Hearing loss secondary to ossicular chain abnormalities is common. Objectives: 1. To determine the etiology of hearing loss. 2. To describe the clinical/ audiometric and tympanometric characteristics in patients with ossicular chain ankylosis and malformations. Materials and methods: A descriptive case study was conducted in sixtysix patients at the Department of ENT, Bachmai hospital. All informations including sex, history, endoscopy, audiometric and tympanometric values were collef!(ted. Results and discussions: Three entities seen were otosclerosis (66.6 percent), ossicular chain malformations (33.3 percent) and tympanosclerosis (0.1 percent). Age range 16 - 45 (57.6 percent) was most common. Malelfemale ratio was 3/1.2. Symptoms were hearing loss (100 percent) with bilateral presentation in 68.2 percent, and tinnitus (68.2 percent). Endoscopy revealed tympanic membranes with normal appearance and mobility in 93.9 percent, those with opaque, calcified tympanic membrane and reduced mobility in 6.1 percent. Audiogram showed conductive hearing loss in 59.1 percent, mixed hearing loss in 40.9 percent
86.4 percent of the cases was moderate-severe level. All types of tympanogram (A, As, At) were found, with As type was the most common (47 percent). Conclusions: The etiology of hearing loss secondary to ossicular chain lesions were otosclerosis (66.6 percent), ossicular chain malformations (33.3 percent) and tympanosclerosis (0.1 percent). Conductive hearing loss and tympanogram type As were 59.1 percent and 47 percent, respectively.