Further development of pneumatization of the mastoid apophysis in long-term drainage of the tympanum

Tubal insufficiency evoked by inflammation or mechanical obstruction due to enlarged adenoids plays an important role in the pathogenesis of chronic serous otitis media. Serous and mucous tympanic effusions in the presence of immature middle ear mucosa and pneumatisation follow. An adhesive process can be the result. Secretory outflow as well as constant pressure compensation between the tympanic cavity and the auditory meatus can only be achieved by a long-term tympanic drainage. Progression of pneumatisation is achieved by recovery of the middle ear mucosa and in most cases an adhesive process can be prevented.     

Secretory otitis and pneumatization of the mastoid process: sexual differences in the size of mastoid cell system

Seventy-nine children (41 girls and 38 boys) were subjected to tympanometry nine times from the age of 2 years to the age of 7 years. In addition, otoscopy was performed, and the children's otologic history was recorded. At the age of 7 years, roentgenograms were taken of the mastoid process, and the area of the air cell system was measured by planimetry. The smallest cell systems were found in ears with a history of secretory otitis or chronic tubal dysfunction--a finding which supports the environmental theory of pneumatization. Boys had significantly smaller cell systems (mean, 7.5 cm2; range, 2.75-16.75) than girls (mean, 9.0 cm2; range, 2.5-15.7). The degree of middle ear pathology was significantly higher in boys, as expressed by the total tympanometric score. The more pronounced middle ear pathology in boys was caused by more frequent and severe episodes of upper respiratory tract infections. The analysis of the sex differences provides substantial support of the environmental theory of pneumatization, since upper respiratory tract infections in childhood often cause tubal dysfunction and secretory otitis, conditions that disturb the normal process of pneumatization and result in hypocellularity.     

Correlation between temporal bone pneumatization, location of lateral sinus and length of the mastoid process.

The relationship between temporal bone pneumatization and the location of the lateral sinus and length of the mastoid process was investigated in 60 fresh frozen adult temporal bones, by plain X-rays, computed tomography and surgical dissection including otomicroscopic findings. Temporal bone pneumatization was classified as small, moderate and large. After drilling, the shortest distances between the middle fossa dura and mastoid tip representing the mastoid length and between the sigmoid sinus and posterior border of external auditory canal were measured and compared to the degree of pneumatization. The distances in the specimens with pathological eardrum and adhesions in the middle ear were compared to the ones without gross pathology. The length of mastoid process was significantly shorter in specimens with small pneumatization than those with large (Mann Whitney P less than 0.001). The specimens with a pathological eardrum and middle ear adhesions had a significantly shorter mastoid length than those without gross pathology. There was no significant difference between degree of pneumatization and the shortest distance between sigmoid sinus and external auditory canal (Mann Whitney P greater than 0.05). It is demonstrated that the 'under-developed' mastoid process can be a consequence of hampered pneumatization.     

The correlation of middle ear aeration with mastoid pneumatization

Summary Atelectatic ears, which by definition are poorly aerated, are also usually associated with poor mastoid pneumatization. On the other hand, otosclerotic patients, whose middle ears are usually exceptionally well aerated, also have excellent mastoid pneumatization. Three unusual cases are presented, in which partial atelectasis developed in stapedectomized patients. In each case the mastoid was later found to be nonpneumatized, and further analysis revealed that their stapes fixation had in effect most probably been of non-otosclerotic origin. Thus, although these three cases had at first appeared to represent exceptions to the general rule of otosclerotics having a well-aerated middle ear, in fact they support the association between atelectasis and poor pneumatization. The linkage of good middle ear aeration with large mastoid pneumatization and vice versa may suggest that the mastoid plays a role of a pressure buffer in the middle ear, which is a system of a gas pocket with fluctuating pressures. Also, otosclerosis may be considered to be an unlikely cause of conductive deafness in cases of poor pneumatization.     

The relationship between mastoid pneumatization and the position of the sigmoid sinus

Using high-resolution computed tomography, we measured the cross-sectional area of mastoid air cells and the shortest distance between the external auditory canal and the anterior edge of the sigmoid sinus (DIST), and then compared the right-left difference in 70 patients with unilateral chronic otitis media and 23 cases without middle ear disease. DIST was significantly short where there was poor mastoid pneumatization (P < 0.0001), regardless of whether it was the right or left ear. Furthermore, on the well-pneumatized temporal bone, the increase in size of the cross-sectional area was closely correlated with the increase in DIST (r = 0.495). We suggest that the relative position of the external auditory canal and the sigmoid sinus is affected by middle ear inflammations in childhood.     

The relationship between traumatic tympanic membrane perforations and pneumatization of the mastoid

We evaluated the possible relationship between tympanic membrane perforations resulting from blast trauma or slap and pneumatization of the mastoid cells. A total of 25 male patients with tympanic membrane perforations resulting from blast injury (n = 7), slap (n = 17), and football hit (n = 1) and 20 healthy male volunteers without any ear problem had temporal bone computed tomographic scans in the axial plane, parallel to the infraorbitomeatal line, with 2 mm slice thickness and 2-mm intervals using bone algorithm with a ProSpeed Spiral tomography machine. The area of air cells in each slice was measured using trace and area measurement functions of the tomography machine, and by multiplying the resulting area by slice thickness, the volume of each slice was calculated. For each ear, the total of volumes of air cells was calculated by adding the volumes of each slice containing air cells. The calculated volumes of mastoid cells were evaluated by comparing microscopic findings. Both patient and control groups consisted of males, and their ages ranged from 17 to 32 (mean 24.5) years. Microscopic examinations revealed that perforations were frequently located in the lower quadrants and that most of them were less than 3 mm. There were no pars flaccida and marginal perforations. Ossicular chain destruction was noted neither in temporal bone tomographic nor during intraoperative examinations. The mean (+/- SD) volumes of right and left ear mastoid air cells in patient and control groups were 6.92 +/- 2.45 vs. 7.00 +/- 2.59 cm(3) and 9.04 +/- 4.55 vs. 8.95 +/- 4.53 cm(3), respectively, and the differences were not statistically significant. It was found that the level of mastoid pneumatization has no statistically significant effect on tympanic membrane pathologies due to blast or other injuries.     

Anatomical relationship between position of the sigmoid sinus and regional mastoid pneumatization

In order to examine the relationship between the location of the sigmoid sinus (SS) and mastoid pneumatization, 25 adult temporal bones were dissected. Pneumatization was evaluated according to findings during dissections of three separate regions of the mastoid: i.e., the sinodural angle (SDA) area, inter-sinofacial area and mastoid apex. In addition, the SDA and distances between the SS and vertical portion of the facial nerve were measured at the second genu (G) of the facial nerve, the junction (J) of the nerve and digastric ridge and the midpoint between G and J. A good correlation was observed between pneumatization of the cells surrounding the SDA and the distance between the SS and facial nerve at the mid-point of its vertical segment. However, pneumatization of the inter-sinofacial air cell tract could not be correlated with this distance. A significant decrease in the values of the SDA was found when the air cells surrounding the SDA were poorly pneumatized. This study indicated a correlation between the position of the SS and pneumatization of the mastoid in the area of the SDA.     

Effect of middle ear infection on pneumatization and growth of the mastoid process. An experimental study in pigs

The intention of this experiment was to investigate whether anatomical variations of the temporal bone such as low middle fossa dura, anterior position of the sigmoid sinus or small mastoid process, which are often seen at surgery in cholesteatoma patients, are caused by inflammation in early childhood. In 7 pigs, 1.5 ml paraffin liquid were instilled into the left tympanic cavity 2 or 7 days after birth in order to produce inflammation of the middle ear and tubal dysfunction. After six and a half months the length and area of the mastoid process were significantly smaller on the left instilled side than on the right, normal side. In all cases there was remarkable hypocellularity and increased thickness of the cortical bone strongly supporting the environmental theory of pneumatization that inflammation suppresses the pneumatization process and growth of the mastoid process.     

A comparison of mastoid pneumatization in adults and children with cholesteatoma

The records of 190 adults who presented over a 10-year period with previously untreated aural cholesteatomas were analyzed with respect to age, mode of presentation at the level of the tympanic membrane, and pneumatization of the mastoid. The findings were compared with those obtained in an earlier study of 109 children (aged 13 years and younger) seen over the same period of time. Two main types of cholesteatomas were found in both adults and children, most of them (82.3%) associated with sclerotic or diploic mastoids (i.e., poorly pneumatized mastoids) and the rest (17.3%) with pneumatized mastoids. The former type was found more often in adults (96.3%) than in children (57.8%), while the latter was more frequent in children (42.2% as compared to 3.7% in adults). In both adults and children, cholesteatomas associated with poorly pneumatized mastoids showed mainly an attic and mastoid distribution communicating with a pars tensa or pars flaccida retraction or marginal perforation. Cholesteatomas associated with pneumatized mastoids appeared most often behind an intact drum (the so-called congenital cholesteatomas) and were distributed mainly in the tympanic cavity.     

The size of the mastoid pneumatization and otitis media with effusion in children

It is generally believed that a cause and effect relationship exists between chronic middle ear inflammatory conditions and suppressed growth of the pneumatized cellulae. We already demonstrated the normal process of pneumatization and the suppressive process of pneumatization in experimental studies using pigs. In that study, the process of suppression of the pneumatization was caused by the continuous inflammatory changes of the epithelium of the middle ear cavity, and the degree of the suppression of the pneumatization was caused by the degree and duration of the air cavity's inflammatory condition at the growing stage of the mastoid process. We also carried out the histological study of the normal process of pneumatization using 100 sides of human fetuses between 16th and 36th week of pregnancy. In these studies the bone metabolisms which were found in the normal processes of pneumatization in pigs and human fetuses were same, and the normal pneumatization occurred at the growing stage of the mastoid process. This growing period of the mastoid is from 0 to 6 months after birth in pigs, and 0 to 15 years in humans. So in humans, we can infer that the suppression of the growth of the cellulae is closely related to a persistent state of otitic inflammation like an otitis media with effusion in the early stages of growth. From these studies, in children who have otitis media with effusion, it will be possible to realize the previous middle ear pathology by the degree of the suppression of pneumatization on x-ray film.(ABSTRACT TRUNCATED AT 250 WORDS)