Effects of Infrasound Exposure on Measures of Endolymphatic Hydrops

Stopped early

Conditions studied: Vestibular Abnormality, Endolymphatic Hydrops

In brief

Persons exposed to infrasound - frequencies below 20 Hz - describe a variety of troubling audiovestibular symptoms, but the underlying mechanisms are not understood. Recent animal studies, however, provide evidence that short-term exposure to low frequency sound induces transient endolymphatic hydrops. The existence of this effect has not been studied in humans. The long-term objective of this research is to identify a possible mechanism to describe the effects of infrasound on the human inner ear. The central hypothesis of the proposed study is that short-term infrasound exposure induces transient endolymphatic hydrops in humans. This will be tested by performing electrophysiologic tests indicative of endolymphatic hydrops among normal hearing individuals before and immediately after a period of infrasound exposure. Recordings of infrasound generated by wind turbines in the field have been established and calibrated by this team of engineers, otologist, and hearing and balance scientists. An infrasound generator reproduces the acoustic signature based on these field recordings. Aim 1: Determine the effect of infrasound on the summating potential to action potential (SP/AP) ratio on electrocochleography (ECoG). Hypothesis 1: Infrasound exposure will cause a reversible elevation of the SP/AP ratio. Aim 2: Determine the effect of infrasound on the threshold response curves of ocular and cervical vestibular evoked myogenic potentials. (oVEMP and cVEMP). Hypothesis 2: Infrasound exposure will cause elevation of the oVEMP and cVEMP thresholds at the frequency of best response. Successful completion of the aims will provide evidence for a possible mechanism of the effect of infrasound on the inner ear. This understanding will benefit individuals exposed to environmental infrasound and those in regulatory, research, and advocacy roles when crafting interventions and future policy.

Key facts

Study ID

NCT03132961

Run by

University of Minnesota

People needed

12

Starts

2018-05-05

Expected to finish

2018-08-23

Last updated by the study team

2018-10-18

Who can join

Age: 18 and older, up to 60. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• Age of 18 to 60 years
• Absence of otologic symptoms based on screening questionnaire
• Normal otoscopic examination
• Audiometric thresholds less than 25 dB at 250, 500, 750, 1000 Hz.

You may not qualify if…

• Age less than 18 or greater than 60 years. Age greater than 60 is considered an exclusion criterion as prior studies have demonstrated elevated VEMP thresholds attributed to age
• Presence of any positive symptom on the questionnaire
• Thresholds greater than 25 dB at the tested frequencies
• Abnormal otoscopic examination (e.g., ear canal occlusion, tympanic membrane perforation, tympanic membrane retraction)
• History of prior ear surgery.

Where it is running

• University of Minnesota — Minneapolis, Minnesota, United States

Full record on ClinicalTrials.gov

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