Acoustic Tumor Surgery

Overview

An acoustic neuroma (also known as a vestibular schwannoma) is a benign, typically slow-growing tumor that arises from the balance (vestibular) nerve between the inner ear and the brain. Once identified, there are three treatment options for an acoustic neuroma. These options are:

• Observation with periodic MRI scans to check for tumor growth
• Stereotactic radiation (discussed in the gamma knife section of our website)
• Surgical removal

Numerous factors are considered in order to decide which is the best treatment option. The decision is made on a case-by-case basis.

The following section discusses the surgical treatment of acoustic neuroma. For further information regarding other aspects of acoustic neuroma please click here.

Acoustic neuroma surgery is classified according to the approach to the tumor. The approach is the route that the surgeon uses to see and remove the tumor. Each approach provides not only a unique view of the tumor, but each approach also requires passage through different anatomical structures. The three main approaches to acoustic neuromas are:

1. Retrosigmoid
2. Middle Fossa
3. Translabyrinthine

The approach used must be selected prior to surgery since each surgical method is through an entirely different route. There are slightly different risks of each of these approaches, which will be discussed in more detail in subsequent sections. The decision for the best approach is based on several factors including:

1. Size of the tumor
2. Location of the tumor
3. Hearing status
4. Patient age/health status
5. Patient and surgeon preferences

The translabyrinthine approach is chosen when the patient has little to no hearing in the involved ear. This is because all hearing is lost with the translabyrinthine approach. The retrosigmoid and the middle fossa approaches are used when hearing may be preserved.

Facial nerve function is electrically monitored during surgery regardless of the surgical approach. Facial nerve monitoring is a valuable tool that aids the surgeon as the tumor is removed from alongside the facial nerve. Auditory (hearing) nerve electrical monitoring may be employed during operations when preservation of hearing is a goal.

Partial versus Total Tumor Removal

Partial Tumor Removal

In the majority of cases, the goal of surgery is the safe removal of all tumor. Under certain circumstances, however, it may be necessary to consider less than complete tumor removal despite the increased risk of regrowth if partial resection is performed. Partial removal of an acoustic neuroma may be indicated in some patients in the following situations:

• Older patients or patients in poor medical condition who have a large tumor that is a threat to life. Partial tumor removal can remove the tumor from vital areas of the brain.
• At the time of surgery, the surgeon may find that the tumor is firmly attached to the facial nerve. The surgeon may judge that total tumor removal carries a high risk of severely damaging the facial nerve.
• If the hearing in the opposite ear is poor, incomplete tumor removal increases the odds of hearing conservation.
• (Rare) During surgery the patient may deteriorate medically or neurologically. In this case, the operation may have to be terminated prematurely.

There are also varying degrees of partial tumor removal. Subtotal resection means that 95% of the tumor is removed. Usually, the 5% of tumor that remains lacks a usable blood supply and does not grow. Tumors that are partially resected with more than 5% remaining almost always continue to grow. Except in the elderly or seriously ill, partial resection with more than 5% remaining will often require revision microsurgery, or more commonly, gamma knife radiosurgery. Surgeons in the Ear Institute of Chicago, LLC are often able to decide how much tumor removal is appropriate prior to surgery. Circumstances during the operation, however, may require the surgeon to change from a planned total removal to a less than total removal.

Since partial tumor removal carries the risk of tumor regrowth, periodic MRI scans are absolutely necessary for routine follow up.

Total Tumor Removal

Many tumors can be removed entirely by surgery. Microsurgical techniques and instruments, along with the high-power binocular operating microscope, have reduced the surgical risks of total tumor removal. Preservation of the facial nerve is of paramount importance to the surgical team of the Ear Institute of Chicago, LLC. Preservation of hearing in the affected ear is also an important goal when a hearing preservation procedure is planned.