The Subtemporal Approach to the Peri-/Mesencephalic Structures with and without Zygomatic Osteotomy—An Anatomical-Morphometric Study

Introduction: The subtemporal approach provides a narrow operative corridor to the cerebral crus and adjacent structures of the crural, interpeduncular, and ambient cistern. Addition of a zygomatic osteotomy widens this narrow corridor, spares retraction of the temporal lobe, and additionally provides a more anterior corridor into the interpeduncular fossa. We investigate and compare the morphometric parameter of the subtemporal approach with versus without zygomatic osteotomy.

Methods: On each side of three cadaver heads, a temporal craniotomy and a subtemporal approach to the cerebral crus and adjacent subarachnoid cisterns were performed. First the operative corridor with and without brain retraction and the working angle of this corridor were measured on each specimen side. Then a zygomatic osteotomy was performed, the temporalis muscle fully reflected downward, and further drilling of the temporal squama was performed. Finally, the three measurements were repeated to allow a comparison.

Results: The subtemporal operating corridor was (mean, min–max) 6 mm (2–9) without retraction, 12 mm (5–16) with retraction, and 12° (5–23) working angle. After addition of a zygomatic osteotomy, the operative corridor was (mean, min–max): 8 mm (4–18) without retraction, 14.5 mm (8–23) with retraction, and 31.5° (27–37) working angle.

Conclusion: A zygomatic osteotomy significantly increases the working angle of the subtemporal approach. Furthermore, a direct approach into the interpeduncular fossa is possible.