Minimally Invasive Meniere’s Office Surgery
Dexamethasone & Gentamycin Perfusion of the Inner Ear
Until fairly recently, surgical options for treatment of Meniere’s disease were limited. However, over the last 10 years, if medical therapy is unsuccessful, minimally invasive office surgical treatments have become the most common procedures performed to control Meniere’s disease. The treatments involve the injection of medication through an anesthetized ear drum. The medication then passes into the inner ear through a membrane, named the round window membrane. These techniques are generally called INNER EAR CHEMICAL PERFUSIONS. The two medications which are most frequently used in inner ear perfusions are Dexamethasone and Gentamycin.
Inner ear perfusion is performed in patients in whom vertigo from Meniere’s disease is uncontrolled with standard medical therapy, and behavioral lifestyle changes. The severity of the vertigo and the frequency of the vertigo attacks are also considered. Of the two techniques, the Dexamethasone inner ear perfusion has become the most frequent front line treatment for uncontrolled Meniere’s disease.
This involves a very strong type of cortisone drug named Dexamethasone. The exact mechanism and reason why this treatment works is not totally understood, but when the drug passes into the inner ear through the round window membrane, either through anti-inflammatory effect or other unknown effect, it results in control of the vertigo attacks in most patients, and it may also improve hearing in some patients.
Gentamycin perfusion of the inner ear is a second stage treatment in those cases where Dexamethasone perfusion of the inner ear is unsuccessful in controlling vertigo. It is usually reserved for patients with some impairment in their hearing. Gentamycin is believed to work by reducing the function of the receptors of the balance nerve; it is very effective but there is a higher risk of further hearing loss with this technique.
Dexamethasone perfusion of the inner ear has certainly become the preferred surgical treatment for the uncontrolled vertigo of Meniere’s disease at many centers around the country. Several studies have shown that the concentration of Dexamethasone that can be achieved in the inner ear is higher than what can be obtained by taking Dexamethasone orally.
Dexamethasone injections into the inner ear are offered to patients with Meniere’s disease if initial medical therapy over a period of several months has failed to control the attacks of vertigo. Studies have demonstrated up to an 80-90% response rate to Dexamethasone perfusions. Different protocols exist but in my practice Dexamethasone perfusion is usually performed in a series of three (3) treatments separated roughly a week apart. The drum is anesthetized locally and then a very small needle is passed through the drum and injected into the middle ear. The patient is advised to keep their head turned and avoid swallowing for approximately 30-40 minutes. During this time, the drug is absorbed through the membrane of the round window.
If the series of Dexamethasone perfusions fail to control the Meniere’s disease, then other options may include Gentamycin perfusion or other surgical techniques are discussed.
The most frequently recommended surgical procedure after inner ear perfusion is termed endolymphatic sac decompression (ELS). The risk of further hearing loss from the ELS procedure is quite low. The inner ear contains an endolymphatic sac which drains fluid from the inner ear. The surgical procedure involves opening the mastoid and decompressing and removing the bone over this sac.
If the sac is identifiable, an opening is generally made in the sac and a shunt, tubing or sheet of Silastic, which is a non-reactive plastic, is placed into the pocket that is created to drain the inner ear. In theory, this surgical procedure should reduce the pressure in the inner ear which would then subsequently reduce the frequency of vertigo attacks and improve the hearing. The operation unfortunately is only successful in approximately 2/3 of patients when results are followed over a 5 year post-operative period.
Additional procedures include vestibular neurectomy, which is generally performed with a neurosurgeon and which results in a high degree of control of vertigo, but is an intracranial procedure.
However, in a young patient with near normal hearing, but uncontrolled vertigo from Meniere’s, vestibular neurectomy offers excellent control of vertigo, generally with preservation of hearing.
If the patient has near complete deafness, a labyrinthectomy procedure destroying the remaining nerve of hearing and balance is also possibly offered. This procedure is offered less often in recent years because some patients with Meniere’s disease will ultimately benefit from a cochlear implant.
Endolymphatic Sac Decompression – I
The actual cause of the fluid accumulation in the inner ear, the condition which sets off the whole process to begin with in Meniere’s Disease, is not known. In animals, experiments have been done which show that if the sac that drains fluids from the inner ear is tied off, fluid will build up in the inner ear and cause changes comparable to those in humans. Because of the observation of fluid build up in the inner ear of animals, the most commonly performed operation in the past involved drainage of the endolymphatic sac in patients with Meniere’s.
The endolymphatic sac decompression operation is performed by making an incision behind the involved ear and exposing the mastoid bone. The mastoid is opened, and the facial nerve is identified in its course through the mastoid. The bone over the endolymphatic sac is then exposed and once identified, the sac is opened. A non-reactive sheet of silastic or a valve is inserted into the sac to allow for future drainage, when fluid reforms. The operation takes about an hour.
In theory, the endolymphatic sac operation should decompress the excessive fluid within the inner ear chambers and allow the inner ear to re-equilibrate, taking pressure off the nerve endings of hearing and balance. Studies have shown little positive effect on hearing from drainage of the endolymphatic sac. ESD often does NOT cure Meniere’s sufferers. Vertigo subsides after surgery in about 70 percent of Meniere’s cases, but vertigo symptoms recurr with the same severity as before in a significant number of individuals within three years of surgery.
The Labyrithectomy – II
Historically, ear surgeons have tried many procedures to cure vertigo. In individuals with complete or near complete hearing loss in one ear due to Meniere’s, a surgical procedure termed a labyrinthectomy is usually curative. Using the same approach through the mastoid bone as the older procedure, the endolymphatic sac operation, the inner ear balance organ (the labyrinth) is exposed. The semicircular canals are then carefully drilled away, exposing the nerve of balance which is completely removed.
Following surgery, there is often severe vertigo for a day or two. This can be controlled with medication. After a week, the patient experiences a period of moderate imbalance without vertigo while the opposite ear takes over the command of the entire balance function and assumes full control. This period can last six to eight weeks. The more active an individual is after surgery, the more rapid the recovery of balance function will be.
The two inner ear balance centers can be thought of as gyroscopes. The gyroscope of each ear helps to control balance by sending signals of the position we are in to the brain. If one gyroscope is faulty, as is the case in Meniere’s, the brain has trouble adapting, since it is intermittently getting wrong signals mixed with correct ones. However, if the inner ear balance nerve is completely shut off on one side and the "faulty gyroscope" removed, the brain will adapt to this new situation, since it now receives only correct signals from the one remaining gyroscope (inner ear) which will control the entire balance function. This is the reason labyrinthectomy is successful.
Labyrinthectomy does not spare any residual hearing. In a young individual, surgery that conserves the remaining hearing in the ear affected by Meniere’s is most important. A certain percentage of young people with Meniere’s may also develop the illness in their opposite ear later in their lifetime: 10 to 20 percent.
Vestibular Neurectomy – III
If there is substantial hearing present, vestibular neurectomy may be a prefered surgical option which can cure vertigo and preserve hearing.
Vestibular neurectomy involves the discrete sectioning of the nerve of balance near where it comes out of the brain. The hearing portion of the nerve is thus preserved. Ninety to 95 percent of vestibular neurectomies will result in cure of vertigo.
Hearing is preserved at the level experienced before surgery in most cases. The operation is a team effort performed by an ear surgeon and a neurosurgeon. Since the nerve must be identified as it exits the brain, the vestibular neurectomy is an intracranial operation.
Recovery from a vestibular neurectomy is similar to that of a labyrinthectomy. However, because it is an intracranial (brain) operation, closer post-operative monitoring will be the order of the day. Younger people (those who are less than 60) who are in good health are offered this operation as the most definitive operation both to cure vertigo from Meniere’s and preserve hearing. This minimally invasive operation takes less than two hours. A hospital stay of three or four days is usually necessary.
Other surgical procedures have been attempted over the years to treat Meniere’s Disease. Although the endolymphatic sac operation seems appealing from a physiologic point of view, the operation fails in many cases. This failure is probably due to the fact that the canal leading to the endolymphatic sac from the inner ear may be obstructed or clogged. Draining the sac can remove the excess fluid within it, but does not allow continuous drainage of fluid from the inner ear to the sac.