Quantification of the presigmoid transpetrosal keyhole approach to petroclival region.

BACKGROUND

Despite the presigmoid transpetrosal approach has been used by different researchers in various ways, the surgical injury rate remains high. Applying a minimally invasive keyhole idea, we devised a presigmoid transpetrosal keyhole approach (PTKA), classified and quantitatively assessed their approach to the petroclival area on a cadaver model by using a neuronavigation system.

METHODS

The presigmoid transpetrosal keyhole approach was divided into four increasingly morbidity-producing steps: retrolabyrinthine, partial labyrinthectomy with petrous apicectomy, translabyrinthine and transcochlear keyhole approaches. Six latex-injected cadaveric heads (twelve sides) underwent dissection in which a neuronavigation system was used. An area of exposure 10 cm superficial to a central target (working area) was calculated. The area of clival exposure with each subsequent dissection was also calculated.

RESULTS

The retrolabyrinthine keyhole approach (RLK) spares hearing and facial function in theory but provides for only a small window of upper clival exposure. The view afforded by partial labyrinthectomy with petrous apicectomy keyhole approach (PLPAK) provides for up to four times this exposure. The translabyrinthine keyhole approach (TLK) and transcochlear keyhole approach (TCK), although producing more morbidity, add little in terms of a larger petroclival window. However, with each step, the surgical freedom for manipulation of instruments increases.

CONCLUSIONS

The presigmoid transpetrosal keyhole approach to the petroclival area is feasible and useful. The RLK has relatively limited utility. For lesions without bone invasion, the PLPAK provides a much more versatile exposure with an excellent chance of hearing and facial nerve preservation. The TLK provides for greater versatility in treating lesions but clival exposure is not greatly enhanced. The TCK adds little in terms of intradural exposure but should be reserved for cases in which access to the petrous carotid artery is necessary.