Nageris B, Adams JC, Merchant SN. (1996) A human temporal bone study of changes in the basilar membrane of the apical turn in endolymphatic hydrops. Am. J. Otol. 17, 245-252.
In a systematic evaluation of 234 human temporal bones, the majority of preparations from patients with Menière's disease (12 of 23 temporal bones) and endolymphatic hydrops (21 of 37 temporal bones) showed extreme displacement of the basilar membrane (BM) towards the scala tympani in the apical turn of the cochlea. The results were significant on the 0.001 level when compared with normal temporal bones (N = 78).
These anatomical results must be considered as definite proof that in these patients BM motion has indeed been impeded.
Of particular interest is the case that is documented in Figs. 5 and 6. Two weeks before his death, this 62-year-old patient with Menière's disease had a nearly normal hearing threshold in his left ear at 125, 250, 500, and 1000 Hz (all 30 dB). Five hours after his death, his left temporal bone was saved for later analysis. The BM in the apical turn of the cochlea was displaced to such an extent that it was lying on the interscalar septum. Obviously, this patient had a near-to-normal hearing at the low frequencies without BM motion. This proves that hearing is effected by hair cell motion alone, without a need of BM motion.
BM motion has a function in damping, but not in excitation of hair cells. (Comment Martin Braun)