by Dr Peter Winkler MB.BS.,FRCS,FRACS,FAICD.

                                            E.N.T. SURGEON 

                                             ( September 2011)

In simple terms tinnitus can be "switched off " either completely or partially. This is generally temporary but in some cases becomes permanent with repeated use. This phenomenon has been known for over 100 years and is technically described as residual inhibition (RI).

The reason that it is called residual is because it invariably follows some form of stimulus applied to the ear or the brain. When residual inhibition follows a sound signal the sound signal is called a masking signal.

The commonest stimulus that produces RI is sound energy. RI has also occasionally been produced by cochlear implants and middle ear implantable devices but these are invasive and not widely used for treatment of tinnitus .

Around 100 years ago a physician named Spaulding recorded that his tinnitus patients did not hear their tinnitus while he played his violin to them (this is  masking) and after he stopped playing his violin it took 30-60 seconds before the tinnitus came back. Seventy years later this phenomenon was named residual inhibition (RI).  Residual inhibition was  defined as the complete or partial absence of tinnitus after exposure to a masking signal.

The problem was that despite extensive research around 1970, no-one could make RI last long enough to be useful in treating tinnitus and the underlying mechanisms were unknown. It was regarded as a clinical curiosity and abandoned.

The Tipa research project was started around 2001 to find out whether using different sounds could make RI last longer. This was done using audio engineering software and digital synthesisers to create new sounds. This is a very slow process because there were no objective correlates of tinnitus which means you could not see tinnitus on a screen. The only way a researcher knew what tinnitus was doing was to ask the patient what they hear.

Great progress has been made. Not only was the TIPA sound signal discovered to be able to switch tinnitus off for hours and even days in some patients but also in August 2011 Magnetoencephalograpy (MEG) was used to demonstrate objective correlates of tinnitus before and after the tinnitus was switched off in the same patient using TIPA. These findings were published at the Tinnitus Research Initiative Conference in Buffalo, New York on August 19th 2011