2026 Proffered Presentations
S240: ANATOMIC CHARACTERIZATION OF THE LONGUS CAPITIS TUBERCLES: A PROPOSAL TO STANDARDIZE SURGICAL LANDMARKS ON THE VENTRAL LOWER CLIVUS
Chiara Angelini, MD; Marco Obersnel, MD; Hao Tang, MD; Roberto Rodriguez Rubio, MD; UCSF
Objective: The extracranial surface of the lower clivus is a region with limited and sometimes inconsistent anatomical description, yet it is of critical importance in approaches to the ventral skull base. Historically, the pharyngeal tubercle and supracondylar grooves have been utilized as major cranial landmarks when exposing the lower clivus and condylar regions. However, paired tubercles frequently encountered on the anterior extracranial aspect of the lower clivus have either been overlooked or inconsistently described in the literature and named as ‘lateral pharyngeal tubercles’ or ‘inferior condylar lines.’ We noticed the absence of a thorough and standardized characterization of these structures—located inferior and lateral, relative to the pharyngeal tubercle, and just superior to the supracondylar groove.
Methods: Bilateral dissections were performed in five cadaveric embalmed and latex-injected heads (n=10), yielding ten tubercles, through a bilateral submandibular retropharyngeal approach. The height and width of each tubercle were measured using intraoperative neuronavigation system (iNtellect [Stryker Inc.]), and the data were analyzed for mean values ± standard deviation. Qualitative descriptions of anatomical relationships to known landmarks—the pharyngeal tubercle, supracondylar groove, and hypoglossal canal—were recorded.
Results: In all our dissections, the tubercles served as attachment points for the longus capitis muscles. Herein, we propose the nomenclature Longus Capitis Tubercle (LCT), and we present their morphologic characterization and potential value as surgical landmarks. All specimens demonstrated bilateral presence of LCT. The mean height and width of the LCT were 8.22 ± 0.92 mm and 6.58 ± 0.28 mm, respectively. Muscle insertions were consistently identified on the extracranial surface in all specimens. The LCTs are located immediately inferior-lateral to the pharyngeal tubercle and superior to the supracondylar groove. In addition, they are situated just medial-inferior to the foramen lacerum.
Conclusion: We report for the first time the consistent anatomical presence of two novel tubercles on the lower clivus serving as longus capitis muscle attachment points. Their morphometrics and predictable relationships to identify other bony and muscular landmarks suggest utility as intraoperative guides, especially during skull base and transclival approaches. Recognition of these structures may reduce the risk of inadvertent injury to adjacent neurovascular features and improve navigation in difficult dissections. The LCTs were readily visualized via a retropharyngeal approach, and their predictable location suggests they may also serve as useful landmarks during expanded endonasal transclival approaches. Further radiological and clinical studies will help to achieve a consensus of the proposed terms for proper surgical and anatomic use of the LCT.
