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

• Auditory Vestibular Nerve Schwannoma
• Cranial Nerve 8 Schwannoma
• Eighth Cranial Nerve Schwannoma

What is Vestibulocochlear Nerve Schwannoma? (Definition/Background Information)

• Schwannomas are mostly benign tumors that arise from the Schwann cells around the nerves; these tumors are nerve sheath tumors. The tumors can occur in the peripheral nerves (arms and legs) and the spinal nerves; intracranial tumors occur in the head
• 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
• It is reported that about 8% of all intracranial tumors are schwannomas, and a majority involve the cranial nerve VIII or the vestibulocochlear nerve. 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. Ten of these pairs originate from the brainstem; two pairs originate from the cerebrum
• When a schwannoma involves the vestibulocochlear nerve, it is termed Vestibulocochlear Nerve Schwannoma. The vestibulocochlear nerve splits into two main branches near the region of the brainstem. The two divisions are known as:
  • Cochlear nerve: The cochlear nerve branch travels to the inner ear and is responsible for the perception of sound
  • Vestibular nerve: The vestibular nerve branch travels to the vestibular system of the inner ear and is responsible for balance
• Schwannomas arising along the cochlear nerve branch are called cochlear schwannomas, while those arising along the vestibular nerve branch are called vestibular schwannomas. The former are extremely rare tumors, whereas the latter are common and form a vast majority of cranial schwannomas. In general, tumors originating in the vestibule, cochlea, and semicircular canals of the inner ear are collectively known as intralabyrinthine schwannomas (or ILSs)
• Currently, no causative factors have been identified for Vestibulocochlear Nerve Schwannoma, although certain genetic, environmental, and occupational factors, have been implicated. The risk factors for the tumor include the presence of neurofibromatosis type 2 (NF2) and a positive family history of schwannoma
• Vestibulocochlear Nerve Schwannomas may be symptomatic or asymptomatic. In some, these tumors can cause a host of symptoms including sensorineural hearing loss, ringing within the ears, and vertigo. Usually the tumors are unilateral; but, if they are associated with NF2 or schwannomatosis, they can be bilateral (seen on both sides of the head). However, this is a very uncommon occurrence
• In some individuals, the healthcare provider may undertake a ‘wait and watch’ approach for small-sized and slow-growing tumors. In a majority of cases, a complete excision by surgery can be curative and the prognosis of Vestibulocochlear Nerve Schwannoma is typically excellent. Nevertheless, follow-up care with regular screening and check-ups are necessary and recommended

Who gets Vestibulocochlear Nerve Schwannoma? (Age and Sex Distribution)

• Vestibulocochlear Nerve Schwannoma is typically observed between the age ranges of 20-60 years. It is observed in young, middle-aged adults, and slightly older adults
• Both males and females are affected with a higher predilection for males. Some reports indicate that more cases are observed in women than men (women to men is 3:2), when the tumor is associated with the genetic disorder neurofibromatosis type 2
• There is no known racial or ethnic preference observed. These tumors are observed in individuals worldwide; an incidence rate of 1 case per 50,000 population per year is noted globally

What are the Risk Factors for Vestibulocochlear Nerve Schwannoma? (Predisposing Factors)

The risk factors for Vestibulocochlear Nerve Schwannoma include:

• In some rare cases, the presence of neurofibromatosis type 2 (NF2) is observed. NF2 is a genetic condition that is characterized by the formation of non-cancerous tumors that affect the nervous system
• Schwannomatosis: It is a genetic condition that is a usually seen in adults and manifests as multiple schwannomas
• Gorlin-Koutlas syndrome: A complex genetic disorder of multiple tumors in the body including multiple schwannomas
• Frequent exposure to ionizing and non-ionizing radiation
• Exposure to dental X-rays regularly may be a risk factor, but is not confirmed yet
• Exposure to constantly high noise levels (or sound pressure) for about 13 years or more, such as through one’s occupation, is observed to increase the risk, especially in women. Both impact noise and continuous noise are deemed risk factors, with the former being more dangerous of the two, since it can cause instant damage to the ear structures and related nerves
• It is believed that individuals with hay fever or other allergies for about 30 years may have an elevated risk
• A correlation between Vestibulocochlear Nerve Schwannoma and allergies to certain plant or animal products, dust allergies, and food allergies has been studied; but, the findings on risks are inconclusive
• Some studies seem to show an increased risk for the tumors from mobile phone usage, due to prolonged exposure to radiofrequency waves (period greater than 5-10 years). However, this is not conclusive yet

Note: According to some studies, a family history of cancer does not seem to increase the risk for Vestibulocochlear Nerve Schwannoma.

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 Vestibulocochlear Nerve Schwannoma? (Etiology)

The exact cause of formation of Vestibulocochlear Nerve Schwannoma is not well-established. It is researched that certain genetic, environmental, and occupational factors may contribute towards its development.

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. Vestibulocochlear Nerve Schwannoma is believed to be caused by the overproduction of Schwann cells that wrap around the nerve.

• It may develop as the result of sporadic mutations; meaning, there is no preceding family history of the condition noted
• Abnormalities in the long arm of chromosome 22 on NF2 gene is the most common finding. This is predominantly observed in individuals with neurofibromatosis type 2

Some research has identified a correlation between one’s educational level, family income, and occupation type with the tumor. However, some experts question this correlation and the study algorithms used in measuring the risks.

What are the Signs and Symptoms of Vestibulocochlear Nerve Schwannoma?

The signs and symptoms of Vestibulocochlear Nerve Schwannoma may differ from one individual to another. It may be mild or severe, depending on several factors. 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.

In tumors with signs and symptoms, these may include:

• The tumors are mostly slow-growing and solitary; they may appear as a firm mass
  • Vestibular tumors may cause symptoms such as dizziness, loss of balance, pain, hearing difficulties, and ringing in the ears (tinnitus)
  • Cochlear tumors may present one-sided hearing impairment, ringing in the ears, vertigo, and loss of balance
• Sensorineural hearing loss: A type of hearing loss that results from a problem in the inner ear. Often, one-sided hearing loss is observed (depending on which ear is affected)
• Facial drop and altered touch sensation on the face (facial paresthesia) may also be observed in individuals where the tumor compresses on the facial nerve
• The tumors may affect one ear (unilateral) or both ears (bilateral), when both the nerves responsible for hearing are affected
• Multiple schwannomas are known to occur in a background of genetic disorders, such as neurofibromatosis type 2 or Gorlin-Koutlas syndrome
• In some individuals, the tumor may also cause unsteadiness, headaches, and ear pain
• When the cranial nerve VIII is damaged, it can additionally present:
  • Travel sickness
  • A false sense of motion even when the individual is stationary
  • Vertigo and balance issues (disequilibrium), especially in low to poor light
  • Impaired taste
  • Hoarse voice
  • Swallowing difficulties
  • Uncontrolled and involuntary eye movement (nystagmus)
  • Gaze-evoked tinnitus (GET), which is a ringing in the ears along-with an awkward eye position; it may take place following a surgical removal of the schwannoma too
  • Facial numbness or tingling sensation; facial paralysis (partial)
  • Confusion

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

How is Vestibulocochlear Nerve Schwannoma Diagnosed?

A majority of Vestibulocochlear Nerve Schwannomas may remain undiagnosed for prolonged periods, because many are asymptomatic and 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 Vestibulocochlear Nerve Schwannoma 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
• Hearing and audiometric tests, including:
  • Otoscopy: Examination using an instrument that allows the physician to look inside the ear
  • Weber and Rinne test, where a vibrating tuning fork is used to assess one’s hearing ability
  • Tympanometry: A test using air pressure in the ear canal to move the eardrum, and measure eardrum mobility (movement)
  • Acoustic reflex: A test that stimulates the stapedius (a tiny ear muscle) to move, in response to a loud sound
  • Static acoustic measures: A test to measure the amount of air in the ear canal
  • Auditory brainstem response: In this test, electrodes are placed on the scalp, to measure the electrical response of the brain to sounds
  • Otoacoustic emissions: A test in which a tiny microphone is placed in the ear to play sounds, and measures the signals produced by the inner ear
• 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)
• Electroencephalography (EEG)
• Electromyography with nerve conductivity tests
• 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 MR angiography: An angiogram involves injecting dye into the bloodstream, which makes the blood vessels to appear visually on X-rays
  • 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
• 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

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 considered to be gold standard 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

Note:

• A differential diagnosis to eliminate other conditions (such as labyrinthitis) or tumor types may be considered, before arriving at a definitive diagnosis
• All newborns should have a hearing screening. If they do not pass a hearing screening, then they are seen by an audiologist (health professional who assess hearing loss) for a complete hearing exam

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 Vestibulocochlear Nerve Schwannoma?

The complications from Vestibulocochlear Nerve Schwannoma could include:

• Emotional and mental stress for both the patient and the caretakers, due to the diagnosis and during treatment of a brain tumor
• Large undetected tumors can severely affect brain function and be disabling or even life-threatening
• Permanent damage to the nerve causing permanent hearing loss (on one side or both sides) and facial drop/paralysis
• Very rarely, schwannomas can become malignant (malignant transformation of schwannoma)
• Complications due to an underlying genetic disorder, if any present, may be observed

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

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, if the tumor is incompletely removed

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 Vestibulocochlear Nerve Schwannoma Treated?

In general, the treatment modality for a benign brain 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, oncologists, surgeons, radiation therapy experts, and other healthcare professionals may be involved in managing the condition.

The treatment measures for benign Vestibulocochlear Nerve Schwannoma may include:

• Wait and watch approach by the healthcare provider:
  • Observation of the tumors is often recommended in individuals with small-sized tumors, slow-growing tumors, tumors with no significant signs and symptoms, elderly patients, individuals where treatment, such as surgery, may be too risky, and individuals, who do not prefer surgical treatment for a variety of reasons (opting out of surgery through personal preference)
  • Recurring brain scans may be taken to observe the rate of tumor growth; if the tumor is small and growing slowly, then there may be no need for invasive procedures
• Symptomatic treatment may involve the use of antiseizure medications, painkillers, steroids (to reduce inflammation), and administration of anti-depressants

Surgical excision and tumor removal are normally recommended for treating Vestibulocochlear Nerve Schwannoma. A very important criterion for surgery is to preserve nerve function that is affected by the tumor. 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 the condition
  • 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)
• 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 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 Vestibulocochlear Nerve Schwannoma be Prevented?

Presently, there are no specific methods or guidelines to prevent the formation of Vestibulocochlear Nerve Schwannoma. 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 high noise areas; using suitable earmuffs when working in noisy environment
• Ensuring early and adequate treatment for any allergies, hay fever, etc.
• 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 Vestibulocochlear Nerve Schwannoma? (Outcomes/Resolutions)

The prognosis of Vestibulocochlear Nerve Schwannoma (benign tumor) is excellent, particularly if the tumor can be removed without damaging the underlying nerve.

• Asymptomatic tumors may require no treatment; unless they cause discomfort, affect the quality of life, or affect functioning of the underlying nerve. In such cases, a close monitoring of the schwannoma is a treatment option
• Bilateral tumors and the presence of neurofibromatosis type 2 can adversely influence outcomes
• If benign schwannomas transform to malignant tumors (in very 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 benign brain tumors 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
• 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
• 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
• 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
• 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 Vestibulocochlear Nerve Schwannoma:

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

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