Acoustic Neuroma Surgery & Skull Based Surgery

Acoustic tumors are tumors of the balance and hearing nerves, which are situated between the inner ear and the brain. The tumor usually grows slowly. As it grows, it presses against the hearing and balance nerves. When extensive, they can press against the brain and other nerves.At first, you may have no symptoms or mild symptoms. They can include:

  • Loss of hearing on one side
  • Tinnitus, (usually a ringing or buzzing) and usually in one ear or louder on one side of the head
  • Dizziness and balance problems
  • Ear pressure or fullness

Large tumors may cause headache, worsening dizziness and facial numbness. These tumors sometimes do grow to a large size while causing few symptoms because they grow very slowly.

Acoustic neuroma can be difficult to diagnose because the symptoms are similar to those of middle ear problems.

Acoustic Neuroma Treatment

Early diagnosis of a vestibular schwannoma (acoustic neuroma) is key to preventing its serious consequences. An MRI scan with gadolinium is the gold-standard test in the diagnosis of acoustic neuromas. Other testing is usually performed after diagnosis to assist in the decision regarding treatment. These may include tests of hearing, balance and the facial nerve. Other tests may be required such as blood flow evaluations and cardiology consultations.

There are three options for managing a vestibular schwannoma:

Surgical Removal

Microsurgical removal is usually recommended in healthy people with growing tumors or when the tumor is very large and there are no other options. The surgery is a fairly extensive operation performed over several hours and requiring observation after surgery in the intensive care unit for on average 1-2 days. Dr. Maw believes in a team approach to this delicate procedure and usually performs the surgery with the assistance of a neurosurgeon. The patient is cared for by a whole team of specialists including Dr. Maw, a neurosurgeon, an anesthesiologist, a specialist who monitors the cranial nerves during surgery and intensive care unit physicians and staff. This approach facilitates the highest standard of care and best outcome for the patient.

Dr.Maw has extensive training and experience in performing microsurgery for the removal of acoustic neuromas. She completed a prestigious fellowship at the Michigan Ear Institute which is one of the world’s largest centers for acoustic neuroma treatment.

The exact type of operation done depends on many factors. The most significant are the size of the tumor and the level of hearing in the affected ear. If the tumor is very small, hearing may be saved and accompanying symptoms may improve. As the tumor grows larger, surgical removal is more complicated and hearing and balance may be lost. The facial nerve accompanies the nerves of hearing and balance along their course from the brain through the ear and this is a very important nerve to protect during microsurgery. The preservation of the facial nerve is of utmost importance, and is more of a priority than the patients hearing. The three approaches to remove an acoustic neuroma are:

The Translabyrinthine Approach: In this approach, the surgeon works through the inner ear, or labyrinth, to remove the tumor. The patient is totally and permanently deaf after this operation, however there are advantages to this procedure that warrant considering this approach even is the patient has residual hearing in the ear before surgery. The facial nerve is most visible, and therefore protected during the surgery. There us usually less stretch and injury to the facial nerve and the facial nerve function results are usually excellent. As most of the exposure of the tumor with this procedure occurs outside of the envelope for the brain, the dura mater, there is less post-operative headache and so this is often a good choice of approach for patients who suffer from migraine or other headaches. If balance problems are present prior to surgery, this is often a good choice of surgery as it allows the abnormal balance function to be removed and the patient can then usually compensate and regain balance. Another complication, spinal fluid leakage, is on average slightly lower with this approach. A fat graft is taken from the abdomen and placed into the ear to seal the hole.

The Retrosigmoid Approach: In this approach, the tumor is exposed via entering the skull and opening the dura mater (a craniotomy) behind the ear. The back of the brain, or cerebellum, is retracted to gain access to the location of most tumors. Removal of some bone is usually required while working within the open dura mater, and this can be a source of headache after surgery. The advantage of this procedure is the possibility to preserve the patients hearing. The surgeon also gains ample access to the area where the tumor is in contact with the brain, and is a good choice in patients with large tumors or when the tumor is not an acoustic neuroma. The skull bone is repaired with bone graft or bone cement to minimize headaches. Spinal fluid leakage may be slightly higher for this approach.

The Middle Fossa Approach: In this approach, the tumor is exposed through the skull above the ear and the temporal lobe of the brain is lifted and gently retracted to access the location of the tumor. The advantage of this approach is the potential ability to preserve hearing and is often chosen in the setting of healthy patients with small tumors and good hearing. Tumors over 1.5 cm are difficult to remove via this approach. Hearing preservation generally depends on the size of the tumor, but is still not guaranteed even with very small tumors. The skull bone is reconstructed with tiny bars of titanium and special screws. In some cases, the facial nerve is on the far side of the tumor with this approach, and stretching of this nerve is sometimes necessary to remove the tumor. This can cause a higher risk of facial weakness but is usually temporary.

Radiation

Stereotactic radiation (gamma knife or LINAC) is considered as a treatment option in many patients and is likely the best treatment option in sick or elderly patients with growing tumors who need treatment. A fine , focused beam of radiation is used to minimize the side effects of radiation on the brain and other nerves. The tumor is not removed. The treatment usually stops the tumor from growing larger, and in some cases causes it to shrink. As in surgery, the complications of hearing and balance function may occur, but often occur more slowly than with surgery. Radiation is not an option for the treatment of very large tumors with pressure effect on the brain. Researches are still evaluating the long-term effectiveness of this therapy in young, healthy patients.

In many cases, it may be reasonable to "watch" the tumor for growth. Repeat MRI over time is used to carefully monitor the tumor. Typically, the tumor is surgically removed (excised). Many tumors grow slowly, a few millimeters a year. They can rarely grow rapidly. If Observation is chosen, a repeat MRI scan is usually obtained in 6 months and then yearly if stable. The hearing may be lost in this approach, as patients with these tumors sometimes do have a rapid deterioration of hearing.

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