What is an Acoustic Neuroma?
An acoustic neuroma, otherwise known as a vestibular schwannoma, is an uncommon benign tumor that arises from the hearing and balance nerve. These tumors typically grow slowly over time.
What are the Symptoms?
The most common symptoms include hearing loss and tinnitus (ringing) on one side. The hearing loss typically worsens slowly over time, but it can sometimes be of sudden onset. Some patients also develop imbalance or spinning dizziness (vertigo). In more advanced cases, there can be chronic headache, facial numbness, clumsiness, and visual loss.
What is the Evaluation Process?
Patients with a suspected acoustic neuroma undergo a full ear, nose and throat evaluation in addition to testing such as an audiogram and imaging studies such as MRI or CT. If an acoustic neuroma is diagnosed, your physician will review these studies and present you with treatment options.
Figure 1 MRI showing left acoustic neuroma
What are the Treatment Options?
There are a variety of possible treatments for an acoustic neuroma. The factors that help determine the best course of action depends on the patient’s age, health status, tumor size, nature and degree of symptoms, and patient preference.
Since many of these tumors grow slowly over time, small tumors may be observed for some time prior to treatment.
Stereotactic radiosurgery has been used for many years in this country. There are various ways to provide this radiation treatment, including gamma knife and cyber knife. In most cases, the radiation is provided in a single dose as an out-patient. The treatment does not result in tumor removal but the tumor growth can be arrested for many years. Depending on the size of the tumor, the hearing function can often be preserved, but may decline over time. The facial nerve can be injured as a result of treatment but the risk of injury is low.
The tumor can be removed using various skull base approaches, depending on the size of the tumor and level of hearing. Complete tumor resection usually results in cure. The surgery involves a craniotomy (brain surgery), so an in-patient hospitalization is needed for 4 to 7 days, including intensive care for 1 to 2 days. The hearing function can be saved in some cases, depending on the tumor size. The facial nerve function is usually preserved well for small to medium size tumors.
Translabyrinthine approach – This technique reduces the amount of brain retraction that is needed by making space through the temporal bone. It results in complete hearing loss on the side of treatment and is usually used when the hearing loss due to the tumor is already severe.
Middle fossa approach – In cases of a small tumor where hearing could be preserved, this is a good approach. It is not used for larger tumors.
Retrosigmoid approach – In cases of very large tumors, this approach provides excellent exposure of the tumor site. This approach can also be used for small tumors where hearing could be preserved.
Figure 2 MRI after acoustic neuroma removal (from Figure 1)
After Surgery Care
Most patients can resume normal daily activities after discharge from the hospital. Some patients develop significant dizziness after surgery requiring balance exercise therapy. Most patients resume regular work within a month.
What is the long-term follow-up?
There is a small recurrence rate after tumor treatment that can become apparent many years after surgery. Patients should undergo periodic evaluation with MRI whether observation or treatment is chosen. There is a risk of significant hearing loss or deafness on the side of treatment, which can be alleviated with a hearing aid device called CROS or an implant called BAHA.
At the Texas Ear Center, we are committed to providing our patients the latest techniques in diagnosis and treatment of skull base tumors. In conjunction with the University of Texas – Houston and Memorial Hermann Hospital Skull Base Program, comprehensive management, including medical treatment, skull base surgery, radiation, sterotactic radiosurgery (gamma knife), and rehabilitation, is provided.