What does this phrase mean? Wer hat Ihnen denn ins Hirn geschissen?

Question

What does this phrase mean?

Wer hat Ihnen denn ins Hirn geschissen?

Answer 1

It could be roughly translated to English as

Who has planted that bullshit into your brain?

or

Who took a crap on your brain?

You should notice that this is very rude, and not appropriate for serious and professional conversation.
If someone attends to you in that way in a professional context, you should probably escalate that to a higher management level for inappropriate behavior, unless it was a response to a really silly, unconscious or absolutely unacceptable statement made from your side.