Gerbilline cholesteatoma development. Part II: temporal histopathologic changes in the tympanic membrane and middle ear.
OBJECTIVE
Determine the sequence of gross and histopathologic change to the normal middle ear (ME), tympanic membrane (TM), and external auditory canal (EAC) during spontaneous gerbilline cholesteatoma development.


METHODS
Sixty-six gerbils were examined weekly and periodically sacrificed for analysis.


RESULTS
Cholesteatoma development followed this sequence: 1) slightly thickened pars flaccida (PF) without ME effusion, 2) thickened PF with ME effusion, 3) continuous buildup of EAC debris, and 4) complete occlusion of the lateral EAC. In the cholesteatoma group, keratinizing epithelium (KE) thickness was increased in all regions over normal controls and regional gradations in the TM remained the same.


CONCLUSIONS
Spontaneous cholesteatoma formation was significantly associated with middle ear effusion, a failure to clear canal debris with resultant retrograde thickening of the EAC, PF, and then pars tensa.


CONCLUSIONS
Inflammatory insult and alteration of the epithelial clearance mechanism appears to result in spontaneous cholesteatoma formation in gerbils as hypothesized for humans.
Tinling
Steven P
SP
Department of Otolaryngology-Head and Neck Surgery, University of California, Davis, School of Medicine, Davis, California 95616, USA. sptinling@ucdavis.edu
Chole
Richard A
RA
D000818:Animals; D016009:Chi-Square Distribution; D018424:Cholesteatoma, Middle Ear / Q000473:pathology*; D018450:Disease Progression; D004424:Ear Canal; D004432:Ear, Middle / Q000473:pathology*; D005260:Female; D005849:Gerbillinae; D008297:Male; D014432:Tympanic Membrane / Q000473:pathology*