Tentorial venous sinuses: an anatomic study.

Abstract

OBJECTIVE: Certain neurosurgical procedures require sectioning of the tentorium cerebelli. The presence of venous sinuses within the tentorium makes these procedures difficult. The aim of this study was to investigate the incidence, size, location, configuration, and pattern of venous drainage of these sinuses. METHODS: The tentorium cerebelli was studied in 80 fresh cadavers. After the skull cap and the supratentorial portion of the brain were removed, the tentorium was inspected for the presence of venous sinuses. Their location, size, configuration, and pattern of venous drainage were noted. Subsequently, the infratentorial structures were removed via the tentorial incisura. The tentorial sinuses were again studied. In certain cases, the sinus was opened and a probe passed inside to confirm its presence. RESULTS: The tentorium cerebelli was revealed to contain sinuses in 86% of the cadavers. These sinuses were classified into the following three types: Type I sinuses constituted 25% of the total and were most often located in the medial one-third of the tentorium. They were larger than the other types, frequently occurring with a branching "stag-horn" configuration and a tendency to drain into the straight sinus, the torcular herophili, and the medial one-third of the transverse sinus. Type II sinuses constituted 25% of the total and were most often located in the lateral one-third of the tentorium. They were smaller than the other types, and tended to drain into the duction of the transverse sinus and superior petrosal sinus and into the lateral one-third of the transverse sinus. Type III sinuses constituted 50% of the total and were located in the medial one-third of the tentorium. Their size ranged from small to medium. Unlike Type I sinuses, no branching pattern was observed. These sinuses tended to drain into the straight sinus, the torcular herophili, and the medial one-third of the transverse sinus. In the present study, the medial one-third of the tentorium was observed to be the most vascular part. No venous sinus was observed in the anterior part of the tentorium. CONCLUSION: Venous sinuses are common in the tentorium cerebelli. In this study, they were observed in 86% of the cases. They can be classified into three types, based on their location, size, configuration, and pattern of drainage. The medial one-third of the tentorium is the most vascular part. A knowledge of these sinuses may be helpful while sectioning the tentorium. The importance of these sinuses in treating vascular and neoplastic diseases of the brain is highlighted. A brief review of the embryology of these sinuses is also presented.