Endoscopic assisted oto-surgery

Abstract

Oto-surgery has been developed using an operative microscope. In the middle ear, however, there is a region where microscopic observation is very difficult because of anatomical features: this is the retrotympanic region where the following important structures exist: stapes, stapedial muscle, tympanic part of facial nerve, pyramidal eminence, tympanic sinus, and round window. It is very dangerous to perform oto-surgery without adequate observation of these structures. To perform safe surgery with a full operative view, we have developed the use of a rigid endoscope, 4 mm in diameter and 15 cm in length with 0° and 30° angles of vision, into oto-surgery. The endoscope was introduced into the tympanic cavity through a perforated or elevated tympanum. Endoscopic observation was monitored on a TV screen and recorded on video cassette. The endoscopic imaging was much clearer and more widely expanded than that with a microscope, because an endoscope can get close to a target, within 5 mm, but microscope has 25 cm focus lens. A disadvantages of the endoscope is that the otosurgeon has to hold the endoscope with the left hand and handle forceps or a suction tube with the right. It might be difficult to handle the endoscope and surgical tools together in the narrow external canal. The endoscope, however, was very useful in oto-surgery, especially to avoid injuring the facial nerve in stapedectomy of otosclerosis, or to find residual cholesteatoma in the tympanic sinus or under the ossicle, and to confirm the position of ossicular reconstructive prosthesis. Our conclusion is that the endoscope should be used and combined with the microscope to perform safe operations with a full view of middle ear cavity.