Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in Various Approaches to the Anterior Communicating Artery Complex Using CT-Based Frameless Stereotaxy

Objective: Endoscopy is a leading technique among minimally invasive neurosurgical procedures and can lend itself well to overcome some of the limitations of minicraniotomy approaches. We quantify and compare surgical exposure of anatomical structures of the ACoA complex as well as surgical freedom afforded by the microscope and endoscope in minisupraorbital (SO), pterional (PT), and orbitozygomatic (OZ) approaches using image guidance.

Methods: We performed a total of 12 operations including SO, PT, and OZ approaches bilaterally in two whole, fresh cadaveric heads. We used a CT-based image-guidance system for intraoperative navigation as well as for quantitative measurements. We estimated the surgical freedom and working area of the ACoA complex region, using a rigid endoscope 4.0 mm in diameter and 18 cm long with 0- and 30-degree lenses, as well as a microscope.

Results: In microscopic exposure, OZ (194.8 ± 20.2 mm²) provided the greatest exposure (p < 0.05) compared with SO (109.5 ± 36 mm²) and PT (158.2 ± 21.6 mm²).With the introduction of 0- and 30-degree endoscopes, the area was significantly improved both in SO and PT approaches (p < 0.05). In the SO approach, both 0- and 30-degree endoscopes provided a working area greater than a conventional PT approach (p < 0.05) and an area comparable to the OZ approach (p > 0.05). However, freedom of surgical movement in both vertical and horizontal planes with the SO approach was significantly restricted compared with conventional PT and OZ approaches (p < 0.05).

Conclusion: Integration of endoscopes in SO can provide comparable surgical exposure of the ACoA complex to that afforded by the conventional approaches. However, restricted surgical freedom inherent to the SO approach will be a limiting factor when approaching this compex region.