Amimia

Amimia, the absence or reduction of expressiveness of the facial musculature, can be a consequence of pareses, paralyses, or ataxias of the aforementioned musculature, and then such amimia is devoid of independent significance. Amimia can also be observed as an isolated disorder while the elementary functions of the facial musculature are preserved, and it is then one of the types of disorders of associated or expressive movements. Such disorders are encountered in diseases of the thalami optici (see) and the extrapyramidal system (see); the most characteristic example can serve as amimia in parkinsonism (see) as a consequence of having suffered lethargic encephalitis. Furthermore, amimia can be characteristic of various mental diseases, in which two types of it are distinguished: asthenic amimia and hypersthenic amimia. Asthenic amimia is observed in dementia, stupor, and in some forms of progressive paralysis; hypersthenic amimia is encountered in catatonia, religious delusion, and in hallucinations.