Neurologists have traced the link between facial blindness and other disorders
Prosopagnosia, or face blindness, is a brain disorder in which people are unable to distinguish faces, including those of relatives and friends. From past research, we know that prosopagnosia can be either acquired or in the form of a genetic disorder. Now scientists have looked more closely at what neurological pathologies face blindness is combined with.
The term "prosopagnosia" (from the Greek prósōpon - "face" and agnōsía - "non-recognition") in 1947 for the first time introduced the German neurologist Joachim Bodamer, but cases of inability to recognize faces are known since the XIX century. People with this disorder cannot mentally combine disparate facial features into one whole. At the same time, they see and often describe individual facial characteristics.
Face blindness makes life very difficult, especially in terms of social contacts and connections, as sufferers may have difficulty remembering the faces of loved ones or even not recognize themselves in the mirror. Congenital prosopagnosia is thought to occur in about two percent of the population. But some studies have shown that the proportion of people with mild forms of this disorder is as high as 10 percent.
In the new paper, which was published in the journal Brain Communications, neuroscientists from the US-based Mayo Clinic looked at data from 336 patients with presumed or diagnosed prosopagnosia between 2000 and 2023. Their analysis revealed which neurological abnormalities are associated with this diagnosis and revealed some other important details.
Just over half of the patients - 55 percent - were women, and the average age of onset was about 66 years old. This suggests that while prosopagnosia can occur at any age, it predominantly manifests later in life, especially if it is an acquired form. A quarter of the patients had other visual perception disorders, indicating a likely overlap with neurological disorders.
Prosopagnosia was acquired in 326 patients. A congenital form was found in ten, and 80 percent of these were men. Among these patients, one suffered from Niemann-Pick disease type C, caused by mutations in the NPC1 and NPC2 genes. In another, a mutation in the FOXG1 gene was a prerequisite for neurologic pathology.
In 235 cases (72.1 percent) acquired prosopagnosia was associated with neurological degenerative diseases, and in 91 cases - with non-degenerative causes. That is, the disorder developed either in the course of progressive neurodegenerative pathology or as a result of a single incident such as brain injury or stroke.
Among the neurodegenerative diagnoses, posterior cortical atrophy, primary prosopagnosia syndrome, dementia in Alzheimer's disease, and semantic dementia were more common among patients. Each accounted for approximately 10 percent of the cases in the group.
The most common non-degenerative diagnoses were strokes (ischemic and hemorrhagic), epilepsy, and primary brain tumors.
The authors noted that in some cases not associated with degenerative diseases, symptoms of facial blindness diminished or disappeared over time. Signs of improved prosopagnosia were seen in patients with migraine, posterior reversible encephalopathy syndrome, delirium, hypoxic encephalopathy, and ischemic strokes.
Neuroscientists have also noticed that some patients with face blindness have developed strategies to make their lives easier. Specifically, they began to rely additionally on other senses, such as hearing and smell, to recognize people.
The researchers have shown the complexity and diversity of causes that can contribute to face blindness. In addition, the work is encouraging with the finding that prosopagnosia is a passing condition in some cases in adults.