I was in an accident when I was 15, severing the nerves for two of my facial muscles (levator labii superioris and zygomaticus minor, to be specific). I am now 40, and my smile is crooked because of this.
The nerves have healed, as confirmed by various tests, but my brain has simply forgotten how to control these muscles. It’s hard to explain, but on the right side of my face I can control those muscles just fine… I just cannot translate the same action into something for the left side.
It’s not really a disability, so I don’t really care that much, but I have considered asking my doctor if he can send me to a neurologist or something.