Short Increment Sensitivity Index (SISI). A small change in the intensity of pure tone is better appreciated by the patient with cochlear lesions than normal subjects or patient having conductive or retro cochlear dysfunction. Hence this test may be used to differentiate cochlear and retro-cochlear lesion. Short Increment Sensitivity Index Short Increment Sensitivity Index Short Increment Sensitivity Index
Procedure: A continuous, supra-threshold tone (20 dB above the hearing threshold) is given to the patient for 2 minutes. Thereafter, the tone is raised by 1 dB every 5 seconds and 20 such tones are given. The patient is instructed to count the number of tones heard.
- In conductive deafness. SISI score < 15%
- In nerve deafness – 0–20%
- In cochlear deafness – 70–100%
Disadvantages: The patients having severe deafness (above 85 dB) cannot be tested with most clinical audiometers. It requires active cooperation of the patient.
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Thereafter, the tone is raised by 1 dB every 5 seconds and 20 such tones are given. The patient is instructed to count the number of tones heard.
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Dr. Rahul Kumar Bagla
MS & Fellow Rhinoplasty & Facial Plastic Surgery.
Associate Professor & Head
GIMS, Greater Noida, India