Acoustic Neuroma Surgical Options

Translabyrinthine Approach

Doctors may use translabyrinthine surgery for any size of tumor that has caused significant hearing loss or where hearing preservation is not possible. During this procedure, the surgeon makes an incision behind the ear and opens the mastoid bone, as well as a portion of the inner ear, which contains structures important for hearing and balance. This gives the surgeon access to the tumor in the internal auditory canal, which acts as the passageway for the eighth cranial nerve—the nerve that runs from the brain to the inner ears—and provides a good view of the nerves so the surgeon can preserve facial function.

The surgeon removes the entire tumor, or as much of it as is safely possible. To reach the tumor, surgeons occasionally remove the cochlea, the part of the inner ear that processes sound, or the otic capsule, which is the bony structure that surrounds the inner ear.

Because a portion of the inner ear is removed during this procedure, hearing is lost in that ear. Balance is usually not a problem because the opposite ear can take over this function, although rehabilitation therapy may be necessary to help the patient compensate for some loss of balance.

In general, the translabyrinthine approach is the best option when hearing has already been severely affected from the tumor or when tumors are large and hearing preservation is not possible.

Pros:

• Oldest approach - longest history
• Approach facilitates identification of facial nerve for preservation
• Allows for excellent exposure of the internal auditory canal and tumor
• Any size tumor can be removed with this approach.

Con:

• Results in permanent and complete hearing loss on tumor side

Retrosigmoid Approach

Surgeons may use a retrosigmoid approach for smaller acoustic neuromas when hearing preservation is possible. They use this approach for tumors that are growing out of the internal auditory canal and approaching the brainstem.

During this surgery, a surgeon makes an incision further behind the ear to open a portion of the skull called the occipital bone, located behind the mastoid. The cerebellum, a part of the brain located above the brain stem, falls back out of the way, and surgeons remove the bone over the internal auditory canal to fully access the tumor. The surgeons can view the facial nerve, the hearing nerve, and the brainstem.

If removing the entire tumor could damage nerves or brain tissue, the doctor may leave some small bits of the tumor behind. The section of the skull opened to perform this surgery is replaced after tumor removal. Fat from the periumbilical region, meaning the area surrounding the belly button, may be removed and used to seal the closure to prevent spinal fluid leaks.

Pros:

• Possible preservation of hearing 
• Approach provides a good view of the AN in relation to brainstem
• Possible preservation of facial nerve
• Any size tumor can be removed with this approach.

Cons:

• Hearing preservation decreases if the tumor is large.
• Headaches are a more prevalent post-op side effect.

Middle Fossa Approach

The middle fossa approach is an option for smaller tumors that have not grown beyond the internal auditory canal. As with the retrosigmoid approach, it is used to help preserve hearing. The surgeon makes an incision above the ear in the lateral skull bone, and then uncovers the internal auditory canal, and removes the acoustic neuroma. This approach is the best for saving hearing, which is possible in the majority of people who have the procedure. Then surgeons replace the skull bone and use fat from elsewhere in the body to help close the opening.

Pro:

• Possible preservation of hearing with small tumors in the right location, typically confined to the internal auditory canal

Con:

• Most often used only with small tumors, typically confined to the internal auditory canal.

Radiation Treatment Options

Stereotactic radiation can either be delivered as single-fraction radiosurgery (SRS) or by dividing the radiation dose over multiple sessions which is termed fractionated stereotactic radiotherapy (FRS). Both forms of radiation (SRS and FSR) work similarly by damaging the DNA within the tumor cells. The cells can no longer divide and eventually die over time, a process called necrosis. Both techniques are performed in the outpatient setting and do not require either general anesthesia or a hospital stay.

Over the last several decades, as the technologies for delivering stereotactic radiation have improved, an increasing number of patients have chosen to receive stereotactic radiosurgery as the primary treatment for their acoustic neuroma. There are several different commercially-available machines that are used to treat acoustic neuromas with the technologies differing in their source of radiation and how the radiation is precisely delivered.

• Gamma Knife® machines derive their radiation from a fixed-array of Cobalt-60 sources. These machines are typically used to deliver SRS in a single-session, although the newest platform (Leksell Gamma Knife® Icon™) allows for fractionated delivery (FRS).
• Linear Accelerator (LINAC) machines work by accelerating electrons to produce high-energy X-rays. The beam of X-rays (photons) is then shaped to the tumor as it exits the machine using a series of collimators and by rotating either the patient or the machine. LINAC machines are produced by a variety of different manufacturers with common trade names including CyberKnife®, Trilogy®, Novalis Tx™, and TrueBeam™ among others, with each machine available for both single-session (SRS) and multi-session (FSR) treatment.
• Proton Beam machines use a particle accelerator to generate radiation energy in the form of protons which can be delivered as either SRS or FSR.

Despite their differences, similar results in terms of effectively treating acoustic neuromas and avoiding side effects have been reported for each of the stereotactic radiation machines. The treatment team should consist of a neurosurgeon and/or a neurotologist and a radiation oncologist. The patient and the treatment team typically consider a number of factors before determining whether radiation therapy is appropriate including the size of the acoustic neuroma and the rate at which it is growing, the patient’s age and overall health, and the patient’s symptoms including the degree of hearing loss, balance problems, and vertigo. Typically, acoustic neuromas that are greater than 2.5 – 3cm in size are not considered ideal candidates for radiation therapy as these larger tumors often compress the surrounding brainstem and the potential for side effects from the radiation is increased.

Advantages of Surgery

• Surgery removes the tumor for those who want it "out of their body."
• Some patients have a fear of very rare, long term effects of radiation, such as induced malignancy.
• Size and/or position of the tumor may make radiation inadvisable, due to post-treatment swelling.
• Radiation may not be recommended for tumors larger than 2.5 to 3 cm.
• Younger age is generally another determining factor for choosing surgery.
• Sub or near-total tumor resection followed by radiation may be considered.

Advantages of Radiation

• Good option for patients in their mid-50's and older or with health issues.
• Radiation is typically an outpatient procedure, though some patients may stay in the hospital overnight. The radiation session itself is relatively quick. Some procedures are done in one session and others take several sessions.
• There is usually no need to take time off from work. Some people are treated on their way to or from work when having multiple sessions.
• There is no recuperation or convalescence time immediately after treatment.
• There are usually no immediate complications. In the medium term, there may occasionally be complications as radiation takes time to fully present symptoms.

Advantages of Observation

• Good option for small tumors, especially in older individuals; AN may not grow and may not require treatment.
• Hearing may be preserved longer in cases where the tumor presents on the only hearing side.
• All medical treatments, surgical or radiation, carry some risks. As ANs are benign and grow very slowly, many physicians will recommend having a second MRI at least 6 months after the first, to establish the growth rate. If the tumor is not growing, avoiding treatment altogether is a possibility.
• In time, safer treatments for acoustic neuromas, other than surgery or radiation, may be found.
• There are no known ways to cure or shrink an acoustic neuroma naturally.

What To Expect

Due to expanded use of MRIs, many acoustic neuroma tumors are discovered when they are relatively small. Because of this and the fact that acoustic neuromas are non-cancerous, the patient and caregivers typically have time to do thoughtful research on treatment options and medical providers. The ANA recommends getting more than one medical opinion about treatment whenever possible. It is also important to learn how various treatments will affect short and long-term quality of life. Depending on a variety of factors, a patient may be more concerned with hearing preservation, facial function, or other side effects.

Surgery

Surgery for an acoustic neuroma is performed under general anesthesia and involves removing the tumor through the inner ear or through a window in your skull. The entire tumor may not be able to be completely removed in some cases. For example, if the tumor is too close to important parts of the brain or the facial nerve.

Surgery can create complications, including worsening of symptoms, if certain nerve or cranial structures are affected during the operation. These risks are often based on the size of the tumor and the surgical approach used.

After surgery, the patient may spend a few days recovering in the hospital while doctor monitor and manage any pain, dizziness, and other symptoms the patient may be experiencing. If hearing has been affected by the surgery, the doctor can work with the patient to explore their options for hearing rehabilitation. Balance is recovered slowly, and most people can return to work in 8 to 12 weeks. (Included with permission by NYU Langone www.nyulangone.com.)

Radiation

If the decision is made to move forward with radiation, the treatment process usually begins by defining the radiation target using an MRI with gadolinium to visualize the acoustic neuroma. The stereotactic radiation planning software is then used to create a 3-dimensional model of the tumor and the surrounding structures. The treatment team along with a radiation physicist then creates dosimetry maps showing the level of radiation to be received by the tumor and the normal tissues and the treatment plan is optimized to focus the radiation as precisely as possible to the acoustic neuroma. The patient’s head is then stabilized with either a molded mask shield or a metal frame that is pinned to the skull. The type of stabilization device and the length of treatment depend on the stereotactic radiation machine being used, but treatments generally last between 30 -120 minutes for SRS and approximately 10-15 minutes for each treatment fraction with FSR.

Once radiation has been used to treat the acoustic neuroma, surveillance imaging, typically with MRI scans, should be performed for at least 10 years after the treatment to ensure that the tumor does not continue to show any signs of growth that would require further treatment.

Observation

Observation has become an accepted ‘treatment’ option for acoustic neuroma when the tumor is small, the patient is asymptomatic, is elderly, or the patient is averse to treatment. Many patients choose to observe their tumor for some period of time before considering treatment.

Monitoring will likely continue with periodic MRIs and other tests; surgery or radiation treatment may be recommended if there is tumor growth and/or an increase in symptoms. Doctors may also recommend treatment to preserve hearing, facial function, or other factors.

The Newly Diagnosed Handbook patient booklet has more detailed information about treatment options.

Balance Issues

Balance and dizziness issues are very common with acoustic neuroma, both pre- and post-treatment and can be long or short-term. Some patients experience vertigo, nausea, or what many describe as ‘wonky headedness’. These symptoms can be mild to severe, may be noticeable only during certain activities, or may impact ability to work or drive. The location of the tumor and its blood supply affect balance more than the tumor size itself.

Acoustic neuromas are also called vestibular schwannomas because they arise from the sheath of the eighth cranial nerve which plays an important role in the body's balance system. With surgery or radiation the balance nerve may be compromised and will take time to heal. If the nerve was severed, the balance nerve on the other side of the brain can take over, but this does not happen immediately. Balance or vestibular therapy can be quite effective for many acoustic neuroma patients. Refer to the ANA patient information booklet - Improving Balance Associated with Acoustic Neuroma.

Cognitive and Emotional Issues

The symptoms, diagnosis, and treatment options for acoustic neuroma can significantly challenge patients’ cognitive and emotional states. Fatigue, depression, relationship challenges, difficulty concentrating, and memory issues are potential side effects. There are therapies available specifically to brain tumor patients, and a neuropsychologist may be able to help. Neuropsychologists have expertise in assessing and treating problems with cognitive skills, psychological functions, and behavior as they relate to the brain and central nervous system. You may want to have an evaluation to determine which course of therapy and rehabilitation will work best for you. Your neurologist or neurosurgeon can help you find a Board Certified neuropsychologist, or you can contact The American Academy of Clinical Neuropsychology (AACN),https://www.theaacn.org/ to search for providers in your area.

Mindfulness and meditation courses, ANA Support Groups, yoga, spirituality or religious belief, improvement in diet, and getting enough sleep can also be helpful. Patients should seek local and online resources. The ANA has several webinars, videos, and articles available, as well as our information booklet Understanding Emotional, Cognitive, and Behavioral Changes.

CSF leaks

Cerebrospinal fluid, or CSF, is a watery fluid that flows in the ventricles (cavities) within the brain and around the surface of the brain and spinal cord. It is continuously produced and absorbed. On occasion, CSF leaks can happen after the microsurgical removal of an acoustic neuroma tumor. They can occur either through the nose or from the incision. Such leaks appear as a clear, watery discharge and can leave a salty taste in your mouth or a dripping feeling from your nose or from the incision. If left untreated, an infection that could lead to meningitis may follow, therefore these symptoms should be reported to your doctor immediately.

Eye Issues

Because of its proximity to multiple cranial nerves associated with eye function, removal of an acoustic neuroma may affect the eye of the patient. These nerves affect facial function, such as blinking and eyelid closure, sensation, tears, eye muscles and movement, and healing abilities.

Acoustic neuroma patients may experience difficulty blinking, excess moisture or dryness, double vision, or eye sensitivity. It is very important that the eye be protected and it may be necessary to apply artificial tears or to tape the eye shut to allow for healing. There are also several surgical options for improving eye issues. The ANA has a patient information booklet that covers eye issues in more depth– Eye Care after Acoustic Neuroma Surgery.

Facial Issues

Acoustic neuroma patients can experience facial pain, weakness, or paralysis, either before or after treatment. Post-surgery facial paralysis is less common than it used to be because of changes in the way surgeons attend to facial nerve concerns.

The 7th cranial nerve, or facial nerve, is often affected in the treatment of an acoustic neuroma. The nerve may be damaged with either surgery or radiation, however it is usually possible to preserve some degree of facial function, even in cases where the nerve is extensively involved. Temporary weakness of the face due to nerve swelling is common; although in some cases there may be permanent facial weakness.

If the facial nerve is damaged, it is possible for it to regenerate slowly. It is also possible to reconnect the facial nerve during or after surgery. When it is not possible to repair the facial nerve, additional surgeries may be necessary to substitute other nerves, allowing partial voluntary movement to return. There are also many non-surgical options including exercises for patients with facial issues. Refer to the ANA patient information booklet – Facial Nerve and Acoustic Neuroma – Possible Damage and Rehabilitation.

Headache

Headache post-treatment can be caused by a variety of reasons. The acute phase refers to headache experienced for the first several weeks post-treatment, due to the incision, variations in cerebrospinal fluid pressure, muscle pain, or even meningitic pain. Depending on the type of treatment, the reported incidence of headache ranges from 23% to 33% of patients. Frequent and severe post-operative headaches have been more often associated with the retrosigmoid/sub-occipital surgery approach than the translabyrinthine or middle fossa approaches. Chronic headache following acoustic neuroma surgery has been noted to be higher than after craniotomy for other causes.

Chronic headaches can persist for months or even years, and many times the exact prevalence and causes are elusive. Younger age, greater anxiety and depression, pre-existing diagnosis of migraine, and presence of headaches prior to treatment are the primary predictors of severe long-term headache disability, while tumor size and treatment modality had little influence. Preventative medications, local therapy to neck muscles, antidepressants, stress reduction, acupuncture, and lifestyle changes are all potential avenues for patients to explore. In the most resistant cases, it may be necessary to treat headaches in a multidisciplinary pain center. Refer to the ANA patient information booklet – Headache Associated with Acoustic Neuroma Treatment.

Migraine - More than a Headache (pdf)

Hearing Loss

Hearing loss in acoustic neuroma patients can vary from no or mild hearing loss to complete deafness (also known as profound hearing loss or single-sided deafness – SSD). Hearing loss on one side (asymmetrical) is the most common first symptom of acoustic neuroma. Approximately 90% of participants report single-sided hearing loss or deafness. Most patients present with a slowly progressive hearing loss; however, some patients experience a sudden loss of hearing on the side of the tumor. Tinnitus on the tumor side is also common. An audiologist will look for asymmetrical hearing loss, particularly high-frequency sensorineural hearing loss. 

Hearing loss may occur whether one chooses observation, radiation therapy, or surgery. Patients and their doctors should discuss the possibility of hearing preservation with each treatment option. There are many options for hearing aids, each with pros and cons. As the degree of hearing loss varies among patients, the type of hearing aid best-suited for each depends on many factors.

Hearing loss can disrupt one’s social and work life; it can contribute to depression and a sense of isolation. Hearing rehabilitation, using hearing aids, and assistive listening devices, can be quite useful and improve quality of life.

Refer to the ANA patient information booklet – Hearing Loss – Rehabilitation for Acoustic Neuroma Patients

Hydrocephalus

A small percentage of patients will suffer from hydrocephalus, caused by an excessive accumulation of CSF in the brain. This condition is alleviated by an operation which places a "shunt" in the area to drain the fluid and relieve the excess pressure.

Meningitis

CSF leaks and infection following surgery are rare occurrences which can lead to meningitis if left untreated. Meningitis is inflammation or irritation of the meninges (fluid and tissue surrounding the brain). One causal factor that is particular to acoustic neuroma surgery is the drilling of bone from within the intradural space for further exposure of the tumor in the internal auditory canal. This process is nearly exclusive to the retrosigmoid approach and is much less common in the translabyrinthine or middle fossa approaches. The drilling often results in bone dust distributed around the meninges in the posterior fossa, which can be difficult to remove completely. Two studies have highlighted the importance of bone dust in inducing meningitis following AN surgery. If this condition occurs, it would require an extended hospital stay.

Mouth Issues

It is not uncommon to experience dry mouth and taste disturbance for a few weeks following surgery or radiation treatment. In some cases the duration is prolonged. Dentists may recommend mouth rinses or other medications. If swallowing becomes a problem, a speech pathologist, nurse, or occupational therapist can provide exercises to help. Facial weakness or paralysis, numbness, or facial pain may impact chewing and drinking, tooth, and oral health. For patients experiencing these side effects, a dentist can help with these issues.

Regrowth of the Tumor

Recurrence of acoustic neuromas can be caused by several factors and usually only occur in a small percentage of patients. There is unfortunately no good way to predict which tumors will recur after treatment. Sometimes a small part of the tumor is left along the facial nerve at the time of initial surgery in an effort to preserve its function. Management options for the recurrence or re-growth of the tumor can include another surgery or oftentimes radiation. Each patient should be counseled on a case-by-case basis by doctors with expertise and experience with treating acoustic neuromas.

Seizures and Strokes

A rare complication of acoustic neuroma surgery is the possibility of a stroke due to damage to major blood vessels in the brain. Fortunately, current microsurgical techniques take great care to preserve all major blood vessels encountered during the removal of the tumor, making a stroke quite rare. However, any significant changes in thought processes or neurological functioning should be immediately reported to physicians.

Tinnitus

Tinnitus is the perception of sound when no actual external noise is present. While it is commonly referred to as “ringing in the ears,” tinnitus can manifest in many different perceptions of sound, including buzzing, hissing, whistling, swooshing, and clicking. In some rare cases, tinnitus patients report hearing music. Tinnitus can be both an acute (temporary) condition or a chronic (ongoing) health malady. – American Tinnitus Association

Tinnitus is a common presenting symptom of acoustic neuroma, and can impact quality of life. Although there is no cure for tinnitus, there are several treatment options that can lessen the impact on the patient. Some hearing aids and devices have features that mitigate tinnitus.

Early Symptoms

Early symptoms of acoustic neuroma (vestibular schwannoma) can be mistaken for other medical issues, and may be ignored or overlooked, thus making diagnosis a challenge. Approximately 90% of patients have single-sided hearing loss at the time of diagnosis. Hearing loss with acoustic neuroma is usually subtle and more pronounced in higher frequencies, although sudden hearing loss can occur. Sometimes the patient or doctor attributes hearing loss to aging, noise exposure, or allergies.

Approximately 70% of patients report tinnitus (ringing or noise in the ear) at the time of diagnosis, and 55% report vertigo/dizziness or balance issues. Other presenting symptoms can include a feeling of fullness/plugging in the ear, headache, facial weakness/paralysis, fatigue, eye problems, cognitive changes, and oral/swallowing issues. Some people find that these acoustic neuroma symptoms may come and go or fluctuate over time.

Since the balance portion of the eighth nerve is where the tumor arises, unsteadiness, vertigo, dizziness, or what many describe as ‘wonky-headedness’ may occur during the growth of the tumor. Acoustic neuroma patients often experience balance issues before diagnosis. The remainder of the balance system sometimes compensates for this loss, and, in some cases, no imbalance will be noticed.

Larger tumors can press on the trigeminal nerve, causing facial or tongue numbness and tingling, constantly or intermittently. Tumor-related increase of intracranial pressure may cause headaches, clumsy gait, and mental confusion. This can be a life-­threatening complication requiring urgent treatment. Even though the facial nerve (the nerve that moves the face) may be compressed by the tumor, it is unusual for patients to experience weakness or paralysis of the face from acoustic neuroma, although this may occasionally occur, either short or long term.

Typical Symptoms Overview

1. Unilateral Hearing Loss (on one side only) - This can sometimes occur suddenly (sudden hearing loss), but it generally can be very gradual, over months or years. In most acoustic neuroma patients, the loss is more pronounced in the higher frequencies. Unilateral hearing loss is usually the first symptom that leads to discovery of this benign brain tumor.

2. Tinnitus (ringing or buzzing in the ears) - Most AN patients do have tinnitus both before and after treatment. Not all patients with tinnitus have a brain tumor.

3. Feeling of fullness in the ear - Acoustic neuroma patients sometimes complain of a feeling that their ear is plugged or "full.”

4. Balance problems, vertigo - Acoustic neuroma patients often experience balance issues before diagnosis. It can occur very gradually and may go unnoticed as the body has many compensating mechanisms.

5. Headaches - Acoustic neuroma patients sometimes recall, after diagnosis, that they had unexplained headaches.

6. Facial pain, numbness, paralysis - Acoustic neuromas are usually discovered before they cause facial symptoms. However, if they are large or impacting one of the facial nerves, they can cause numbness, tingling or even facial paralysis.