Was there anything in the study that indicated efficacy for severe tinnitus as opposed to more moderate cases?
Unless specific data points are released, I don't think we'll ever really know the specifics to that level.
I'm trying to look at this device from a high level, there's plenty of great low level analysis already on this thread.
I do believe that tinnitus comes around from maladaptive neuroplasticity. Something somewhere gives up and lets the tinnitus through in some people, but not in others. The specific causal reasons behind tinnitus are inconsequential at a high level.
I think this device slowly but surely introduces positive neuroplasticity back into the malfunctioning circuit. Tinnitus generally gradually appears in patients and gets louder and louder as this circuit malfunctions more and more. In other cases it's a light switch. Boom, loud tinnitus all of a sudden. I believe this is the point where the brain can no longer deal with this malfunction and lets all of the previously filtered out noise through.
If we use the device for a few weeks and see an improvement, the majority of the circuit is still malfunctioning. So if we stop using it, the 'fixed' parts will follow this maladaptive behaviour and return to produce tinnitus. If we use it long enough (6 months, a year, three years?) this positive plasticity becomes the new learned behaviour within the whole circuit and the effects become permanent. Just as the maladaptive behaviour became permanent at one point.
Think of temporary tinnitus after a concert. The brain generally deals with it in 24 hours. But if you keep inducing that behaviour, eventually the damage leads to it becoming learned within the circuit and you develop tinnitus. Some people will have the hearing loss without the tinnitus, because for some reason this behaviour doesn't become learned.
If the mis-firing cells is accurate as proposed by Dr. Shore, then there is no reason their timing can't be permanently fixed in a beneficial way either. So it really might not matter how severe your tinnitus is, that just might mean more of your circuit needs fixed than someone with moderate tinnitus and so it'll take a bit longer.
Copium? Maybe. High expectations? Probably. But when you look at it from a high level, if this device works at all, there's no reason it can't work in this way.