Many people, myself included, have a gnawing primeval fear of becoming hopelessly lost. This Op-Doc video examines that fear in a most extreme form. My subject is Sharon Roseman of Denver, who gets lost every day — in the streets she’s lived in for 20 years, even in her own house. When she wakes, her walls seem to have moved overnight. Her world can be transformed in the blink of an eye.

Ms. Roseman has Developmental Topographical Disorientation (D.T.D.), a rare neurological disorder that renders people unable to orient themselves in any environment. Ms. Roseman cannot form cognitive maps — the brain’s way of representing spatial relationships. She has no inner compass.

Before she was given the D.T.D. diagnosis, doctors told her she might have epilepsy or a brain tumor. She kept her condition a secret from her husband, worked close to home and was terrified of not being able to take care of her children in the event of an emergency. After the diagnosis, she says she felt validated for the first time in her life: “I can now talk freely about D.T.D. and teach others what it is, so that someday a young child can be diagnosed and not have to grow up being afraid.”

Dr. Giuseppe Iaria, a cognitive neuroscientist at the University of Calgary who is credited with discovering D.T.D., says there is not yet an effective treatment. His Web site, gettinglost.ca, provides resources and a test for orientation skills.