Acoustic neuroma surgery

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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 is the mainstay of treatment for acoustic neuroma.[1]

Surgery

There are three main surgical approaches for the removal of an acoustic neuroma: translabyrinthine, retrosigmoid or sub-occipital, and middle fossa. The approach used for each individual person is based on several factors such as:[2]

  • Tumor size
  • Location
  • Skill and experience of the surgeon
  • Whether hearing preservation is a goal
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

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.[1]

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.

Advantages of surgery

  • Tumor is completely removed and risk of recurrence is less than 0.1%
  • One follow-up MRI is needed
  • Hearing is preserved and it is stable over time

Disadvantages of surgery

  • In some cases, hearing cannot be saved
  • Long period of recovery, 4-6 day of hospital stay and 4-6 weeks to regain strength and balance
  • Leakage and infection of cerebrospinal fluid through the wound
  • Hearing loss
  • Facial numbness and weakness
  • Ringing in the ear
  • Balance problems
  • Persistent headaches
  • Stroke or brain bleeding

Stereotactic radiosurgery

In single dose treatments, many hundreds of small beams of radiation are aimed at the tumor. This results in a high dose of radiation to the tumor and very little to any surrounding brain structures. Many patients have been treated this way with high success rates. Facial weakness or numbness, in the hands of experienced radiation physicians, occurs in only a small percent of cases. This can be performed with either the linear accelerator or gamma knife. Radiosurgery is a treatment option for patients with smaller tumors (<3 cm) or for patients with enlarging tumors who are not candidates for surgery.

References

  1. 1.0 1.1 Vestibular Schwannoma. Wikipedia(2015) https://en.wikipedia.org/wiki/Vestibular_schwannoma Accessed on October 2 2015
  2. Acoustic neuroma. Medline Plus(2015) https://www.nlm.nih.gov/medlineplus/ency/article/000778.htm Accessed on October 2 2015

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