Source: http://psych.fullerton.edu/swillis/agnosia305.htm
The most common cause for prosopagnosia is a posterior cerebral artery stroke , although any process which can damage the occipitotemporal lobes maybe responsible (Goldsmith and Liu, 2001). Thus, other causes include a transient ischemic attack, carbon monoxide poisoning, temporal lobectomy, encephalitis, right temporal lobe atrophy, trauma, Parkinson's disease, and Alzheimer's disease (Goldsmith and Liu, 2001). More diffuse processes include alcohol intoxication, Asperger's syndrome, psychosis due to schizophrenia and mescaline. Genetic transmission is another possible cause for prosopagnosia(Goldsmith and Liu, 2001).
One study found that prosopagnosia occurred with more frequently in males than in females, which might be either a reflection of a higher incident of stroke in males or a differences in facial recognition between males and females (Goldsmith and Liu, 2001).
Covert recognition of faces in prosopagnosia, in which people cannot overtly recognize faces but nevertheless show recognition when tested in certain indirect ways, has been interpreted as the functioning of an intact visual face recognition system deprived of access to other brain systems necessary for consciousness (Farah, O'Reilly, & Vecera 1993). Another explanation is that the visual face recognition system is damaged but not completely destroyed in these people and that damaged neural networks will display a minimal side knowledge in just the kinds of tasks used to measure covert recognition (Farah, O'Reilly, & Vecera 1993).
Many patients with prosopagnosia studied by postmortem or neuroimaging have lesions involving the occipitotemporal regions on both sides (Goldsmith and Liu, 2001). On the other hand, some patients had one sided right-sided lesions, which were sufficient to cause the deficit. There is a growing evidence for a right-sided dominance in the brain for facial recognition in humans. (Goldsmith and Liu, 2001).
Thank you