Hi there. I suggest that you do a MRI cervical spine to rule out any vertebral or intervertebral disc issue creating this intensified pain. A pain physician consultation is warranted if an epidural steroid injection under fluoroscopy could help. Panic attack could also be aggravating the pain. Take care.
He is not bipolar. But pain can cause panic... I know, that's what happened to me when back pain from a car wreck drove me over the edge. I initially did not make the mental connection with my discomfort and panic. Your son needs to see an orthopedist group about his neck injury, they should scan it, give him a neck brace/collar, get him into physical therapy, and prescribe him pain meds that will KILL THE PAIN. Your boy has compression fractures of C-1 and 2, apparently the disc in between has vaporized, and this is NOT a good place for the spine to be injured, so he MUST see an orthopedist... the neuro and chiropractor can do NOTHING to repair his spine, but an orthopedist can. It is even possible an orthopedist will want to do surgery, but normally they try the moderate treatment I have just told you about.
His psychiatrist, in my humble opinion, is not well-versed in panic disorder. Apparently he has never heard of panic disorder. I HAVE PANIC DISORDER and I knew instantly your son has the same thing I got. It is a dreadful place to be. The treatment and medication for it are specific to the disorder... treating him for bipolar will not help him AT ALL. In other words, if I can say so, all the docs he's seeing are inadequate. I just HOPE you can find a top orthopedic surgeon group, perhaps connected with a hospital in a university setting, they have the best docs, and at the same place, have a psychiatrist hook him up with a behaviorist psychologist who specializes in panic disorder. You may have to travel and spend some time in another town to get this accomplished, but I personally believe your son is not receiving adequate treatment, I think his injury is severe, and it will take some top people to get him straight. I feel SO sorry for him and for you. But there is plenty of room for improvement, if you will seek out the correct help.
Let us know how things go. And if you have any concerns with switching up docs and traveling to another place, keep in mind that it's okay to get a "second opinion." That's all in the world you would be doing. For my back pain and my panic disorder, I take four medicines, they are life drugs and I will always take them, but I don't mind one bit, because I can do basic sorts of things (I'm older) that keep me happy. Your son is young, though, and has a good chance of recovering completely in a short length of time (a couple months), with the PROPER care. He should NOT be in pain this far out from his injury, thus confirming my thoughts that he needs better care.
Oh, and a tip I learned amongst many tips whilst being treated for panic disorder is, whenever your son starts to lose it, suggest he take some nice deep breaths, blow it out, breathe normal a couple times, and take another deep breath and so forth, do it ten times, and he won't get to ten. Deep breathing slows the heart, and thus the panic. And just seeing a qualified orthopedist should have the additional effect of calming him becuz SOMEONE will finally be listening to him and giving him what he desperately needs. I will be interested in what happens to your son, since I've been thru the same misery.