Spinal cord ischemia remains a dreadful complication after thoracoabdominal aortic aneurysm repair. The role of cerebrospinal fluid drain in such patients needs further clarifications. Tam and colleagues carried out an interesting decision analysis study that supports the routine use of the cerebrospinal fluid drain after thoracoabdominal aneurysm repair. They also demonstrated that the use of the cerebrospinal drain was safe. Here, we firstly discuss the paper's finding and methodology and, secondly, we try to simply explain what a decision analysis study is and, broadly, and how to construct a Markov model.