This chapter is a question and answer style article that contains past FRCA paper examples related to neurosurgery, neuroradiology and neurocritical care. It also guides trainees on the most effective manner in which to approach these questions. The discussion covers the following: the implications for the patient of an inadvertent wrong-sided peripheral nerve block (25%); the recommendations of the 'Stop Before You Block' campaign and list factors that have been identified as contributing to the performance of a wrong-sided block (45%); and the term 'never event' as described by the National Patient Safety Agency and three never events of relevance to anaesthetic or intensive care practice.