Experimental CO2 laser myringotomy: a preliminary animal study

Myringotomy--a procedure in which a perforation is made in the tympanic membrane (TM) is performed to gain access to the middle ear for diagnostic or therapeutic reasons. Some medical conditions, especially middle ear infections require an opening that remains patent for weeks or even months. A conventional myringotomy usually closes in a few days which is insufficient time for an underlying disease to resolve. There have been studies reporting modest closure delays of myringotomies done by CO2 laser from the beginning of 1980's and the procedure has not gained popularity in clinical practice. Many of the mechanisms affecting TM healing delays remain unknown. In an animal model we investigated the closure rates of TM perforations after different types of myringotomies. The animals formed three experimental groups: (1) both ears had a semicircular myringotomy produced either with a knife or with a CO2 laser; (2) both ears had a round laser myringotomy (1.2 mm in diameter) produced either in a single shot or by a series of small overlapping shots; (3) both ears had laser myringotomy either kidney shaped (1.2 X 2 mm) or round (1.2 mm in diameter) produced by a series of small shots. All myringotomies closed within 42 days without complications. The mean patency of knife myringotomies was significantly shorter (9.8 days) than that of similar laser myringotomies (19.5 days). The mode of laser delivery did not have an effect on the closure rate. Kidney shaped CO2 laser myringotomies stayed patent significantly longer (mean 25.8 days) than circular (mean 11.4 days). The patency of smaller semicircular laser myringotomies was significantly longer than that of larger circular. The results indicate that certain geometries as well as use of the CO2 laser delays the closure of myringotomy. When myringotomy is performed for therapeutic reasons not only the size but also the shape should be considered as a factor for extending its length of patency. In the future CO2 laser may become an instrument for creating reliable myringotomies of different shapes and sizes.