Differences in size and shape between the right and left sigmoid sinuses.

Whether or not the shape and size of the sigmoid sinus are affected by middle ear inflammation is still controversial. Using high-resolution computed tomography (CT), we examined the shape and cross-sectional area of the sigmoid sinus in 80 patients with unilateral chronic otitis media. Forty patients had right otitis media, and the others left otitis media. Whether chronic inflammation involved the right or left ear, a protrusive type of sigmoid sinus was found more frequently on the right than the left, while the cross-sectional area was significantly greater on the right. These findings suggest that a side difference affecting the sigmoid sinus would thus appear not to be caused by postnatal otitis media, but to originate in fetal life. The shape of the sigmoid sinus greatly varies among individuals and according to whether it is on the right or the left. Findings also indicate that a temporal bone CT is desirable to optimize surgical safety.