Balloon catheter dilatation treatments have resulted in successful outcomes in various specialties and have been used in many regions of the human body. Balloons were first introduced into otorhinolaryngology in 2005 for use in treating the sinus ostia, with encouraging patient outcomes. Eustachian tube dysfunction has been referred to as a ‘black box’ because of the poor knowledge of its pathophysiology. Understandably, the mechanisms that underlie the efficacy of eustachian tube balloon dilatation have yet to be determined.
Possible hypotheses previously proposed by McCoul and Anand include: submucosal microhaemorrhages, resulting in fibrosis that expands the cross-sectional diameter as the tissues heal; fibrocartilaginous cartilage of the eustachian tube retaining a ‘memory’ of dilatation more than hyaline cartilage would; improvement of epithelial ventilation through a transient reduction in mucosal oedema, permitting the recovery of mucociliary flow; and the initiation of a local signalling pathway within the mucosa that modulates the function of cartilage and muscle. Despite an increasing number of technological advances, access to the eustachian tube remains challenging. Furthermore, a number of key anatomical structures lie close to the eustachian tube, which, if damaged, could result in serious morbidity or mortality. Several senior otologists have warned against surgical procedures on the eustachian tube because of a lack of high-level evidence of efficacy and previously reported mortality from procedures in the eustachian tube region.
Balloon dilatation of the eustachian tube can be performed via two approaches: transnasally, which is the more common and well known; or transtympanically, which has limited and conflicting evidence to support its use to date. Various authors have asserted that the cartilaginous portion of the eustachian tube is the most likely site of pathology in eustachian tube dysfunction, and this has certainly correlated with histopathological analysis of the region. Limiting dilatation techniques to the cartilaginous portion has the added safety advantage of an increased distance buffer from the carotid artery.
However, a competing school of thought is that both the cartilaginous and bony portions should be targeted in balloon dilatation of the eustachian tube. The bony portion was certainly the primary target of historical surgical approaches, which were later abandoned given the morbidity associated with the approach. Increasing the minimum cross-sectional area should be the main objective in eustachian tube dilatation, as it is with almost all other clinical applications of balloon dilatation catheters. A group of researchers from Pittsburgh used three-dimensional computer-aided reconstructions of histological slides to accurately measure the eustachian tube dimensions.