Accessing the Anterior Mesencephalic Zone: Orbitozygomatic Versus Subtemporal Approach.

Area of Science:

• Neurosurgery
• Surgical Anatomy

Background:

• Surgical management of intrinsic brainstem lesions is challenging despite advancements.
• Safe surgical entry points are crucial for minimizing morbidity.
• The anterior mesencephalic (AM) zone is a key entry point for accessing the anterior midbrain surface.

Purpose of the Study:

• To quantify and compare surgical exposure of the AM zone using orbitozygomatic (OZ) and subtemporal (ST) approaches.
• To analyze angular exposure along horizontal and vertical axes for the AM zone with each approach.

Main Methods:

• Dissection of 10 cadaveric heads using OZ and ST approaches.
• Utilized a neuronavigation system for 3D coordinate determination.
• Software analysis evaluated surgical exposure area, angular exposure, and anatomical limits.

Main Results:

• Subtemporal (ST) approach provided significantly larger surgical exposure (369.8 mm²) compared to Orbitozygomatic (OZ) (164.7 mm²).
• Orbitozygomatic (OZ) approach offered greater vertical angular exposure (37.7°) than ST (18.4°).
• Both approaches provided significant horizontal angular exposure to the AM zone (OZ: 37.9°, ST: 47.0°).

Conclusions:

• The Orbitozygomatic (OZ) craniotomy, despite reduced exposure area, offers a superior trajectory to the anterior mesencephalic (AM) zone.
• This finding is critical for optimizing surgical approaches to brainstem lesions.