Endonasal access to lower cranial nerves: From foramina to upper parapharyngeal space

Abstract

Lesions arising from the upper parapharyngeal space (UPPS) often involved the jugular foramen region (JFR), occasionally extending into the posterior cranial fossa. This study aims to investigate the surgical anatomy of the JFR and UPPS from the perspective of an expanded endoscopic approach (EEA), tracing the lower cranial nerves from their extracranial foramina to the UPPS. Six cadaveric specimens (12 sides) underwent a transpterygoid EEA to expose the JFR and UPPS. Distances from the medial pterygoid plate (MPP) to the internal carotid artery (ICA), hypoglossal canal (HC), and jugular tubercle (JT) were measured on anonymized Computed tomography angiography images previously obtained from 30 patients with pulsatile tinnitus. Full access to the JFR, and its medial, superior, and anterior aspects, could be adequately achieved via an EEA. Upon exiting the jugular foramen, the glossopharyngeal nerve courses posterior to the ICA, traveling inferiorly into the UPPS between ICA and IJV. The vagus nerve is in close proximity to the hypoglossal nerve traveling posterior to the ICA. The accessory nerve courses lateral to the vagus nerve, running posterior to the IJV. The minimal distances from the MPP to ICA, HC, and JT were 2.52 ± 0.34, 2.86 ± 0.36, and 3.18 ± 0.33 cm, respectively. This anatomical study strongly suggests the feasibility of using an EEA to access to the medial, superior, and anterior aspects of the jugular foramen and the adjacent UPPS.

Transoral Approach to the Jugular Foramen Region with Preservation of the Eustachian Tube

“…16,17 However, transection of the ET was inevitable to facilitate adequate exposure, which may cause subsequent complications, including hearing loss and middle ear dysfunction. 22,23 Although, strategies of ET preservation with use of a multi-portal approach have been reported in a cadaveric study, adding an additional incision may increase operative time and delay the healing process. 10 The most interesting feature of the transoral approach as described in the present study was sparing resection of the ET, and even exposure of the ET was not necessary.…”

“…Through the transoral corridor, the entire pICA and the lower cranial nerves (IX to XII) deserve particular attention. 12,22 With a 0 scope or microscope, magnification can help better identify and preserve the vessels and lower cranial nerves when dividing the mass conducted through the transoral corridor. Moreover, intraoperative image guidance, doppler, and intraoperative neurological monitor could also provide additional assistance for identification and preservation of important neurovascular structures, further safeguards during the procedure.…”

“…Of note, neural structures coursing in a longitudinal direction along the outside of the mass should be carefully separated and preserved. 22 It is imprudent to transect any longitudinal neural structure prior to being further confirmed by the neurological monitor. Therefore, an intraoperative neurological monitor may be helpful to avoid additional nerve injury.…”

“…Both the far medial and extreme medial approaches through an endonasal corridor can provide adequate exposure of the JFR 16,17 . However, transection of the ET was inevitable to facilitate adequate exposure, which may cause subsequent complications, including hearing loss and middle ear dysfunction 22,23 . Although, strategies of ET preservation with use of a multi‐portal approach have been reported in a cadaveric study, adding an additional incision may increase operative time and delay the healing process 10 .…”

“…Through the transoral corridor, the entire pICA and the lower cranial nerves (IX to XII) deserve particular attention 12,22 . With a 0° scope or microscope, magnification can help better identify and preserve the vessels and lower cranial nerves when dividing the mass conducted through the transoral corridor.…”