Comparative Study of Morphometric Analysis Between Endoscopic Endonasal and Midline Suboccipital Subtonsillar Approaches to the Jugular Tubercle

Background: Jugular tubercle (JT) meningiomas are rare lesions that differ from jugular foramen meningiomas. They are difficult to access surgically and remove completely due to their deep location and the critical neurovascular structures surrounding them. Traditional skull base approaches such as the laterally directed presigmoid infralabyrinthine, posterior transpetrosal, transcervical retropharyngeal, and posterolaterally directed far lateral, along with its variations (retrocondylar, supracondylar, and transcondylar) require extensive bone drilling and soft tissue dissection to reach the JT. Recently, minimal access far medial endoscopic endonasal approaches (EEA) have been developed for JT exposure. Others have suggested an alternative minimally invasive route to the JT, the midline suboccipital subtonsillar approach (STA). However, no quantitative laboratory evidence exists to support the clinical application of this approach. This cadaveric study, conducted in a controlled laboratory setting, provides a morphometric comparison of the EEA and STA for accessing the jugular tubercle.

Methods: Seven fresh pre-injected human cadaveric specimens (14 sides) were dissected with neuronavigation, completing EEA and microscopic STA on each side. We studied three morphological variables: angle of attack (AoA), surgical freedom, and angle of endoscopic exposure (AoEE). As traditional AoA is unreliable for comparing EEA and transcranial approach, we measured AoEE specifically for EEA to compare it with the conventional AoA of STA. We measured AoEE by stereotactically calculating the angle between three points: jugular tubercle, IX/X cranial nerves above, and the hypoglossal canal below.

Results: The mean AoA for the JT was higher in STA (42 ± 6.402 degrees cranio-caudally, 53.09 ± 8.55 degrees medio-laterally) than in EEA (12.79 ± 1.693 degrees cranio-caudally, 10.49 ± 2.582 degrees medio-laterally). However, the mean AoEE of EEA (96.77 ± 12.489 degrees craniocaudal, 132.66 ± 10.745 degrees mediolateral) was significantly higher than the AoA offered by STA (p < 0.05). STA showed significantly greater surgical freedom (1,291.22 ± 183.65 mm²) than the EEA (1,003.28 ± 136.248 mm², p < 0.05) to access the JT.

Conclusions: When considering minimal access surgical approaches for pathologies around JT, the EEA method offers less surgical freedom than STA. However, EEA provides superior visualization and angle of endoscopic exposure (AoEE) compared to STA. The surgical approach chosen should also factor in the position of the lower cranial nerves in relation to the lesion. As the JT is anterior to the lower cranial nerves and JT meningiomas tend to push these nerves more posterior, making an anterior approach like the far medial EEA more advantageous than the posterior STA. With EEA, the tumor is addressed first, and the nerves are visible once the tumor is removed. In contrast, with STA, one must navigate between the lower cranial nerves to reach the lesion, increasing the risk of lower cranial nerve morbidity ([Figs. 1]–[3]).

Fig. 1 Suboccipital subtonsillar approach to the jugular tubercle: T = tonsils, JT = jugular tubercle, VA = vertebral artery, IX = glossopharyngeal nerve, X = vagus nerve, XI = accessory nerve, XII = hypoglossal nerve.

Fig. 2 Far medial EEA to the jugular tubercle: pcICA = paraclival internal carotid artery, ET = Eustachian tube, LCM = longus capitis major, RCA = rectus capitis anterior, V = vidian nerve, SCG = supracondylar groove, T = tubercular compartment, C = condylar compartment, IPS = inferior petrosal sinus, JT = jugular tubercle, PA = petrous apex, HC = hypoglossal canal.

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Artikel online veröffentlicht:
05. Februar 2024