varying inflammatory components such as mast cells and lymphocytes, are also present in neurofibromas. A population of CD34-positive cells with an unknown histogenesis is also found.[9][10]
Diagnosis
Magnetic resonance imaging (MRI) is typically used in spinal nerve sheath tumor diagnosis.[1] Each nerve sheath tumor type has a few different associated features on MRI imaging, though neurofibromas and malignant peripheral nerve sheath tumors can be difficult to distinguish from each other and may require additional testing, including PET scans (18FDG-PET).[1] Biopsies may be performed to further characterize any tumors found.
Management
Treatment of spinal nerve sheath tumors typically depends on presence and severity of symptoms.[1] For asymptomatic or incidental tumors, only continued imaging is typically indicated to assess whether tumor growth is occurring.[1] Surgical resection may be an option for tumors causing extensive radicular pain or other symptoms, and for tumors exhibiting aggressive behavior.[1]
Outcomes
Epidemiology
References
External links
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