Schwannoma

Overview

What is a schwannoma?

A schwannoma is a tumor that develops from the Schwann cells in your peripheral nervous system or nerve roots. Schwannomas are almost always benign (noncancerous) but can sometimes be malignant (cancerous). They’re usually slow-growing.

Schwann cells assist the conduction of nerve impulses. They wrap around peripheral nerves and provide protection and support. Your peripheral nervous system includes nerves that travel from your spinal cord and brain to carry signals to and from the rest of your body.

A common area for schwannomas is in the nerve that connects your brain to your inner ear (vestibular schwannoma). Cancerous schwannomas most frequently affect the sciatic nerve of your leg, the brachial plexus nerves in your arm and the group of nerves in your lower back called the sacral plexus.

Schwannomas are sometimes called neurilemmomas or neuromas. If a schwannoma is malignant, it may be referred to as a soft tissue sarcoma.

Schwannomas are solitary in 90% of cases, meaning there’s only one tumor.

What is a vestibular schwannoma?

A vestibular schwannoma, also known as acoustic neuroma, is a type of schwannoma that develops from the balance and hearing nerves supplying your inner ear. It’s usually benign (noncancerous) and slow-growing.

But as the tumor grows, it affects the hearing and balance nerves, usually causing hearing loss in the affected ear, tinnitus (ringing in your ear) and dizziness.

Is schwannoma a brain tumor?

It can be, but not always. A schwannoma can form in your brain or head, but it can also form elsewhere in your body. This is because schwannomas develop from cells (Schwann cells) in your peripheral nervous system, which consists of nerves in your brain and throughout your body.

The most common type of schwannoma, vestibular schwannoma, is considered a brain tumor.

Who do schwannomas affect?

Schwannomas most commonly affect people between the ages of 50 and 60 years. They rarely occur in children.

Schwannomas usually develop randomly in otherwise healthy people. In some cases, a schwannoma is caused by a genetic condition, such as neurofibromatosis 2 (NF2), schwannomatosis or Carney complex. People with these genetic conditions usually have more than one schwannoma.

How common are schwannomas?

Schwannomas are rare. They affect fewer than 200,000 people each year in the United States. About 60% of benign schwannomas are vestibular schwannomas (acoustic neuromas).

Symptoms and Causes

What are the symptoms of a schwannoma?

Schwannomas grow slowly and may exist for years without any symptoms. As schwannomas can form in several different areas of your body, the symptoms vary greatly. Some people may have more symptoms than others, and they can range from mild to severe.

Schwannoma symptoms can include:

  • A visible lump that may feel tender when you put pressure on it.
  • Numbness.
  • Muscle weakness.
  • Pins-and-needles feeling (paresthesia).
  • Pain that’s aching, burning or sharp.

Vestibular schwannomas can affect hearing and balance and/or cause ringing sensations (tinnitus).

Tumors by your facial nerve can affect swallowing, eye movement and taste sensations or cause facial paralysis.

Sciatic nerve schwannomas can mimic disk herniation with low back pain, with radiating pain down your leg.

What causes a schwannoma?

The cause of schwannomas isn’t known in most cases. Approximately 90% of cases occur sporadically (randomly).

Genetic disorders such as Carney complex, neurofibromatosis 2 (NF2) and schwannomatosis can cause schwannomas. Genetic studies show that the NF2 gene on chromosome 22 plays an essential role in schwannoma development.

Diagnosis and Tests

How is schwannoma diagnosed?

You may have a schwannoma for several years before getting diagnosed, as they grow slowly and often cause no symptoms at first. If you’re experiencing symptoms, your healthcare provider will likely order imaging tests. They may also find a schwannoma accidentally when reviewing imaging test results you had for another medical reason.

Imaging tests that can help diagnose a schwannoma include:

  • Magnetic resonance imaging (MRI): MRI is a painless test that produces very clear images of the organs and structures within your body using a large magnet, radio waves and a computer to produce detailed images. This is the preferred imaging test for locating and diagnosing schwannomas.
  • Computed tomography (CT) scan: A CT scan uses X-rays and computers to produce images of the structures inside of your body.
  • Ultrasound: Ultrasound uses high-frequency sound waves to create real-time pictures or videos of internal organs or other soft tissues. Healthcare providers can use ultrasound to detect schwannomas under your skin.

Your healthcare provider may also perform a biopsy to check if the tumor is schwannoma. This involves taking a small sample from the tumor with a needle. An expert called a pathologist will study cells from the sample under a microscope and run other tests to see what kind of tumor it is.

Management and Treatment

How is schwannoma treated?

Treatment for schwannoma depends on where the tumor is in your body and how quickly it’s growing.

Some treatment options include:

  • Observation/watch and wait: If the tumor is benign, growing very slowly and you’re experiencing no or very mild symptoms, your healthcare provider may recommend closely monitoring it instead of treating it. If it eventually grows larger and/or causes symptoms, they’ll likely recommend medical treatment for it.
  • Surgery: If the tumor is growing more quickly or causing other problems, your healthcare provider may recommend removing it with surgery. While the goal is usually to completely remove the tumor, the surgeon may only be able to remove part of it. As schwannomas form in the sheath surrounding the nerve, the surgery can often be completed without any damage to the nerve. However, surgery for vestibular schwannomas often leads to hearing loss.
  • Radiation therapy: Stereotactic radiosurgery (SRS) uses many precisely focused radiation beams to destroy tumors. Your healthcare provider may recommend SRS instead of surgery if the tumor is near vital blood vessels or nerves to prevent possible complications.

Malignant (cancerous) schwannomas may be treated with immunotherapy and chemotherapy medications as well.

Prevention

Can schwannomas be prevented?

Unfortunately, schwannomas can’t be prevented. In most cases, they happen randomly for unknown reasons. About 10% of cases are linked to certain genetic conditions that make it more likely that you’ll develop certain types of tumors.

If you have a biological relative who’s been diagnosed with neurofibromatosis 2 (NF2), Schwannomatosis or Carney complex, talk to your healthcare provider. They may recommend genetic counseling to see if you also have the genetic condition.

Outlook / Prognosis

What is the prognosis (outlook) for schwannoma?

The prognosis (the estimate of how a disease will affect you long-term) for schwannoma depends on a few factors, including:

  • Where the tumor is in your body.
  • How big the tumor is.
  • How much of the tumor was taken out during surgery (if applicable).
  • If the tumor is benign or cancerous.

In general, the prognosis for schwannoma is usually good. In the majority of cases, the tumor doesn’t come back (recur) if it’s been totally removed.

Most of the possible complications of schwannoma occur after surgery to remove the tumor. The occurrence of postoperative complications is significantly higher in the following circumstances:

  • If the tumor is large.
  • If the tumor is located deep inside of your body.
  • If the tumor originates from your ulnar nerve (one of the three main nerves in your arm).

Living With

When should I see my healthcare provider about schwannoma?

If you’ve been diagnosed with schwannoma and develop new or worse symptoms, see your healthcare provider for guidance on how to manage your schwannoma.

If your healthcare provider has advised you to observe the tumor instead of going through treatment, you’ll need to see them at least yearly so they can monitor the growth and condition of the tumor through imaging tests.

A note from Cleveland Clinic

Finding out you have a tumor can be scary. The good news is that schwannomas are almost always benign and slow-growing. Your healthcare team will help you determine the best treatment plan for you, whether that means simply observing the tumor, surgically removing it or something else. Don’t be afraid to ask questions. Your provider is always available to help you.

Last reviewed by a Cleveland Clinic medical professional on 06/24/2022.

References

  • Genetic and Rare Diseases Information Center. Schwannoma. (https://rarediseases.info.nih.gov/diseases/4767/schwannoma) Accessed 6/24/2022.
  • National Cancer Institute. Schwannoma. (https://www.cancer.gov/pediatric-adult-rare-tumor/rare-tumors/rare-soft-tissue-tumors/schwannoma) Accessed 6/24/2022.
  • Sheikh MM, De Jesus O. Schwannoma. (https://www.ncbi.nlm.nih.gov/books/NBK562312/) [Updated 2022 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022. Accessed 6/24/2022.

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