乌鸦传媒

A case report showed what may be the first realistic visualizations of the face distortions experienced by a patient with prosopometamorphopsia (PMO).

The 58-year-old patient, V.S., had a 31-month history of seeing peoples' faces as distorted and, in his words, appearing "demonic," reported Brad Duchaine, PhD, of Dartmouth College in Hanover, New Hampshire, and co-authors, in a clinical picture study in .

The distortions involved severely stretched facial features, with deep grooves in the forehead, cheeks, and chin.

Though every face he saw was distorted, the patient could still recognize people. The distortions were not accompanied by delusional beliefs about the identities of the people he saw. Notably, the patient reported no distortions when viewing facial images on a screen or on paper.

Prosopometamorphopsia is a rare neurologic disorder of visual perception in which facial features appear altered in shape, texture, position, or color. Face processing depends on a complex network of brain regions, and can produce a variety of distorted perceptions.

The duration of PMO varies, as does its etiology: it can occur with head trauma, cerebral infarction, epilepsy, migraine, and hallucinogen-persisting perception disorder. It also can emerge without detectable structural brain changes and can be misdiagnosed as schizophrenia or other psychiatric conditions.

Around about PMO have been published in the past century. For most patients, face distortions occur all the time -- on screens, on paper, and in person -- which made V.S.'s case extremely rare.

"Most individuals with PMO see distortions on screens, so they are unable to confidently assess the accuracy of visualizations of their distortions," Duchaine said.

"V.S., though, does not see distortion on screens, so he can judge whether a visualization of what he sees matches his perception," Duchaine told 乌鸦传媒.

V.S. had a history of bipolar affective disorder and post-traumatic stress disorder. He also had a significant head injury at age 43 that led to hospitalization.

He had possible carbon monoxide poisoning at age 55, which occurred 4 months before his distortion symptoms started. He was not prescribed any medications and reported no use of illicit substances.

On MRI, V.S. had a round lesion of approximately 1 cm in the left hippocampus, which was thought to be an arachnoid cyst. Despite this, the internal anatomy of the left hippocampus was preserved. A repeated MRI at 1 year showed no change in the size of the cyst.

"We can't rule it out, but we think the cyst is unlikely to contribute to V.S.'s distortions," Duchaine observed. "It is not in the vicinity of regions specifically involved in face perception. In addition, cysts like that are not rare and often have no detectable effects."

Whether carbon monoxide poisoning played a role also is unknown. "If I had to bet, I'd put my money on the carbon monoxide exposure a few months before the onset of the distortions," Duchaine said.

"However, I do not feel confident about that," he added. "We hear from many people with PMO who, like V.S., are unaware of a neurological event that coincided with the onset of their distortions."

On initial assessment, V.S. appeared well and not distressed. Testing showed no obvious abnormal cognitive function, and his Mini-Mental State Examination (MMSE) score was 30/30. His visual acuity was 10/10 in both eyes and he had no color vision deficits.

Because V.S. did not see distortion when he looked at facial images on screen or paper, Duchaine and co-authors asked him to compare an in-person face with on-screen photos of that person taken in the same room with the same light.

Alternating between looking at the in-person face and on-screen photos, V.S. provided feedback about the differences he saw. The researchers then used image-editing software to modify each photo until it matched his perception.

"This case allows us to glimpse the world through the eyes of someone with PMO for the first time," said co-author Antônio Mello, a PhD candidate at Dartmouth, explaining the process.

"We believe that visualizations of face distortions are critical to understanding PMO," he noted. "They not only demonstrate the severity of this condition, but also emphasize the need for effective treatments."

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