No loss of consciousness is necessary.
It is a common misconception that loss of consciousness is necessary for a brain injury to be sustained.
A disruption to the brain’s ability to lay down clear and continuous memory is all that is necessary. Sometimes the person will be confused or disorientated in the initial hours after a head injury but even this disorientation is not essential. Other ‘red flags’ are the injured person being quiet and distant, repeating themselves or being sick or displaying dizziness. People often mistake these signs for the patient being in shock.
The effects of diffuse axonal injury to the brain can take up to 72 hours to become apparent so the injured person may gradually deteriorate over this period.
This is why such injuries are invariably missed by A&E departments. Medical staff are usually focused on treating the injuries that they can see as opposed to those that they cannot. If the injured person is conscious and can answer simple questions they are usually described as ‘alert and orientated’ and discharged, often without any head injury advice. This problem is often compounded by the patient telling A&E staff that they are alright and don’t remember being unconscious, even though their ability to lay such memory may be impaired.