Novel Imaging of the Eustachian Tube; Patient Study

Introduction Dysfunction in the auditory tube / Eustachian tube (ET) is a frequent problem that may cause a series of middle ear conditions. Middle ear atelectasis, retraction of the tympanic membrane, in some cases "retraction pocket type-cholesteatoma" (5), chronic otitis, perforation of the tympanic membrane and conductive hearing loss due to poor middle ear ventilation are all associated with ET-dysfunction. The ET consists of two parts, the mobile cartilaginous part medially, and the fixated bony part laterally. The bony part is demarcated by thin bony walls and situated in the close proximity of vulnerable anatomical structures, while the cartilaginous part is supported by parapharyngeal soft tissue. Recent years, a new treatment procedure of ET balloon dilation has emerged. Restoration of ET function has offered a new approach for this large group of patients with great reduction of symptoms and secondary middle ear disease.

Only the cartilaginous part of the ET is accessible for treatment procedures. We also know that 20% of the patients dilated do not respond to dilation, and relapse of middle ear disease occurs (2). At present, no diagnostic procedure can distinguish between later responders and non-responders to dilation. Therefore, level diagnostics of obstruction and possibly identification of other discriminating parameters are important. Computer tomography (CT) is considered necessary before any type of tube intervention, mainly to exclude obstruction in the bony part of the tube or identification of any other pathoanatomical condition to contraindicate balloon dilatation. Visualisation of obstructions in the cartilaginous part is not possible with today's methods. Nor does the method provide any information on tube function.

There is a need for better diagnostic imaging of the ET. In this project we plan to develop a method for contrast medium application to the ET via the middle ear followed by CT imaging. The purpose is to tell whether the ET is open or on which level it is obstructed. So far some publications have showed that contrast media can pass through the ET (6,7,8), but no systematic trials have been published, clarifying the potential of the method.

We have recently conducted studies on temporal bone specimens from human cadavers and on 8 living rabbits. Results from these studies are not yet published, but our hypotheses are supported that the method for ET visualisation is feasible, safe, and that contrast media passes unhindered through a normal ET after application in the middle ear (6,7,8).

Hence the next step of the trial is to explore whether the method provides new information in human subjects with and without tube dysfunction.