Complex sentence: Towards the end of season 4, Booth suffered from a brain tumor (that led to him hallucinating that Stewie Griffin was having conversations with him), which was successfully removed but left him with residual memory loss and a lack of confidence in the field.
Split into simpler sentences: Towards the end of season 4, Booth suffers from a brain tumor that leads him to hallucinate conversations with Stewie Griffin. The tumor is successfully removed, but it leaves him with residual memory loss and a lack of confidence in the field.