By Wafaa Kaf, Ph.D., and Carol Stoll
Electrocochleography (ECochG) is a commonly used assessment of the auditory system, specifically the inner ear and the hearing nerve. ECochG is most often elicited by a brief acoustic stimulus, known as a “click,” at a relatively low repetition rate. It measures two key responses: summating potential (SP) and action potential (AP), which assist in the diagnosis of Ménière’s disease, an inner ear and balance disorder. Previous research has established that individuals with Ménière’s disease are likely to have abnormally large SPs and a large SP/AP ratio. Though click ECochG has great potential to detect Ménière’s disease, it lacks sensitivity, or the ability to correctly identify those with the disease. Only 69% of those with Ménière’s disease are correctly diagnosed, while 31% of those with the disease have normal ECochG results. This lack of accuracy prevents its use as a definitive diagnostic tool. Hearing Health Foundation 2015 Emerging Research Grants recipient, Wafaa Kaf, Ph.D., is researching the use of a novel analysis technique called Continuous Loop Averaging Deconvolution (CLAD) to best improve the sensitivity of ECochG to high click rate for diagnosing Ménière’s disease. Findings were recently published in Ear and Hearing 2017.
In a recently published paper in Frontiers in Neuroscience, Kaf’s research team shares its findings on the effects of altering the parameters of the acoustic stimulus on ECochG responses to quantify the effect of stimulus rate and duration of the elicited stimuli. Kaf and her research team obtained SP measurements to 500Hz and 2000Hz tone bursts that varied in duration and repetition rate from 20 adult females with normal hearing. CCLAD was used to interpret the tracings elicited by the differing stimuli of tone bursts.
They found that SP amplitude was significantly larger when using the highest stimulus repetition rate. It is believed that the high stimulus repetition rates minimize the neural contributions and mostly reflect hair cell responses, the target of ECochG. In addition, longer duration stimuli is believed to better reflect hair cell involvement while shorter stimuli may be useful in eliciting responses reflective of neural contributions. Lastly, 2000Hz tone bursts produced larger SP amplitude as compared to 500Hz tone bursts. Therefore, 2000Hz tone bursts with a high repetition rate and long duration can be used as parameters to minimize neural contributions to SP measures whereas short duration stimuli can be used if one wishes to asses neural activity.
The data that Kaf’s team published is a critical initial advancement towards ultimately understanding the SP measurement in diseased ears. Their findings not only provide normative data for tone burst ECochG across stimulus frequencies, stimulus rates, and stimulus durations, but also help others better understand how to improve sensitivity of ECochG for early diagnosis of Ménière’s disease.
WE NEED YOUR HELP IN FUNDING THE EXCITING WORK OF HEARING AND BALANCE SCIENTISTS. DONATE TODAY TO HEARING HEALTH FOUNDATION AND SUPPORT GROUNDBREAKING RESEARCH: HHF.ORG/DONATE.