A NEW CONCEPT IN DORELLO CANAL MICROANATOMY - THE PETROCLIVAL VENOUS CONFLUENCE

The so-called Dorello's canal was studied in 32 specimens (16 human ca daver heads) injected with colored latex and fixed in formalin (28 spe cimens) or studied with microscopic and ultrastructural methods (four specimens). To avoid the differences usually encountered in the descri ption of this area, the authors preferred to consider a larger space t hat they have named the petroclival venous confluence (PVC). It was lo cated between two dural layers: inner (or cerebral) and outer (or oste operiosteal). The PVC was quadrangular on transverse section. The post erior petroclinoid fold and the axial plane below the dural foramen of the abducent nerve (sixth cranial nerve) limited the PVC at the top a nd bottom, respectively. Its anteroinferior limit was the posterosuper ior aspect of the upper clivus and outer layer of the dura mater. Its anterior Limit was the vertical plane containing the posterior petrocl inoid fold, and its posterior limit was the inner layer of the dura. T he PVC was limited laterally by the medial aspect of the petrous bone apex and medially by the virtual sagittal plane extending the medial l imit of the inferior petrosal sinus upward. The PVC was a venous space bordered by endothelium and continuous with the cavernous sinus, the basal sinus of the clivus, and the inferior petrosal sinus. There were trabeculations between the two dural layers. The petrosphenoidal liga ment of Gruber may be regarded as a larger trabeculation, and it divid ed the PVC into a superior and an inferior compartment. The abducent n erve generally ran through the inferior compartment, where it was fixe d to the Surrounding dura mater. This nerve was only separated from ve nous blood by a meningeal sheath of varying thinness lined with endoth elium. The clinical implications of these findings are discussed.