Risks and Complications of Acoustic Tumor Surgery
It is not possible to list every complication that might occur before, during or following a surgical procedure. The following discussion is included to indicate some of the risks and complications peculiar to acoustic neuroma surgery.
In general, the smaller the tumor at the time of surgery, there is less chance of complications. As the tumor enlarges, the incidence of complication becomes increasing greater.
In small tumors it is sometimes possible to save hearing by removing the tumor. Most tumors are larger, however, and the hearing is lost in the involved ear as a result of the surgical procedure. Therefore, following surgery the patient hears only with the remaining good ear. However, there are now new techniques to help cross the sound over from the deaf ear to the “good ear” such as CROS hearing aid, a Bone Anchored Hearing Aid (BAHA).
Tinnitus (ear noise) remains the same as before surgery in most cases. In 10% of the patients the tinnitus may be more noticeable.
Taste Disturbance and Mouth Dryness
Taste disturbance and mouth dryness are not uncommon for a few weeks following surgery. In 5% of patients this disturbance is prolonged.
Dizziness and Balance Disturbance
In acoustic tumor surgery it is necessary to remove part or all of the balance nerve and, in most cases, to remove the inner ear balance mechanism. Because the balance nerve usually has been damaged by the tumor, its removal frequently results in improvement in any preoperative unsteadiness. Dizziness may occur, nonetheless, following surgery and may be severe for days or a few weeks. Imbalance is prolonged in 30% of the patients until the normal balance mechanism in the opposite ear compensates for the loss in the operated ear. Some patients notice unsteadiness for several years, particularly when fatigued.
At times the blood supply to the portion of the brain responsible for coordination (cerebellum) is decreased by the tumor or the removal of the tumor. Difficulty in coordination with arm and leg movements (ataxia) may result.
Acoustic tumors are in intimate contact with the facial nerve, the nerve which controls movement of the muscles which close the eyelids as well as the muscles of facial expression. Temporary paralysis of the face and muscles which close the eyelids is common following removal of an acoustic tumor. Weakness may persist for six to twelve months and there may be permanent residual weakness.
Facial nerve monitors pioneered here at Michgan Ear Institute have dramatically improved our ability to preserve the facial nerve.
Facial paralysis may result from nerve swelling or nerve damage. The facial nerve is usually compressed and distorted by the tumor in the internal auditory canal. Careful tumor removal, with the help of an operating microscope, usually results in preservation of the nerve but nerve stretching may result in swelling of the nerve with subsequent temporary paralysis. In these instances facial function is observed for a period of months following surgery. If it becomes certain that facial nerve function will not recover, a second operation may be performed to connect the facial nerve to a nerve in the neck (facial hypoglossal anastomosis).
In 5% of cases the facial nerve passes through the interior of the acoustic tumor. On occasions the tumor may even originate from the facial nerve (facial neuroma). In either instance it is necessary to remove all or a portion of the nerve to accomplish tumor removal. When this is necessary it may be possible to immediately reconnect the facial nerve or to remove a skin sensation nerve from the upper part of the neck to replace the mission portion of the facial nerve. If this is not possible a second operation may be performed to help reanimate the face.
Should facial paralysis develop the eye may become dry and unprotected. Care by an eye specialist may be indicated. It maybe necessary to apply artificial tears to tape the eye shut. When prolonged facial nerve paralysis is expected, implantation of a gold weight or spring into the eyelid helps keep the eye moistened as well as providing comport and improved appearance.
Other Nerve Weaknesses
Acoustic tumors may contact the nerves which supply the eye muscles, the face, the mouth and throat. These areas may be injured with resultant double vision, numbness of the throat, weakness of the face and tongue, weakness of the shoulder, weakness of the voice and difficulty swallowing. These problems may be permanent.
Brain Complications and Death
Acoustic tumors are located adjacent to vital brain centers which control breathing, blood pressure and heart functions. As the tumor enlarges it may become attached to these brain centers and usually becomes intertwined with the blood vessels supplying these areas of the brain.
Careful tumor dissection, with the help of an operating microscope, usually avoids complications. If the blood supply to vital brain centers is disturbed, serious complications may result: loss of muscle control, paralysis, even death. In our experience death occurs rarely as the result of the removal of small acoustic tumors and occurs in less than 1% in the larger tumors.
Postoperative Spinal Fluid Leak
Acoustic tumor surgery results in a temporary leak of cerebrospinal fluid (fluid surrounding the brain). This leak is closed prior to the completion of the surgery with fat removed from the abdomen. Occasionally this leak reopens and further surgery may be necessary to close it.
Postoperative Bleeding and Brain Swelling
Bleeding and brain swelling may develop after acoustic tumor surgery. If this occurs a subsequent operation may be necessary to reopen the wound to arrest bleeding and allow the brain to expand. This complication can result in paralysis or death.
Infection occurs in less than 5% of the patients following surgery. This infection may occur at the wound site or could present as meningitis (extremely rare), which an infection of the fluid and tissue surrounding the brain.
When the complication occurs, hospitalization is prolonged. Treatment with high doses of antibiotics is often indicated. These antibiotics can cause allergic reactions, may suppress the body’s blood-forming tissues or may produce hearing loss in the good ear. Fortunately these antibiotic complications are rare.
Although extremely rare, it may be necessary to administer blood transfusions during acoustic tumor surgery. Immediate adverse reactions to transfusions are uncommon. A late complication of a transfusion is vital infection of the liver (hepatitis). This occurs in less than 5% of transfused patients. When this complication occurs, medical treatment is necessary, at times requiring rehospitalization. Many patients will consider banking their own blood in advance of surgery. Please ask your doctor for details of such “auto-donations”.