Discussion
To our best of knowledge, this is the first study radiologically
assessing the association of the paranasal sinus volumes and mastoid,
petrous apex, and perilabyrinthine pneumatization in patients with COM.
A study 11 investigating the association of the
length, height, and weight of the paranasal sinuses and mastoid
pneumatization in COM patients was published while we were in the
data-gathering stage of our study. We included only the patients with
unilateral middle ear disease, creating an internal control group while
they included both unilateral and bilateral disease and an external
control group, including healthy participants. Although the methodology
of the studies was different, both have reached similar outcomes. In our
study, the volumes of sphenoid sinus were significantly smaller in COM
(with isolated tympanic membrane and with cholesteatoma/retraction
pocket) side than the contralateral healthy side. There was no
difference in volumes of other sinuses. Similarly, Arai et
al.11 found that the anterior-posterior length of the
sphenoid sinus was smaller in cholesteatoma patients than control
subjects. However, there was no difference in width. In contrast, while
the width was smaller in patients with COM without cholesteatoma, no
difference was seen in the length. Both studies also agreed to that poor
mastoid cell pneumatization is associated with lower sphenoid sinus in
patients with cholesteatoma. The pneumatization of the sphenoid sinus
might be restricted more than other sinuses by childhood chronic
rhinosinusitis, as it needs a longer time to complete its development16. Arai et al.11 hypothesized that
childhood chronic rhinosinusitis might play an essential role in the
etiopathogenesis of the acquired cholesteatoma based on their results.
However, it is logical to expect that bilateral COM and bilateral
smaller sphenoid sinus length should have been observed, considering the
chronic rhinosinusitis is a disease that generally affects all mucosa of
the nasal cavity and paranasal sinuses. However, they observed smaller
sphenoid sinus only in patients with unilateral cholesteatoma. The
outcome of our study seems to support their hypothesis. However, we
included patients with unilateral COM. The reduced volume of sphenoid
sinus on both sides would be expected if the cholesteatoma was caused by
childhood chronic rhinosinusitis in these patients. Therefore, we
propose another hypothesis suggesting that long-standing childhood COM
and middle ear ventilation problems might restrict to pneumatization of
the same sided sphenoid sinus. This restriction might be explained the
changing of the bone resistance against pneumatization due to the
inflammatory mediators triggered by adjacent chronic inflammatory
tissue. Unfortunately, our study did not have enough data to prove both
hypotheses.
Mastoid pneumatization starts
primarily in the mastoid antrum at 21st-22nd weeks during the embryogenesis, and by the
34th week, the pneumatization of the antrum is nearly
completed 17. The development of the mastoid bone
continues until puberty, thus influenced by genetic and environmental
factors 18. For more than half a century, clinicians
have been exploring the association between mastoid aeration and middle
ear disease. In a cadaveric study in 1940 by Diamant19, the mastoid cell system of the sides with COM was
determined to be smaller and underdeveloped. In 1959, Tumarkin suggested
that mastoid bone hypocellularity is one of the most important risk
factors for COM 20. After that, many studies have been
done on this subject. The study of Tos et al.7 with 79
patients between the ages of 2-7 in 1985; and Sade and Fuch’s study8 in 325 patients with cholesteatoma in 1994 are the
striking ones which state the insufficient mastoid aeration increases
the risk of otitis. Aria et al. 11 and our study
showed that mastoid aeration is reduced in cholesteatoma patients,
comparable to literatüre 7,8. However, the mastoid
pneumatization was normal in COM without cholesteatoma in both studies.
This can be explained by the possible presence of a single attack of
acute otitis media-related perforation and traumatic tympanic membrane
perforation in this group. Besides, effects on COM with or without
cholesteatoma to adjacent structures may vary at the molecular level.
Also, mastoid bones with low pneumatization are thought to have limited
ability to buffer pressure changes, resulting in atelectasis, retraction
pocket, or a cholesteatoma 21.
The development of the mastoid cells and paranasal sinuses are affected
by environmental factors, genetic diseases, and previous infections. The
interplay of mastoid cell and paranasal sinus development can be
explained as 3,5,10:
- The anatomical contiguity : the drainage pathway of the mastoid
cells and paranasal sinuses have similar routes. Furthermore, petrous
apex cells and sphenoid sinuses are in close contact.
- Similar physiological characteristics : both structures are
lined with respiratory epithelium.
- Similar embryological development: as stated above, the
embryologic development of the mastoid cells and paranasal sinuses are
similar.
The connection between sinonasal diseases and ear diseases has been
interest. The first large scale study has been published by Van
Cauwenberge et al. 7 in 1983, which stated that in
children with septum deviation and allergic rhinitis, the risk for
otitis media with effusion is increased. In the following years, studies
indicating that septum deviation increases the risks of COM have been
published. Gopalakrishnan and Kumar 22 observed that
in patients with COM between 18-49 of age, septum deviation is present
in 73%. Moreover, in the study of Sajitha et al.10,
at least one sinonasal pathology was found in 82 of 100 patients with
COM; thus, routine endoscopic nasal cavity examination was suggested.
One possible explanation for sinonasal diseases and increased COM
incidence is secondary eustachian tube dysfunction and consecutive
mastoid aeration disruption.
The relation between the mastoid and paranasal sinus pneumatization has
also been investigated. In 2005 Karaskas and Kavaklı23 published their study showing the strong
correlation between the right, left, and total paranasal sinus volume
and right, left, and total mastoid volume, respectively. However, no
correlation between any specific sinus and the mastoid bone was
determined. Lee et al.4 described the correlation
between age and the development of the mastoid cells and paranasal
sinuses in their study in 62 pediatric patients with an age average of
13.4. Similarly, they also failed to show any correlation between any
specific sinus and the mastoid bone. On the other hand, Kim et al.24 and Hindi et al. 25 found a
correlation between the sphenoid sinus and mastoid pneumatization.
In our study, unlike the above studies, the relation between mastoid
aeration and paranasal sinus volumes was investigated on patients with
suffering unilateral COM. This can be explained by the close
neighborhood of the mastoid cells and the sphenoid sinus and mucosal
lining contiguity. Also, delayed development of the sphenoid sinus in
comparison with other sinuses may increase exposure to various
pathological conditions. Both Aria et al. 11 and us
suggested it could be the reason for the developmental insufficiency of
the sphenoid sinus in patients with COM. However, in our study, reliable
history of childhood sinonasal and middle ear diseases were not present.
Besides, no molecular and histopathological data of affected structures
were available to prove these hypotheses. Therefore, further prospective
cohort studies with a large population, and animal studies, modeling COM
and chronic rhinosinusitis, should investigate these diseases’ effect on
the related anatomical structures.
Conclusion
There are studies in the literature investigating the relationship
between mastoid cell pneumatizion and paranasal sinus volumes, but none
of them investigate the relation between mastoid pneumatizion and
paranasal sinus volumes in patients with unilateral COM. Our study’s
attractive finding is that although there is no statistically
significant difference in the maxillary and frontal sinus volumes,
sphenoid sinus volumes were significantly lower at the affected side of
patients with unilateral COM.
Further studies with larger groups are needed to obtain more information
about the relation between sphenoid sinus pneumatization and COM.