Would tinnitus be explained by perpetually-bent/opened hairs in the cochlea?

Question

When I look around for what causes tinnitus and the like, the usual response is "Well, loud sounds and hearing damage" but I feel like that's a little plain and I am curious about the underlying mechanism / explanation on a physiological level.

My previous understanding of how the ear works can be found in my previous question (with a terrific answer by AliceD).

So my question is this: Let's say a really loud, fierce sound occurs - the sort of thing that is said to cause tinnitus. This is equivalent to a really strong pressure wave approaching the eardrum. I imagine it would hit the eardrum, causing it to move violently / harshly, causing a similarly strong movement in the stapes, which is already providing something like a 20x pressure amplification to the cochlea.

So the stapes hammers hard on the oval window of the cochlea, causing a harsh pressure wave through the perilymph / endolymph, also causing the basilar membrane to move very harshly and violently. To me this would imply a fierce smashing/dragging of the hair cells against the tectorial membrane above, possibly causing sufficiently harsh wear-and-tear along the tops of the hair cells, leaving them bent or maybe even chopped, allowing their channels to remain perpetually open.

If these channels are always open, they're always accepting potassium, always creating the action potentials, always triggering the nerves underneath, which would mean the person is always hearing that particular tone all day, every day, 24/7.

Is this more or less what happens, or am I way off in my little thought experiment daydream here? Is this why tinnitus is difficult to cure, because it would require somehow rebuilding / closing up hair cells that are always open?

Answer 1

What you're describing would likely cause hearing loss, which could later result in tinnitus, but not by the mechanism you describe.

Hair cells transduce sound via remarkably fragile connections between stereocilia. The channels are closed until tension pulls the channels open (see Fettiplace 2011 for a review that covers pretty much all of sound transduction including a detailed description of the tip links and channels involved). Disconnection would result in the channels being perpetually closed, not perpetually open.

Anything like the trauma you describe would irreversibly damage the tip links and sound transmission would fail. There are mechanisms in the ear to prevent this sort of damage, but for sufficiently loud sounds the damage is not avoidable.

@AliceD has another excellent answer on tinnitus specifically here for more realistic mechanisms proposed for tinnitus: What is the mechanism behind tinnitus?. These are all centrally derived in some way. In short, the absence of proper input to the auditory processing parts of the brain results in compensation that induces an illusory perception. Similar sensations are experienced in other parts of the body as well, such as phantom limb.

---

Fettiplace, R. (2011). Hair cell transduction, tuning, and synaptic transmission in the mammalian cochlea. Comprehensive Physiology, 7(4), 1197-1227.