Introduction
Schwann cells are specialized cells that form insulating layer sheaths around peripheral nerves. Early embryonic nerve glial cells are precursors to Schwann cells. They develop from the neural crest and produce immature Schwann cells as a result. While the nucleus remains stationary, the inner glial cell membrane turns spirals around the axon to add membrane layers, or lamellae, to the myelin sheath. The plasma membrane of Schwann cells exhibits extremely high levels of lipids, and cholesterol is an essential component of the myelin sheath. Myelination increases the speed of conduction along the axon, permitting saltatory conduction of impulses and supplying nutrients to axons. If these Schwann cells uncontrollably grow and multiply rapidly, it can cause schwannomatosis, which this article discusses.
What Is Schwannomatosis?
Multiple benign tumors developing in the peripheral nerves due to the uncontrollable growth of Schwann cells are known as schwannomas (nerve tumors). And the condition is referred to as schwannomatosis. It does not spread to other tissues and can grow on all the nerves, including spinal nerve roots. Even though they are benign tumors, they cause uncomfortable symptoms as they put pressure on the surrounding structures. Schwannomatosis is usually considered a part of a family of diseases called neurofibromatosis. It is a group of diseases characterized by tumors in the nervous system.
There are three recognized forms of neurofibromatosis, namely:
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Neurofibromatosis type 1 (NF1).
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Neurofibromatosis type 2 (NF2).
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Schwannomatosis.
The symptoms of schwannomatosis are similar to those of neurofibromatosis type 2, but the specific feature of type 2 neurofibromatosis is inner ear tumors, known as vestibular schwannomas, which do not occur in schwannomatosis.
What Are the Other Names of Schwannomatosis?
The other names for this condition are:
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Multiple schwannomas.
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Neurilemmomatosis.
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Meurinomatosis.
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Multiple neurilemmomas.
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Congenital cutaneous neurofibromatosis.
What Are the Causes of Schwannomatosis?
Schwannomatosis occurs due to mutations in the two genes, SMARCB1 and LZTR1. The proteins produced in these genes help suppress the multiplication and growth of the cells in a disorderly fashion, and they are known as tumor suppressors. When these proteins are not produced due to abnormalities, the cells start to grow and divide rapidly to form a tumor.
It is said that mutations in the SMARCB1 and LZTR1 genes are not enough to trigger schwannomas, but some additional somatic changes that have been acquired in the life of an individual also trigger schwannomas. The common somatic mutation that causes schwannomas is the mutation in the NF2 gene and a loss of chromosome 22 as SMARCB1, LZTR1, and NF2 genes rely on chromosome 22. In some cases, schwannomatosis does occur in people who do not have identified mutations in LZTR1 and SMARCB1 genes. In such cases, the cause of the disorder is still unknown.
What Are the Symptoms of Schwannomatosis?
The symptoms of schwannomatosis are seen in early adulthood, and the characteristic symptom is the growth of schwannomas (nerve tumors) throughout the body. The schwannomatosis symptoms are similar to those of neurofibromatosis type 2, but NF2 involves the eight cranial nerve (the vestibulocochlear nerve, which helps in balance and controls hearing), causing vestibular schwannomas, whereas schwannomatosis does not. Therefore, schwannomatosis and neurofibromatosis type 2 are managed differently. The life expectancy of people with this condition is average. However, neurofibromatosis type 2 is associated with a shorter-than-average life expectancy. When the nerve tumors associated with this disease are left untreated, they can cause nerve pain and other symptoms.
Some common symptoms of schwannomatosis are:
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Long-lasting or chronic pain can occur in any part of the body.
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In some cases, pain may be felt where there are no tumors.
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Pain associated with schwannomas ranges from mild to severe, and it is difficult to manage.
The other symptoms depend on the location and size of the tumors and the nerves involved.
When spinal schwannomas put pressure on the spinal nerves, it can result in:
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Tingling.
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Pain.
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Trouble controlling bowel and bladder function.
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Clumsiness.
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Weakness.
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Trouble walking.
What Are the Risk Factors of Schwannomatosis?
Schwannomatosis results due to the change in the gene called SMARCB1. It is said that the change in the SMARCB1 and LZTR1 genes can be inherited, but it does not always run in families or pass to the offspring. However, studies have said that 15 to 25 percent of schwannomatosis cases run in families. These familial cases are said to have an autosomal dominant pattern of inheritance. In other cases, the reason for schwannomatosis is unknown when there is no change in SMARCB1.
How Is Schwannomatosis Diagnosed?
Schwannomatosis can be diagnosed with various imaging tests. To look at the growth of the nerve tissue MRI (magnetic resonance imaging) and CT scans (computed tomography) may be performed.
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MRI (Magnetic Resonance Imaging) - This scan utilizes radio waves, computer technology, and magnets to build pictures of organs and tissues such as the brain and spinal cord. Schwannomatosis is diagnosed by MRI if two or more non-intradermal schwannomas (one with pathological confirmation) including no bilateral vestibular schwannoma.
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CT (Computed Tomography) - It is a combination of X-ray and computer technology to construct clear images of bones and soft tissues.
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Biopsy - Pathologists use the removed tissues to identify the type of tumor with the help of a biopsy.
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Genetic Test - This test is performed to examine the changes associated with schwannomatosis. It is available for the SMARCB1 gene mutation, which is associated with some cases of schwannomatosis, and another recently identified gene, LZTR1.
How Is Schwannomatosis Treated?
The treatment of schwannomatosis will depend on the size and location of the tumor, and symptoms.
1. Monitoring and Observation:
If the tumors do not put pressure on nearby tissues, they should be observed with an annual MRI. It is advised to consult the doctor on the recommended appointments to see if the tumor is developing, to prevent serious complications which develop if left untreated.
2. Surgery:
Surgical removal is usually recommended for larger tumors (symptomatic) or tumors showing growth over time. Complete removal of tumors can be achieved using the:
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Surgical microscope.
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Magnificent instruments.
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An array of microsurgical techniques.
These techniques and treatment options will benefit most people and help patients improve their neurological function. In the case of large dumbbell tumors, fusion, and spinal stabilization are performed before the complete removal of the tumor.
3. Stereotactic Body Radiation Therapy
When the tumor is located near the artery, vein, or nerve, then stereotactic body radiation therapy is used to confine the damage to the vital tissues. This technique helps in delivering radiation precisely to a tumor without incision and with no damage to the surrounding tissues. With the help of radiation therapy, the symptoms might be improved, and the spread of the tumor can be controlled.
Conclusion:
Schwannomatosis is a very rare genetic disorder that has to be distinguished from other forms of neurofibromatosis. However, the available treatment options help to improve symptoms, remove the tumor and prevent its spread. In case of any abnormal symptoms and uncontrollable pain, it is advised to seek prompt medical care as it could be managed effectively.
