Granular Foveolae in the Groove of the Sigmoid Sinus: Anatomical Study

Abstract

Abstract Granular foveolae in the groove of the sigmoid sinus have rarely been reported in the literature compared to numerous published reports on the granular foveolae near the superior sagittal sinus and its sulcus on the internal aspect of the calvaria. The present study was performed to better elucidate their prevalence and locations. One hundred and ten adult dry skulls (220 sides) were analyzed for the presence of granular foveolae within the groove of the sigmoid sinus. The exact position of the foveolae was documented and the diameter of the granular foveola were measured. Granular foveolae were found in the groove of the sigmoid sinus on 3.6% of sides. These were at or within a mean of 1.3 cm inferior to the transverse-sigmoid junction. When a mastoid foramen was noted in the groove, it was always located more inferior to the granular foveolae when present. The mean diameters of the granular foveolae of the left groove of the sigmoid sinus was 2.8 mm and 4 mm for right grooves. The mean depth of the granular foveolae of the left groove of the sigmoid sinus was 2.7 mm and 3.5 mm for right grooves. Granular foveolae were statistically larger and deeper on right versus left sides (p < 0.05). Granular foveolae of the groove of the sigmoid sinus were identified most commonly on right sides and on 3.6% of all sides. If identified on medical imaging, these uncommon structures at the skull base should be considered normal anatomical variations.