The device itself could perhaps be better shielded, before implantation.
I could be wrong, but if that's how it is - well, it's not trivial to shield a needle to prevent it acting as an antenna.
Would be great if someone who knows this stuff can tell us how it really is.
You only need to shield the exposed parts.
I know if someone's opened up my skull. I assume everyone has some sort of multi-band wireless transceiver in their pocket, because that's a cell phone.