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Xenellis JE, Linthicum FH Jr, Webster P, Lopez R (2004) Basilar membrane displacement related to endolymphatic sac volume. Laryngoscope 114, 1953-1959. Comment: Of 52 temporal bones with the histopathologic diagnosis "Endolymphatic Hydrops" Xenellis et al. (2004) identified 19 (36.5%) with various degrees of basalward displacement of the basilar membrane (BM) in the apical and middle segments of the cochlea to such an extent that it appeared to be adhered to the bony interscalar septum. Clearly, in these segments of the cochlea a traveling wave along the BM could not occur, because the BM was pressed against the bony interscalar septum and thus could not vibrate. Interestingly, patients (n = 12) where the BM adhered to the bony interscalar septum in the apical cochlear turn had the same thresholds of hearing at 500 Hz and 1000 Hz as hydrops patients without BM displacement (n = 33). At 250 Hz their thresholds were only worse by 4 dB (their Tab. IV). This means that hearing sensitivity was as good as unchanged by impediment of BM vibration. Again, we have to conclude that BM vibration cannot have a role in hair
cell excitation. (Comment Martin Braun) |