Study of Sigmoid Sinus Variations in the Temporal Bone by Micro Dissection and its Classification - A Cadaveric Study

Area of Science:

• Anatomy
• Neurosurgery
• Otolaryngology

Background:

• Existing classifications of sigmoid sinus (SS) variations lack clinical applicability.
• Understanding SS anatomy is crucial for safe surgical access, particularly in transmastoid approaches.

Purpose of the Study:

• To propose a clinically relevant classification system for sigmoid sinus (SS) position.
• To correlate SS positioning with the posterior semicircular canal (PSCC) and presigmoid dural plate exposure.
• To analyze the relationship between SS position, mastoid volume, and mastoid pneumatization.

Main Methods:

• Microdissection of 94 human cadaveric temporal bones.
• Performance of complete mastoidectomy to expose the SS, PSCC, and presigmoid dural plate.
• Classification of SS position into three grades based on anatomical relationships.

Main Results:

• Grade I demonstrated optimal exposure of the presigmoid dura and PSCC; Grade III showed the poorest.
• Grade I SS was associated with greater mastoid volume and superior mastoid pneumatization.
• Significant anatomical variability in SS positioning was observed.

Conclusions:

• The proposed three-grade classification provides a clinically relevant assessment of SS anatomy.
• Favorable SS positioning, linked to larger mastoid volumes and pneumatization, enhances surgical safety.
• Preoperative imaging analysis is vital for predicting SS position and optimizing transmastoid surgical planning.