done it a few times. There are two solutions and you need to pick your route:
a) embrace it, reduce culture, pick up the -5 tokens, get the revolt, revert to stable/tier II and rebuild. There is a lot to recommend this, as you can invest in your army and gain a lot of legacy on the way to the madhouse
b) deal with it, key here is the HCR is (current culture+average 50 turns)/2. You need to go heavily for culture production, to get this as high as you can, you may want to run down your army to balance the budget (ie you are likely to lose some regions but perhaps more controlled than via the civil war route). The new objectives model perhaps makes this a bit more feasible as you can't run out of objectives unlike the earlier versions. The problem is that trying to reach any objectives may add to your decadence so I'd go the cultured and decadent route via top tier progress tokens.
Bigger problem here is it is 2 steps back to normality (decadent-old-stable)
Key is you have to be utterly single minded in your choice as I think the 2 are mutually contradictory. Also in both, you will lose some regions, in (b) you may even look to deliberately shed a few decadence heavy regions by choice.