Examination of foramen tympanicum: an anatomical study using cone-beam computed tomography

Abstract

Considering that FT was present in 11.75% of patients, radiologists and clinicians should be aware of the possible presence of this defect. It is known that this developmental dehiscence may cause herniation of temporomandibular joint, formation of salivary otorrhea, and spread of tumour or infection to the infratemporal fossa from external auditory canal. This study showed that CBCT may be preferred for imaging these conditions. (Folia Morphol 2018; 77, 2: 335-339).

Surgical Anatomy of the Temporal Bone

“…Peris-Celda et al reported that the SSC dehiscence can be observed approximately 1.5 cm posterior to the middle point of the EAM in 86% of the cases [9]. In newborn, the tympanic membrane is infiltrated with air and the tympanic ring forms a bony plate, which may cause the development of a cleft, the auricular fissure, posteriorly and a cleft, the tympano-squamous fissure, anteriorly [19,20].…”

“…Medially, it fuses with the petrous portion, whereas a free lateral part of it constructs the major part of the EAM and also serves an attachment for the cartilaginous part of the external auditory canal (EAC). Its inferior margin is free, and it has two parts on the lateral surface; posterosuperior part forms the EAM, and anteroinferior part limits the mandibular fossa posteriorly [5,19].…”

“…The tympanic part grows from the tympanic ring, which is open U-shaped possessing two edge anterior and posterior. The anterior edge forms the tympano-squamous fissure within the anterosuperior part of the EAM and the petrotympanic fissure within the middle ear, whereas the posterior edge forms the tympano-mastoid fissure within the posteroinferior part of the EAM near the stylomastoid foramen (SMF) [2,4,19].…”

“…Normally, the tympanic ring fuses until the age of 5 year but a dehiscence may persist (range 4.6−22.7%) at the anteroinferior aspect of the EAM, called foramen of Huschke (foramen tympanicum). This fusion defect is not a true foramen, but it may cause a connection between the EAM and the posteromedial part of the TMJ and results in TMJ herniation and the secretion of the parotid gland and also the dissemination of tumor and infections into the EAM [1,14,19,20]. Anteriorly, the EAM may communicate with the retromandibular part of the parotid gland via the fissures of Santorini within the anterior cartilage.…”

“…Behind the trigeminal impression, the roof of the IAM is indicated as a shallow fossa, then it continues with the AE, which is a surgical landmark for the middle fossa approach and located at the junction of the posterior third and the anterior two-thirds of the petrous portion (Figure 2). It is a valuable guide to signify the SSC and the roof of the vestibule up to 93% of the temporal bones [19,22].…”