[Subtemporal approach according to house versus Wigand in intrameatal CPA tumors type A]

The subtemporal approach is indicated in intrameatal CPA tumors type A in order to preserve hearing. The exploration of the inner auditory canal for tumor exposure varies. It reaches from a locally limited uncovering of the bony inner auditory canal to a complete removal of the surrounding bony bed with the circular skeletization (360 degrees ) according to Wigand of the 7 (th) and 8 (th) nerve. Concerning the preservation of the function of the cranial nerve as well as an avoidable hyperelevation of the temporal cerebral lobe with a possible consecutive organic brain syndrome, both approaches have often been discussed controversially.

In a quality assurance analysis, we examined patients suffering from a unilateral, intrameatally limited CPA tumor type A in tumor stages 1 to 5. The functions of the 7 (th) and 8 (th) cranial nerves were assessed according to the consensus conference "Systems for reporting results in acoustic neuroma", Tokyo, November 2001, under consideration of the recommendations of the "American Academy of Otolaryngology, Head and Neck Surgery -- Committee on hearing and equilibrium guidelines for the evaluation of hearing preservation in acoustic neuroma", 1995, as well as indications for a possible organic brain syndrome. The results then were compared to current literature.

37 patients with an intrameatal confined CPA tumor after subtemporal tumor exstirpation were evaluated. In these patients, the inner auditory canal was only exposed in the area of the bony tectum (90 degrees - 120 degrees ) adjusted to the volume of the tumor, as described by House: 1 patient with tumor stage 1, 2 patients stage 2, 12 patients stage 3, 16 patients stage 4 and 6 patients with a tumor stage 5. The N. VII was anatomically preserved in 100 %. Immediately after surgery the function of N. VII was assessed in 32 % of the cases as stage I, 43 % stage II, 3 % stage IIIa, 14 % stage IIIb, 3 % stage IV, 0 % stage V, 5 % stage VI. All patients in stage VI had a restricted function of N. VII in stage II or IIIa already before surgery. N. VIII could be preserved anatomically in 78 % of the cases. 1 to 6 months postoperatively the hearing was at stage A in 10 % of the cases, at 25 % in stage B, 33 % in stage C, 16 % in stage D, 5 % in stage E and 11 % in stage F. One patient demonstrated signs of a possible organic brain syndrome postoperatively even after 12 months of latency (headache, unsteady walking, attention disorders).

When comparing own data with the clinical results from literature, no differences can be found concerning the function of the 7 (th) and 8 (th) cranial nerves. There are no data concerning the incidence of a potential organic brain syndrome. The advantage of the House method is a noticeably reduced drilling time as well as possibly a reduced elevation of the temporal cerebral lobes. The Wigand method, however, allows a better overview and is needed for extrameatally growing tumors anyway.