Experimental paralysis of tensor veli palatini muscle.

In an effort to study the effects of experimental paralysis of tensor veli palatini (TVP) muscle on Eustachian tube (ET) function and middle-ear (ME) status, botulinum toxin A (Oculinum) was injected into the TVP muscles of 8 Rhesus monkeys. Tubal function was tested longitudinally in 2 animals with tympanostomy tubes using the forced-response test, while in the remaining 6 animals; ME condition was documented daily using tympanometry. The postinjection tubal function was characterized by abolished active muscular function and decreased closing pressure. Activity associated with tubal dilations gradually reappeared by the fifth week. The lack of lumen constrictions following injection suggested that the TVP muscle is the cause of constriction as well as normal dilation. In 6 animals with intact tympanic membranes, 10 of the 12 ears developed flat tympanograms associated with otitis media with effusion (OME) within 8-30 days of injection and serous effusions were recovered by tympanocentesis in seven ears. These results show that a non-traumatic reversible functional obstruction of the ET was created by injecting botulinum toxin A into the TVP muscle. This functional obstruction was associated with the development of high negative ME pressure and serous effusion.