On August 10, 2017 some American diplomats stationed in Cuba complained of some auditory and some vestibular symptoms. Recently one of our other editors at HearingHealthMatters.org, Brian Taylor, reported on some opinions from Dr. Jerry Punch about the possible cause.

Ultrasound, infrasound, and other sources have been proposed as the possible cause of these complaints.

There is no evidence in the literature that ultrasound- sound above our normal auditory range- could be the culprit.  The harmonics of this potentially offending sound would be even higher.  There is evidence however, that the hair cells in our vestibular system can transduce sounds even higher than 20,000 Hz, but the dynamic range would be small.  In short, ultrasound, other than perhaps heating up skin tissues slightly, would have no auditory effects.

Courtesy of www.FathomFrontiers.com

There have been some suggestions that “intermodulation” distortion products of this ultrasound could be in our audible bandwidth (e.g., 2F1-F2) but the amplitude of these combination tones would be quite low relative to the ultrasound primaries.

Turning our attention to sound that is below the range of human hearing- infrasound- this may be slightly more possible as a culprit, but also unlikely.

Low frequency sound can indeed travel through long distances and don’t “acoustically see” obstructions such as brick walls as easily as do higher frequency sounds.  That is, while 1000 Hz (about two octaves above middle C) may bounce off a wall of a building and not heard by its inhabitants, 100 Hz or 10 Hz is more likely to pass right through the wall.

Courtesy of www.Theparanormalmd.com

Very low frequencies or infrasound below 20 Hz have many non-auditory side effects but as far as the literature is concerned, does not cause hearing loss.  Some of these effects may be a feeling of discomfort, a lump in the throat feeling, or even an increased urge to urinate.  A table at the end of this blog from a Bruel and Kjaer Technical Review (1982) provides a nice listing.

While these effects are tactile (and bothersome) they do not cause hearing loss.  And like ultrasound, even if there are higher frequency harmonics (within our auditory bandwidth of hearing), they would be easily heard and not be infrasound.

So…. I am not sure what has caused these diplomats to report some of these auditory sensations.

We can’t rule out airborne ototoxins that they may have come in contact with and while this does sound a bit like James Bond, this etiology is more likely than an infrasound or an ultrasound attack.

Or maybe…. The diplomats were at a great party the night before and are all suffering from TTS and hangovers….?

 

 

Serotonin is a massively large molecule. In fact, it is so large that it cannot cross the blood brain barrier. We can’t simply take Serotonin orally or eat foods that have high levels of Serotonin- this won’t be able to get to the brain. Serotonin is like Las Vegas- what happens in Las Vegas, stays in Las Vegas….or so I am told. (I actually have never been there.)

Seratonin is a very large molecule. Courtesy of panama-guide.com

All we can do is block or prevent the natural time-course of Serotonin from being reabsorbed by the tissues of the central nervous system. There is a class of antidepressants called selective serotonin reuptake inhibitors, or SSRIs for short.  SSRIs, as the name suggests, inhibit or block the central nervous system’s propensity to wanting to do away with the Serotonin. The result is that more Serotonin is available for the various neurologic and metabolic processes that occur in the brain.

The biochemistry of SSRIs is actually pretty clever- if you can’t add more, then block the re-uptake of it.  SSRIs are a common medication given for people as antidepressants.

 

In a recent study in Cell Reports researchers at the Oregon Health and Science University found that too much Serotonin can be a bad thing, at least when it comes to the treatment of tinnitus. 

Earrings and necklaces have been made out of the Serotonin molecule….. I think that they forgot the double bonded carbon atoms, but then again, its only jewelry. Courtesy of www.etsy.com.

In examining the Dorsal Cochlear Nucleus of mice, the researchers found that a special type of neuron called fusiform cells exhibited hyperactivity and increased sensitivity when exposed to higher levels of Serotonin. This may explain why many people who are prescribed SSRIs as an antidepressant often report an increase in the level of tinnitus.

I should point out that for many people SSRIs are an important tool in the treatment of their depression and despite the increased prevalence of tinnitus that they may experience, the benefits may far outweigh the potential side effects.  

The researchers wanted to better understand the biochemistry and physiology leading to tinnitus.   One of the areas of further study, perhaps the most important area, would be the study of the various ion channels that allow the Serotonin to enter a cell and perhaps by altering this pathway, the benefits of SSRIs may increase or maintain, while minimizing the potential side effects such as tinnitus.