Roentgenological investigation of cavernous sinus structure with special reference to paracavernous cranial nerves.

We have evaluated the anatomical structure of cavernous sinuses in parasellar blocks obtained from adult cadavers to gain clinically useful information. Ten microdissectional studies of parasellar blocks (20 sides of cavernous sinus) were carried out with special emphasis on the course of paracavernous cranial nerves (3rd to 6th). These were also examined on plain radiographs. Secondly, CT investigations of the cavernous sinuses (notably as to paracavernous cranial nerves) were undertaken in twenty clinical cases having presumed parasellar lesions and in three parasellar blocks from cadavers. The results from microdissectional studies and plain radiographs were as follows. It was found that the 3rd cranial nerve entered the lateral wall of the cavernous sinus close to the antero-inferior part of the posterior clinoid on lateral projection. The 4th cranial nerve, on the other hand, entered near the postero-inferior portion of the posterior clinoid on the same view. Variations in Parkinson's triangle were fairly often noted, although marked asymmetry was not seen in individual cases. From CT findings, it was found that a postenhanced, magnified direct coronal study was essential for identifying paracavernous cranial nerves more clearly. The 3rd and 5th cranial nerves were fairly well identified on axial and coronal projections. Careful radiological investigation including plain skull radiographs & CT seems to be of value for those who diagnose or treat parasellar lesions.