Imaging Case of the Month Enlarged Bony Portion of the Eustachian Tube in Oculoauriculovertebral Spectrum

The patulous eustachian tube (ET) has been reported as the cause of cholesteatoma, otitis media, and tinnitus. Almost all reports on the patulous eustachian tube men-tioned the patulous lumen in cartilaginous portion of the ET and atrophy of peritubal tissue, especially fat tissue. In contrast, enlarged bony portion of the ET is rare (1) and its pathophysiology remains unknown. Radiological studies are extremely useful to detect this anomaly. In this case of oculoauriculovertebral spectrum (OVAS), the multi-detector row computed tomography (1-mm collimation, 1-mm interval) reveals the enlarged bony portion of the left ET (Figs. 1 and 2). The width of the bony portion of the ET, which is closed to the junc-tional portion of the ET (2), is 7 mm and is much wider than that in normal children (1.5 mm) as reported by Suzuki et al (3) (Fig. 1). Huge bony dehiscence is rec-ognized in the carotid canal (Fig. 2). Moreover, under-developed vestibule and semicircular canals, complete absence of the cochlea (Fig. 1 and 2), and anomalous ossicles are observed. In the right ear, which has a nor-mal aspect in the middle ear and inner ear, the shape and width (1.3 mm) of the bony portion of the ET are normal (Fig. 3). Embryologically, the tubotympanic recess and pri-mary tympanic cavity are derived from the expanding terminal end of the endoderm-lined first pharyngeal pouch and probably the second pharyngeal pouch (4). The endoderm of the tubotympanic recess approached the surface that comes in contact with the ectodermal membrane of the first branchial groove. Near the end of the second month, the tubotympanic recess undergoes a bottleneck constriction, then the medial constricted por-tion lengthens and becomes the ET (4). The bony portion Address correspondence and reprint requests to Dr. Shin-Ich