A.N. Treatment Options

Size Matters

The size of your AN may restrict your treatment choices. However, not only the tumor's size, but also its shape and position, have an impact as well. This is why doctors often talk of stages rather than size. Note that when only one size figure is given, it is usually the longest dimension, including the part within the internal auditory canal (IAC) plus the part that may extend into the cerrebelopontine angle (CPA). However, it is sometimes understood to be only the diameter of the roughly spherical part in the CPA.

Very Small

Very small click to animate When the AN is less than 10 mm and has few ongoing symptoms, one course of action is watch and wait. It may never grow. When considering surgery, the patient can generally expect that the smaller the tumor and the fewer the symptoms prior to treatment, the better the outcome afterward. Similarly, if radiation treatment is your choice, the chances of total hearing preservation will be greater with early treatment.


Small click to animate When the AN is between 10mm and 20mm, all treatment options are usually available to the patient. Radiation is suitable. Likewise, surgery is suitable, and complications are unlikely in the hands of an experienced surgeon (repeat: in the hands of an experienced surgeon). Even watch & wait remains an option at the lower end of this range.


Medium click to animate When the AN is between 20mm and 30mm, all options usually remain open. However, with surgery, complications such as facial paresis(1) are more likely, even in the hands of an experienced surgeon. At the lower end of this size range all types of radiation treatments are suitable. As the tumor size gets near the upper limit of this range fractionated stereotactic radiation treatments might avoid complications from swelling. Watch & wait would not normally be recommended for medium-sized tumors.


Large click to animate When the AN exceeds 30mm, options tend to become more limited. Surgery has a higher chance of side effects. With radiation, Single-session treatment is not usually an option when the part in the CPA exceeds 30mm. Fractionated stereotactic radiation is also often considered unadvisable in this size range, but, in expert hands it is reported to have treated large ANs with good results. Here position, shape and the choice of radio-surgeon become vital considerations. A final option is "debulking" (surgical removal of a large portion of the AN, while avoiding the nerves) followed by radiation to avoid re-growth.

What to do?

When both surgery and radiation are viable options, the choice will depend on personal fears and preferences.

  • Some people "want it out". They will choose surgery.
  • Others will avoid open surgery unless they have no other option. They will choose radiation.
  • There are those who decide their tumor may never grow much, and who have mild symptoms. They might choose to watch & wait

The Golden Rule

Whatever your choice, seek the best AN expert you can find. Between an excellent AN expert and a good doctor who is not an AN expert, the difference in outcomes can be life-changing. We have a list of questions for your interview with the doctors you will be trusting with your brain.

(Note all dimensions are in millimeters (mm) - 25 mm = approximately one inch)
1 Facial paresis is the medical term for facial paralysis, usually partial, often temporary, which results in a lopsided face and/or difficulty in closing the eye.