Anatomical Limits of the Endoscopic Contralateral Transmaxillary Approach to the Petrous Apex and Petroclival Region

Abstract

Objectives This study aimed to establish the anatomical landmarks for performing a contralateral transmaxillary approach (CTM) to the petrous apex (PA) and petroclival region (PCR), and to compare CTM with a purely endoscopic endonasal approach (EEA). Design EEA and CTM to the PA and PCR were performed bilaterally in eight human anatomical specimens. Surgical techniques and anatomical landmarks were described, and EEA was compared with CTM with respect to ability to reach the contralateral internal acoustic canal (IAC). Computed tomographic scans of 25 cadaveric heads were analyzed and the “angle” and “reach” of CTM and EEA were measured. Results Entry to the PA via a medial approach was limited by (1) abducens nerve superiorly, (2) internal carotid artery (ICA) laterally, and (3) petroclival synchondrosis inferiorly (Gardner's triangle). With CTM, it was possible to reach the contralateral IAC bilaterally in all specimens dissected, without dissection of the ipsilateral ICAs, pterygopalatine fossae, and Eustachian tubes. Without CTM, reaching the contralateral IAC was possible only if: (1) angled endoscopes and instruments were employed or (2) the pterygopalatine fossa was dissected with mobilization of the ICA and resection of the Eustachian tube. The average “angle” and “reach” advantages for CTM were 25.6-degree greater angle of approach behind the petrous ICA and 1.4-cm more lateral reach. Conclusion The techniques and anatomical landmarks for CTM to the PA and PCR are described. Compared with a purely EEA, the CTM provides significant “angle” and “reach” advantages for the PA and PCR.

Endoscopic Approaches to the Paramedian Skull Base: An Anatomic Comparison of Contralateral Endonasal and Transmaxillary Strategies

“…8 During the skull base dissection, the nasoseptal flap may be stored in the nasopharynx or across the planum. 8,11 The latter may be more useful when more inferiorly located lesions are approached.…”

“…Potential disadvantages of using a CTMA include facial swelling, upper dentition and ipsilateral facial paresthesia/pain, cosmetic distortion, injury to the nasolacrimal system, and development of oroantral fistula. 8,11,17…”

“…Prior studies have compared various angles and trajectory between each technique. 7,8,10,11 In this regard, this work seeks to add to the literature and delve further into the intricacies of the CTMA.…”

Endoscopic trans‐lateral oropharyngeal wall approach to the petrous apex and the petroclival region

“…23,24 Efforts to preserve the Eustachian tube and maximize visualization via creating additional corridors were exerted to enhance exposure of the petrous apex and petroclival region. 16,25 Of note, the contralateral transmaxillary approach designed by Patel et al could maximally expose the petrous apex and petroclival region, without injuring the pterygopalatine fossa, Eustachian tube, or manipulating the ICA bilaterally. 14,15 Through the TLOWA, however, sufficient exposure of the petrous apex and the petroclival region could not be achieved when the Eustachian tube is left intact.…”

“…The Eustachian tube often becomes an obstacle when accessing the petrous apex and petroclival region through an EEA corridor 23,24 . Efforts to preserve the Eustachian tube and maximize visualization via creating additional corridors were exerted to enhance exposure of the petrous apex and petroclival region 16,25 . Of note, the contralateral transmaxillary approach designed by Patel et al could maximally expose the petrous apex and petroclival region, without injuring the pterygopalatine fossa, Eustachian tube, or manipulating the ICA bilaterally 14,15 .…”