We investigated the membranous architecture of the abducens nerve at the petroclival region and describe the characteristics of this area in cadaveric specimen and two children with hydrocephalus and sixth nerve palsy using magnetic resonance imaging (MRI).MATERIALS AND METHODS
Five adult cadaver heads were used to investigate the petroclival part of the abducens nerve. The heads were injected with colored latex for microsurgical dissection, and the length of the dural sleeve of the abducens nerve and its width at the apex were measured. In one cadaver head, the area between the petroclival entrance porus of the abducens nerve and the cavernous sinus was histologically studied under light microscopy. In two patients with hydrocephalus and abducens nerve palsy, the petroclival area was screened by using the MRI fat suppression technique.RESULTS
In the cadavers, the arachnoid membrane on the clivus extended within the dural sleeve as far as the petrous apex, as an extension of the subarachnoid space. The average length of the dural sleeve was 9.5 mm and the average width was 1.5 mm at the apex, where the nerve entered the cavernous sinus. MRI scans showed that the cerebrospinal fluid distance of the petroclival region was 5 mm in the first patient and 7 mm in the second.CONCLUSION
The subarachnoid space inside the dural sleeve of the abducens nerve can be defined by using thin-slice MRI scans. Enlargement of the dural sleeve at the petroclival region may coexist with the abducens nerve palsy. It has been documented in this study that the arachnoid membrane forms a membraneous barrier between the subarachnoid and subdural spaces within Dorello's canal.