The anatomical variations are a chapter of major importance in the practice of human macroscopy due to their high clinical and surgical implications. Many of these variations, in all body segments, are biological atavisms or phylogenetic remnants and result from narrow osteofibrous formations in association with neurovascular structures -in part of their pathways.In the skull, due to its structural and developmental complexities, one notices several foraminal formations, complete or incomplete, which originate, in great part, from idiopathic calcifications of ligaments or fibrous laminae in the exocranium as well as in the endocranium. These foramen, sometimes denominated canals, are formed from ossifications or calcifications of ligaments and are intimately related to neurovascular structures, causing, on the one hand, compressive neuropathies and, on the other hand, making surgical access difficult. Thus, we indicate as relevant the following variant foramina in their completely ossified presentations: petrosphenoidal, pterygoalar, pterygospinous, caroticoclinoid, and interclinoid.The petrosphenoidal foramen (or the Dorello's canal) is a generally osteofibrous formation delimited by the superior petrosphenoidal ligament (or the Gruber's ligament) between the apex of the petrous part of the temporal bone (petrous tubercle) and the occipital clivus. Therefore, connecting the posterior and middle cranial fossae. The superior petroesphenoidal ligament constitutes one of the limits of the inferomedial paraclival triangle and can ossify to varying degrees, forming a completely osseous passage in rare cases (figures 01 and 02). The petrosphenoidal foramen is responsible for the transition of structures -the abducens nerve, the inferior petrosal sinus, and the dorsal meningeal branch of the meningohypophyseal trunk. Historically, what justifies the eponym, is considered the first description of the foramen by the Italian anatomist Primo Dorello in the work "Considerazioni sopra la causa della paralisi transitoria dell'abducente nelle flogosi dell'orecchio medio" [1].
The foramen pterigoalar (porus crotaphitico-buccinatorius or the foramen ofHyrtl) is a resistant osteofibrous formation and, evolutionarily, atavistic. Thus, the foramen is formed, in part, by the homonymous ligament of the skull base -the pterygoalar ligament. However, this ligament can, to varying degrees, and for unknown reasons, be ossified and, when completely mineralized, becomes a relatively dense bony bar (Figures 03 and 04) that interposes between the foramen ovale and the infratemporal fossa. This complicates the course of mandibular nerve branches and extracranial surgical access to the foramen ovale and the parapharyngeal