Also known as: Brain aneurysm
Joe has a basilar artery aneurysm the size of a golf ball with subarachnoid bleeding. Derek performs a high-risk standstill surgery (circulatory arrest procedure) where Joe's body is cooled, heart stopped, and blood drained to allow 45 minutes to clip the aneurysm. This is the central medical case of the episode.
Also known as: TTTS
Pregnant patient with conjoined fetal twins connected by blood vessels in the placenta, causing one twin to receive too much blood and the other too little. Addison performs laparoscopic surgery to separate the fetal blood vessels. The case develops complications showing beginning heart failure in the twins.
Also known as: Unplanned pregnancy
Cristina reveals she is pregnant and experiencing morning sickness. She is concerned about how pregnancy will affect her surgical career and makes an appointment at a clinic, designating Meredith as her emergency contact person.
Also known as: Sexually transmitted infection
Referenced from previous episode - George contracted syphilis from Alex's sexual partner. Mentioned multiple times as ongoing treatment/aftermath.