Comparison of far lateral approach versus presigmoidal approach for exposing inferior clivus by virtual reality technique

Objective To compare the three-dimensional anatomic differences of far lateral approach versus presigmoidal approach to expose inferior clivus by virtual reality technique.  Methods CT and MRI image data of 15 cadaver heads (30 sides) were inputted into Vitrea virtual reality system to establish three-dimensional anatomy model of posterior cranial fossa. Three points including anterior edges of bilateral tubercula jugulare and tubercula pharyngeum were selected to form a plane. The region of inferior clivus was defined as area under the aforementioned plane. The anterior edge of intersection curve between the plane and the clivus was selected as skull base landmark to expose. The mastoidale and posterior edge of occipital condyle articular surface were selected as craniotomy landmarks of presigmoidal and far lateral approaches. Cylinder with 1 cm diameter was outlined to simulate surgical approach, of which the axis passed through the aforementioned craniotomy landmarks. The superior edge of bottom surface of cylinder on the side of skull base was located in the aforementioned landmark of skull base. Anatomic exposures of the above two approaches were compared by paired t test.  Results The far lateral approach located at the lateral edge of foramen magnum, anterior to the cerebellum, lateral to the brain stem, medial to the jugular bulb, lateral and inferior to the accessory nerve, involved hypoglossal nerve and reached inferior clivus. Bone drilling through presigmoidal approach began with mastoidale. The approach passed through inferior edge of jugular bulb, anterior to the sigmoid sinus, inferior to the accessory nerve, involved hypoglossal nerve at the lateral edge of foramen magnum, reached inferior clivus anterior to the brain stem. The volumes of surgical route [(4629.80 ± 81.00) mm 3 vs. (2622.60 ± 72.58) mm 3 ; t = 91.532,  P = 0.000] and route involving hypoglossal nerve [(10.15 ± 0.17) mm 3 vs. (7.15 ± 0.20) mm 3 ;  t = 52.413, P = 0.000] through presigmoidal approach were more than those through far lateral approach. Osseous structures involved in far lateral approach was more than that in presigmoidal approach [(2362.90 ± 80.18) mm 3 vs. (1851.60 ± 63.62) mm 3 ;  t = 25.714, P = 0.000].  Conclusions Passing through hypoglossal nerve and drilling partial osseous structures will help to avoid cerebellum and brain stem and expose inferior clivus through far lateral approach and presigmoidal approach. DOI: 10.3969/j.issn.1672-6731.2017.12.008