Correlating the site of tympanic membrane perforation with Hearing loss

A cross-sectional prospective study of consecutive adult patients with perforated TM conducted in the ENT clinic of University College Hospital Ibadan between January 1st 2005 and July 31st 2006. Instruments used for data collection/processing include questionnaires, video and micro-otoscopy, Pure tone audiometer, image J and SPSS packages.Sixty-two patients (22-males, 40-females), aged 16–75 years (mean = 35.4 +/- 4) with 77 perforated ear drums were studied and 15(24.2%) had bilateral TM perforations, 21 (33.9%) right unilateral and 26(41.9%) left unilateral. The locations of the TM perforations were 60(77.9%) central, 6(9.6%) antero-inferior, 4(5.2%) postero-inferior, 4(5.2%) antero-superior and 3(3.9%) postero-superior respectively with sizes ranging from 1.51%–89.05%, and corresponding hearing levels 30 dB – 80 dB (59% conductive and 41% mixed). Fifty-nine percent had pure conductive hearing loss and the rest mixed. Hearing losses (dBHL) increased with the size of perforations (P = 0.01, r = 0.05). Correlation of location of perforations with magnitude of hearing loss in acute TM perorations was (P = 0.244, r = 0.273) and for chronic perforations (p = 0.047 & r = 0.31).The location of perforation on the tympanic membrane (TM) has no effect on the magnitude of hearing loss in acute TM perforations while it is significant in chronic ones.Apart from conduction of sound waves across the middle ear, the tympanic membrane, also sub-serves a protective function to the middle ear cleft and round window niche. Intact tympanic membrane protects the middle ear cleft from infections and shields the round window from direct sound waves which is referred to as 'round window baffle'.[1] This shield is necessary to create a phase differential so that the sound wave does not impact on the oval and round windows simultaneously. This would dampen the flow of sound energy being transmitted in a unilateral direction from the oval window through the perilymph. It has been found that