[Anatomic study of the supra-infratentorial presigmoid partial labyrinthectomy keyhole approach assisted by neuro-navigation].

OBJECTIVE: To design a new supra-infratentorial presigmoid partial labyrinthectomy keyhole approach assisted by neuro-navigation system, and to explore the possibility of removing the approach-correlated bone precisely.

METHODS: Navigation data were established on 8 cadaveric heads fixed by formalin and perfused intracranial vessels with colored silicone. Before the operation, the important structures were outlined with different colors in the navigation system. A 7-cm "C" shape skin incision was performed 1cm behind the helix. On elevating the skin flap and musculofascial flap respectively, a 3.5 cm x 3 cm bone window was performed. After skeletonized the sigmoid sinus, bony labyrinth and the canal for facial nerve assisted by neuro-navigation, the amount of dura exposed and the maximal angle of vision were measured before and after partial labyrinthectomy with petrous apicectomy, the anatomic structures were observed as well.

RESULTS: The incision of the supra-infratentorial retrolabyrinthine keyhole approach fully met the needs of the presigmoid partial labyrinthectomy keyhole approach. The approach-correlated bone could precisely be drilled with the aid of neuro-navigation, which could avoid the bewilder in drilling process. This approach provided wide exposure to petroclival region, cerebellopontine angle, prepontine region and posterior cavernous sinus. After partial labyrinthectomy with petrous apicectomy, the horizontal exposure was increased to (18.8 +/- 1.6) mm (left side) and (17.7 +/- 1.2) mm (right side); the maximal angle of vision was increased to (59.3 +/- 9.2) degrees (left side) and (57.0 +/- 11.0) degrees (right side); the vertical exposure increased (10.0 +/- 1.0) mm (left side) and (10.0 +/- 0.8) mm (right side); there were significant differences between before and after partial labyrinthectomy with petrous apicectomy (P < 0.01).

CONCLUSION: It is feasible to perform the supra-infratentorial presigmoid partial labyrinthectomy keyhole approach. The exposed field and the maximal angle of vision can be obviously increased by partial labyrinthectomy with petrous apicectomy.