Thanks for writing your query.
Due to the head injury
, your grandfather might have sufferd from concussion injury
. It can result in memory loss
, persistent headache, nausea or vomiting
It is advisable that you should get a scan of his head done and consult a Neurophysician for neurological examination.
Concussion injury takes few days to weeks for complete recovery. Proper rest quickens the recovery.
I hope this is useful to you.