Tomography in Congenital Malformations of the Middle Ear

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Abstract
In the past decades several publications on tomography in atresia of the external meatus and of the middle ear have appeared. Apart from the papers of Ombrédanne et al. (18), Mündnich and Frey (15), James et al. (3), Frey (10), and Terrahe (20), most series are small, comprising only a few cases. At Rigshospitalet (University Clinics), Copenhagen, tomography has been performed in all patients with ear malformations since 1962, and we feel justified in presenting this contribution to the experience in the field of congenital malformations. Material Our material is comprised of 40 patients with atresia of the middle ear and/or the external acoustic meatus. The age and sex distributions are shown in Table I. A total of 47 ears have been examined. In 22 cases the right ear was malformed, in 11 cases the left ear was involved, and in 7 the malformation was bilateral. In all but 3 cases a pure-tone audiogram was obtained in connection with the roentgen examination. In 21 patients a hearing impairment in the affected ear of more than 60 decibels was registered, corresponding to complete loss of air conduction. Only 4 patients had a hearing loss of less than 40 decibels. Six of the patients had accompanying malformations in other organs: three had the Franceschetti (Treacher-Collins) syndrome, two a cleft palate, and one patient various malformations of the eyes. Technic Besides tomography, conventional radiography was employed in 32 of the patients. This was done in an effort to evaluate the pneumatization of the mastoid process. The projections used were the Stenvers, the Runström II, and the Towne. The tomography was performed with the Massiot-Philips Polytome, using its hypocycloidal movement. The anteroposterior projection was employed in all cases, but the lateral and the Stenvers projections in only 13. The present technic implies a distance between the cuts of 1.5 mm in the anteroposterior projection, and 1.0 mm in the others. In the anteroposterior projection a diaphragm with two holes is used, allowing simultaneous visualization of both ears. The field in this projection is 70 mm in diameter, in the other projections 55 mm. An exposure time of 11.6 seconds (corresponding to two full hypocycloids) is used in order to reduce the voltage. For the same reason, no grid is applied. A focal spot of 0.3 × 0.3 mm is employed. The exposure data are 60–65 kV, 40 mA, and 11.6 seconds. The described technic has been used for the past two years. Before that time, a different technic resulted in pictures with far less contrast. Results Conventional roentgenograms were obtained in 32 cases. The pneumatization findings have been grouped in three categories: normal, diminished, and none (Table II). The tomographic findings are classified according to Frey (11) (Table II): Group I: Solitary malformation of the ossicles. Group II: Diminished or atretic external meatus, small atresia plate, a tympanic cavity of normal size, and, as a rule, malformed ossicles.

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