Susannah's test results soon come back negative for a number of infectious and autoimmune diseases. Her MRIs and CT scans are also clean, and Mom and Dad sense that the doctors are starting to worry that they won't figure out what the problem is. On the afternoon the results come back, Mom waits eagerly for Dr. Siegel. When he doesn't come, she searches him out. He brushes her off and says he's no longer on Susannah's case.
Cahalan will later explain that not every autoimmune disease is included on initial testing panels like these, though her disease is eventually included on standard panels. This situates Susannah's story as very much a product of its time, one in which a very treatable condition is a perplexing medical mystery.
Later, when Dr. Russo comes in, she tells Mom that she and Dr. Najjar would like to do a second spinal tap. She explains that Dr. Najjar is a brilliant doctor who's now working on Susannah's case. Susannah tells the reader that he has a reputation for solving mystery cases, and Dr. Siegel had asked him for help. Dr. Najjar believes that Susannah's illness is some form of autoimmune encephalitis (brain inflammation), and he decides to start her on an experimental treatment called IVIG.
Again, the fact that Susannah's condition attracts the attention of someone like Dr. Najjar for being such a mystery situates it firmly as something that could only happen in 2009. In this way, Cahalan offers ways for a reader to track how far the medical community has come since then. For example, IVIG is now listed in the World Health Organization's list of essential medicines.