The following Clinical Trial was first published at the Frontiers in Otolaryngology Meeting of the Garnett Passe and Rodney Williams Foundation in Sydney, Australia, August 2014 and subsequently at the Annual Scientific Meeting of the Australian Society of Otolaryngology Head and Neck Surgeons, April 2015, Sydney, Australia.
TINNITUS IMPROVEMENT AFTER VERY LOW FREQUENCY SOUND
Dr Peter Winkler
MB, BS. FRCS. FRACS. FAICD
Macquarie Street Tinnitus Clinic
Residual inhibition is the absence or reduction of tinnitus that occurs after a tinnitus masking signal ceases. Although this phenomenon is well known, the duration of inhibition produced by conventional masking was only 30 to 60 seconds and therefore not considered to be therapeutically useful.
A new series of non sinusoidal low frequency sounds below 30Hz (TIPA) and playing for 12 minutes has been developed and produces prolonged residual inhibition that may last from hours to days.
Tinnitus theory suggests that if tinnitus is repeatedly suppressed, induced development of brain plasticity will produce longer term reduction of the tinnitus.
This study was therefore designed to determine whether repeated residual inhibition induced by TIPA would induce longer term tinnitus suppression.
Patients were selected on the basis of having demonstrated positive residual inhibition of tinnitus following an initial single test exposure to the 12 minute TIPA sound.
36 patients who responded were then provided with a digital player and fully enclosed headphones. The player contained 50 copies of the TIPA signal. Patients were instructed to listen to the sound signal daily at a comfortable volume above the Minimum Masking Level. The stimulus was applied to both ears simultaneously.
Tinnitus Handicap Inventory (THI) scores were recorded at the commencement of treatment and on completion of the program. The THI is a standard measure of tinnitus severity with scores ranging from 0 to 100 with higher scores indicating greater tinnitus handicap. A reduction of 7 points in the THI is regarded as the minimum clinically important improvement resulting from treatment.
19 (53%) of the 36 patients in the trial reported improvement resulting from the treatment. The average reduction in THI score was 27 points with a range of 8 to 62 points, including two patients recording a reduction of 58 points. The greater the reduction in in the THI score, the greater is the improvement in tinnitus. Three patients reported absence of tinnitus after treatment.
Low frequency sound stimulation can produce significant amelioration of tinnitus and does so after a relatively short duration of stimulus exposure.
TIPA is an acronym for Tinnitus Inhibitory Pathway Activation and was first published in 2008. It is postulated that Long Term Potentiation of inhibitory cells in the cochlear nucleus could explain the longer term post stimulus suppression of tinnitus produced by these low frequency pulse trains.
Further laboratory investigation is continuing.