Can whiplash cause extreme headaches seizures and back pain. It was unnoticed and untreated by icu.

Whiplash. Headaches can be caused by whiplash, but seizures and back pain are unrelated to whiplash.
Concussion . The injury that caused the "whiplash" may be the cause of the symptoms you listed. A ct scan of the head, neck and spine might reveal a previously unnoticed injury.