Contralateral Transmaxillary Corridor as an Extension to the Endoscopic Endonasal Approach to the Petrous Apex

Introduction: The endoscopic endonasal approach (EEA) has been shown to be a safe and effective means of accessing petrous apex lesions. Lateral lesions can be accessed with extended approaches such as skeletonization and lateralization of the paraclival internal carotid artery (ICA), or a transpterygoid infrapetrous approach. These approaches introduce significant risk to the ICA and are limited to the area immediately posterior to the ICA. This paper studies the feasibility of adding a contralateral transmaxillary corridor (CTM) to provide a more lateral trajectory for access to lateral lesions of the petrous apex with a decreased need for manipulation of the ICA.

Method: An EEA with CTM extension was performed bilaterally on five cadaver heads with image guidance. Screen captures of the lateral most trajectory by EEA and by CTM were captured. These images were then analyzed to measure the angle from the sagittal plane and the angle from the axis of the horizontal petrous carotid (HPICA). The clinical application of this approach was demonstrated in a patient with a recurrent clival chordoma.

Results: The CTM corridor required a partial medial maxillectomy to be performed on the side of the maxillotomy to provide a clear trajectory. EEA alone allowed for a mean angle of 15.0 +/−3.13 degrees from the sagittal (range: 11–22 degrees). The CTM corridor allowed for a mean angle of 39.7 +/−4.62 degrees (range: 34–47 degrees). This was an average increase in lateral approach by 24.7 degrees +/−2.58. When measured from the axis of the HPICA, CTM decreased the angle from 44.8 +/−2.78 to 20.1 +/−4.31. Drilling through the CTM corridor allowed the drill to reach lateral aspects of the petrous apex posterior to the ICA that would otherwise have required lateralization of the ICA. Similar benefits were noted in the clinical case.

Conclusions: The CTM corridor is a feasible extension to EEA for the petrous apex which safely offers a more lateral trajectory. This may reduce the need for extensive dissection of the ICA, thereby reducing risk and morbidity in accessing more lateral lesions of the petrous apex. The benefits of this approach have been demonstrated in a surgical setting.