Anatomical analysis of transoral surgical approaches to the clivus.

Object: The authors conducted a cadaveric anatomical study to quantify and compare the area of surgical exposure and the freedom available for instrument manipulation provided by the following four surgical approaches to the extracranial periclival region: simple transoral (STO), transoral with a palate split (TOPS), Le Fort I osteotomy (LFO), and median labioglossomandibulotomy (MLM).
Methods: Twelve unembalmed cadaveric heads with normal mouth opening capacity were serially dissected. For each approach, quantitation of extracranial periclival exposure and freedom for instrument manipulation (known here as surgical freedom) was accomplished by stereotactic localization. To quantify the extent of extracranial clival exposure obtained, anatomical measurements of the extracranial clivus were performed on 17 dry skull bases. The values (means +/- standard deviations in mm2) for periclival exposure and surgical freedom, respectively, for the surgical approaches studied were as follows: STO = 492 +/- 229 and 3164 +/- 1900; TOPS = 743 +/- 319 and 3478 +/- 2363; LFO = 689 +/- 248 and 2760 +/- 1922; and MLM 1312 +/- 384 and 8074 +/- 6451. The extent of linear midline clival exposure and the percentage of linear midline clival exposure relative to the total linear midline exposure were as follows, respectively: STO = 0.6 +/- 4.9 mm and 7.8 +/- 11%; TOPS = 8.9 +/- 5.5 mm and 24.2 +/- 16.7%; LFO = 32.9 +/- 10.2 mm and 85.0 +/- 18.7%; and MLM = 2.1 +/- 4.4 mm and 6.7 +/- 11.1%.
Conclusions: The choice of approach and the resulting degree of complexity and associated morbidity depends on the location of the pathological entity. The authors found that the MLM approach, like the STO approach, provided good exposure of the craniocervical junction but limited exposure of the clivus. The TOPS approach, an approach attended by a lesser risk of morbidity, provided adequate exposure of the extracranial inferior clivus. Maximal exposure of the extracranial clivus proper was provided by the LFO approach.