MIDDLE-EAR MECHANICS IN SUBJECTS WITH RHEUMATOID-ARTHRITIS

The incudo-malleolar and incudo-stapedial joints are true diarthroses and therefore may be subject to the same rheumatic lesions as any othe r articulation in the body. The existence of this involvement in rheum atoid arthritis (RAJ, however, is highly controversial, The present st udy investigates modifications of the mechanical properties of the mid dle ear in a group of subjects with RA by evaluating the resonance fre quency obtained with multiple-frequency tympanometry (MFT). Thirty pat ients with RA, aged 20 to 68 years (mean age: 45.8+/-12.4 years), part icipated in the investigation. Their data were compared with those obt ained in a control group of 48 age-matched subjects. Results obtained in both ears were examined in all subjects. The two groups displayed a lmost equal hearing levels with mean air conduction thresholds ranging from 10 to 22 dB HL. None of the subjects displayed an air-bone gap g reater than 5 dB. Normal resonance frequency, calculated at the 95th p ercentile from the control group, ranged From 900 to 1250 Hz. Twelve r heumatoid arthritis patients (40 per cent) displayed abnormal resonanc e values. These findings were monolateral in 9 patients and bilateral in 3, Eleven out of 15 ears with abnormal multiple-frequency tympanome try data were characterized by an increase in resonance and 4 by a dec rease, A correlation between abnormal resonance values and more aggres sive RA was established. The results of this study suggest that rheuma toid arthritis may involve the incudo-malleolar and incudo-stapedial j oints, altering the ossicular mechanics in response to static air pres sure modifications. This does not impair sound conduction through the middle ear, but might reduce the protective mechanisms of the middle e ar towards high static pressures.