What is Neurilemmoma (Schwannomas)?
Most tumors found in the peripheral nervous system (which includes all the nerves outside of the brain and spinal cord) actually come from Schwann cells and not from the nerve cells themselves. Schwann cells, also known as neurilemma, create a protective layer known as the myelin sheath around nerve fibers. Most of these tumors are not cancerous, and are called “schwannomas” or “neurilemmomas.” They can occur on their own, or be a part of a different health condition like neurofibromatosis. The majority of these tumors grow slowly and are enclosed within a collagenous matrix, which is a protective structure made primarily of collagen, a protein in the body.
What Causes Neurilemmoma (Schwannomas)?
Neurilemmomas are tumors that develop from Schwann cells, which are cells that surround and insulate nerves. These tumors can occur on their own or can be associated with certain medical conditions like Neurofibromatosis type 2, Schwannomatosis, and Carney complex.
Risk Factors and Frequency for Neurilemmoma (Schwannomas)
Vestibular neurilemmomas are a type of tumor that occurs in the nervous system. They are quite rare, affecting about 0.01% to 0.1% of the general population. These tumors are mainly seen in people between the ages of 20 and 50, and affect both males and females. In a study of elderly patients with a condition known as neurofibromatosis type 2, a different type of tumor called a central schwannoma was found in 4.5% of the cases, which is significantly higher compared to the general population.
Signs and Symptoms of Neurilemmoma (Schwannomas)
Neurilemmomas, or nerve sheath tumors, usually present as a painless lump. However, as the tumor grows, it may press on the nerve, causing pain and abnormal sensations spreading across the nerve’s path. If the tumor affects the sensory nerves at the back of the spinal cord, it can cause changes in sensation. If it compresses the motor nerves at the front of the spinal cord, it may lead to motor weaknesses.
During a physical exam, doctors may feel a lump that can be moved sideways but not lengthways along the nerve’s path.
These tumors are most often found in the neck and the area between the lungs (mediastinum). When they occur in the arms or legs, they’re usually found along the flexor surfaces, the parts of the body that bend, such as the inside of the elbow or back of the knee.
Testing for Neurilemmoma (Schwannomas)
In simple terms, neurilemmomas, a type of tumor that forms in the nerves, often appear as lighter areas compared to muscles on CT scans, especially after a contrast dye is used. On MRI scans, which provide a different way to visualize the body’s internal structures, these tumors match the color of muscles in T1-weighted images and appear brighter in T2-weighted images. Sometimes, one may also see low-signal areas, which might be cysts, within these tumors.
Distinguishing a neurilemmoma from a neurofibroma, another type of nerve tumor, can be challenging. However, oftentimes, seeing the nerve offset to one side of the tumor, as well as a varied appearance with areas that look like liquid-filled sacs (cystic degeneration), can indicate a neurilemmoma, also known as a schwannoma.
Still, to confirm that a tumor is a neurilemmoma, a sample of it needs to be obtained through a biopsy. Upon examination of this sample, doctors typically look for a distinct fibrous capsule surrounding the tumor and specific structures known as Antoni A and Antoni B bodies.
Treatment Options for Neurilemmoma (Schwannomas)
Neurilemmomas and neurofibromas are types of tumors that grow on nerves. Often, if they do not cause symptoms or are causing only minor problems, they can be closely observed rather than removed. However, if these tumors are suspected to be malignant (cancerous) or are causing significant discomfort or problems, surgery can be used to remove them. The goal of this surgery is to get rid of the tumor while avoiding any damage to the nerve. Neurilemmomas are generally easier to remove than neurofibromas because they have a fibrous capsule, which is like a protective shell around the tumor.
During the removal of neurilemmomas, it’s important to monitor the electrical activity of the nerves. This is done using a process called electrophysiologic monitoring. Once the tumor site is identified, a small, lengthwise cut is made in the skin over the top of the tumor. The surgeon will expose the healthy nerve tissue both above and below the tumor. The surgeon can sometimes use vessel loops, which are soft, flexible loops used to isolate and protect the healthy nerve sections from damage.
Then, the surgeon will gently separate the tumor from the nerve using a specific type of surgical scissors called Metzenbaum scissors. Whenever possible, the surgeon will aim to remove the tumor in one piece. This tactic can help prevent any leftover tumor cells from growing back after the surgery.
What else can Neurilemmoma (Schwannomas) be?
Solitary neurofibromas are non-cancerous tumors that grow from cells in our peripheral nerves called Schwann cells. These tumors typically start in the skin or the tissue just beneath our skin. They’re very similar to tumors called neurilemmomas in that they grow very slowly. However, they’re different in some key ways. For example, neurilemmomas are surrounded by a capsule, but neurofibromas are not. When doctors examine these tumors under a microscope, they see that the pattern of protein staining in neurilemmomas is usually restricted to the peripheral axons, which is not the case with neurofibromas.
What to expect with Neurilemmoma (Schwannomas)
In simpler terms, a study by Kim and associates examined how patients fared after having neurilemmomas – tumors that develop on nerves – in the brachial plexus – a network of nerves in the shoulder area, surgically removed. They found that if the patients had full strength before the surgery, 88% of them maintained their normal strength after the procedure. Moreover, 90% of those who experienced weakness after the surgery had strength that either improved or remained the same as before the surgery.
Another group of researchers, from a different study conducted by Young and associates, found that when these tumors were removed, 52% of the patients were relieved of their symptoms, and 18% had symptoms that improved. This shows that surgery can be beneficial in treating this condition.
Possible Complications When Diagnosed with Neurilemmoma (Schwannomas)
Neurilemmomas, or tumors in the limbs, usually don’t cause symptoms and only create a lump. Sometimes, the size of the tumor can negatively affect the nerve and produce symptoms. The main symptoms are usually pain in the area of the affected nerve and sensory issues such as tingling sensations. But neurilemmomas affecting the front nerves of the spinal cord may also cause symptoms like weakness and motor issues, impacting movement.
When these tumors are surgically removed, they usually don’t cause damage to the nerve. This is because the tumor comes from Schwann cells that surround the nerve and not from the nerve fibers themselves. However, like any surgery, there are risks. It’s uncommon, but possible, that the nerve itself could get injured during the surgery because of pulling injuries or disruption to the nerve fibers. Wound complications could also occur as with any surgery. While the tumor could come back, this is quite rare for benign (non-cancerous) tumors of the nerve sheath.
Common Concerns:
- Pain in the affected nerve area
- Sensory issues such as tingling sensations
- Symptoms of weakness and motor issues impacting movement
- Possible nerve injury from surgery
- Wound complications post-surgery
- Possibility of tumor recurrence, although rare
Preventing Neurilemmoma (Schwannomas)
Neurilemmomas are harmless growths that can sometimes cause discomfort due to their size and effect on nearby body tissues. However, they are usually not something to worry about. If a patient experiences pain, changes in their neural functions, physical deformities, or bleeding, or if there’s a suspicion that the growth could turn into cancer, a surgical procedure may be recommended. Surgery to address a neurilemmoma generally has very positive results. However, there can be a small risk of damage to the nerves related to the growth.
