Commentary

• cholesteatoma
• middle ear disease
• ventilation tube insertion

Acquired cholesteatomas are characterized by migration of keratinized squamous epithelium from the external aspect of the tympanic membrane into the middle ear and mastoid cavity. They are thought to arise from chronic negative middle ear pressure and tympanic membrane retraction. Due to their low incidence, most cholesteatoma studies have been retrospective cohort series or reported aggregate data. The strength of the current study is that it reports data from a very large population of patients at risk for cholesteatoma over a long study period. The observed 1% incidence of cholesteatoma in children with a history of VTI is in line with previous reports.1,2

The increasing risk of cholesteatoma associated with increased number of VTI procedures might lead one to conclude that VTI may cause cholesteatomas.2 In fact, the increased number of VTI procedures likely reflects worse underlying chronic middle ear disease and longer-standing Eustachian tube dysfunction, which are causal factors. Children with a history of cleft palate, who inherently have poor Eustachian tube function and significant rates of chronic middle ear disease, have up to 1,000-fold higher rates of cholesteatoma.3,4 The observation by the current study’s investigators that children who had VTIs in quick succession had a significantly lower rate of cholesteatoma compared to those who had the same number of tubes placed but at longer time intervals suggests it is the long-standing negative middle ear pressure, and not the VTI, that predisposes to cholesteatoma. This hypothesis is supported by the finding that a history of adenoidectomy, and presumably resultant better Eustachian tube function, was protective against cholesteatoma. Further, an older age at first VTI placement (presumably from delayed treatment) also was associated with an increased cholesteatoma incidence, which argues that longer periods of untreated negative middle ear pressure may result in higher rates of cholesteatoma. Finally, rural patients (with presumably less access to longitudinal care) also were found to have increased rates of cholesteatoma. Taken together, the study’s findings make a compelling, but not definitive, argument that longstanding undertreated negative middle ear pressure may result in an increased risk for cholesteatoma.

Despite the very large number of patients, the study has several limitations. First, the authors do not report on the overall incidence of cholesteatoma in a general Western Australian population (including patients without a history of VTI). Generally in Caucasians these rates are reported to be 6 to 9/100,000 children.3,4 Because children of Aboriginal ethnicities have comparatively higher rates of chronic middle ear disease, it is possible they also have higher rates of cholesteatoma at baseline. Second, there was no ability to determine whether the type of ventilation tube used or the severity of underlying disease had any effects on the rate of cholesteatoma. Finally, a definite correlation between VTI and cholesteatoma ear laterality in all cases (although most VTI are done bilaterally), could not be established. Regardless, the robust nature of the review, coupled with the main findings, reinforce the conclusion that longstanding untreated Eustachian tube dysfunction, and not VTI itself, leads to a subsequent long-term increased cholesteatoma incidence.