Nerve sheath tumor is an abnormal growth originating from the insulating layer surrounding the nerves. Nerve is a fiber that connects the body to the nervous system, i.e. brain and spinal cord carrying electrical impulses. Nerve sheath tumors can arise on any nerve of the body, be it, cranial nerves, spinal nerves or peripheral nerves (nerves found outside the brain or spinal cord). Nerve sheath tumors are mostly benign and tend to grow slowly. However, they need to be treated if they grow large enough to interfere with underlying nerve. Schwannomas and neurofibromas are the most common type of nerve sheath tumors.
Causes Of Nerve Sheath Tumor
The cause of nerve sheath tumor is unknown. However, some are linked to inherited syndromes, such as neurofibromatosis (type 1 and type 2) and schwannomatosis. Some of the nerve sheath tumors are also related to past exposure to radiation therapy.
What Are The Symptoms Of A Nerve Sheath Tumor?
Nerve sheath tumors are quite rare and malignant forms of these tumors are rarer. Some forms of nerve sheath tumors include schwannoma, neurofibroma, desmoid tumors, acoustic neuroma, benign peripheral nerve tumors and malignant peripheral nerve sheath tumors.
In most cases, the nerve sheath tumors present being asymptomatic to having minimal symptoms, until they press on surrounding nerve, blood vessel or tissues or from direct effect on the main nerve. Symptoms when noticeable will present as a palpable or visible mass with or without pain along with nerve palsy. Although, these symptoms are more common in malignant tumors, they can also be found in benign tumors. Rapid enlargement of nerve mass along with neurologic deficits predict toward malignant propensity of the nerve sheath tumor. Pain at rest is more common in malignant nerve sheath tumor as compared to benign tumor such as schwannoma or neurofibroma.
Hearing deficit, ringing in ears and loss of balance is commonly seen in acoustic neuroma.
The part of the body involved depends on the type of nerve affected, be it cranial nerve, spinal nerve or peripheral nerve. Depending on the above nerves involved, face, head, neck, back, legs, arms or any other part of the body may be affected by the tumor.
Diagnosis Of Nerve Sheath Tumor
The diagnosis of nerve sheath tumor starts with the past medical history, evaluation of signs and symptoms along with physical and neurological evaluation. Sometimes, the physician may need imaging tests and other tests to identify the cause of signs and symptoms, also the type of tumor (malignant vs benign) and its location and spread.
These extensive tests include MRI and CT scan for a detailed view of nerves and its surrounding tissues, electromyogram and nerve conduction study to record electrical activity in the muscles and tumor and nerve biopsy to determine the cause, type and confirmation of nerve sheath tumor.
Treatment Of Nerve Sheath Tumor
The treatment of nerve sheath tumor depends on the type of tumor; nerves and tissues affected, spread of tumor and associated symptoms. If the tumor is benign and small, monitoring suffices without the need of any surgery.
Surgery is needed when the nerve sheath tumor is malignant, large or associated with non-manageable symptoms. The goal of surgery is to remove the entire nerve sheath tumor keeping intact the nearby nerves the tissues. In some cases, radiation therapy and chemotherapy are needed along with or post surgery to prevent recurrence of tumor, especially if it is a malignant nerve sheath tumor. High dose radiation therapy may be needed in cases where the tumor is non-resectable, due to its proximity to vital nerves or tissues.
The prognosis of the tumors depends largely on early diagnosis and treatment of the nerve sheath tumor. Benign nerve sheath tumors carry better prognosis as compared to the malignant tumors, which in general have poorer prognosis with more associated complications such as limb amputation or loss of function/mobility or paralysis of the affected body part.