The head injury may be to blame. Did it only start after that? I would think that a neurologist or an ENT would have some insight. I do know that head injuries can create very wierd symptoms, as well as cause damage to the pituitary gland or the central nervous system.
my dad also suffers from these kind of unexplainable "turns" they can come on suddenly, and he explains a smell, that nobody else can smell, and breaks out in a cold sweat and feels sick, and has to sit down for about 10 minutes, then he can get up again and back to normal. He is currently waiting on a brain scan to see if specialists can pinpoint the underlying problem. He was diagnosed with alzeimer's disease two years ago
search the internet for "epileptic auras" and see if there are similarities in your husband's symptoms
I have the same symptoms. Go outside for fresh air he will feel much better. Staying in the house always maks me feel worse.