Interpretation of sonotubometry. A critical view of the acoustical measurement of the opening of the eustachian tube.

The principle of sonotubometry for recording the opening of the Eustachian tube is based on the assumption that this opening increases the sound transmission from the nasopharynx to the external ear canal. However, the clinical validity of the method remains to be documented. In the present study the results in 37 normal ears were compared with those of 11 ears which showed signs of Eustachian tube dysfunction. In these glue was found in the middle ear at a subsequent myringotomy. In 13 of the subjects a comparison was made of the signals picked up from the ear canal and from the contralateral nostril. It was concluded that the interpretation of the signals from the ear canal is very complicated. They may be due to an opening of the Eustachian tube, but they may also be caused by a change of the acoustic conditions in the nasopharynx during the swallowing procedure. Despite the fact that this test principle in theory is ideal, much research seems to be required before the clinical value of the method can be confirmed.