Denervation of the Eustachian Tube and Hearing Loss Following Trigeminal Schwannoma Resection

Development of a rat model of patulous eustachian tube by mandibular nerve resection

OBJECTIVE

Patulous eustachian tube (PET) is currently treated using a variety of conservative or surgical approaches. To further elucidate the pathology of PET and to establish new therapies, the development of an animal model is necessary. The objective of this study was to develop a highly reproducible and sustainable rat model of PET by mandibular nerve resection.

METHODS

Sixteen rats underwent mandibular nerve resection. Following an external incision, the main trunk of the mandibular nerve at the foramen ovale was identified in the pterygoid fossa, and its branches were resected. This surgery was performed on the right side, with the unoperated left side used as the control. To determine eustachian tube (ET) function, passive opening pressure (POP) was measured using inflation method up to Week 16 post-surgery. Changes in POP were statistically compared to the preoperative level on the operated and control sides. In addition, specimens of the ET and its surrounding tissue at Week 16 post-surgery were prepared for morphological evaluation in eight rats.

RESULTS

On the control side, POP did not significantly decrease across the 16 weeks post-surgery compared to the preoperative level. In contrast, on the operated side, POP was significantly decreased at Week 2 and continued to be lower than the preoperative level until at least Week 16 post-surgery. POP dropped 10% or more on the operated side examined in thirteen rats. Histologically, the medial pterygoid muscle was atrophied on the operated side mainly.

CONCLUSION

Mandibular nerve resection in rats may be an effective method for generating an animal model of PET. It was suggested that this rat model may be useful for verifying new treatments for PET.

[The patulous Eustachian tube syndrome: the current state of the problem and our own clinical observation. Part 1]

The patulous Eustachian tube syndrome was described more than 150 years ago, but up to the present time some of its aspects continue to be a challenge for both fundamental and clinical medicine. Certain issues of etiology and pathogenesis of this condition have until recently remained unclear which probably accounts for the failure of choosing the adequate methods for its medical correction. Despite the seemingly broad spectrum of the modern tools for the purpose including first and foremost the endoscopic and radiological techniques, verification of the patulous Eustachian tube may encounter difficulties for the specialists. In connection with this, we have undertaken to summarize the views and opinions as regards the syndrome of interest available in the relevant world literature. In the first part of this communication, the authors discuss the modern concepts of etiology and pathogenesis of the patulous Eustachian tube syndrome with special reference to its clinical manifestations and methods of diagnostics.

Patulous Eustachian Tube and Otitis Media With Effusion as Complications After Trigeminal Nerve Injury

OBJECTIVES

To describe three patients of patulous Eustachian tube (pET) after trigeminal nerve injury and to demonstrate for the first time their magnetic resonance imaging (MRI) findings to hypothesize the mechanism of the pET after trigeminal nerve injury.

PATIENTS

Three patients presented with autophony after trigeminal nerve injury caused by the removal of intracranial tumors.

MAIN OUTCOME MEASURES

Clinical patient records, audiological data, and MRI.

RESULTS

Each patient initially developed transient otitis media with effusion (OME) within a few months after surgery and subsequently developed pET. The MRI of the three patients when they developed pET demonstrated atrophy and fat infiltration of the muscles innervated by the mandibular branch of the trigeminal nerve.

CONCLUSION

All three patients transiently manifested OME before pET was diagnosed. Based on the MRI findings and anatomical considerations, this chronological transition from OME to pET was speculated as an initial motor paralysis of the tensor veli palatini muscle, followed by volume decrease of the muscles in the vicinity of the ET due to denervation atrophy and fat infiltration, which resulted in ET closing failure.