This is an outstanding and well written paper showing why the Transotic (TO) approach provides better tumor exposure and facial nerve preservation than the translabyrinthine (TL) approach. The TL appr. does not give direct exposure of the anterior cerebello-pontine angle. With the TO approach the separation of the intracranial facial nerve from the anterior pole of the tumor is done under direct vision working anteriorly to the skeletonized tympanic and mastoid segments of the fallopian canal without need to displace the cerebellum. The disadvantages of the TO over the TL approach are the resulting total loss of hearing and the longer operative time; on the other hand, the advantages of the TO approach include better exposure and preservation of the facial nerve and significantly reduced incidence of immediate and delayed cerebrospinal fluid leaks with possible meningitis.
With the TO approach Y.Xia et al were able to preserve the anatomic integrity of the FN in all patients. 94% of the patients had at 6 weeks following surgery a postoperative HB grade I or II i.e. (using the quantitative scale of Fisch a DEFS of 100% or 77-83%). The results obtained by Y. Xia et al are in agreement with the data published by Fisch U. and Mattox D (1988) in the book Microsurgery of the Skull Base (G.Thieme): pp 74-135 and by Browne JD and Fisch U. (1992) in Otolaryng Clin N Am 25: 331-346.
I congratulate Y. Xia et al for having demonstrated so well that the TO approach has proven of value for the removal of vestibular schwannomas op to 5.0 cm in the presence of temporal bone contraction (reduced pneumatisation, anteriorly located sigmoid sinus, high jugular bulb, low middle cranial fossa) as determined by preoperative imaging (CT and MRI).
PS. In my opinion the conversion from the HB system to DEFS is desirable because the HB system puts the patient in a category (normal, slight, moderate, severe, total) whereas the Fisch DEFS allows to define a percentage figure for each single patient. The difference between both classifications is particularly evident for the HB III “moderate” class of results. The HB III is confusing because it includes patients having a 75% to 51% result. The 59 - 51 % facial palsy cannot be considered a moderate result and should be placed – at best - in a special category (s. Rickenmann J, Jaquenod C, Cerenko D et al (1997) Comparative value of facial nerve grading systems. Otolaryngol Head Neck Surg 117:322–325).