It wasn't like Nero couldn't stand or walk on his own. It was simply that, for whatever reason, the exertion required to do so was immense. It took up an immense amount of mental concentration to keep himself standing, as if he needed to maintain control over each individual muscle consciously.
He took a moment to stand up, gain his balance, and then straighten out his expression. It would take away somewhat from the seriousness of this conversation if he were making funny faces in between.
Once he was ready, he gave a nod to the lieutenant's assigned assistant. A lieutenant was not quite high enough rank to get an assigned Aide-de-Camp (ADC), but a normal assistant was naturally necessary.
