A Quantitative Comparison between the Transcranial Transcavernous Approach and the Endoscopic Endonasal Transsphenoidal Pituitary Hemitransposition to Upper Clivus Region

Introduction: The base of the skull is a potential site of various pathologies, either malignant or benign, including tumor and vascular disorders. Surrounded by osseous barriers and neurovascular tissue, surgically managing clivus region lesions is challenging. For that reason we performed quantitative anatomical assessment of two different skull base approaches to the upper clivus region.

Methods: Five cadaveric heads underwent a transcranial transcavernous approach to the upper clivus and five heads underwent an endoscopic endonasal pituitary hemitransposition approach to the same region. Heads were rigidly fixed with a three-pin head holder to mimic surgery. We preestablished four constant spatial coordinates points on the outer surface of the clivus (A and B, superior limits = posterior clinoid processes; C and D, inferior limits = level of Dorello canal on anterior surface of the clivus). The lateral limit was the internal carotid artery (ICA) bilaterally. These points were recorded with frameless stereotaxy and the areas created by these points were calculated. The area of bone drilled from superior to inferior limits was compared for both approaches. After drilling, a new area on the surface of the clivus was generated and new points were recorded to calculate the new area. In addition, the ipsilateral and contralateral lengths of cranial nerve III (CN III), posterior carotid artery (PCA) and superior cerebellar artery (SCA) exposed after bone drilling were assessed with stereotaxy and compared. All approaches were performed on the left side (craniotomy and pituitary transposition) for data consistency.

Results: The area of bone drilled by the endoscopic endonasal approach was higher than the transcranial approach (205 ± 51.6 vs. 78 ± 32.3 [mean ± SD, mm²], p < 0.01). The percentage of bone drilled by the endoscopic endonasal approach was higher than the transcranial approach (90.9 ± 5.9 vs. 34.7 ± 11.9 [mean ± SD, %], p < 0.01). However, the lengths exposed using the transcranial approach of ipsilateral CN III (31 ± 5.2 vs. 14.7 ± 2.1 [mean ± SD, %], p < 0.01), contralateral CN III (9 ± 4.2 vs. 0 ± 0 [mean ± SD, %], p = 0.01), and contralateral PCA (8 ± 2.2 vs. 2 ± 3.5 [mean ± SD, %], p = 0.02) were higher than for the endonasal approach. There was no significant difference between measurements of ipsilateral PCA and SCA on both sides.

Conclusion: The endoscopic endonasal pituitary hemitransposition approach resulted in a greater area of bone removed from the upper clivus than the transcranial transcavernous approach. This results in a larger exposure of the upper clivus region and can facilitate the resection of pathologies that cross the midline. However, even with greater exposure, pathologies that extend laterally, beyond the ICA (lateral limit) are obscured via endoscopic endonasal approach. On the other hand, the transcranial transcavernous approach can offer a better exposure for pathologies limited or restricted to one side even with lateral extension beyond the ICA.