Contralateral Transmaxillary Corridor to the Cavernous Sinus: A Useful Adjunct to the Endoscopic Endonasal Approach to the Parasellar Region

Background: Cavernous sinus (CS) invasion influences the extent of resection and is a prognostic factor for recurrence for many sellar/parasellar tumors. The internal carotid artery (ICA) limits access to the parasellar region with a standard endoscopic endonasal approach (EEA), and is at increased risk for injury. The contralateral transmaxillary approach (CTM) has been shown to improve access to the petrous apex deep to the petrous and paraclival ICA. The aim of this study was to investigate the utility of the CTM approach for CS compartments deep to the parasellar ICA.

Methods: With the aid of image guidance, EE and CTM approaches were performed by two right-handed surgeons on six colored silicone-injected human head specimens (12 CS). Qualitative and quantitative analysis of EE and CTM approaches to CS were conducted using 0-degree lens endoscope only. A comparative subanalysis of EEA and CTM to the oculomotor triangle and parapeduncular space was conducted by evaluating the area of exposure of the oculomotor triangle, and the angle of surgical trajectory to the oculomotor triangle and the lateral limit of the parapeduncular space (mesial temporal lobe, and MTL).

Results: The angle of the surgical trajectory relative to the parasellar ICA was significantly greater (p < 0.001) for the CTM approach (left CS, 51.6 ± 9.2 degree; right CS, 56.9 ± 9.6 degree) compared with EEA (left CS, 31.9 ± 7.8 degree; right CS, 34.6 ± 7.7 degree). Improved visualization of superior and posterior CS compartments was provided by CTM without the need for ICA manipulation. Overall mean area of exposure of the oculomotor triangle was significantly wider (p = 0.012) with the CTM (23.1 ± 13 mm²) compared with EE (13.4 ± 9 mm²) approach. The angle of the surgical trajectory to the oculomotor triangle was significantly greater (p < 0,001) for the CTM (left CS, 48 ± 10.1 degree; right CS, 56.1 ± 12.3 degree) compared with EE (left CS, 29 ± 6.8 degree; right CS, 34 ± 9.5 degree) approach. Moreover, the angle of surgical trajectory to the MTL was significantly greater (p < 0.001) for CTM (left MTL, 52 ± 9.8 degree; right MTL, 60 ± 9.6 degree) than for EE (left MTL, 33.3 ± 5.3 degree; right CS, 38.2 ± 10 degree) approach. Right-handness of both surgeons likely accounts for the slight difference in CTM and EEAs’ angle of attack to left and right CS. Direct access to the lateral and inferior CS compartments did not benefit from the CTM approach ([Fig. 1]).

Conclusion: In combination with an EEA, the CTM approach provides a more direct working angle into the superior and posterior CS compartments, with enhanced access to the oculomotor triangle and parapeduncular space. This may improve resection of CS tumors and decrease risk to the ICA, while avoiding a combined transcranial approach. The utility and efficacy of a CTM approach still needs to be evaluated in a clinical setting ([Figs. 2] and [3]).

Fig. 1 Superior and inferior compartments.

Fig. 2 EEA and CTM exposures and working angels.

Fig. 3 EEA and CTM compartments.