The tumors that begin to develop in the tissues that surround and support nerve cells are called nerve sheath tumors. While most of them are benign (noncancerous), in rare cases, some of them can become malignant (cancerous). Usually, noncancerous tumors are removed with surgery, and they do not return after treatment. Neurofibromas, schwannomas, and malignant peripheral nerve sheath tumors are the most common types of cancerous tumors.
In general, these abnormal growths occur rarely and appear in the surrounding tissues of the nerves. Normally, nerves send and receive electrical signals between the brain and the rest of the body. These nerves have connective tissues and protective membranes called the myelin sheath. Most types of nerve sheath tumors develop in the peripheral nervous system (PNS). This nerve system includes all nerves except those of the spinal cord and brain.
Types of Nerve Sheath Tumors
Check below for the most common types of nerve sheath tumors:
- Schwannoma – Approximately 60% of all nerve sheath tumors are schwannomas. They usually affect the inner ear nerve, but they may also develop under the skin or in organs. In most cases, schwannomas cause just one tumor that is not cancerous.
- Neurofibromas – This type of nerve sheath tumor accounts for about 10% of all cases. While most of them are benign, they may turn into cancerous ones (such as plexiform neurofibroma).
- Malignant peripheral nerve sheath tumors – This is a cancerous form of nerve sheath tumors, and it may occur on its own or when a neurofibroma turns cancerous.
However, there are other types of nerve sheath tumors that occur less commonly. For example:
- Granular cell tumor
- Hybrid nerve sheath tumor
- Perineuroma
- Nerve sheath myxoma
- Solitary circumscribed neuroma
Symptoms
Usually, these tumors do not cause pain or other symptoms, especially in mild forms. However, if it becomes large enough, it may cause the following symptoms. Check some examples below:
- Muscle weakness
- Numbness
- Difficulty coordinating the muscles
- A painless lump under the skin
- Pins and needles
- Pain that is burning, aching, or sharp
Sometimes, these tumors may cause additional symptoms when they put pressure on major nerves. For example:
- Facial nerve – Difficulty smiling, chewing, or facial paralysis
- Sciatic nerve – Low back pain that may spread to the leg (sciatica)
- Vestibulocochlear nerve – In such cases, people may experience tinnitus (ringing in the ears), hearing loss (deafness), and problems with balance.
Immediately contact your healthcare provider if any of the previous symptoms occur because they can indicate nerve sheath tumors.
Causes and Prevention
Usually, genetic mutations (changes) cause nerve sheath tumors. Normally, genes contain DNA that holds instructions that tell cells when to grow, multiply, and die. When a DNA mutation occurs, cells receive different instructions that cause them to grow and multiply in a different way. As a result, these cells begin to multiply abnormally and, over time, can form a mass called a tumor. Without treatment, this tumor may break and spread to other parts of the body. In such cases, the condition is called metastatic cancer.
In most cases, these genetic changes often occur randomly, and experts do not fully understand what exactly causes them. In rare cases, people develop nerve sheath tumors due to a hereditary condition called neurofibromatosis (NF). Other types of these tumors may run in families. However, more than 50% of people with nerve sheath tumors do not have a family history of the disease.
Unfortunately, there is no way to reduce the risk or prevent nerve sheath tumors. The only thing you can do is a genetic test to make sure you do not have the following abnormal genes, because they may cause nerve sheath tumors. For example, NF1, NF2, SMARC-B, and LZTR). You may need additional tests if doctors suspect neurofibromatosis.
Diagnosis
Healthcare professionals usually perform a neurological and physical examination to check for irregularities linked to the disease (such as a lump under the skin). Check below some tests often used to confirm or exclude nerve sheath tumors:
- Imaging tests – These tests are done to get detailed images of different structures and organs in the body. In this case, they help identify the exact location and size of the tumor. Doctors commonly perform an MRI (magnetic resonance imaging) scan, a PET (positron emission tomography) scan, or an ultrasound.
- Nerve conduction studies and electromyography
- Hearing tests
- Genetic tests – To perform a genetic test, doctors will take a sample of blood. It helps determine whether you have gene mutations that may cause these tumors.
- Biopsy – During this procedure, doctors will remove a small sample of the tumor for testing. They will check for cancerous cells.
Treatment
The treatment for nerve sheath tumors often requires a team of healthcare professionals from neurosurgery, neuro-oncology, radiation oncology, plastic surgery, neurology, and orthopedic oncology. In some cases, doctors may choose to wait on treatment, especially if you have a benign tumor, but regular checkups are recommended to monitor it.
In moderate or severe cases, when the tumor causes symptoms, doctors will recommend surgery to remove it. Some people may get a prescription for stereotactic surgery. This procedure does not involve incisions (cuts), but radiation that is delivered directly to the tumor to shrink and destroy it. It is usually recommended by doctors when the tumor is near nerves with vital functions.
Furthermore, in the U.S., the FDA (Food and Drug Administration) has approved some targeted therapies for people with neurofibromatosis or schwannomatosis. This therapy involves specific medicines that target some proteins in the cancerous cells, causing them to die. In addition, cancer treatments may also include chemotherapy.
Frequently Asked Questions
When should I see my healthcare provider?
You should visit a doctor if you experience symptoms or have signs of nerve damage and disability. In general, nerve sheath tumor recovery occurs with different types of therapy (including physical, speech, and occupational).
What is the survival rate for a nerve sheath tumor?
While most nerve sheath tumors do not affect life expectancy, the 5-year survival rate for people with malignant peripheral nerve sheath tumors ranges from 23% to 69%. For more details, discuss it with your physician.
What are the symptoms of a schwannoma tumor?
Usually, people who develop this type of nerve sheath tumor experience the following symptoms. These include, problems with hearing and balance, pain, weakness, and tiredness. If any of the previous symptoms occur without an obvious reason, do not hesitate to see a doctor. If you have additional questions, ask your healthcare provider.
