Expanding the Inferior Access to the Craniovertebral Junction through Contralateral Nasofrontal Trephination and Posterior Palatectomy: A Cadaveric Comparative Study with Quantitative Analysis

Background: Recently, the minimally invasive endoscopic endonasal approach (EEA) has emerged as the preferred alternative for the anterior decompression of the craniovertebral junction (CVJ) over the previous standard surgery using a microscopic transoral approach. The transoral route, while providing a direct pathway, often involves extensive soft tissue mobilization that may disrupt respiratory and alimentary functions. The EEA to the CVJ reduces the risk of velopharyngeal insufficiency and facilitates faster recovery by minimizing the injury of the pharynx; thus, avoiding the need for postoperative tracheostomy and gastrostomy. Comparative studies indicate that both approaches provide adequate exposure at the level of the C1 vertebra; however, the endonasal approach is limited in reaching lesions at a lower level. This preclinical cadaveric study investigates the feasibility of using the contralateral nasofrontal trephination (CNT) or posterior palatectomy (PP) to improve the inferior access afforded by the endonasal corridor to the CVJ.

Methods: Surgical dissections were carried out in 15 latex-injected cadaveric specimens. An initial EEA included spheno-ethmoidectomies, clivus drilling, and CVJ exposure. A contralateral nasofrontal incision was carried down to the bone exposing the meeting point of the frontal, nasal, and frontal process of the maxillary bones, which was then trephined to reach the frontonasal recess. A subsequent Draf 2b connected the nasal cavity with the external nasofrontal window. A PP included the drilling out of the horizontal plate of the palatine bone and the posterior nasal spine preserving the underlying periosteum. The area of target exposure, volume of surgical freedom, reach, and angles of attack were quantified with a dedicated neuronavigation system with adjuvant software and compared statistically for EEA, EEA combined with CNT, and EEA combined with PP to the CVJ.

Results: EEA afforded a significantly smaller area of target exposure (979.53 ± 223.93 mm²) compared to EEA + PP (1,278.52 ± 235.37 mm²; p < 0.01), and EEA + CNT (1,762.52 ± 325.31 mm²; p < 0.001). The volume of surgical freedom at the odontoid process was similar for EEA and EEA + PP (1,494.22 ± 251.51 mm³). These volumes were significantly lower than the combined EEA + CNT (2750.46 ± 461.48 mm³, p < 0.001). Surgical freedom was measured at the lowest limit of each approach. EEA mean surgical freedom at the C1–C2 junction was 749.94 ± 80.55 mm³, while EEA + PP was 596.4 ± 46.8 mm³ at the C2–C3 junction, and EEA + CNT was 600.91 ± 66.1 mm³ at C3–C4 junction. EEA + CNT lowest reach extended significantly below the odontoid process (6.35 ± 0.81 cm) when compared to EEA+PP and EEA (2.17 ± 0.3 cm, 0.89 ± 0.11 cm, respectively; p < 0.001). The angle of attack provided by EEA+ CNT (50.1 ± 3.1 degrees) was significantly greater than EEA +PP and EEA (21.4 ± 2, 16.6 ± 1.13 degrees, respectively; p < 0.001).

Conclusion: Both the EEA + PP and EEA + CNT provided greater inferior reach and maneuverability compared to the conventional EEA corridor. Furthermore, the EEA + CNT technique demonstrated superior instrument maneuverability and angle of attack providing an excellent alternative for minimally invasive access to the CVJ region.

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Artikel online veröffentlicht:
07. Februar 2025