The Petrotympanic Canal (Civinini’s Canal): An Integrated Digital, Dissective, and Evolutionary Approach

The petrotympanic canal, historically identified as Civinini’s or Huguier’s canal, represents a crucial anatomical interface linking the middle ear to the temporomandibular joint. Despite its early description, its structural complexity and functional significance have frequently been underestimated in classical literature. This study provides a comprehensive re-evaluation of the structure through a multidisciplinary approach that integrates digital anatomy, with three-dimensional reconstructions from CT scans, dissective anatomy through macroscopic dissection, and evolutionary anatomy. Morphometric analysis of 195 recent human skulls confirms the canal’s constant presence, revealing a funnel-shaped architecture with an average intermediate diameter of 0.5 mm. Detailed statistical analysis demonstrates that the structure is sexually monomorphic and lacks significant bilateral asymmetry. Conversely, a comparative assessment across 27 primate specimens reveals a striking evolutionary pattern: the canal is consistently present in humans and great apes but systematically absent in non-anthropoid, quadrupedal primates. This distribution strongly suggests that Civinini’s canal is a derived feature associated with craniofacial reorganization linked to bipedal or facultative bipedal posture and to the evolutionary reduction of the postglenoid process. Functionally, rather than acting primarily as a mechanical shield, the canal should be interpreted as a specialized conduit enabling anatomical and functional continuity between two closely related systems. It transmits a neurovascular and ligamentous complex, including the chorda tympani nerve, anterior tympanic artery, and the discomalleolar and anterior malleolar ligaments, thereby allowing dynamic interactions between temporomandibular joint mechanics and the ossicular chain. Within this framework, mandibular and disc-ligamentous dynamics can be understood to functionally interface with the malleus, supporting a coordinated biomechanical relationship between temporomandibular joint activity and middle-ear function. From a medical perspective, these findings clarify the anatomical basis for the correlation between temporomandibular joint dysfunctions and otological symptoms, such as tinnitus and otalgia, and support the role of the petrotympanic canal and fissure in mediating temporomandibular joint–middle-ear interactions. In addition, they identify the canal as a potential pathway for the spread of inflammatory or neoplastic processes between the infratemporal fossa and the middle ear, with relevant implications for surgical planning and the prevention of iatrogenic damage in otological and maxillofacial procedures. From an evolutionary perspective, the selective presence of Civinini’s canal in humans and great apes points to a specialized osteofibrous adaptation emerging within the hominoid clade. This pattern is consistent with broader cranial base remodeling associated with bipedalism, altered temporomandibular joint–middle-ear spatial relationships, and the increasing integration of masticatory, vestibular, and auditory demands in anthropoid evolution. Within this framework, Civinini’s canal can be interpreted as a small but informative marker of the complex biomechanical, sensory, and developmental constraints that shaped hominid craniofacial architecture.