At one point in the comics ( I forget when) Matt gets kidnapped by bad guys for whatever reason (I have no details, sorry!) and tried for a crime. His punishment is to be gassed by this stuff filled with nanotech that attacks his brain and robs him of his remaining senses, starting with his sense of taste and eventually graduating through smell and touch to his hearing and his radar sense, leaving him completely trapped within himself apart from the occasional flash of sensation. The avengers fix him in the end, but until then the thought of that really freaked me out, but obviously not enough because I'd really like to see something similar in fic form. The reason for it can be anything, the original ploy is irrelevant, for me it's all about the angst and the terror. And possibly the being comforted bu Foggy when it's all over.