3 guides on this topic
differential-diagnosis
What each differential-diagnosis question is really asking, how to structure the answer, and where the marks are likely to sit.
Two diagnostic questions and one about examination technique. The third is the one that separates a case write-up from a diagnosis you happened to reach.
Six questions applied to three scenarios is eighteen answers, and the differentials are what get graded. The second scenario is designed to catch anyone who reaches for major depressive disorder.
The case gives you the data. The four questions have to be answered from it — the mechanism, the straight leg raise, the imaging finding — not from a general account of back pain.