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Previous studies in humans have indicated that functional obstruction of the eustachian tube (ET) is an important factor in the pathogenesis of otitis media with effusion (OME). This type of obstruction appears to be related to the structural properties of the tube, or to an inefficient active tubal opening mechanism, or both. In this study, functional ET obstruction was created in 22 rhesus monkeys ( Macaca mulatta) by surgically altering the tensor veli palatini (TVP) muscle using three different procedures: 1) complete excision of the muscle; 2) transection of the superficial muscle bundle; or 3) transposition of the muscle tendon medial to the hamular process. Prior to surgery, weekly tympanometry, pneumatic otoscopy, and otomicroscopic examinations were performed for a period of at least six months to document middle ear (ME) status. A minimum of four ET function tests were performed on each animal using the inflation-deflation and forced-response tests. Following surgery, these tests and examinations were continued for periods of up to one year. Postoperatively, the animals in which the TVP had been excised developed a sterile ME effusion which proved to be a chronic condition which persisted throughout the follow-up period. Eustachian tube function tests showed a complete absence of any active tubal dilation by swallowing. Animals that had the muscle transected developed abnormal ME pressures, or effusions, or both, which returned to normal in some ears, but which were recurrent or chronic in others. Eustachian tube function tests in these animals showed an initial loss of active tubal function which gradually improved, but not to normal levels, presumably as a result of healing of the muscle. In cases in which the muscle was transposed the ME pathology and ET dysfunction were similar after the surgery, but improved within a short period of time. These data suggest that alteration of the TVP muscle can create functional obstruction of the ET. The severity of ET obstruction depends upon the surgical procedure undertaken. The results of postoperative ET function tests were similar to those recorded from children with recurrent and chronic OME.

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