What are the other Names for this Condition? (Also known as/Synonyms)

• Central Nervous System Schwannoma
• Intracerebral Schwannoma
• Intraparenchymal Schwannoma in Cerebrum

What is Schwannoma of the Central Nervous System? (Definition/Background Information)

• Schwannomas are mostly benign tumors that arise from the Schwann cells around the nerves; these tumors are nerve sheath tumors. Schwannomas involving the central nervous system (CNS) are classified as grade I tumors of the cranial and paraspinal nerves, according to the World Health Organization (WHO)
• WHO grade I brain tumors are the most benign of the brain tumors that are slow-growing and are not known to infiltrate into surrounding tissues. They offer a very high chance for surgery to be curative, and thus, have the best prognosis amongst all brain tumors; long-term survivals are usually noted
• Schwannoma of the Central Nervous System are uncommon tumors that generally involve the cranial nerves. Cranial nerves are 12 pairs of sensory and/or motor nerves having specific functions that connect parts of the head and neck region to the brain. In a majority, the cranial nerve VIII is affected (in 90% of the cases); and, in such cases, it is known as vestibular schwannoma
• The development of schwannoma at other regions in the brain and/or spinal cord, termed intraparenchymatous schwannoma, is unclear because Schwann cells are notably absent in the CNS. In many, since the tumors are noted at a young age, it is believed to form due to some developmental abnormality. Some researchers propose that these tumors develop in the CNS from Schwann cells found in the perivascular plexus (of the autonomic nerve) and large arteries of the meningeal layers (subarachnoid spaces)
• Currently, no causative factors have been identified for Schwannoma of the Central Nervous System, although certain genetic, environmental, and occupational factors have been implicated in schwannoma development. Very rarely, the risk factors for the tumor may include the presence of neurofibromatosis type 2, which is a genetic disorder
• The signs and symptoms of Schwannomas of the Central Nervous System depend on the location of the tumor. Individuals may experience headaches, nausea and vomiting, seizures, weakness in different parts of the body, vision and speech disturbances. Large-sized tumors may compress adjacent brain tissue resulting in complications. In rare cases, schwannomas are known to undergo malignant transformations
• Infrequently, the healthcare provider may undertake a ‘wait and watch’ approach for small-sized and slow-growing benign tumors. In many cases, a complete excision by surgery or treatment using Gamma Knife radiosurgery can be curative. The long-term outcome of a benign Central Nervous System Schwannoma is typically excellent with appropriate management and follow-up care. However, malignant schwannomas have higher WHO grades and poorer prognosis

Who gets Schwannoma of the Central Nervous System? (Age and Sex Distribution)

• Schwannoma of the Central Nervous System is a rare tumor that constitutes about 7-8% of all intracranial neoplasms
• These tumors are typically seen within age 20. Apart from this age group, these tumors are also diagnosed in older adults. CNS Schwannomas are very rare in young children
• Both males and females are affected, although a slight female preference is noted, according to some literature. Some reports inform that the tumor is more common in males than females
• There is no known geographical bias and racial/ethnic preference observed

What are the Risk Factors for Schwannoma of the Central Nervous System? (Predisposing Factors)

Many cases of Schwannoma of the Central Nervous System are sporadic in nature and no well-established predisposing factors are observed.

• The presence of neurofibromatosis type 2 (NF2) is noted in some cases of CNS Schwannoma. NF2 is a genetic condition characterized by the formation of non-cancerous tumors affecting the nervous system
• In general, for schwannomas the risk factors may include:
  • A family history of the tumor
  • Frequent exposure to ionizing and non-ionizing radiation

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Schwannoma of the Central Nervous System? (Etiology)

The exact cause of formation of Schwannoma of the Central Nervous System is unknown; these tumors may be described as being sporadic or syndromic. Most tumors are the result of sporadic mutations; this implies that they may not have a preceding family history of the condition. Syndromic tumors develop against a background of certain inherited genetic disorders.

Schwannomas typically arise from an overproduction of Schwann cells that form the myelin sheath (an insulating layer wrapping the nerves). Hence, these tumors are also termed nerve sheath tumors.

Overall, the following factors have been identified as playing a role in schwannoma development:

• Abnormalities in chromosome 22
• Multiple schwannomas are known to occur in a background of genetic disorders, such as NF2, Gorlin-Koutlas syndrome, or a positive family history

It is researched that certain genetic, environmental, and occupational factors may contribute towards the development of schwannomas. In general, it is known that tumors form when normal, healthy cells begin transforming into abnormal cells - these cancer cells grow and divide uncontrollably (and lose their ability to die), resulting in the formation of a mass or a tumor.

What are the Signs and Symptoms of Schwannoma of the Central Nervous System?

The signs and symptoms of Schwannoma of the Central Nervous System may differ from one individual to another. It may be mild or severe and depend on several factors, but primarily on the location and size of the tumor. The onset and speed of progression of the tumor can vary. In many individuals, tumors that grow slowly and remain asymptomatic, are only diagnosed during certain radiological imaging studies of the head and neck region, which are performed for unrelated health conditions.

Schwannomas can arise either in the cranial nerves or in the cerebrum (supratentorial region). When they occur in the cerebrum, it is mostly in the frontal and parietal lobes. Intracranial schwannomas observed at non-cranial nerve locations and non-neurofibromatosis individuals are highly unusual. In individuals without NF2, they usually arise in the trigeminal nerve (CN V), facial nerve (CN VII), or vestibulocochlear nerve (CN VIII).

Depending on the nerve(s) involved, a set of associated signs and symptoms may be noted:

• The tumors are slow-growing and usually solitary; some schwannomas may rarely grow to large sizes. As they grow, they compress the affected nerves
• The most common nerve involved is cranial nerve VIII (in over 90% of the cases); in which case, the tumor is called acoustic schwannoma (or vestibular schwannoma). Bilateral CN VIII tumors are associated with neurofibromatosis type 2
• In general, any cranial nerve can be involved causing a variety of symptoms, such as impaired vision, loss of taste, hearing loss, loss of touch sensation, twitching of facial muscles, difficulty in eating and chewing, etc.
• When the tumor involves the dorsal spinal nerve root of the spinal cord, it can result in potentially significant signs and symptoms

Other signs and symptoms of CNS Schwannoma may include:

• Headaches
• Seizures
• Nerve dysfunction that can cause numbness and tingling sensation and a host of symptoms
• Weakness of facial muscles
• Large-sized tumors may cause motor (muscle) dysfunction
• Unilateral paresis or one-sided body weakness may be noted
• Convulsions and memory impairment are generally uncommon
• Multiple schwannomas are known to occur in a background of neurofibromatosis type 2 disorder
• Involvement of the spinal cord may lead to:
  • Back pain
  • Pain in the arms and legs, depending on the nerves that are compressed by the tumor
  • Severe cases may result in loss of bowel and bladder control

Large tumors can cause significant signs and symptoms. Also, associated symptoms of the underlying condition, if any, may be noted.

How is Schwannoma of the Central Nervous System Diagnosed?

Schwannoma of the Central Nervous System may remain undiagnosed for prolonged periods, since they may not present any significant signs and symptoms and are generally slow-growing. The slow development of symptoms may contribute to a delayed detection and diagnosis of these tumors. The tumors are detected when there is a sudden worsening of symptoms prompting the healthcare provider to perform radiological studies of the brain.

A diagnosis of Schwannoma of the Central Nervous System may involve the following tests and examinations:

• Complete physical examination with thorough evaluation of the individual’s medical history (including family history of NF2 or schwannoma)
• Assessment of the presenting signs and symptoms
• Cranial nerve examination
• Neurological, motor skills, and cognitive assessment:
  • Checking intellectual ability, memory, mental health and function, language skills, judgment and reasoning, coordination and balance, reflexes, and sensory perceptions (space, sight, hearing, touch, etc.)
  • The healthcare provider/neurologist may use the Karnofsky Performance Scale in order to assess the neurological functioning of the individual’s central nervous system (CNS)
• Electromyography with nerve conductivity tests
• Electroencephalography (EEG)
• Imaging studies that may be performed include:
  • X-ray of head and neck and/or vertebral column
  • Computerized tomography (CT) scan of the head and neck region; CT with contrast
  • Magnetic resonance imaging (MRI) scan of the central nervous system; MRI with contrast agents such as gadolinium
  • Cerebral angiographic studies or magnetic resonance angiography: An angiogram involves injecting dye into the bloodstream, which makes the blood vessels to appear visually on X-rays. The X-ray may show a tumor in the brain or the blood vessels leading into the tumor
  • Magnetic resonance spectroscopy: This radiological technique is used to study the chemical profile of the tumor. It is often performed with and compared to corresponding MRI scan images of the affected region
  • Positron emission tomography (PET scan): A PET scan is a nuclear medicine imaging technique that uses three-dimensional images to show how tissue and organs are functioning. It may be performed to detect any malignancy, and if there is a metastasis (spread) of the tumor to other regions
• Cerebrospinal fluid analysis, where a spinal tap or lumbar puncture procedure may be performed: This diagnostic test is used to remove a sample of cerebrospinal fluid (CSF) from the spaces in and around the brain and spinal cord. The sample is removed from the lower spinal cord using a thin needle, and it is then checked for the presence of cancer cells

Tissue biopsy: A biopsy of the affected region (brain) is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy sample under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy sample under a microscope by a pathologist is helpful in arriving at a conclusive diagnosis.

There are two ways to perform a biopsy:

• First, a biopsy can be performed as part of a surgical procedure to remove the brain tumor
• Second, a stereotactic needle biopsy can be performed when the tumor is deep within the brain or located in a sensitive area. In this procedure, the surgeon drills a small hole (called a burr hole) into the skull. A thin needle, guided by CT or MRI scanning, is then inserted through the hole to help in the removal of tissue

A differential diagnosis to eliminate other conditions or tumor types may be considered, before arriving at a definitive diagnosis. In general, these may include:

• Leiomyoma
• Leiomyosarcoma
• Malignant peripheral nerve sheath tumor (MPNST)
• Meningioma
• Metastatic melanoma
• Palisaded encapsulated neuroma
• Pigmented neurofibroma
• Plexiform neurofibroma
• Traumatic neuroma

Pathological differential diagnosis may include:

• Astrocytoma
• Fibroblastic meningioma
• Hemangiopericytoma
• Solitary fibrous tumor
• Subependymoma
• Tanycytic ependymoma

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Schwannoma of the Central Nervous System?

The complications from Schwannoma of the Central Nervous System could include:

• Emotional and mental stress for both the patient and the caretakers, due to the diagnosis and during treatment of a CNS tumor
• Permanent damage to the cranial nerves or other nerves due to progression of the tumor (mass effect and compression)
• Severe facial paralysis, hearing loss, and vision impairment
• Large undetected tumors can severely affect brain function and be disabling or even life-threatening
• Very rarely, schwannomas can become malignant (malignant transformation of schwannoma), especially in children and individuals with NF
• Malignant tumors grow far more rapidly, present pronounced symptoms, and can additionally cause bone erosion, depending on the tumor location
• Such malignancies can spread to other parts of the body, such as the bone and lungs. In some cases, skin nodules have been observed, due to metastasis
• Complications due to an underlying genetic disorder, if any present, may be observed

Complications may arise from surgery, radiation therapy, chemotherapy, or other treatment modalities.

Surgery:

• Damage to the muscles, vital nerves, and blood vessels, during surgery to remove the tumor; injury to unaffected brain tissue during surgery
• Post-surgical infection at the wound site is a potential complication
• Sometimes, removing the tumor can worsen the signs and symptoms in some individuals
• Infrequently, recurrence of the tumor after surgery is observed, due to incomplete tumor removal
• A complete surgical removal of malignant schwannoma is difficult; thus, the recurrence rates are higher with malignant tumors

Chemotherapy side effects depend on the type of chemotherapy medication used and may include:

• Nausea and vomiting
• Hair loss
• Mouth sores
• Loss of appetite
• Diarrhea
• Fatigue
• Increased risk for infections
• Easy bruising

Radiation therapy can cause short-term side effects. It depends on the type used and may include:

• Nausea and vomiting
• Hair loss
• Dryness of mouth; loss of taste
• Headaches
• Fatigue
• Skin color changes; usually darkening of skin on the face and neck may be noted
• Speech and hearing difficulties
• Memory issues
• Seizures
• Long-term side effects (seen after 6 months or beyond) may include loss of memory, impaired brain function, and appearance of symptoms that mimic stroke

How is Schwannoma of the Central Nervous System Treated?

In general, the treatment modality for a benign brain and spinal cord tumor is chosen depending on the size, location, and stage of the tumor, tumor growth rate, age and health status of the individual. Tumors that are small and slow-growing usually may be observed and no treatment necessitated, based on the healthcare provider’s specific case-by-case assessment. Often, a multidisciplinary team of specialists including ophthalmologists, otolaryngologists, neurologists, neurologists, oncologists, surgeons, radiation therapy experts, and other healthcare professionals may be involved in managing the condition.

The treatment measures for benign Schwannoma of the Central Nervous System may include:

• Wait and watch approach by the healthcare provider may be rarely considered for small and benign tumors that are not associated with any underlying genetic disorders such as neurofibromatosis
• Symptomatic treatment may involve the use of antiseizure medications, painkillers, steroids (to reduce inflammation), and administration of anti-depressants

Surgical excision and tumor removal may be recommended for treating Central Nervous System Schwannoma. A very important criterion for surgery is a possibility of injury to the involved nerve(s), based on where the tumor is located. Permanent post-operative injury and compromised nerve function may be reported in some cases. The surgical treatment options may include the following:

• Microsurgery: The surgery is performed using microsurgical techniques, which can help minimize damage to the accompanying nerve. Since the tumor mostly affects the covering around the nerves, it can be completely removed without affecting the nerve in most cases. The following techniques may be employed:
  • Subtotal removal; when the tumor is incompletely removed
  • Near total removal; when most of the tumor is removed and there is very little tumor remnants
  • Total tumor removal; when the tumor is removed completely
• Craniotomy: It is a surgical procedure wherein a tiny hole is created in the cranium to remove the tumor
• Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals

Surgical procedures to remove brain tumors carry risks, including infection, possible damage to healthy brain tissue, swelling, or possible fluid build-up in the brain.

In case of malignancy, additional treatment options, such as chemotherapy and/or radiation therapy, may be considered.

• Chemotherapy may be used to destroy the tumor cells:
  • It is not reportedly a very useful method to treat schwannomas
  • The response of the tumor to chemotherapy is an important consideration while using this treatment modality
  • Whether to use chemotherapy as a treatment modality is determined by healthcare provider on case-by-case basis
• Radiation therapy may be useful in individuals who are not candidates for surgery. Such cases include:
  • Individuals with overall poor health status
  • The presence of bilateral schwannomas
  • Individuals with minimal symptoms
• Stereotactic radiosurgery is a relatively new treatment method that can be helpful in some individuals. It is a radiation therapy technique and not an invasive surgical procedure. It can be administered using a Gamma Knife (Gamma Knife radiosurgery) and is considered for tumors that are less than 3 cm in size. This method is known to be beneficial in many cases and is preferred nowadays
• External beam radiation therapy using a linear accelerator is helpful in preserving neurological function, especially when tumors are smaller
• Treatment of the underlying neurofibromatosis type 2 or any other genetic condition, if present

Clinical trials: In advanced stages of tumor progression, there may be some newer treatment options, currently on clinical trials, which can be considered for some patients depending on their respective risk factors.

Regular observation and periodic checkups to monitor the condition is strongly recommended following treatment. In order to avoid a relapse, or be prepared for a recurrence, the entire diagnosis, treatment process, drugs administered, healthcare recommendations post-treatment, etc. should be well-documented and follow-up measures initiated accordingly.

How can Schwannoma of the Central Nervous System be Prevented?

Presently, there are no specific methods or guidelines to prevent the development of Schwannoma of the Central Nervous System. However, if it is associated with a genetic disorder, the following points may be considered:

• Genetic counseling and testing: If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Regular health check-ups might help those individuals with a history of the condition in the immediate family, in order to help diagnose the tumor early

In general, the factors that may help reduce the incidence of schwannomas and other brain tumor include:

• Reducing exposure to ionizing radiation
• Avoiding cigarette smoke inhalation
• Weight loss, in case one is obese or overweight; maintaining a good BMI
• Availing early treatment for infections
• Using safety gear including wearing helmets when playing sports or while riding two-wheelers
• Wearing seatbelts while driving automobiles to minimize the risk for head/body injury

Regular medical screening at periodic intervals with blood tests, scans, and physical examinations are mandatory. Often several years of active vigilance are crucial and necessary.

What is the Prognosis of Schwannoma of the Central Nervous System? (Outcomes/Resolutions)

The prognosis of benign Schwannoma of the Central Nervous System is excellent, particularly if the tumor can be removed without damaging the underlying nerve. However, resolution of some post-treatment symptoms may not be achieved in all cases.

• In very rare cases, asymptomatic (benign) tumors may require no treatment; unless they cause discomfort, affect the quality of life, or affect functioning of the underlying nerve. In such cases, close monitoring of the schwannoma is a treatment option
• If benign schwannomas transform to malignant tumors (in rare occasions), then the prognosis may depend upon a variety of factors such as the stage of the tumor, overall health of the individual, and response to therapy

In general, the prognosis of brain tumors (both benign and malignant) may vary considerably from one individual to another and is dependent on a set of factors, which include:

• Tumor histology or grade of the tumor: The lower the grade, the better is the prognosis. Benign schwannomas are grade I tumors
• Stage of tumor: With lower-stage tumors, when the tumor is confined to site of origin, the prognosis is usually excellent with appropriate therapy. In higher-stage tumors, such as tumors with metastasis, the prognosis is poor
• Age of the individual: Older individuals generally have poorer prognosis than younger individuals
• Overall health of the individual: Individuals with overall excellent health have better prognosis compared with those with poor health
• The size of the tumor: Individuals with small-sized tumors fare better than those with large-sized tumors
• Location of the tumor is an important prognostic factor: Tumors at certain sites involving the central nervous system are more difficult to surgically excise and remove. They can also cause considerable neurological damage at certain sites in the brain and/or spinal cord. Tumors located near vital structures of the brain have poor prognosis
• Tumors that are slow-growing have better prognosis than rapidly-growing tumors
• Presence of certain genetic abnormalities may result in a rapid progression of tumor growth and development
• Sporadic tumors have generally better prognosis than syndromic tumors; tumors in a background of genetic disorders/syndromes may have additional complications
• The ease of accessibility and surgical resectability of the tumor (meaning, if the primary tumor can be removed completely). This is an important prognostic factor, since it may determine if the tumor can be completely resected or not
• Extent of residual tumor in the body following a surgical resection: A complete surgical excision with entire tumor removal presents the best outcome. In some cases, large portions of the tumor may be removed; or, only a small portion for tissue biopsy
• Individuals with bulky disease may have a poorer prognosis
• Involvement of other vital organs may complicate the condition
• Metastatic spread: Spread of the malignancy to other body sites portrays a poorer prognosis
• Whether the tumor is occurring for the first time or is a recurrent tumor. Recurring tumors have worse prognosis compared to tumors that do not recur 
• Response to treatment and absence of post-operative complications: Tumors that respond to treatment have better prognosis compared to tumors that do not respond to treatment
• Functional neurologic status based on neurological evaluation of the patient: A higher score on the Karnofsky Performance Scale may indicate a more favorable outcome

An early diagnosis and prompt treatment of the tumor generally yields better outcomes than a late diagnosis and delayed treatment.

Additional and Relevant Useful Information for Schwannoma of the Central Nervous System:

Please visit our Cancer & Benign Tumor Health Center for more physician-approved health information:

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