“The main character is a young doctor called Edward Eischer (? or sth), who hears voices and performs lobotomies/brain experiments on patients and also himself (he literally has a hole in his forehead). I think he believes some supernatural entity is talking to him and he tries to summon it thru his experiments. In the end he ends up in a ward himself. There are a bunch of other evil doctors in the hospital, one is called Barnard I think. The movie is mostly black and white but has a few colored scenes for when he has visions or sth particularly gory is happening. I unfortunately missed the ending credits and only caught the year it was released in, which is 2004. The movie is very graphic, definitely 18+”
It’s not Next Victim (2003).
https://www.reddit.com/r/whatisthatmovie/comments/1g0dhqc/comment/lrgs5sg/?context=3