I have no medical training but ventriculopleural shunts can cause some complications, and I think you're probably right in suspecting that the revision that was done in January might be causing your son's problems now. You say he's had many tests,
and I'm wondering if anyone has thought to look into the question of the shunt.

I hope you'll ask your son's doctor about the shunt. I hope that something can be done soon so he won't have to suffer like this.