Small Tympanic Membrane Perforations in the Inferior Quadrants Do Not Impact the Manubrium Vibration in Guinea Pigs

Abstract

BackgroundIt has been believed that location of the perforation has a significant impact on hearing loss. However, recent studies have demonstrated that the perforation sites had no impact on hearing loss. We measured the velocity and pattern of the manubrium vibration in guinea pigs with intact and perforated eardrum using a laser Doppler vibrometer in order to determine the effects of different location perforations on the middle ear transfer functions.MethodsTwo bullas from 2 guinea pigs were used to determine stability of the umbo velocities, and 12 bullas from six guinea pigs to determine the effects of different location perforations on sound transmission. The manubrium velocity was measured at three points on the manubrium in the frequencies of 0.5–8 kHz before and after a perforation was made. The sites of perforations were in anterior-inferior (AI) quadrants of left ears and posterior-inferior (PI) quadrants of right ears.ResultsThe manubrium vibration velocity losses were noticed in the perforated ears only below 1.5 kHz. The maximum velocity loss was about 7 dB at 500 Hz with the PI perforation. No significant difference in the velocity loss was found between AI and PI perforations. The average ratio of short process velocity to the umbo velocity was approximately 0.5 at all frequencies. No significant differences were found before and after perforation at all frequencies (p>0.05) except 7 kHz (p = 0.004) for both AI and PI perforations.ConclusionsThe manubrium vibration velocity losses from eardrum perforation were frequency-dependent and the largest losses occur at low frequencies. Manubrium velocity losses caused by small acute inferior perforations in guinea pigs have no significant impact on middle ear sound transmission at any frequency tested. The manubrium vibration axis may be perpendicular to the manubrium below 8 kHz in guinea pigs.

Effects of Recurrent Acute Otitis Media on Cortical Speech-Sound Processing in 2-Year Old Children

“…All the children in the RAOM group had tympanostomy tubes inserted unlike controls. The perforation of tympanic membrane may attenuate the peripheral transmission and the frequency content of sounds (Voss et al 2001; see also Zhang et al 2012) but there is a lack of studies comparing accurately the hearing of children with tympanostomy tubes versus children with intact tympanic membrane. Our results support the idea that the effect of inserted tubes was not reflected at the cortical level, because no differences in the early cortical sound encoding between the groups were observed.…”

Hearing loss in tympanic membrane perforations: an analytic study

“…3 Zhang et al in their study on the effect of small tympanic membrane perforations in inferior quadrant on manubrium vibrations in guinea pig suggested that loss in vibration velocity of manubrium in perforations were dependent on the frequency of sound and more loss will be at a lower frequency. 4 Vaidya et al reported greater degree of hearing loss in posterior perforations. 5 Saliba et al concluded that conductive hearing loss resulting due to perforation of TM is frequency dependent; with the greatest loss occurring at the lowest sound frequencies.…”