Sporadic schwannomas and neurofibromas are tumors that arise from the nerve sheaths of cranial nerves, nerve roots, spinal nerves, and peripheral nerves. Most schwannomas originate from the eighth cranial nerve, whereas neurofibromas more commonly arise along the spinal nerve roots. Maximal surgical resection is the treatment of choice for many of these tumors, but radiation therapy can be appropriate in selected cases. Systemic therapies are still under investigation for therapeutic potential. In this update, the authors discuss the pathophysiology, clinical presentation, treatment, and outcomes of these conditions.
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• Schwannomas are benign (WHO grade I) slow-growing, extra-axial tumors that can arise from Schwann cells in any cranial nerve, spinal nerve root, or peripheral nerve. They can frequently arise from the eighth cranial nerve.
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• Neurofibromas are benign (WHO grade I) peripheral nerve sheath tumors that involve Schwann cells as well as nerve fibers, fibroblasts, and cutaneous tissue. They can occur in superficial (cutaneous, subcutaneous) and deep (visceral, spinal, orbital) locations.
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• When intervention is indicated, surgical resection is the treatment of choice for most schwannomas and neurofibromas. Complete resection can be curative.
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• In selected cases, stereotactic radiosurgery or fractionated radiotherapy may be effective for local control of tumor growth
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• There is currently no well-defined role for chemotherapy in sporadic schwannomas and neurofibromas.
Historical note and terminology
Cruveilhier is credited with the most complete initial description of both the clinical and pathologic features of a vestibular schwannoma (10). Sir Charles Balance performed the first successful surgical resection of a vestibular schwannoma in 1894. The neurosurgical community thereafter quickly developed interest for vestibular schwannoma surgery (95), and over the next 30 years, surgical techniques were refined to such a degree that operative mortality was reduced from 50% to 60% in the early 1900s to 4% by 1931 (50). Additional advances, such as the advent of antibiotics, anesthesia, and refinement in surgical techniques have further improved surgical morbidity and mortality.
Schwannomas and neurofibromas are benign (WHO grade I) tumors arising from peripheral nerve sheaths (49). Schwann cells are the neoplastic cells of origin in both schwannomas and neurofibromas, but the latter also contain intratumor nerve fibers and a large variety of additional cell types, such as fibroblasts, perineurial cells, and mast cells (85).