5 Major Features

Concussion may be due to a direct blow to the head or elsewhere on the body with transmission of that force to the head.
It is characterised by short term neurological impairment which in most cases resolves spontaneously.
These acute symptoms are due to functional disturbance of normal brain function (at an electrochemical and neurotransmitter level) rather than a structural injury to the nerve cells themselves or either bleeding or swelling within the confined space of the skull or the brain itself.
Concussion can occur with or without a loss of consciousness, and typical imaging studies such as CT and MRI are usually normal immediately after the injury during a recovery period

Rapid onset of short-lived impairment of neurologic function that resolves spontaneously
Acute symptoms usually due to functional disturbance rather than structural injury
Results in graded set of clinical syndromes that may or may not involve loss of consciousness (LOC)
Typically associated with grossly normal neuroimaging studies