Pinched Nerve?

My little Sammy is a one year old short haired black cat. He has always been very active and playful. Last Wednesday night he became very sick and I thought he wouldn't make it until morning. I took him to the vet and they said he was pretty blocked up from constipation. They gave him an enema and laxatives and a second enema a few days later. He was just laying around with no personality and he even bit and scratched me over the weekend. He was in bad shape but still going normally and eating and drinking. Two days ago he started dragging his lower half around so I called the vet back and they said he most likely pinched a nerve straining to go to the bathroom over the last week. So now I give him liquid cortizone twice a day. He's only had two doses so far but his personality is coming back already. He's meowing a little again. Eating drinking going to the litter box normally but he's still dragging himself around. He didn't move for days and now with the steroids he's moving very quickly even though he's only using his front legs and he's back to trying to get into everything. Is this a good sign that he really does only have a pinched nerve?

I would say his response to the med is a very encouraging sign. I hope he continues to improve quickly.
Did the vet diagnose what caused the bad constipation in the first place?

He didn't really say. He is back to going normal now and still eating and drinking normally. Last night about two hours after his first dose he was up and moving much better than he had all week. Still dragging his legs out behind him but other than that he is getting back to his old self. He hates the taste of his medication so he has an attitude right now which is still better than him just laying in a heap all day