THE MOST IMPORTANT contribution of diagnostic audiometry to the total evaluation of the vertiginous patient is the differentiation between cochlear and eighth nerve disorders. There are four auditory tests of particular value in this regard. Used in combination as a unified test battery they have proven effective as valid and reliable indices of site of lesion.1
The four tests, and their interpretation, are summarized in the Table. The first test in the battery, the short increment sensitivity index (SISI), measures the patient's ability to hear small, short changes in sound intensity. Twenty 1-db increments of 200-msec duration are superimposed at 5-sec intervals on a continuous pure tone signal at a sensation level of 20 db. The patient is instructed to respond whenever there is a change in the loudness of the steady sound.
Patients with cochlear hearing loss yield high (positive) scores on this test, usually above 55% correct.
Jerger J. The Audiological Examination as an Aid in Diagnosis. Arch Otolaryngol. 1967;85(5):552–554. doi:10.1001/archotol.1967.00760040554017