Introduction:
According to the World Health Organisation, tympanic
membrane (TM) perforation rates are the highest for Australian
Aboriginal and Torres Strait Islander (ATSI)
children1. TM perforations in ATSI children become an
ongoing problem into adulthood2 and previous work from
our group in remote ATSI communities in South Australia demonstrated
perforation rates of 31-50% with up to 30% of individuals
demonstrating activity at any one time3. TM
perforations can result in hearing losses as high as
50dB4. Within Australia, ATSI children are
particularly affected as data from the Australian Bureau of Statistics
showed ATSI children experienced 3 times the rates of chronic otitis
media (COM) as non-Indigenous Australian children3,
creating a devastating public health problem and secondary educational
disadvantage in this particularly vulnerable
population5.
It has been generally accepted that hearing loss (HL) is greater
with an increase in size of the TM perforation6.
However, perforation site and the effect on hearing is more
controversial with contradictory evidence regarding
this6-12. Whilst early work showed worse hearing
with posteroinferior based perforations13, 14, others
have found posterosuperior defects to be worse11, 15and more recent work demonstrated no difference between
sites4, 6, 7, 12. Theories such as loss of the round
window baffle effect resulting in phase-cancellation, as well as an
increase in ossicular chain abnormalities have been proposed to explain
increases in HL with posterior perforations. The association between an
increase in size and severity of HL4, 6, 10, 12, 16 is
reinforced by bio-mechanical studies confirming the progressive loss of
catenary lever ratio with enlarging perforations17.