My setting is sci-fi, with a pretty futuristic level of technology. This guy is an alien and their species have spaceships and faster-than-light engines and all that, but very little medical technology. They're regenerators and haven't had much need to develop medical technology, and what they have is more bioengineering than healing. At the time of the injury, the character was all alone and had no access to any technology, healing or not.
Now, I want him to be unable to actually speak out loud, and I'm trying to figure out what the best explanation is. A lot of it can be handwaved as he's an alien with some decidedly non-human anatomy details (The species is technically a primate-insectoid hybrid. Thanks, canon. That isn't a biological nightmare at all…), but I do want some realism to go with the sci-fi weirdness. The species' healing speed is directly tied into how recently they fed, and so I'm explaining the permanent damage by having him have been starved for too long to fully heal, and possibly have something implanted to keep the damage from healing, as the injury was deliberate.
So there are a few things I'm wondering about:
1. What would be the best way to deliberately cause permanent voice loss? Originally I thought about having his vocal cords removed, but I'm unsure if that would permanently silence a person. From what I can tell, it doesn't always seem to lead to complete lack of speech. (The injury was made with a knife and some metal claws, not particularly neatly, and without any aftercare, would that affect it?) I also considered recurrent laryngeal nerve damage, but when that's bilateral, it seems to often cause breathing problems, which I don't want. For the same reason, complete laryngeal removal is not quite what I want, and for various other reasons, I'd rather not remove his tongue. Regarding brain damage – I know it'd be a fairly obvious solution, but it'd be much harder for someone with no real medical knowledge to inflict purposely. I imagine ripping someone's throat out, even if aiming for a specific result, is easier than brain surgery. Feel free to tell me otherwise, though.
2. Would it be possible for someone to make sounds of any sort without being able to speak actual words? I know it's possible with tongue removal, but as I mentioned, I'd rather not do that. (This isn't a must, I'm just curious.)
3. How much would lack of aftercare and lack of motivation to try to improve his ability to speak do? The injury is about a century old, at least ten of which the character was without any help or care (the ten years after the injury). He couldn't replenish his energy nearly as efficiently during these years. His species also do not communicate vocally as their main way of socializing, so would the lack of a need to speak cause a psychosomatic effect? (I know, hard to say with an alien. They have a lot of similarities with humans, though, so I use humans as a template.
Obviously, this guy is not a very realistic creature, so I can make something up if I have to, but it'd be nice to base it at least vaguely in reality. If not, then well, he's a telepathic alien human-bug hybrid with technical immortality and a life-drain ability. I think I can wriggle my way out of it if I have to. *chuckles* I just like using proper biology as a springboard, at least.
Search terms used: cordectomy, total cordectomy, laryngeal nerve damage, vocal cord paralysis, laryngotomy, aphonia, dysphonia