AN ANATOMICAL STUDY OF THE SIGMOID SULCUS AND RELATED STRUCTURES

Variations in the shape and size of the sigmoid sulcus were investigat ed in 561 temporal bones (438 isolated temporal bones, 49 skull bases and 25 half skull bases) and measurements of related structures were m ade. Right-left differences were analysed. The sigmoid sulcus was sign ificantly wider (12 mm) and longer (38 mm) in the skull bases, while n o differences were observed in the isolated temporal bones. The distan ce from the most prominent point of the mastoid process to the Frankfo rt horizontal plane (FHP) was 33 mm; no right-left difference was foun d. The distance from the genu of the sigmoid sulcus to the external ac oustic meatus was 24.06 mm on the right side and 24.74 mm on the left side and this difference is significant, being considerably longer on the left side. The jugular foramen diameter was 7.8 mm; no right-left- difference was observed. The relationship of the mastoid air cells to the sulcus was analysed and air cells were found just behind the sulcu s in 66% and behind and posterior to the sulcus in 5% of temporal bone s.