Nerve sheath tumors are a class of tumors of nerve and surrounding structures. To understand these tumors, it is first important to understand nerve anatomy. A normal nerve consists of a central axon, surrounded by Schwann cells. Endoneurium is formed by the connective tissue of the axons, which comprises of Schwann cells, fibroblasts, mast cells, capillaries and collagen. Perineurium surrounds groups of these axons along with Schwann cells termed as fascicle. This group of fascicles is surrounded by epineurium.
What Is The Surgery For Nerve Sheath Tumor?
Almost all symptomatic nerve sheath tumors should be excised, either as a part of diagnosis or treatment of the tumor. The surgery needs to be performed by an experienced and expert neurosurgeon, as most of these tumors form within the nerve itself and are surrounded and intertwined with functional nerve fibers that should be preserved during tumor removal.
In most cases, nerve sheath tumor can be removed without any paralysis of the involved nerve. Removing a schwannoma poses less complication of paralysis, while removing a neurofibroma is more complex. The surgery to remove plexiform neurofibromas or a malignant nerve sheath tumor poses significant challenge for a neurosurgeon as these nerve sheath tumors are thick, tortuous and can entwine supportive structures. This can be visualized in a magnetic resonance imaging. These tumors often require the removal of the involved nerve, where nerve transfer or grafting plays a significant role for function restoration post-surgery.
The proper treatment of a nerve sheath tumor is the complete surgical removal of the tumor. The surgical approaches depend on the site and size of the nerve sheath tumor that allows optimal view of the surgical site with minimal dissection. Newer techniques, advances and instruments allow neurosurgeons to reach tumor sites that once could not be accessed. Microsurgery is a surgical advancement using high-powered microscopes, which make it easier to distinguish between a tumor and a non-tumor tissue. It also facilitates the monitoring of the nerve function during the surgical process, which is vital in the preservation of healthy tissue.
Stereotactic radiosurgery can be recommended for peripheral nerve tumors or tumors that are in or surround the brain. SRS uses high-power energy directed at a small area for destroying the tumor without the need of any incision. The complications of stereotactic radiosurgery include weakness and/or numbness of the area treated and on occasion failure of treatment, i.e., continued growth of nerve sheath tumor.
Radiation therapy and chemotherapy are used as an adjunct to surgery as on occasions the complete removal of the tumor is not possible with surgery without compromising the surrounding healthy tissues and damaging the nerve. In such cases, radiation therapy and/or chemotherapy may be used to limit the nerve sheath tumor growth.
Post-surgery, the nerve sheath tumor patient may need physical rehabilitation. The patient might need a brace or a splint to keep the extremities in position during the healing time. Physical therapy might also be needed for the recovery of function and the lost mobility due to damage to nerve or amputation of limb.
Clinical Presentation Of Nerve Sheath Tumors
Nerve sheath tumors are mostly benign (non-cancerous) and do not metastasize to other parts of the body. These are slow growing that form within the substance of the nerve and lead to gradual nerve expansion. This may lead to soft tissue mass or growth in the area of the involved nerve along with pain, and neurologic symptoms, including numbness, weakness, paresthesias and in worse case scenarios paralysis or loss of function of the affected part of the involved nerve.
Neurofibromas are tumors arising from within the nerve or axon, therefore, to excise this type of tumor, the nerve must be excised too. Schwannomas are tumors that arise from Schwann cells that surround the axon; hence, the tumor can be excised without damaging the involved nerve. Generally, nerve sheath tumors are benign tumors and neurofibromas and schwannomas are the commonest type of benign tumors. On rare occasions, these tumors may be malignant known as malignant peripheral nerve sheath tumors (MPNSTs), which include the malignant schwannoma, neurofibrosarcoma and neurogenic sarcoma.
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