EFFECTS OF STAPEDIAL ARCH FRACTURES ON CONDUCTIVE HEARING-LOSS AND STAPEDIAL REFLEXES

Objective: It has been stated in the clinical literature that stapedia l fractures could produce a significant conductive hearing loss while leaving the contralateral stapedial reflex intact. The objective of th is study is to test this hypothesis in an animal model. Design: Nine h ooded rats underwent acoustic-stapedial reflex (ASR) and cochlear micr ophonic (CM) threshold determinations before and after middle ear surg ery. An argon laser was used to divide the tensor tympani tendon, the anterior stapedial crus, and the posterior stapedial crus, sequentiall y. The initial functional measures were repeated after each laser proc edure to document its effect. Results: Dividing the tensor tympani ten don and the anterior stapedial crus had variable and small effects on ASR and CM thresholds. Division of the second (posterior) crus elimina ted stapedial reflexes and produced a significant hearing loss. Conclu sions: This study refutes the hypothesis that fracture of one (anterio r) stapedial crus will significantly alter ossicular sound transmissio n, but it supports the hypothesis that measured stapedial reflexes wou ld not be significantly altered by a single crus fracture. Therefore, the surgeon exploring an ear for a conductive hearing loss with an int act contralateral stapedial reflex should look carefully for another s ource of the hearing loss if finding only a single stapedial arch frac ture.