Lots of roots... is it pot bound?If so I say you put it in a bigger pot or maby carefully trim the roots down With a very sharp, sterilized knife or sissors. It should be kept evenly moist but not soggy at all. Don't let it dry out befor watering! But again don't let it stay to wet. It's kind of a picky
plant. Keep it in bright indirect light. What were the conditions you had it in befor? Basicly what I can say about why it's leaves died are being in a cold temp or cold drafts cause mainly lower leaves to turn yellow and wilt(maby on the way to your place it got exposed to too much cold)
but since it was small maby all the leaves were efected. Dry air is also bad especialy for young leaves. And finally if they were turning brown/drying up then the compost was alowed to dry out to much. If it looks like I know alot it's because I'm reading it out of a book!
I'm pretty new to the
plant word also and I have a dumb cane as well. I think mines a picta camilla. Also the piece of stem as already mentioned can be used as a cutting using a rooting hormone and provide bottom heat. If you already thruogh it out go get it, it's worth a shot I'd think, as long as it's still solid! Just make shure you remember which side was up. Wash it well and make a new cut.
P.S. They call it a dumb cane cause of the efect it has on the mouth and throt so don't lick it.
Just making shure you wash your hands after cut it!