I have had this cactus since i was 9. It is now 22 years old and in big trouble. I have come back from travelling for 3 months and it is in a terrible condition. It has been in the greenhouse over the winter months and i fear this has contributed to the damage. It appears to be rotten at the top as half of steam looks eaten away. The bottom i am not so sure of. I gather that some breads do tend to go a little brown at the around the bottom anyway. I am just wondering what the best course of action is. Can i cut the top off where it is rotten? If so, should i do this and repot the remainder of the plant? Any advice would be most welcome as i have previously had no trouble with the plant so i am not knowledgeable about treating them.

Thanks in advance.

Paul.