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 eustachian tube (ET) on vascular permeability and the development of middle ear (ME) effusion. After collection of baseline data for ME pressure and MRI, the right tensor veli palatini muscle of 10 cynomolgus monkeys was injected with botulinum toxin A to induce ET obstruction. The left tensor veli palatini muscle was injected with saline in 4 monkeys. Right and left ME pressures and compliances were measured twice daily over a follow-up period of 36 days, and MRI scanning sessions including administration of a contrast agent, gadopentetate dimeglumine, were repeated 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 underpressures, 5 developed persistent underpressures, and 3 developed underpressures that resolved. No changes in MRI parameters were noted for the ears that did not develop underpressures, but a progressive brightening of the ME on T2-weighted images, indicative of the development of inflammation and effusion, was noted for the others. Also, an increasing raze of transfer of the contrast agent between the vascular and ME compartments, indicative of increasing vascular permeability, was observed to track the temporal changes in ME pressure. These results support a causal relationship between ET dysfunction, ME underpressures, increased vascular permeability, and otitis media with effusion.