If hearing in one ear is substantially worse than in the other ear this can be a symptom of a benign tumour called an acoustic neuroma or a vestibular schwannoma. They grow on the main hearing nerve between the ears and the brain and can cause tinnitus. I had an MRI scan to check for this because of the way my hearing was deteriorating in one ear much faster than the other (my scan was negative).
https://www.macmillan.org.uk/cancer-information-and-support/brain-tumour/acoustic-neuroma
https://en.wikipedia.org/wiki/Vestibular_schwannoma
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Another cause of tinnitus is Normal Pressure Hydrocephalus (NPH) (although the name, in some cases, can be misleading. Pressure in the head might be higher than normal.) I had NPH which was discovered by accident when I was suspected of having had a stroke. (I hadn't had a stroke.) Doctors told me that tinnitus wasn't a symptom of NPH but it was for me, and the surgery I had for it reduced the severity a lot. (Edit : I just remembered. It was actually headaches I was told weren't a symptom of NPH, not tinnitus. But I definitely got headaches!)
https://en.wikipedia.org/wiki/Normal_pressure_hydrocephalus
It took several years but I was eventually given a surgery called an Endoscopic Third Ventriculostomy (ETV) which was a big success.
https://en.wikipedia.org/wiki/Endoscopic_third_ventriculostomy
This achieved several things for me :
a) It reduced the severity of my tinnitus a lot.
b) It eliminated the headaches I'd had almost constantly for decades. (They were usually mild, but not always.)
c) I used to get visual disturbances when I woke up - they almost completely stopped too, after the surgery.
c) It improved my balance tremendously. I'm much less clumsy than I used to be, but I still can't heel/toe walk. If I was ever asked to do USA-style sobriety tests while stone-cold sober I would fail spectacularly.
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Some people with tinnitus have found raising their vitamin B12 levels to top of the range or higher will help reduce their tinnitus (Vitamin B12 is not toxic). It also helps some people eliminate TMJ? TJD? i.e. Temporomandibular joint dysfunction.
https://cks.nice.org.uk/topics/temporomandibular-disorders-tmds/
https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfunction
https://www.healthline.com/health/tmj-tinnitus
There are multiple different types of B12 supplements. People might have to experiment to find which one gives the best results (if they get any results at all). The only one that improves things for me is methylcobalamin, in conjunction with methylfolate. Others do best with one of the others : cyanocobalamin, hydroxocobalamin, adenosylcobalamin.
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Another possible cause of tinnitus might be teeth grinding. Gadgets can be created to order by dentists to prevent teeth grinding (bruxism), but they are horrifyingly expensive. I've been quoted about £300. I have no idea how that price is justified but I couldn't afford it anyway.
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