[The spontaneous herniation of temporomandibular joint into external auditory canal: diagnosis of otoscopy, CT and MRI]

Abstract

Objective: To summarize the otoscopy, CT and MRI features of spontaneous herniation of the temporomandibular joint(TMJ) into the external auditory canal(EAC) through the persistence Huschke's foramen(PHF).

Methods: The otoscopy, CT and MRI images of three cases with the herniation of the TMJ into the EAC through the PHF were analyzed retrospectively.

Results: Otoscopy revealed the masses located in the antero-inferior aspect of the bony EAC, and the mass displayed an alternative of forward and backward motion during opening and closing of the mouth.CT of the temporal bone showed a bony defect and a consecutive soft mass in the antero-inferior wall of the bony EAC. The margin of the bony defects were well-defined in all cases, the bone adjacent to PHF was pressed and partially wrapped around the soft mass as 'holding ball' in two cases, partly peripheral pseudo bony shell of the soft mass were showed in two cases. The soft mass in EAC appeared equal attenuated with the soft tissue of TMJ, and on enhanced CT scans showed no enhancement of the soft mass. On MRI scans, the imaging displayed a bony defect in the antero-inferior wall of the EAC with a soft mass which was formed by the capsule of the TMJ, and the mass showed iso-signal to the capsule of the TMJ on all sequences, and there was no enhancement after contrast administration.

Conclusion: The otoscopy, CT and MRI features of the spontaneous herniation of the TMJ into the EAC through the PHF is special, and the above examinations are valuable for diagnosis of the disease.