Round window and promontory movements during bone conduction with different middle ear conditions in Thiel embalmed specimens.

ABSTRACT

BACKGROUND: Thiel conservation is mainly based on a watery solution of salts. We have shown that bone conduction (BC) evokes motion in normal middle ears of Thiel embalmed specimens that is comparable to the motion for other cadaveric models. AIMS/OBJECTIVES: We evaluated whether promontory and round window (RW) motion identifies differences in BC transmission for different middle ear conditions. METHODS: We investigated the conditions of mobile ossicle chain, cement-fixed stapes and stapedectomy in seven ears. A retroauricular bone anchored hearing system provided BC stimulation. The motions of the promontory and the RW were measured using single point laser Doppler vibrometer (LDV, HLV1000, Polytec). RESULTS: The averaged differences between the conditions were small for RW motion and for promontory motion. However, for RW motion we found differences of more than one standard deviation at some frequencies. These differences in RW motion were more apparent when we limited the analysis to three selected specimens. CONCLUSIONS AND SIGNIFICANCE: Extracochlear measurement of the RW motion with LDV allowed differentiation between BC for different middle ear conditions. These changes could be detected best in a small frequency range in selected specimens. Promontory motion could not be used to differentiate between different conditions of the middle ear. ABBREVIATIONS LDV laser Doppler vibrometry; Prom cochlear promontory; RW round window; ST stapes; TM tympanic membrane; VProm velocity of the promontory; VRW velocity of the round window.