The Short Increment Sensitivity Index (SISI) test is a valuable tool in audiology for evaluating the function of the inner ear and auditory nerve. Let’s delve into what this test entails, its purpose, and how it aids in diagnosing hearing disorders.
What Is the SISI Test?
The SISI test measures an individual’s ability to recognize small changes in sound intensity. Specifically, it assesses the patient’s capacity to detect 1 dB increases in intensity during a series of bursts of pure tones. These pure tones are presented at a level 20 dB above the pure tone threshold for the test frequency.
Why Is the SISI Test Important?
Differentiating Cochlear and Retrocochlear Disorders:
Patients with normal hearing typically struggle to perceive these subtle intensity changes.
However, the SISI test becomes particularly informative when distinguishing between cochlear and retrocochlear disorders.
A patient with a cochlear disorder will be able to perceive the 1 dB increments, while a patient with a retrocochlear disorder will not.
Test Procedure:
The SISI test requires the following equipment:
Headphones or insert phones
A response button
Here’s how the test is conducted:
Select the desired test frequency and set the input level 20 dB above threshold.
In the most common type of SISI test, the incremental steps are set to 1 dB.
Prior to the actual test, a trial with 2 or 5 dB steps ensures patient understanding.
The patient is informed that they will hear a series of tones.
If there’s a sudden change in loudness during tone presentation, the patient presses the response button.
The system counts the number of reactions over 20 presentations to calculate a SISI score.
Repeat the test for all desired test frequencies.
Interpreting Results:
The SISI test should be conducted at 20 dB SL (Sensation Level) for all tested frequencies.
A low SISI score may indicate retrocochlear damage.
Conclusion
The SISI test provides crucial insights into the functioning of the auditory system. By assessing the ability to detect minute intensity changes, audiologists can better diagnose and manage hearing-related conditions. Remember, though, that this test is just one piece of the comprehensive audiological puzzle.
Comments