EPIDEMIOLOGICAL STUDY ON CHOLESTEATOMA IN FUKUOKA CITY TO REVEAL THE PATHOGENESIS OF CHOLESTEATOMA

Shumei Shibata

Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

It is true that the retraction theory mainly gets support as a pathogenesis of primary acquired cholesteatoma. It has been said that retraction of the ear drum is caused by Eustachian tube blockage as a result of otitis media. Since Eustachian tube blockage usually causes otitis media with effusion, the idea that cholesteatoma develops from OME is widely accepted. However, in our daily clinical practice, we do not usually observe the process from OME to cholesteatoma. Furthermore, several studies have reported that a patulous Eustachian tube may contribute to the pathogenesis of cholesteatoma. So it is still unclear what causes the retraction of the ear drum.

To reveal the pathogenesis of cholesteatoma, we carried out a epidemiological study. At first, we considered a cohort study, which has the advantage that it allows us to perform a prospective study which provides the direct measurement of absolute risk. However, a cohort study is time consuming and costly to carry out, and if the incidence is rare, it is impossible to carry out in a reasonable number of patients. Therefore, it is very difficult to select the right group for the study and very difficult to establish an appropriate system to follow up the patients.

Fortunately, we have a good example of a cohort study group near our University in Fukuoka (Japan), next to the town of Hisayama. Hisayama is the place where a prospective cohort study of lifestyle-related diseases has been carried out since 1961. Since the Hisayama study has established a great system for a cohort study, we planned to use the same population group in that study. However, if the incidence of cholesteatoma is too low, it would be impossible to perform a cohort study in Hisayama with its population of only 8,000. It is hard to determine how high the incidence of cholesteatoma is, because the epidemiological survey of cholesteatoma is seldom performed, and in particular not much study has been done including the non-operated cases. So, we first tried to predict the annual incidence of primary acquired cholesteatoma including the non-operated cases in a larger population, which is 1.4 million in the city of Fukuoka.

We collected the information of patients newly diagnosed with primary acquired cholesteatoma in Fukuoka City in 2008 during the period of six months. We sent questionnaires to all otolaryngologists in Fukuoka City and included those in surrounding towns, in case residents of Fukuoka city had consulted them. The surveyed area includes two university hospitals, 20 general hospitals and 87 ENT clinics. As a result, we collected 70 cholesteatoma cases during this six-month period: 37 males and 32 females. The mean age was 52 and biggest number of incidence was found amongst the age group of 60 years and older. Since the population of Fukuoka City is about 1.4 million, the annual incidence of acquired cholesteatoma was calculated to be 10.0 cases in a population of 100,000.

However, more detailed investigation revealed the difficulty of cholesteatoma diagnosis. From the clinical side, 20 cases were reported to be sent to hospitals. On the other hand, the hospital side reported 39 cases were sent to them by the clinics. Furthermore, only 13 cases out of 20 were found in these 39 cases reported from the hospitals, which means that seven cases were missing, and 26 other cases were not diagnosed as cholesteatoma in the clinics and sent to a hospital. In many cases, inflammation and otorrhea were severe. Therefore, it is possible that these cases were diagnosed as other otitis media cases in clinics without appropriate equipment, such as a CT scan. When we only use 48 cases from the hospital side, which seem to be highly reliable in diagnosis, the annual incidence of cholesteatoma was calculated as 6.8 cases in a population of 100,000. Among 48 cases, 27 were operated cases.

So, the annual incidence of acquired cholesteatoma was calculated as 3.9 from operated cases, 6.8 from hospital cases and 10.0 from the total number of cases in a population of 100,000.

When we compare our results with previous reports, this value is higher than those reported before from only operated cases, however, not considerably higher. When we apply this value to the population of 8,000 in Hisayama, it would take ten years to find only five to eight cholesteatoma cases! This number is too low to elucidate the pathogenesis of cholesteatoma by a prospective cohort study in the town of Hisayama.

Then we started a case-control study on cholesteatoma. A case-control study can be carried out only by retrospective study and it cannot provide direct measurement of absolute risk. However, even if the incidence is rare, it is possible to carry out.

To perform the case-control study, we selected the cholesteatoma patients at Kyushu University Hospital since 2009. As control cases, we chose newly-diagnosed patients with other diseases than cholesteatoma in the same hospital. We carried out a questionnaire survey. The items of the questionnaire were divided into three categories: environmental factors; past history of otitis media; and past history of other diseases related to Eustachian-tube functions. In a case-control study, selection bias of cases and controls can be a problem. So we tested the profiles of both groups and found no significant difference in age and sex between choles-teatoma and control cases.

First, we asked about environmental factors. A history of smoking and drinking are general factors. A history of breast feeding and group nursing are factors believed to be connected with infantile recurrent otitis media. A family history of ear surgery is a factor for potential genetic factors. We found no statistically significant differences in these environmental factors.

Next, we asked about past history of otitis media. Interestingly, 73% of cholesteatoma patients have suffered from otitis media before, while only 26% of the control group have. Our results suggest that a past history of otitis media may contribute to the pathogenesis of cholesteatoma. Among those who have a history of otitis media, we asked what kind of otitis media they have suffered from, and compared cholesteatoma cases with controls. We expected more cholesteatoma cases than controls have suffered from OME, however, we did not find statistical evidence that cholesteatoma cases develop through OME.

We also expected that frequent recurrence of otitis media may increase the risk of cholesteatoma development. However, our results showed no significant difference in frequency of otitis media between cholesteatoma cases and controls.

Then we inquired about past history of other diseases related to Eustachian tube functions. We found no significant differences in adenoid diseases, GERD and nasal diseases that may cause Eustachian tube blockage. On the other hand, we found significant differences in patulous Eustachian tube-related items between cholesteatoma cases and controls.

Twenty-three percent of cholesteatoma cases complain of ‘hearing own breathing sounds’, while only 9% of the control cases do. Forty-three percent of the cholesteatoma cases have ‘habitual sniffing’ while only 23% of control cases do. ‘Hearing own breathing sounds’ directly indicates patulous Eustachian tube. But ‘habitual sniffing’ can also be caused by nasal symptoms. So we asked the patients with habitual sniffing why they sniff. ‘Ear fullness’ and ‘autophonia’ that could indicate patulous Eustachian tube were significantly high in the cholesteatoma cases. On the other hand, we did not see a difference in nasal symptoms. Our results suggest that patulous Eustachian tube is highly suspected as a cause of habitual sniffing in the cholesteatoma cases.

Based on our case-control study, the otitis media may contribute to the pathogenesis of cholesteatoma although the process is still unclear. Our results also suggest that patulous Eustachian tube may contribute to it.

In summary, our epidemiological study showed the annual incidence of cholesteatoma including non-operated cases was calculated as 6.8 to 10.0 in a population of 100,000 in Fukuoka City, Japan. And the results of our case-control study suggest that a past history of otitis media and patulous Eustachian tube may contribute to the pathogenesis of cholesteatoma.


Address for correspondence: Shumei Shibata, shu-mei@qent.med.kyushu-u.ac.jp

Cholesteatoma and Ear Surgery – An Update, pp. 15–16

Edited by Haruo Takahashi

2013 © Kugler Publications, Amsterdam, The Netherlands