SISI test
The SISI test (Short Increment Sensitivity Index) is an audiometric method of ear, nose and throat medicine , with which the detectability of small volume fluctuations is examined. Since the volume fluctuations are offered above the hearing threshold , the SISI test counts as supra-threshold audiometry. The test allows conclusions to be drawn about the existence of a recruitment and thus about the location of the damage in the case of sensorineural hearing loss . Like the Lüscher test , the test is based on the increased detection of small intensity fluctuations in cochlear sensorineural hearing loss (related to the hearing threshold) compared to normal hearing people. Compared to the Lüscher test, the test represents a methodological simplification that considerably simplifies the test process for the person being examined and the examiner alike. The test was developed by James Jerger and co-workers in 1959.
Investigation process
To carry out the test, a tone audiometer is required which, based on a volume level that can be selected as desired , can offer a volume increase of 1 dB with a duration of a quarter of a second at intervals of 5 seconds . 20 such volume increases (increments) 20 dB above the individual hearing threshold are offered. The test person has the task of indicating every detected volume change by pressing a button or by characters.
Examination result
The person with normal hearing cannot detect changes in intensity of 1 dB 20 dB above the hearing threshold. A patient with cochlear sensorineural hearing loss, i.e. with damage to the hair cells in the cochlea, can usually detect such volume increases 20 dB above the hearing threshold with great certainty if the extent of the hearing impairment is at least 40 dB. The SISI test is therefore only meaningful from a hearing loss of 40 dB or more; a measurement with a hearing threshold below 40 dB is therefore not useful. In the presence of retrocochlear sensorineural hearing loss (damage to the auditory nerve, neural hearing loss), these small changes in intensity are not recognized. The result of the test is given as a percentage of the recognized volume increases, with a value of 60% and more as a sign of recruitment, a value of 15% or less as a sign of neural hearing loss.
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- ↑ James Jerger, Joyce Lassman Shedd and Earl Harford: On the Detection of Extremely Small Changes in Sound Intensity . In: Archives of Otolaryngology . tape 69 , 1959, pp. 200–211 , doi : 10.1001 / archotol.1959.00730030206015 .