Characterization of severely and profoundly hearing impaired adults attending an audiology clinic.

Despite the fact that around 12 per cent of adult patients attending an audiology department will be severely hearing impaired (pure tone averages of 0.5, 1, 2 and 4 kHz of 70 dB HL or worse in the better hearing ear), their clinical and audiometric characteristics have not been well documented. These characteristics were collected prospectively in 132 adult patients attending a Severe Impairment Clinic, set up to manage their specific problems. The inability to provide sufficient masking makes audiometric assessment of the severity of the impairment uncertain in the poorer hearing ear in 52 per cent of these patients. In addition, the limited bone conduction output makes it almost invariably impossible to assess the masked bone conduction thresholds and hence the air-bone gap in the poorer ear. Hence, accurate characterization is only practical of the better hearing ear in such patients. In 67 per cent of the better hearing ears, there was a mixed hearing impairment, the air-bone gap being 20 dB or greater. The aetiology of the conductive component was almost equally otosclerosis and chronic otitis media. In only 19 per cent was the impairment of a pure sensorineural type, broken down as 6 per cent congenitally acquired, 5 per cent due to meningitis and 9 per cent being adult in onset. In the remaining 14 per cent of patients the type of impairment could not be classified as the bone conductive thresholds were off scale. Having had experience of managing these patients at a special clinic and knowing the workload involved, it is argued that consideration be given to setting up such clinics in most departments.