MAGNETIC-RESONANCE-IMAGING OF THE DEVELOPMENT OF OTITIS-MEDIA WITH EFFUSION CAUSED BY FUNCTIONAL OBSTRUCTION OF THE EUSTACHIAN-TUBE

In this study, magnetic resonance imaging (MRI) was used to define in vivo the effect of experimental functional obstruction of the eustachi an tube (ET) on vascular permeability and the development of middle ea r (ME) effusion. After collection of baseline data for ME pressure and MRI, the right tensor veli palatini muscle of 10 cynomolgus monkeys w as injected with botulinum toxin A to induce ET obstruction. The left tensor veli palatini muscle was injected with saline in 4 monkeys. Rig ht and left ME pressures and compliances were measured twice daily ove r a follow-up period of 36 days, and MRI scanning sessions including a dministration of a contrast agent, gadopentetate dimeglumine, were rep eated on days 3, 6, 11, 15, 21, 29, and 36 in 6 animals and on days 15 , 21,29, and 36 in 4 animals. Two right ears did not develop underpres sures, 5 developed persistent underpressures, and 3 developed underpre ssures that resolved. No changes in MRI parameters were noted for the ears that did not develop underpressures, but a progressive brightenin g of the ME on T2-weighted images, indicative of the development of in flammation and effusion, was noted for the others. Also, an increasing raze of transfer of the contrast agent between the vascular and ME co mpartments, indicative of increasing vascular permeability, was observ ed to track the temporal changes in ME pressure. These results support a causal relationship between ET dysfunction, ME underpressures, incr eased vascular permeability, and otitis media with effusion.