Identification of Foramen of Huschke with Reversible Herniation of Temporomandibular Joint Soft Tissue Into the External Auditory Canal on Multidetector Computed Tomography

Abstract

The foramen of Huschke, or foramen tympanicum, is a developmental defect in the bony part of the external auditory canal (EAC) due to a defect in ossification of normal bone in the first 5 years of life. Seen in the anteroinferior part of the EAC, it can be asymptomatic or present with salivary discharge into the EAC during mastication or as soft tissue swelling in the EAC in the absence of any inflammation, tumor, or trauma. We present a case of a man who presented with herniation of soft tissues of the temporomandibular joint into the EAC through a persistent foramen tympanicum.

Surgical Anatomy of the Temporal Bone

“…This notch is closed by the pars flaccida of the tympanic membrane. The notch of Rivinus corresponds to the junction between the squamous and tympanic portions [1,4,14,20].…”

“…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.…”

“…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].…”

“…Then, it enters the tympanic cavity and forms an angle ranging from 19 to 107° with tympanic segment of the FC [7,20]. Because of this segment is the narrowest part and lack of arterial anastomoses, it is susceptible to embolic attacks and vascular compression.…”

“…Pyramidal segment (second part of the tympanic segment) forms second genu at the posterior wall of the ME above the pyramidal process. It forms an angle ranging from 95 to 125° with mastoid segment of the FC [7,20].…”