The preprogrammed Rate Study test is designed to evaluate the integrity of the auditory nerve and look for retrocochlear lesion abnormalities. Changes in response latency between fast stimulation rates and slow stimulation rates are recorded and compared. The Eclipse offers both slow and fast markers and performs the calculation between the inter-peak Wave V latencies (between Left and Right) as well as the intra-peak latency shift change from slow to fast rate.
The test is run like a traditional ABR. The clinician tests at a high intensity (i.e.. 90dBHL) with a slow rate (i.e. 7.7Hz). A second run is completed using a fast rate (i.e. 57.7Hz). The Wave V for all four tracings is marked with the appropriate markers. After they are marked, the interaural wave V and the intra-aural shift from the rate change is calculated.
An interaural wave V latency difference greater than 0.2 to 0.4ms is generally considered abnormal (Bauch et al., 1996; Selters & Branckmann,1977).
Bauch, C.D., Olsen, W. O., & Pool, A. F. (1996) ABR indices: Sensitivity, specificity, and tumor size. American Journal of Audiology. (5) 97-104.
Selters, W. A. & Brackmann, D. E. (1977) Acoustic Tumor Detection with brain stem electric response audiometry. Archives of otolaryngology. (103) 181-187.