Anatomical Variability of the Transverse and Sigmoid Sinus Grooves: Implications for Skull Base Surgery

Abstract

Introduction

The transverse and sigmoid sinus grooves (TSGs and SSGs) contain the corresponding sinuses within the posterior cranial fossa. Bony groove morphology remains insufficiently studied, while venous sinus variants are well-documented. The present study investigates the morphological variability of TSG and SSG and their clinical implications.

Materials and Methods

Ninety adult dried skulls were analyzed for the presence, width, and bony projections of the TSGs and SSGs. Emissary foramina (EF), including the mastoid emissary foramina (MEF) and posterior condylar canals (PCCs), were identified and measured. Statistical analysis assessed differences by side and sex, and correlations between groove dimensions were evaluated.

Results

The SSG was present bilaterally in all specimens. Incomplete bony projections were identified in 27.2% of SSGs, more commonly on the left (p = 0.029). TSG was absent from 19.4% of sides, with bony prominences present in 7.8%. MEF were observed in 48.3% of SSGs, and occipital emissary foramina (OEF) in 9.1% of TSGs. A strong positive correlation was found between the widths of the SSG and TSG (R = 0.506, p < 0.001).

Conclusion

Significant morphological variability exists in the TSG and SSG, including bony bridges and EF. These features have direct surgical relevance, particularly in procedures such as retrosigmoid craniotomy, where accurate localization of venous structures is essential. Recognition of these variants is critical for surgical planning, minimizing intraoperative risk, and enhancing imaging interpretation in posterior cranial fossa and skull base approaches.

Keywords

transverse sinus - sigmoid sinus - transverse sinus groove - sigmoid sinus groove - emissary foramen - retrosigmoid approach - variation - skull base surgery

Contributors' Statement

George Triantafyllou Contributed To Project Development, Data Collection And Management, Statistical Analysis, Data Analysis, And Manuscript Writing. H.P. Was Involved In Data Analysis And Manuscript Editing. P.P.M. Contributed To Data Collection And Manuscript Editing. I.P. Participated In Data Analysis And Manuscript Editing. George Tsakotos Assisted With Data Collection And Manuscript Editing. M.P. Provided Supervision And Contributed To Data Collection, Data Analysis, And Manuscript Editing. All Authors Have Read And Approved The Final Version Of The Manuscript.

Ethical Approval and Informed Consent

The dried skulls belong to the skeletal collection of the Anatomy Department, School of Medicine, National and Kapodistrian University of Athens. The collection was derived from the Body Donation Program of the National and Kapodistrian University of Athens (informed consent of the corpses before death).[19]

Publication History

Received: 01 June 2025

Accepted: 03 July 2025

Accepted Manuscript online:
04 July 2025

Article published online:
11 July 2025

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