Acoustic neuroma surgery
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Acoustic neuroma Microchapters | |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Surgery
| Tumor Size | Treatment line | Treatment |
|---|---|---|
| Tumor < 1 to 1.5 cm | ||
| No tumor growth | First | Observation |
| Second | Focused radiation or surgery | |
| With tumor growth | First | Focused radiation or surgery |
| Adjunct | Salvage radiation or surgery | |
| Second | Observation | |
| Tumor 1.5 to 3cm | ||
| No tumor growth | First | Focused radiation or surgery |
| Adjunct | Salvage radiation or surgery | |
| Second | Observation | |
| With tumor growth | First | Focused radiation or surgery |
| Adjunct | Salvage radiation or surgery | |
| Second | Observation | |
| Tumor > 3cm | First | Surgery |
| Second | Observation |
There are three main surgical approaches for the removal of an acoustic neuroma:
- Translabyrinthine
- Retrosigmoid/sub-occipital
- Middle fossa.
Removing an acoustic neuroma is more commonly done for:
- Larger tumors
- Tumors that are causing symptoms
- Tumors that are growing quickly
- Tumors that are pressing on the brain
Surgery is done to remove the tumor and prevent other nerve damage. Any hearing that is left is often lost with surgery.The approach used for each individual person is based on several factors such as tumor size, location, skill and experience of the surgeon, and whether hearing preservation is a goal. Each of the surgical approaches has advantages and disadvantages, and excellent results have been achieved using all three of the techniques. Removing an acoustic neuroma is more commonly done for:
Surgery generally results in satisfactory long term control of vestibular schwannomas; however, one group has reported a 10 year recurrence rate for partially resected schwannomas of 20 percent and a similar rate for incompletely resected tumors.
Surgical techniques — There are three standard operative approaches. Selection of a particular approach is determined by a number of factors, including the size of the tumor and whether or not preservation of hearing is a consideration.
●Retromastoid suboccipital (retrosigmoid) - The suboccipital approach can be used for any size tumor with or without attempted hearing preservation. ●Translabyrinthine - The translabyrinthine approach has been recommended for acoustic tumors larger than 3 cm and for smaller tumors when hearing preservation is not an issue [24]. ●Middle fossa - The middle fossa approach is suitable for small (<1.5 cm) tumors when hearing preservation is a goal. In many institutions, a team consisting of a neurosurgeon and an otologist perform the procedure. The experience of both the surgeon and the hospital are important in optimizing the surgical outcome and minimizing the risk of complications
Microsurgery
Microsurgical tumor removal can be done at one of three levels: subtotal removal, near total removal or total tumor removal. Subtotal removal is indicated when anything further risks life or neurological function. In these cases the residual tumor should be followed for risk of growth (approximately 35%). If the residual grows further, treatment will likely be required. Periodic MRI studies are important to follow the potential growth rate of any tumor. Near total tumor removal is used by experienced centers when small areas of the tumor are so adherent to the facial nerve that total removal would result in facial weakness. The piece left is generally less than 1% of the original and poses a risk of regrowth of approximately 3%. Periodic MRI studies are important to follow the potential growth rate of any tumor. Many tumors can be entirely removed by surgery. Microsurgical techniques and instruments, along with the operating microscope, have greatly reduced the surgical risks of total tumor removal. Preservation of the facial nerve to prevent permanent facial paralysis is the primary task for the experienced acoustic neuroma surgeon. Preservation of hearing is an important goal for patients who present with functional hearing.
Translabyrinthine approach
The translabyrinthine approach may be preferred by the surgical team when the patient has no useful hearing, or when an attempt to preserve hearing would be impractical. The incision for this approach is located behind the ear and allows excellent exposure of the internal auditory canal and tumor. This also results in permanent, and complete hearing loss in that ear, but the surgeon has the advantage of knowing the location of the facial nerve prior to tumor dissection and removal. Any size tumor can be removed with this approach and this approach affords the least likelihood of long-term postoperative headaches.
Retrosigmoid/sub-occipital approach
The incision for this approach is located in a slightly different location. This approach creates an opening in the skull behind the mastoid part of the ear, near the back of the head on the side of the tumor. The surgeon exposes the tumor from its posterior (back) surface, thereby getting a very good view of the tumor in relation to the brainstem. When removing large tumors through this approach, the facial nerve can be exposed by early opening of the internal auditory canal. Any size tumor can be removed with this approach. One of the main advantages of the retrosigmoid approach is the possibility of preserving hearing. For small tumors, a disadvantage lies in the risk of long-term postoperative headache.
Middle fossa approach
This approach is in a slightly different incision location and is utilized primarily for the purpose of hearing preservation in patients with small tumors, typically confined to the internal auditory canal. A small wind of bone is removed above the ear canal to allow exposure of the tumor from the upper surface of the internal auditory canal, preserving the inner ear structures.