Welcome to HCM!
I have rad your question carefully and from my clinical experince I can say that during the fall your brother had a
head injury.
Even though he is ok at present but you must take him to the doctor once, and get him checked throughly.
The fact that he had :
-a period of unconsciousness
-pain in head and neck
-with rigidity of body, and
-later twisting movements of jaw, ----> all point towards some injury.
Exact nature of injury can be assessed after examining the patient and some relevant test.
Had I been seeing your brother, I would check his reflexes, do a fundus examination, and may go for an
MRI brain to rule out any neurological problem.
So, there is no need to panic right now, as currently there are no issues, but a visit to the doctor will be a wise thing to do.
Hope the answer is able to guide you
Feel free to ask more questions
Dr. Manisha Gopal