Various Surgical Approaches
and Pros and Cons of each
There are currently three types of AN surgery:
The unfortunate fact of AN-ology still remains that surgery increases the incidence of headaches and may cause facial paralysis, for all approaches. Your surgeon's experience with the particular approach being considered is more important that any overall statistics of one approach vs. another - talk to your surgeon!
Also, neurosurgeons differ somewhat in the "exposure" they feel is important to see what they are doing. Just from retrosigmoid, you can see widely variant scar sizes, some in the shape of a large "cane" or "question mark", others much smaller. The bottom line is we need to ask a lot of questions before deciding on our medical team and on the best approach to putting an end to our ANs.
Translabyrinthine is an approach through the mastoid and semicircular canals to the internal auditory canal. See this site for pictures of the translab approach: http://www.earsite.com/tumors/tr1.html (click next to see steps in the procedure.)
Pros: The one taught in medical schools, this surgical approach is preferred by many surgeons since it gives an excellent view of the tumor in the internal canal. Translab provides direct exposure of the tumor without the need to push aside any brain tissues to get at it. Translab makes it easiest to avoid the risk of facial nerve damage and facial paralysis (according to an article by a prominent neurosurgeon Dr. Brackmann, this is because translab permits positive identification of the facial nerve). Also, few muscles are attached to the mastoid so that there is little muscle pain after surgery. This surgical approach can be performed relatively quickly for small tumors.
Cons: Total deafness and loss of vestibular apparatus (balance organ) are guaranteed. The exposure is relatively small, so removal of large tumors may take longer and may be riskier. For such tumors, even when the facial nerve is preserved, there is a risk of a significant drop in the quality of life as a result of accidental damage to the brain; here are some translab stories.
Middle Fossa approach
Pros: Middle Fossa approach (MF) has the best record for preserving hearing for ANs under 2cm, which is why it is preferred by the AN specialists who have extensive training in AN surgery.
Cons: MF is limited to relatively small ANs (under 2cm). and mostly in the inner auditory canal. Also, MF is dangerous to the facial nerve, requiring extra training. Also, this approach involves the retraction (pushing aside) of the temporal lobe (part of brain responsible for speech and memory). The longer it is retracted, the more risk there is for problems, which would include difficulty finding words in speech, and slippages in memory.
By AN patients:
The approach opens the inner auditory canal from the top. The facial nerve is on top of the bundle of nerves running through the inner auditory canal. Beneath it is the vestibular (balance nerve) which the AN usually grows from. Beneath the balance nerve is the hearing nerve. Since the approach opens the inner auditory canal from the top, the surgeon must go around the facial nerve to get to the AN. Each AN is different, and often times there are no problems, but occasionally, the facial nerve is in the way of the AN. If it is in the way, and I don't think they are able to tell if it will be in the way or not from the MRI, and you have already opened the inner auditory canal from this approach I think it's too late to switch to another approach.
Here is how my doctor described the procedure: "After we get you asleep we give you a very strong diuretic, which lowers fluid levels throughout your body. This has the effect of shrinking the brain. After we cut the silver-dollar sized hole in front of and above your ear, we have to retract (push out of the way) the (I think he said cerebral cortex) a little bit to get at the internal auditory canal. The area we push on has two functions: speech and language. There's a very small chance we can do some bruising there, which can lead to varying degrees of impediment."
See this site for pictures of the middle fossa approach: http://www.earsite.com/tumors/mf1.html (click next to see steps in the procedure.)
Retrosigmoid / suboccipital
The retrosigmoid approach is used when the tumor is located mostly outside the internal auditory canal and adjacent the brain stem.
I had retrosigmoid removal of a 3.8 cm AN two years ago. The tumor was large, located "high "and was compressing the brain stem. My surgeon felt he would not get good visualization of the tumor with a trans lab approach...
It is also used when hearing preservation is desired, by those with ear training.
Pros: this approach does not guarantee hearing loss, and is less risky to the facial nerve;
Cons: More than a half of the patients still lose their hearing. Also, according to medical literature, retrosigmoid patients are at highest risk of suffering persistent postoperative headaches; reported is a "10% incidence of severe postoperative headaches" with this approach. These headaches are often caused by damage to the occipital nerve, so-called occipital neuralgia. Suprisingly, those with small tumors (< 1 cm diameter) fare worse than with larger ones! With some incision styles (such as long vertical nuchal incisions) headache and neck pain are more common than others. Also, this approach often involves the retraction (pushing aside) of the cerebellum (part of brain responsible for balance and muscle control). The longer it is retracted, the more risk there is for problems
See this site for pictures of the retrosigmoid approach: http://www.earsite.com/tumors/sa1.html (click next to see steps in the procedure.)
For completeness, we mention the possibility of the endoscopic approach to AN surgery. This is a minimally invasive technique, creating a dime-sized incision behind the ear. A miniature fiberoptic videocamera is snaked in through the holem so the tumor site can be viewed on a screen.
The consensus among neurosurgeons is that this approach is too risky:
I asked four doctors about that and they all said it is VERY, VERY risky!! If the surgeon inadvertently cut a blood vessel, you could bleed to death before they could get your skull open to fix it.
Last Edited: Tuesday, November 18, 2003