Dorello's Canal: A Tridimensional Endoscopic Endonasal Perspective

Background: Dorello's Canal is a complex anatomic formation, in which the sixth cranial nerve traverses to reach the cavernous sinus. It is characterized by a multiplanar configuration, which makes its understanding particularly complicated. Although the transcranial microsurgical anatomy of this passage has already been described, due to the increasing use of extended endoscopic endonasal approaches to the clivus and paraclival regions, a revision of Dorello's Canal from a ventral perspective is valuable. The increasingly popular use of stereoscopic 3D documentation in surgical education is particularly appealing in this subject, given the multi-angled pathway undertaken by the abducens nerve within skull base.

Objective: Provide a novel endoscopic endonasal 3D perspective of the surgical anatomy of Dorello's Canal.

Materials and Methods: Four adult human cadaveric heads were used for anatomical dissection of 8 Dorello's Canals with endoscopic endonasal technique. These dissections were documented with an endoscopic system: full HD microscope camera head with a resolution specified for 1080p Full HD (1920 × 1080 pixels), zero degrees endoscope and a smartscreen imaging system. We adopted an innovative technique for the 3D images: a special rigid frame was adapted to the endoscope to take the two images necessary to proper software (open source software) to create a three-dimensional perspective.

Results: The tridimensional anatomy of Dorello Canal was defined. The use of nasal speculum or endoscopic holders limited the depth perception provided by the endoscope, which can be enhanced by dynamic endoscope positioning. The complexity of Dorello's canal and its correlated anatomical structures given by multiplanar relations was well studied using three-dimensional visualization, which confirms to be a great tool to study detail anatomy in endoscopic endonasal approaches. The sixth cranial nerve was observed piercing the posterior fossa dura with a medial-lateral and infero-superior direction entering the canal constituted by the petrous apex, Gruber's ligament and posterior clinoid.

Conclusion: Knowledge of the anatomy of Dorello's Canal is crucial in endoscopic endonasal clivus surgery to avoid sixth cranial nerve injuries. Its tridimensional description from a ventral perspective is useful for neurosurgeons approaching the clival region.