Is this an anxiety attack?

My neighbor has an 18 yr old son. The mom described one of his "episodes". One time he was depressed for no reason, she talked to him at length but he couldn't pinpoint a reason why he felt this way. A few minutes later his back started to hurt badly, his hands stiffened up, and he was alot of pain. Other times it (the episodes) just show up, hands shake, he can't move, legs become weak and he's extremely upset and nervous, he says he's having trouble breathing. ER doc said it could be siezures or anxiety. The neurologist wants to do more tests. Does anyone have any idea what this could be or any experience?