I have had the same situation. Lady across the streets son's friend had two that were dying so they were given to me. I pruned off all the dead roots, which was ALL of them, and put the rest in water so the bottom was in the water but the top was out.
I kept them alive over a year that way but finally one succumbed to the previous over watering. Time for DRASTIC measures! I took the remaining one and ripped off the lowest leaf to expose fresh tissue that I then dipped in Rootone. I wrapped the bottom where the Rootone was with cotton (all I could think of that I had) to keep the end moist to provide water for the remaining leaves and the Rootone area damp.
Like a sick child, I took it with me when ever I left for more that a day, even to Iowa to visit my son. This picture is the result as of several years ago. The pink thing at the left is the remains of an old bloom stalk. It is still growing and will be a long time before it is big enough to bloom.
On yours, I would cut off everything below the leaves starting at the end and going up half way from the end to the leaves. Then cut off half of that, etc. until you stop seeing dead tissue OR you are an inch or two from the leaves. Then apply Rootone to the whole base (or you could try
KeikiPro) and cover to keep it moist. You will need to mist the whole plant daily especially keeping the moss or cotton, like I used, damp.
Good luck!!! If it works you will have a good satisfied feeling.