Did you know that some people cannot differentiate faces, even of people they have known for decades? A rare group of people are affected by a neurological disorder which, in its most severe form, restricts them from recognising their face or even distinguishing a person’s face from something like a basket or a box.

Prosopagnosia is a brain disorder characterised by an inability to differentiate, recognise, or even register faces. This form of visual agnosia differs in severity, with patients being unable to distinguish between faces of strangers or even between faces of loved ones - and that’s just in less severe forms. In more severe forms, affected individuals may be unable to differentiate faces from objects or even recognise their own faces. This face blindness often results in impaired social abilities and general difficulties in daily life.

If you or someone you know suffers from such a disorder, this article encompasses the important information you need to understand, help, and cope with the condition. Of course, if you are simply curious about prosopagnosia or how prosopagnosia arises, all you have to do is read on!

Introduction

Prosopagnosia, also termed face blindness or facial agnosia, is a neurological disorder differing in severity. Primarily characterised by difficulty or complete inability to recognise or distinguish faces, this disorder affects an individual’s daily life, particularly social or interpersonal interactions.¹

Facial recognition is a foundation stone for social interaction. In day-to-day life, our ability to recognise people serves as a basis for our ability to function in a society. From friends to co-workers, family to other important people, being unable to recognise faces is a major deterrent to how we conduct ourselves with others. Prosopagnosia, while being a rare disorder (1 in 33 suffering from mild forms, 1 in 108 suffering from severe forms),² is one that severely impacts social and general quality of life.

Types of prosopagnosia

While the pathology of the disease is relatively unknown, Prosopagnosia comes in two forms - Developmental Prosopagnosia - is a congenital form caused either due to genetic or developmental dysfunction.

Developmental prosopagnosia

In this form of prosopagnosia, affected individuals are born unable to recognise faces. The disorder is not accompanied by any form of intellectual disability or visual malfunction and, therefore, is a form of selective non-recognition. However, patients can develop their ability to use non-facial features to identify individuals, such as clothing, walking style, speech, etc.

Also known as congenital prosopagnosia or congenital face blindness, those born with the disorder suffer from it for the entire length of their lives, even without suffering any brain trauma. Memory and cognition in these individuals are also unaffected, indicating a genetic or developmental cause of disease.

While the underlying genetic cause of the disease remains relatively unknown, there have been studies which indicate a genetic component, including twin studies and others correlating the inheritance pattern to a typical autosomal dominant form of inheritance.^3,1

As onset becomes apparent early on, children with the disorder begin to suffer in social settings as early as school, with an inability to recognise friends and teachers, impairing their ability to make social connections. They often experience traumatic social experiences due to this inability, particularly when the disorder remains undiagnosed for long periods of early life. This results in anxiety in social situations and feelings of guilt regarding their inability to identify even long-time friends and family.¹ Frequently, this may lead to antisocial personalities, with developmental prosopagnosics avoiding professions where social contact is necessary and generally avoiding face-to-face interactions in their daily lives.

Acquired prosopagnosia

Acquired Prosopagnosia is a form of prosopagnosia where individuals who may have been born with normal facial-recognition ability abruptly lose this faculty. This is most often a result of acute brain trauma. Injuries of the brain, including brain trauma, stroke, encephalitis and tumours or lesions in the brain.

An inability to recognise faces is also commonly seen in neurological disorders associated with neurodegeneration, such as Alzheimer’s and Dementia. These are also considered acquired cases of prosopagnosia.

The acquired form of this disorder differs from the developmental form in two major aspects.

Firstly, the onset of the inability to recognise/distinguish faces may begin at any point following birth. In other words, it is not congenital. Thus, patients go through most of their life being able to recognise friends and family, and then following onset, face severe difficulties in these distinctions. Naturally, this may lead to new complications in social and career settings, resulting in eventual social withdrawal. 

Secondly, as the cause of Acquired prosopagnosia is usually brain injury, lesions or a loss of brain cells due to neurodegenerative disorders, the condition is often accompanied by loss of other brain functions, such as memory and cognition or even visual or other sensory defects.¹

Symptoms and manifestations

Patients suffering from prosopagnosia are characteristically unable to recognise faces. This is the most significant symptom, with the afflicted patient often developing social anxiety, stress and even trauma from interactions where they have been unable to recognise familiar faces, either in person or even in photographs. This may also lead to confusion when watching plays or movies with multiple characters, especially creating difficulty in crowds.⁴

Prosopagnosics often rely on non-facial clues such as clothing, speech, and gait to determine an individual's identity. Their confusion leads to them preferring not to greet people by name or even meet new people.^1,4

Most people with the disorder can use the non-facial clues sufficiently enough to function in day-to-day society, however, they may still struggle in situations where people are uniformed or wear similar clothing.⁵

Diagnosis and Assessment

Face recognition tests

An ideal evaluation method to determine whether someone suffers from prosopagnosia is to test for the hallmark symptom, that is, their inability to recognise faces. Facial familiarity tests determine whether a person can recall a face they have previously seen. The Cambridge Face Memory Test (CFMT) is the most prevalent test.^1,5

The FCMT and other facial familiarity tests, like the Glasgow Face Matching Test, work by showing patients a face (with external identifying features like hair, jewellery, and clothing removed) for a short time (around 3 seconds). They then show the patient three faces, only one of which is identical. In the final round of the test, thirty groups of three faces are shown, where only one face in one group of thirty is identical to the target face. Patients are made to select the matching face in both rounds of testing, and a score is determined to determine whether they are prosopagnosic.⁷

Neuroimaging and neurological examinations

Recent research has determined the areas of the brain associated with facial perception. Neuroimaging studies have seen activity in regions delineated as the occipital face area (OFA), fusiform face area (FFA) and others, establishing these as the networks associated with determining, distinguishing, and recognising facial identity. It has also been determined that the brain's right hemisphere is more strongly associated with facial recognition.

Neuroimaging can, therefore, be used to determine the activity of these brain regions in association with exposure to new/familiar faces to diagnose patients as prosopagnosics. Often, lesions in these regions can be captured using technology like MRI, and therefore associated with the impact on facial recognition. Neuroimaging technologies, therefore, serve as an important tool for research and diagnosis, especially in the acquired form of prosopagnosia.

Treatment and management

There is currently no cure for prosopagnosia. The disorder remains poorly understood and relatively less characterised. Until more research and insight are gained into the mechanism and functioning of the disease, not much can be expected by way of curative therapies.

Treatment is, as of now, limited. Some forms of face recognition ability rehabilitation have been studied, with some effect if undertaken in early/developmental stages in children affected with the disorder.⁷ Affected individuals rely instead on non-facial clues to improve social interactions and general day-to-day functioning. As such, the development of one’s ability to associate voice, speech patterns, accents, walking style and gait, posture, clothing or accessories - is a method of coping and mitigating the effects of the disorder.⁴

It is evident, therefore, that more research must be conducted into prosopagnosia to understand the disease and find solutions to it.

Summary

Prosopagnosia is a relatively rare neurological disorder characterised by an inability to recognise faces. Affected individuals cannot differentiate even between the faces of friends or family. In severe cases, prosopagnosics cannot recognise their face or even differentiate faces from objects. 

There are two forms of the disorder - Developmental Prosopagnosia a congenital form where people are unable to recognise faces from birth. This form is usually not accompanied by any other neurological disorder, having otherwise normal cognition, memory and vision. In Acquired Prosopagnosia, individuals may have been born with normal facial perception, however, due to brain injury, lesions or neurodegenerative disorders, they lose this ability. As this may be a form of brain damage, it is often accompanied by loss of other brain functions, usually decreased memory and cognitive abilities. Affected individuals often face social anxiety, experience traumatic memories associated with interpersonal interactions and find themselves withdrawn from society. They rely on non-facial clues such as behaviour, speech and clothing when required. Prosopagnosia requires more research to understand the disorder and develop solutions for it fully. Currently, very little is known about how the disorder develops specifically. The cause of the developmental form is still unknown, although a genetic component is believed to be at play. Diagnosis is through facial memory and facial perception tests such as the Cambridge Face Memory Test. Neuroimaging using MRI scans poses another potential method to improve diagnosis of the disorder.