Acoustic Schwannoma which is also called by the name of Vestibular Schwannoma is quite a rare and slowly progressive tumor found in the inner ear, specifically of the nerve that connects the ear to the brain (the hearing nerve). Despite usually being benign, an Acoustic Schwannoma or Vestibular Schwannoma that grows and is not treated can severely affect neurological function and becomes life-threatening.
Acoustic Schwannoma is a type of brain tumor that develops in the eighth cranial nerve, which controls hearing and balance and is located in the inner ear near the back of the skull. One part of the eighth cranial nerve transmits sound and the other part sends balance information to the brain from the inner ear. It is one of the 12 cranial nerves that originate in the brainstem.
About 5% of all primary brain tumors are Acoustic Schwannoma or Vestibular Schwannoma.
What Is The Cause Of Acoustic Schwannoma or Vestibular Schwannoma?
Acoustic Schwannoma or Vestibular Schwannoma are believed to develop from an over production of Schwann cells that press on the hearing and balance nerves in the inner ear. Schwann cells are cells that normally wrap around and support nerve fibers. If the tumor becomes large, it can press on the facial nerve or brain structure. This type of brain tumor usually develops in adults between the ages of 30 and 60.
People with the genetic condition neurofibromatosis 2 often develop acoustic schwannoma or vestibular schwannoma in both ears. Neurofibromatosis 2 causes tumors on the nerves of the head and spinal cord and can cause brain tumors.
What Are The Symptoms Of Acoustic Schwannoma or Vestibular Schwannoma?
The following are the most common symptoms of acoustic schwannoma or vestibular schwannoma. However, each individual may experience symptoms differently.
When a neuroma develops, it may cause any or all of the following:
- Hearing Loss
- Tinnitus (ringing in the ears)
- Paralysis of a facial nerve
- Life-threatening problems in the brain
The symptoms of acoustic schwannoma or vestibular schwannoma may resemble other conditions or medical problems. Always consult your physician for a diagnosis.
How Is Acoustic Schwannoma or Vestibular Schwannoma Diagnosed?
Because symptoms of acoustic schwannoma or vestibular schwannoma resemble other middle and inner ear conditions, they may be difficult to diagnose. Preliminary diagnostic procedures include ear examination and hearing test. Computerized tomography (CT) and magnetic resonance imaging (MRI) scans help to determine the location and size of the tumor.
Early diagnosis of acoustic schwannoma offers the best opportunity for successful treatment.
A diagnosis of acoustic schwannoma or vestibular schwannoma at Johns Hopkins involves:
Hearing Test (Audiometry): A test of hearing function, which measures how well the patient hears sounds and speech, is usually the first test performed to diagnose acoustic schwannoma. The patient listens to sounds and speech while wearing earphones attached to a machine that records responses and measures hearing function. The audiogram may show increased “pure tone average” (PTA), increased “speech reception threshold” (SRT) and decreased “speech discrimination” (SD).
Brainstem Auditory Evoked Response (BAER): This test is performed in some patients to provide information on brain wave activity as a response to clicks or tones. The patient listens to these sounds while wearing electrodes on the scalp and earlobes and earphones. The electrodes pick up and record the brain’s response to these sounds.
Scans Of The Head: If other tests show that the patient may have acoustic schwannoma or Vestibular Schwannoma, magnetic resonance imaging (MRI) is used to confirm the diagnosis. MRI uses magnetic fields and radio waves, rather than x-rays, and computers to create detailed pictures of the brain. It shows visual “slices” of the brain that can be combined to create a three-dimensional picture of the tumor. A contrast dye is injected into the patient. If an acoustic neuroma is present, the tumor will soak up more dye than normal brain tissue and appear clearly on the scan. The MRI commonly shows a densely “enhancing” (bright) tumor in the internal auditory canal.
How Is Acoustic Schwannoma or Vestibular Schwannoma Treated?
Acoustic Schwannoma or Vestibular Schwannoma can often be removed completely with surgery. However, many Acoustic Schwannoma are so small that they may not need immediate treatment.
The Treatment For Acoustic Schwannoma or Vestibular Schwannoma depends on many factors, including:
- The size of the tumor
- The patient’s age
- The patient’s general health and preferences
- A multi-disciplinary team of doctors work together to recommend the most effective and safest treatment options for each patient.
Surgical Treatment Options For Acoustic Schwannoma or Vestibular Schwannoma: Treatments include surgery, radiosurgery and sometimes observation. Neurosurgeons and neuro-otologists at Johns Hopkins perform several types of craniotomy to remove acoustic neuromas. Surgical craniotomy approaches include the suboccipital, translabyrinthine approach and middle fossa approaches.
- Keyhole Brain Surgery (Retro-sigmoid craniotomy)
- Translabyrinthine craniotomy
Non-Surgical Treatment Options For Acoustic Neuromas: Surgery for larger tumors is complicated by the probable damage to hearing, balance, and facial nerves. Another treatment option is radiosurgery, which uses carefully focused radiation to reduce the size or limit the growth of the tumor.
For patients with smaller Acoustic Schwannoma or Vestibular Schwannoma, surgery and radiation therapy are equally effective. Doctors at Johns Hopkins generally recommend radiation therapy to treat older patients.
Radiation therapy (radiotherapy and stereotactic radiosurgery) — For radiosurgery, single vs. fractionated (multiple smaller treatments rather than one large treatment) are options. The fractionated stereotactic radiosurgery (FSR) appears to offer very high rates of control with preservation of hearing and preservation of the facial strength.
Observation — For some slow-growing Acoustic Schwannoma or Vestibular Schwannoma observation with delayed treatment may be acceptable. This is a common treatment option for elderly or infirm patients with mild symptoms where the risks of therapy may be greater and where the tumor may not grow during their lifespan.
Post-Surgical Treatment For Acoustic Neuromas: After treatment for Acoustic Schwannoma or Vestibular Schwannoma, some patients experience hearing loss, cerebrospinal fluid leak, damage to the nerves in the face and other problems. Johns Hopkins offers comprehensive surgical treatment and rehabilitation care for all of these problems.