Special Tests
The Short Increment Sensitivity Index (SISI) is a highly specialized audiological test used to evaluate the ear’s ability to detect very small changes in sound intensity.
Advanced Diagnostic Test to Identify Cochlear (Inner Ear) Function
It helps audiologists understand how well the cochlea—particularly the outer hair cells—respond to minimal variations in loudness. This makes SISI an important tool in distinguishing between cochlear (sensory) and retrocochlear (neural) types of hearing loss.
During the test, the patient listens to a continuous tone, and tiny intensity increments (usually 1 dB) are introduced. The number of increments the patient can correctly identify provides valuable insight into the health of the inner ear. This information is crucial for accurate diagnosis, treatment planning, and hearing aid recommendations.
✨ Why the SISI Test Is Done
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To determine whether hearing loss is cochlear or retrocochlear
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To assess the ear's sensitivity to small increases in sound intensity
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To support differential diagnosis of sensorineural hearing loss
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To guide appropriate rehabilitation options, including hearing aids
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To monitor certain progressive or inner-ear–related disorders
🩺 What the Test Involves
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A continuous tone at a specific frequency is presented
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Small, brief increments of 1 dB are added to the tone
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The patient indicates whenever they perceive these tiny changes
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The final score helps identify the site of lesion within the auditory system
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The procedure is painless, quick, and highly accurate
📊 How SISI Helps in Diagnosis
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High SISI scores (70–100%)
Indicate cochlear pathology, typically involving outer hair cells -
Low SISI scores (0–30%)
Suggest retrocochlear involvement, like auditory nerve issues -
Intermediate scores require further correlation with other test results
The SISI is often used alongside other special tests such as ABLB, Tone Decay, and Bekesy audiometry to build a complete clinical picture.
🎯 Benefits of SISI Testing
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Helps identify the exact site of hearing disorder
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Provides guidance for hearing aid suitability
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Helps detect early inner-ear dysfunction
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Supports clinical decision-making for treatment and rehabilitation
👨⚕️ Expert Diagnostic Care at MAFAS Hearing Solutions
At MAFAS, our audiologists use advanced diagnostic equipment to perform SISI and other special tests with precision. This ensures an accurate understanding of your hearing condition and enables us to provide the most effective treatment plan tailored to your needs.