I had extreme tinnitus in my left ear constantly, like all day long. I had other problems too like constant right eye twitching, numb fingertips, etc.
I researched this and found my problem and cure: Heavy metal toxicity, namely mercury from my tooth fillings. I had them removed and it was about a month later when I realized, hey, no more ear ringing or eye twitching.
Do some research about this if you have dental mercury for mercury has an affinity for central nervous system tissue and can cause a multitude of nerve problems, including MS.