The Posterior Auricularis Muscle as Superficial Landmark for the Sigmoid Sinus and Transverse-Sigmoid Sinus Junction: An Anatomical Study

Carmine Antonio Donofrio; Juan J Cardona; Lucia Riccio; Arada Chaiyamoon; Devendra Shekhawat; Joe Iwanaga; Aaron S Dumont; Neal Jackson; Filippo Badaloni; R Shane Tubbs; Antonio Fioravanti

doi:10.1016/j.wneu.2024.04.040

The Posterior Auricularis Muscle as Superficial Landmark for the Sigmoid Sinus and Transverse-Sigmoid Sinus Junction: An Anatomical Study

World Neurosurg. 2024 Apr 12:S1878-8750(24)00603-X. doi: 10.1016/j.wneu.2024.04.040. Online ahead of print.

Affiliations

¹ Department of Neurosurgery, ASST Cremona, Cremona, Italy; Division of Biology and Genetics, Department of Molecular and Translational Medicine, Faculty of Medicine, University of Brescia, Brescia, Italy. Electronic address: carmine.donofrio@hotmail.com.
² Department of Neurosurgery, Tulane University School of Medicine, New Orleans, Louisiana, USA.
³ Department of Neurosurgery, ASST Cremona, Cremona, Italy.
⁴ Department of Neurosurgery, Tulane University School of Medicine, New Orleans, Louisiana, USA; Department of Anatomy, Faculty of Medicine, Khon Kaen, Thailand.
⁵ Department of Otolaryngology, Tulane University School of Medicine, New Orleans, Louisiana, USA.
⁶ Department of Neurosurgery, IRCCS Istituto Delle Scienze Neurologiche di Bologna, Bologna, Italy.
⁷ Department of Neurosurgery, Tulane University School of Medicine, New Orleans, Louisiana, USA; Department of Neurosurgery and Ochsner Neuroscience Institute, Ochsner Health System, New Orleans, Louisiana, USA; Department of Anatomical Sciences, St. George's University, St. George's, Grenada; Department of Surgery, Tulane University School of Medicine, New Orleans, Louisiana, USA.

PMID: 38616028
DOI: 10.1016/j.wneu.2024.04.040

Abstract

Objective: Neuronavigation systems coupled with previously reported external anatomical landmarks assist neurosurgeons during intracranial procedures. We aimed to verify whether the posterior auricularis muscle (PAM) could be used as an external landmark for identifying the sigmoid sinus (SS) and the transverse-sigmoid sinus junction (TSSJ) during posterior cranial fossa surgery.

Methods: The PAM was dissected in 10 adult cadaveric heads and after drilling the underlying bone, the relationships with the underlying SS and TSSJ were noted. The width and length of the PAM, and the distance between the muscle and reference points (asterion, mastoid tip, and midline), were measured.

Results: The PAM was identified in 18 sides (9 left, 9 right). The first 20 mm of the muscle length (mean 28.28 mm) consistently overlay the mastoid process anteriorly and the proximal half of the SS slightly posteriorly on all sides. The superior border was a mean of 2.22 mm inferior to the TSSJ and, especially when the muscle length exceeded 20 mm, this border extended closer to the transverse sinus; it was usually found at a mean of 3.11 mm (range 0.0-13.80 mm) inferior to the distal third of the transverse sinus.

Conclusions: Superficial landmarks give surgeons improved surgical access, avoiding overexposure of deep neurovascular structures and reducing brain retraction. On the basis of our cadaveric study, the PAM is a reliable and accurate direct landmark for identifying the SS and TSSJ. The PAM could potentially be used for guiding the retrosigmoid approach.

Keywords: Anatomy; Posterior auricular muscle; Posterior cranial fossa; Retrosigmoid approach; Sigmoid sinus; Skull base surgery; Transverse-sigmoid sinus junction.