Surgical Approach to the Anterior Brainstem: Comparative Cadaveric Analysis between Anterior Transpetrosal Petrosal and Endoscopic Transorbital Route

Introduction: Because of the deep location, anatomical complexity, and close proximity to important neurovascular structures, surgical access to the petrous apex and petroclival region is still challenging. During petrous apex drilling, the anterior petrosal approach (APA) and the endoscopic transorbital approach (ETOA) employ the same bony landmarks to access the posterior fossa. However, because of their dissimilar surgical axes, they are anticipated to exhibit variations in surgical view and maneuverability ([Fig. 1]). The purpose of the study was to implement comparative analysis between approaches through cadaveric dissection.

Methods: APA and ETOA were performed in four human cadaveric heads (eight sides and four sides in each procedure). The measurements of the angle of attack (AOA) and surgical depth were conducted at the target area of interest, namely the root exit zone (REZ) of cranial nerves V, VI, and VII. The area of exposure was determined by dividing the anterior brainstem into two areas (anterior and lateral brainstem), based on the longitudinal line that intersected the entry zone of the trigeminal root. Subsequently, the area of each region was quantified ([Fig. 2]).

Results: APA demonstrated significantly greater values at the trigeminal REZ than ETOA for both vertical (31.8 ± 6.7° vs. 14.3 ± 5.3°, p = 0.006) and horizontal AOA (48.5 ± 2.9° vs. 15.0 ± 5.2°, p < 0.001). The AOA at facial REZ was also greater in APA than ETOA (vertical, 27.5 ± 3.9° vs. 8.3 ± 3.3°, p < 0.001; horizontal, 33.8 ± 2.2° vs. 11.8 ± 2.9°, p < 0.001; [Fig. 3]). APA presented significantly shorter surgical depth (CN V, 5.8 ± 0.5 cm vs. 9.0 ± 0.8, p < 0.001; CN VII, 6.3 ± 0.5 cm vs. 9.5 ± 1.0, p = 0.001) than ETOA. The mean area of brainstem exposure did not differ between the two approaches. However, APA showed significantly greater exposure of anterior brainstem than ETOA (240.7 ± 9.6 mm² vs. 171.7 ± 15.0 mm², p < 0.001), while ETOA demonstrated greater lateral brainstem exposure (174.2 ± 29.1 mm² vs. 231.1 ± 13.6 mm², p = 0.022; [Fig. 4]).

Conclusions: ETOA is a valid surgical option that provides a ventral route directly to the brainstem. ETOA demonstrated less surgical maneuverability than APA; however, it offered comparable brainstem exposure and better exposure of the lateral brainstem.

 

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Artikel online veröffentlicht:
05. Februar 2024