Extent of facial nerve decompression at the geniculate ganglion and labyrinthine segment via transmastoid supralabyrinthine approach: cadaveric study.

OBJECTIVE

To quantitatively assess the extent of facial nerve decompression achievable at thegeniculate ganglion and labyrinthine segment using the transmastoid supralabyrinthineapproach in cadaveric specimens.

METHODS

Eleven formalin-fixed human cadaveric heads (22 temporal bones) underwentpreoperative high-resolution computed tomography (CT) to measure the lengths of thegeniculate ganglion and labyrinthine segment within their bony canals. A standardizedtransmastoid supralabyrinthine approach was then performed to decompress the facialnerve. Postoperative CT was used to determine the length of nerve segments successfully decompressed. Pre- and postoperative measurements were compared tocalculate the percentage of decompression achieved.

RESULTS

Complete exposure of the geniculate ganglion was achieved in all specimens. Themean total length of the labyrinthine segment was 3.28 ± 0.80 mm. Followingdecompression, a mean length of 1.37 ± 0.84 mm of the labyrinthine segment wassuccessfully unroofed, corresponding to an average decompression of 40 ± 22%. Noinjury to the ossicular chain, semicircular canals, or labyrinth was observed onpostoperative CT imaging.

CONCLUSION

The transmastoid supralabyrinthine approach enables safe, hearing-preservingdecompression of the geniculate ganglion and partial decompression of thelabyrinthine segment. Despite limited exposure of the labyrinthine segment, it mayserve as a feasible alternative in selected cases where more extensive approachesentail higher morbidity.