For years, Roseman did her best to navigate the world in silence, worried what people would think if she told them of her secret. When she was 29, her brother called her, sick, to ask for a ride to the hospital. On her way over, she got lost two blocks away from his apartment and eventually had to call him from a payphone for directions. Though he was able to direct her from his house to the hospital, her secret was out. After he had recovered, he pressed her to tell him and their other sister more about the condition she had kept hidden.

Soon after the hospital incident, Roseman’s siblings convinced her to seek help. It was the first time Roseman opened up to doctors about her inability to navigate, but it wasn’t her last. Though she sought both neurological and psychological help for her condition, no one could tell her what the problem was. Ten years after seeing her first neurologist without any luck, she tried another in Denver. When this doctor told Roseman she could have multiple-personality disorder, she became so upset she stopped looking for a diagnosis.

Then, in 2006, she happened to see a documentary about faceblindness, or prosopagnosia. The topic piqued her interest, and she did some more investigating online at faceblind.org, a website run by a researcher who was studying the condition. Out of curiosity, she took the site’s assessment on facial-recognition abilities, which included some questions about navigation. Her quiz answers alerted Brad Duchaine, a neuroscientist then at University College London (now at Dartmouth University) and one of the researchers who was running the site. He contacted Roseman directly, she said: “He sent me an email to tell me I wasn’t the only person who has this.” Though her symptoms fell outside his area of expertise, he promised to keep her case in mind and, and to introduce her to someone who was studying her condition as soon as he learned of the right person.

Duchaine stayed true to his word. In July of 2008, when he learned about the research of Giuseppe Iaria, a neuroscientist at the University of Calgary, he reached out to Roseman to ask if he could put them in touch. At that point, Iaria and his colleagues had just published a paper identifying the first recorded case of DTD.

Initially, Iaria had planned to focus his research on the variability of people’s navigational skills, or why some people are better at following maps and spatial directions than others. But in 2007, he met a woman who had come to the university’s neuropsychology department seeking help with a peculiar problem: Other than her constant disorientation, she was perfectly healthy, mentally and physically. After extensive testing, Iaria realized that she had something that hadn’t yet been documented anywhere. “She was something exceptional … She didn’t have any brain damage, she didn’t have any neurological conditions, or anything else other than getting lost in extremely familiar surroundings,” he said.