Bony prominence and variations of the transverse sinus groove: novel anatomical findings in relation to sinus pathologies.

The transverse sinus (TS) is often involved with pathology for structural reasons. The aim of this study was to improve understanding of the anatomy along the groove of the TS and sigmoid sinus (SS), to discuss the relationship between the bony features and pathologies affecting the TS. Seventy dry skulls (140 sides) were used for detailed observation of the TS and SS grooves using gross investigation coupled with transillumination. Bony features such as the mastoid foramen (MF), occipital foramen (OF), granular foveolae (GF), and absence of the TS groove were evaluated, and a classification based on numbers of findings was proposed. The most common internal groove finding was MF (79.3%), followed by absent TS groove (32.9%), and OF (14.3%). MF was statistically more frequent on the left side (91.4%) than the right (67.1%) (p = 0.036); OF was statistically more frequent on the right side (24.3%) than the left (4.3%) (p = 0.008). Absent TS groove was more prevalent on the left side (54.3%) than the right (11.4%) (p = 0.000). A bony prominence (BP) was identified in 15.7% (11 skulls) and there were significant differences from the controls. The type III class (three internal groove findings) was the most prevalent, followed by type II (two findings). The complex and integral role of the bony features described here, and their particularities in normal patients or in those with DVS pathologies, is not well understood.