Take an oversized (and wore out if you have one) brass cleaning jag. For 22, I'd start with a 6mm but larger will work. Shove it up into the neck portion until snug and pull the brass brush and the case remains out. This works for 223 case head separations in rifles so it should work here. If the 6mm brush doesn't grab enough try a 30 cal. Might take a few tries to get it wedged enough.
Also consider soaking it in WD-40 or another penetrating lubricant before trying to brute force it out. Don't spritz it, but submerge it in a glass jar filled with penetrating oil. I'm getting lazy in my old age. I soaked a 243 die in WD-40 overnight after almost stripping the threads off it. Amazing how easy it slipped out after that.
Don't give up, it'll come out.