I concur with Russ.  I had trans-lab to ensure ALL vestibular nerves/fibers were removed, basically the entire inner ear.  With middle fossa, they can leave some nerves/fibers, as well as with retro-sigmoid.  This can cause problems however.  Read below the piece by rtigger where the remaining nerve fibers from middle fossa kept causing her problems.  Me, have ongoing serious dizziness issues but appear to be something else (Mal de Debarquement).
Here's her story:
Hi Everyone-
I have been discussing Nan's dizziness with her off line but wanted to share my story.  I am not so sure of the MdD diagnosis.  I was diagnosed with an AN in my left ear in 11/03 (1.0 x0.9 cm but growing out of the EAC towards my brain stem). I had it removed by Dr Fayad/Hitz at House Ear in Los Angeles, CA on 12/3/03 via Middle Fossa approach. I was in the hospital 6 days because I developed a CSF Leak on day 2 and required a spinal drain for 3 days.  No more clear fluid from my nose at that time.  I had the usual balance/dizziness/fatigue problems before and then more so post surgery.  I recovered and for several months I was doing quite well. I lost my hearing in the left ear but minimal facial problems. I had a BAHA hearing aide placed 4/04 which has considerably assisted in my recovery and my return to work.  My balance was functional, not perfect but very functional.  I returned to work 7/04 as a nurse case manager in a community hospital.  Then in January 2004 I started to feel progressive balance and dizziness problems resulting in my inability to function/work, I felt awful. I went on disability again 5/05.  I had vestibular testing that was negative except for some mild nystagamus.  My physician stated because I had a middle fossa approach and they tried to save my hearing (unsuccessfully) they did not cut the complete vestibular nerve (the vestibular nerve has an upper and a lower branch, the lower branch does not always respond to standard vestibular testing).  Because I was cotinuing to get worse my physician started me on gentamycin injections into the affected ear.  The first one lasted about 2 months and then the dizziness started again.  We tried 3 more gentamycin injections which were not as helpful.  After working with my neurotologist and my nerurosurgeion we decided to procede with a laybrynthectomy and vestibular nerve resection which was done 7/05. The belief was that I was growing a neroma on my vestibular nerve that was damaged during my original surgery and this  was giving off bad signals to my brain, causing my problems.  After surgery I was told that I had vestibular nerve fibers growing in my hearing nerve (quite unusual, they discussed my case at grand rounds, Dr Hitz/neurosurgeon states he had not seen this before and he as done thousands of ear surgeries, talk about one in a million). Therefore, they also resected my hearing nerve since I was already deaf in that ear.  I was significantly more dizzing with very poor balance post op with  nystagamus,  my physicians felt this was a good sign,  if the nerve was completely dead then cutting it should not have made my condition worse.  I went to vestibular rehab for 4 weeks and progressively improved.  I was able to return to work in September 1995 with minimal balance/dizziness problems.  A success!!!