Mounting microphone in Fabia

I just purchased a Parrot Rythm N'Blue autoradio with builtin bluetooth handsfree and I am now looking forward to installing it in my Fabia. It should be easy as it's all ISO connectors. However, there is still a single wire connecting the external microphone to the back of the radio. Any tips on how to best get that wire from the back of the radio to the top of the left A-post, or to the rear mirror?

Thanks, Michael