An unusual finding of the posterior cranial fossa: one case report.

Variations of the posterior cranial fossa can alter surgical approaches to this region and pose a definite hazard if not considered. Inadvertent tearing of these large structures can result in morbidity and even mortality. We report an unusually large occipital sinus (1.5 cm x 6 cm) that instead of draining into the marginal sinus inferiorly, drained laterally into the jugular foramen and thus the internal jugular vein. On this side, the occipital sinus was larger than the sigmoid or transverse sinus. Knowledge of such venous variations may decrease morbidity during surgical procedures and decrease misdiagnosis of posterior fossa lesions.