EFFECTS OF MASTOID CAVITY OBLITERATION ON THE GROWTH OF EXPERIMENTALLY PRODUCED RESIDUAL CHOLESTEATOMA

The effects of obliteration of the mastoid cavity on the growth of res idual cholesteatoma were histologically studied in an animal model. A dermal cyst was produced by grafting a piece of autologous auricular s kin in the otic bulla of 11 guinea-pigs. Three weeks after grafting, p art of the cyst wall facing the cavity was removed and the debris accu mulated inside was inserted into the surrounding granulation using a m icropick. This procedure simulates the growth mechanism of cholesteato ma residue which sometimes occurs after middle ear surgery in human su bjects. In six animals, the bulla was then obliterated with plaster of Paris. The remaining five animals were used as controls. Animals were killed for histological study at 2, 4 or 8 weeks postoperatively. Mic roscopic examinations revealed that in the obliteration group, severe inflammatory reactions were induced in the otic bulla, although the gr aft epithelium survived there; dermal cyst reformed in only one of six animals. In the controls, cyst reformation was recognized in all anim als. This indicated that severe inflammation induced by plaster preven ted growth of the graft epithelium in the otic bulla.