Quantitative Analysis of “Kawase's Triangle” versus “Modified Anterior Petrosectomy (MAP) Rhomboid” Approach for Extended Middle Cranial Fossa Lesions Extending into Posterior Cranial Fossa

Objective: Extended middle cranial fossa approach with transtentorial extension (Kawase's Triangle approach) is an established operative technique for anterior petrosectomy. We used cadaveric model and performed computerized quantitative analysis to compare 'Kawase's' and 'Modified Anteior Petrosectomy (MAP) ie Dolenc's + Kawase's' approach for lesions around petroclival region.

Methods: 20 cadaveric specimens were dissected and analyzed (both sides in each cadaver; 10 Kawase's Triangle and 10 MAP approach). With Kawase's approach, we obtain triangular area after drilling of anterior petrous bone while with MAP approach, a significantly larger rhomboid area is created with no additional neurosurgical risk. Clival and brainstem working areas, degree of freedom and angulation were compared with both techniques using computer science algorithms for vision and graphics.

Results: MAP provides larger exposure to the petroclival region (rhomboid versus triangular area) as compared with Kawase's approach. With added exposure, drilling was straight at anterior petrous bone with greater degree of freedom. Abducent nerve could be easily visualized and preserved with MAP which is seldom possible with Kawase's approach. Surgical freedom at Meckle's cave and Dorello's canal was superior in MAP as compared with Kawase's approach.

Conclusion: MAP using anterior petrosectomy along with exploration of posterior cavernous sinus provides better exposure and access to extended middle cranial fossa with variable anterio-posterior extensions. Advantages of MAP as compared with Kawase's are lesser temporal lobe retraction, venous, arterial and cochlear injuries. The only disadvantages are more time required for drilling and exposure of posterior cavernous sinus, which can be mastered with proper learning.