Facial dysmorphopsia: a notable variant of the "thin man" phenomenon?

Abstract

The aim of this work is to investigate the facial distortion (dysmorphopsia) experienced by patients with homonymous paracentral scotomas and to analyze the interrelationship with the previously described "thin man" phenomenon. Routine neuro-ophthalmological examination and brain MRI in three patients who suffered from small homonymous paracentral scotomas due to infarction or arteriovenous malformations of the occipital lobe. They all complained of distortion and shrinkage of their interlocutor's face contralateral to the brain lesion. The phenomenon appeared some seconds after steady fixation on the interlocutor's nose and was evident with both left and right homonymous scotomas. The patients did not notice a gap in the area corresponding to the scotoma and objects other than faces were perceived normally. Homonymous paracentral scotomas can lead to focal displacement of facial features towards the center of the field defect with resulting distortion of the face on the affected side. This so-called "dysmorphopsia" makes faces appear regionally narrower than they are in reality and may be induced even by visual field defects that remain undetected by conventional perimetry using 6A degrees x 6A degrees grids. Predilection for faces is probably associated with the superior location of scotomas or specific impairment of face processing abilities related to the lesion site. Facial dysmorphopsia is most probably associated with cortical "filling-in" and spatial distortion, and can hence be regarded as a special entity of the "thin man" phenomenon.