You are assessing a patient shortly after a head injury and want to establish whether they have retrograde amnesia. Before revealing the answer, decide how you would assess for it during the interview.

Ask the patient directly what is the last thing they remember before the injury, and work backwards from there to establish how far back the gap extends. Cross-check their account against a witness or the notes wherever possible, since patients are often unaware of the true extent of the gap. Because the gap in acute post-traumatic retrograde amnesia typically shrinks over the following days, re-assess it on more than one occasion rather than relying on a single early estimate, and record the length of the gap as it is at each assessment rather than assuming it is fixed.