Imagine you wake up in a hospital without a single memory of the last month. Doctors say you had a series of violent episodes and paranoid delusions. You'd become convinced you were suffering from bipolar disorder. Then, after a special test, a neurologist diagnoses you with a rare autoimmune disease called anti-NMDAR (Anti-N-methyl-d-aspartate receptor) encephalitis. This is what happened to Susannah Cahalan, a New York Post reporter who would go on to write the best-selling memoir Brain on Fire: My Month of Madness.