Think of your body as a busy city powered by a vast wiring network. Your nerves act like electrical cables. They send messages back and forth between your brain and every part of your body. These vital nerve cells and their clusters need protection. They also need help sending electrical signals very quickly.
To keep them safe, special protective sleeves wrap around these nerve fibers. You can picture this like the plastic insulation covering an electrical wire. Sometimes, growths can form inside or around these protective outer covers. Doctors call these growths nerve sheath tumors.
Let us take a close, easy-to-understand look at what nerve sheath tumors are. We will explore their types, causes, symptoms, and how doctors diagnose and treat them.
Key Takeaways.
- Nerve sheath tumors grow in the protective layers or covers that surround your nerves.
- Most of these tumors are benign, meaning they are non-cancerous and rarely spread.
- Common types include schwannomas and neurofibromas, each with distinct features.
- Symptoms often include lumps under the skin, numbness, tingling, or localized pain.
- Doctors use imaging scans like MRIs and sometimes biopsies to make an accurate diagnosis.
What Are Nerve Sheath Tumors?
Simply put, nerve sheath tumors develop in the protective covers that surround your nerves. These protective layers consist of several distinct parts and structures:
- Schwann cells: These cells wrap around the long part of a nerve cell called the axon. They act just like electrical insulation around a wire.
- Endoneurium: This is the connective tissue wrapped around each person nerve fiber. It resembles the thin sheath around a single copper wire inside a larger cable.
- Perineurium: This tissue layer wraps around bundles of nerve fibers together.
Our nervous system splits into two main parts:
- Central nervous system: This includes your brain and your spinal cord.
- Peripheral nervous system: This is the branching network of nerves that travels from your brain and spinal cord out to every other part of your body.
Most nerve sheath tumors develop within this peripheral nervous system.
What Are the Types of These Tumors?
There are several main types of nerve sheath tumors. Let us look at what makes each type unique.
Schwannomas.
These tumors form in the Schwann cells mentioned earlier. About 60 percent of all schwannomas develop on the vestibular nerve located inside your inner ear. This specific nerve helps control your body balance. Other schwannomas can grow right under your skin or deep inside body tissues and organs. Common locations include:
- Your arms and your legs.
- Your head and neck.
- Your torso, which is the area between your shoulders and hips.
Schwannomas usually stay enclosed inside a thin tissue layer, acting like an encapsulated capsule. Doctors classify these growths as non-cancerous, benign tumors in the vast majority of cases. However, in very rare instances, a tumor that stays for a long time can become cancerous.
Neurofibromas.
When a neurofibroma develops, it involves multiple tissue types within the nerve sheath. These include Schwann cells, the endoneurium, and the perineurium. They commonly appear as bumps right under your skin. Sometimes, they can also grow deep inside your nerves within your body.
Unlike schwannomas, neurofibromas do not have a protective capsule around them. Instead, they grow right in between and through nerve bundles. A specific type called plexiform neurofibromas can spread like a web, wrapping around multiple nerve bundles and growing into nearby tissues.
Most neurofibromas are also non-cancerous. However, about 5 percent to 10 percent of them can turn into cancerous tumors. Doctors call these malignant peripheral nerve sheath tumors. About half of the people diagnosed with these aggressive tumors already have cancer that has spread to other parts of the body.
How Common Are These Tumors?
Non-cancerous nerve sheath tumors are relatively rare overall.
- Schwannomas most commonly appear in adults between 50 and 60 years old.
- Neurofibromas often develop in younger adults between 20 and 40 years old.
- Plexiform neurofibromas usually start growing before a child turns 5 years old.
Malignant peripheral nerve sheath tumors are extremely rare. They affect only about 1 person out of every 10 million people each year.
Why Do These Tumors Develop? What Are the Causes?
Genetic changes play a major role in the formation of nerve sheath tumors.
- Changes in the NF2 gene are closely linked to schwannomas.
- Changes in the NF1 gene are linked to neurofibromas.
Most of the time, these genetic changes happen randomly for no clear reason. Doctors call this sporadic occurrence. However, a small percentage of schwannomas and neurofibromas happen because of rare genetic conditions passed down through families, known as neurofibromatosis.
Neurofibromatosis Types.
There are three main types of this genetic condition:
- Neurofibromatosis type 1 (NF1): People with NF1 develop many neurofibroma tumors. They also face a higher risk of developing plexiform neuromas and malignant peripheral nerve sheath tumors. Other conditions seen in people with NF1 include a larger head size called macrocephaly, a curved spine called scoliosis, and learning disabilities.
- Neurofibromatosis type 2 (NF2): Almost everyone with NF2 develops vestibular schwannomas on both ears before turning 30 years old. They can also develop other schwannomas and tumors on their skin, eyes, and central nervous system.
- Schwannomatosis: In this condition, a person develops multiple schwannomas throughout the body, but does not have vestibular tumors on both ears.
What Are the Symptoms of These Tumors?
Many people who have a nerve sheath tumor experience no pain or other symptoms at all. However, if the tumor grows large or starts pressing on a nerve, you might notice symptoms such as:
- A lump or growth underneath your skin that might feel sore when pressed.
- Muscle weakness in the affected area.
- Numbness or a loss of normal feeling.
- Aching, burning, or sharp pain.
- A tingling sensation that feels like mild electricity.
Specific symptoms can also depend on where the tumor is located. Here are a few examples:
- Tumor on the sciatic nerve: Pain traveling from your lower back down your leg, known as sciatica.
- Tumor in your wrist: Symptoms similar to carpal tunnel syndrome.
- Tumor on the vestibular nerve: Hearing loss, ringing in your ears known as tinnitus, and balance problems.
Usually, a person with a nerve sheath tumor has just a single growth. However, people with neurofibromatosis often develop multiple growths, often beneath the skin.
How Do Doctors Diagnose These Tumors?
Your doctor will start by performing a physical exam and reviewing your overall health. This includes discussing your medical history, your family medical history, and any symptoms you are having.
If you have a visible lump or if your doctor suspects a hidden tumor, they may recommend further tests:
- Medical imaging: Scans like magnetic resonance imaging, known as an MRI, ultrasound, or PET scans help doctors view the tumor clearly.
- Biopsy: A doctor takes a tiny tissue sample from the tumor and examines it under a microscope to identify the type of cells. This test is the only way to know for sure if a tumor is cancerous.
If you have multiple tumors, your doctor may recommend genetic testing to check for conditions like NF1, NF2, or schwannomatosis.
What Are the Treatment Options?
If a nerve sheath tumor does not cause any symptoms, your doctor may suggest a watch and wait approach. This means your care team will monitor you closely with regular checkups to see if the tumor grows or changes.
For tumors causing bothersome symptoms, or if you want the tumor removed for cosmetic reasons, surgery is usually the main option.
Some neurofibromas, especially plexiform neurofibromas, grow directly into nerves and between tissue layers. This makes removing them completely quite difficult. If surgery cannot remove the entire tumor, your doctor will monitor you closely because the tumor can grow back.
Treatment for Schwannomas in the Head.
Schwannomas in the head, such as vestibular schwannomas, often involve nerves that control vital body functions. In these cases, doctors often use stereotactic radiosurgery, such as Gamma Knife therapy, to protect nearby nerves from damage.
This treatment does not involve a traditional surgical cut. Instead, it delivers a precise beam of radiation through your skin to shrink or destroy the tumor safely.
Treatment for Cancerous Nerve Sheath Tumors.
Doctors treat malignant peripheral nerve sheath tumors using surgery combined with cancer treatments like radiation therapy and chemotherapy.
What Are the Possible Complications of Surgery?
Like any surgery, operations to remove nerve sheath tumors carry common risks:
- Bleeding at the surgical site.
- Wound infection.
- Post-operative pain.
- Scar tissue formation.
In addition, because these procedures involve nerves, there is a risk of nerve damage and permanent disability. Your medical team will help you manage any long-term effects after surgery. Rehabilitation therapies like physical therapy, occupational therapy, and speech therapy can help you regain strength and function.
Can These Tumors Be Prevented?
There is no known way to prevent nerve sheath tumors from forming. However, a doctor may recommend genetic counseling and testing if:
- You have a family history of nerve sheath tumors.
- You have developed multiple nerve sheath tumors, which can be a sign of neurofibromatosis.
What Is the Long-Term Outlook?
Most nerve sheath tumors are non-cancerous. Surgery can cure them successfully, and they rarely return. However, if a tumor cannot be removed completely during surgery, you will need ongoing medical checkups.
About 3 out of 4 people who receive treatment for vestibular schwannomas are able to preserve their hearing.
The risk of a nerve sheath tumor turning into cancer is very low. The highest risk occurs in people with the NF1 condition who develop plexiform neurofibromas. Malignant peripheral nerve sheath tumors have a more serious outlook, especially if the tumor is larger than 2 inches. Fewer than half of people with this diagnosis live for five years after finding out they have it.
When Should You See a Doctor?
If you notice a lump under your skin, or if you experience any symptoms that might point to a nerve sheath tumor, schedule an appointment with your doctor right away. Also, be sure to mention it to your doctor if anyone in your family has a history of these tumors.
When to Seek Emergency Help.
Call 911 (US/Canada) or 999 (UK), or go to your nearest Emergency Department right away if you experience sudden, severe neurological symptoms such as sudden paralysis, loss of bladder control, sudden severe balance loss, or rapidly worsening weakness and numbness.
💡 Take-Home Message.
Remember that nerve sheath tumors are usually non-cancerous and grow very slowly. If you have no symptoms, your doctor may decide to simply monitor the condition. If you need surgery to remove a tumor, operations are generally very successful. Complications like nerve damage or cancerous transformation happen rarely. Your doctor will help you create a personalized treatment and follow-up plan to manage your health safely. Do not worry; speak openly with your doctor about any questions you have.
Quick Comparison of Nerve Sheath Tumor Types.
| Tumor Type. | Main Characteristics. / Typical Location. / Cancer Risk. |
|---|---|
| Schwannomas. | Main Characteristics.: Enclosed in a capsule, grows from Schwann cells. Typical Location.: Vestibular nerve, arms, legs, head, and neck. Cancer Risk.: Very low (rarely becomes cancerous). |
| Neurofibromas. | Main Characteristics.: Not encapsulated, weaves through nerve bundles. Typical Location.: Under the skin or deep within nerve tissues. Cancer Risk.: Low to moderate (5% to 10% risk). |
| Malignant Tumors. | Main Characteristics.: Aggressive cancerous growths requiring combined care. Typical Location.: Any peripheral nerve, often linked with NF1. Cancer Risk.: High (malignant cancer). |
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