Even if there is some ambiguity about the replication of Worf's spine in "Ethics", there is none about the replication of Ptera's brain stem neural tissue in "Emanations".
EMH: "It's a simple process, really. She died of a cancerous growth on the brain stem. I removed the tumor, replicated new neural tissue and used the standard Starfleet postmortem resuscitation technique for a Class 5 life form."
Whether the EMH is making use of the now-perfected technique of Dr. Russell, or some other technique, we don't know. But the good holo-Doctor doesn't have access to the sort of special instrumentation Russel brought aboard, and he still says he replicated neural tissue - whereas there are no references in Star Trek to it being impossible to replicate living tissue. (It's merely difficult, as evidenced by the slow progress in Russell's technique, and by the fact that Tal'Shiar wasn't able to create perfect fake blood in "Data's Day" despite no doubt desiring to do so.)
However, he does not replicate an entirely new brain stem, does he?