Dr. Najjar had Cahalan perform a “clock test", which involves the patient drawing the face of a clock. When Cahalan drew her clock, she was only able to recreate half of it, indicating injury to one side of her brain. After a brain biopsy, it was concluded that Cahalan's issue was not psychiatric, but the result of anti-NMDA encephalitis, a brain-inflammation disease with an unknown cause. She was only the 217th person diagnosed with this illness.