Diagnosing Acoustic Neuroma Initial symptoms of acoustic neuroma are difficult to distinguish from more common medical problems. In the beginning, 90 percent of people with an acoustic neuroma experience a reduction in hearing in one ear, often accompanied by tinnitus (ringing). Unsteadiness or balance problems may also be experienced, since the tumor originates on the eighth cranial nerve. As the tumor increases in size, it presses on other cranial nerves, including those that control facial movement and sensation.
Diagnosing an acoustic neuroma begins with specialized hearing tests, performed in the Koss Hearing and Balance Center at Froedtert & The Medical College of Wisconsin, to determine whether the cochlea and acoustic nerves are functioning properly. An Auditory Brainstem Response (ABR) test is performed to measure the passage of sound information from the ear to the brain.
If abnormalities are identified with audiologic testing, a Magnetic Resonance Imaging (MRI) test will be used to define whether an acoustic neuroma is present and to pinpoint its size and location. Sometimes, a facial nerve test is done to measure the tumor's impact on the nerve.
Multidisciplinary Treatment At the Froedtert & The Medical College of Wisconsin Neurosciences Center, diagnosis and treatment of acoustic neuromas and other skull base tumors is provided by a multidisciplinary team of specialists, including otolaryngologists, neurosurgeons, neurologists, radiation oncologists, neuro-ophthalmologists, medical geneticists, and rehabilitation specialists. Treatment plans are tailored to the individual patient and involve input from relevant disciplines.
In situations where the tumor is very small when discovered and there are few or no symptoms, it may be recommended that no treatment be undertaken at the time of diagnosis, but that the tumor be carefully observed and its growth monitored.
For most patients, complete or partial eradication of the tumor is necessary. Because of the tumor's location near vital brain centers, the procedure for removing an acoustic neuroma requires the utmost precision, in both locating and excising the tumor.
Surgical Options The most common option involves microsurgery, in which the tumor is surgically removed. The tumor is accessed through one of three approaches (translabyrinthine, retrosigmoid [suboccipital], or middle cranial fossa). The selection of the approach is based on tumor size and location, as well as the amount of hearing that the patient has before surgery.
Microsurgery is performed using high-powered microscopes and delicate surgical instruments. The surgery usually lasts between 4 to 12 hours and involves an experienced neurosurgeon and otolaryngologist (neuro-otologist) team who perform the surgery together. Hospital stays range from four to seven days, with an average of four to six weeks recovery time.
The second surgical option is radiosurgery, or stereotactic radiation therapy, a non-invasive procedure that uses high-dose-rate radiation to destroy the tumor. Unlike conventional radiation therapy, in which multiple doses of radiation are delivered over several weeks of treatment, radiosurgery involves only a single dose-delivered to the precise location of the tumor.
The third option is fractionated radiosurgery, in which multiple fractions of radiation-delivered at varying angles-are focused on the tumor site. The Froedtert & The Medical College of Wisconsin Neurosciences Center is the first in Wisconsin to have advanced Gamma Knife technology available for this use. The Gamma Knife unit is the world standard for superselective irradiation of tumors and uses advanced imaging technology to identify the exact size, shape and location of the tumor. Once the tumor has been pinpointed, the Gamma Knife directs 201 converging beams of radiation on the site, sparing adjacent tissue of clinically significant radiation.
An important characteristic of the Acoustic Neuroma Program is that a surgical team approach is used not only for the microsurgical removal of tumors but also for the stereotactic radiosurgical treatment of tumors.
This collaborative approach utilizing the expertise of a neuro-otologist and neurosurgeon team is designed to enhance clinical outcomes.
In addition to the Gamma Knife, the surgical team has access to a LINAC-based radiosurgery system. In this system, a relocatable, mask-based, stereotactic head ring is used to direct the fractionated radiation beams. The system uses the same stereotactic localizing technique as used for Gamma Knife treatments, thereby assuring that the radiation dose tightly conforms to the shape of the targeted tumor. The fractionated LINAC-based system is typically used for tumors that are too large to be treated using Gamma Knife technology.
All three surgical options are available within the Froedtert & The Medical College of Wisconsin Neurosciences Center. Medical and surgical specialists are available to consult with patients and help them choose the most appropriate treatment option.
Last Review Date: 10/15/08
Online Editor(s): Tracey Brand