Hypomimia

Hypomimia, also called masked facies, masking of facies or mask-like facial expression, is a medical sign describing a reduced degree of facial expression. It can arise from two broad causes: a motor impairment, such as weakness or paralysis of the facial muscles, notably seen in Parkinson's disease, where the muscles themselves cannot move normally; or a psychological or psychiatric cause, where a person does not experience the underlying emotion and so shows no corresponding facial expression even though the muscles themselves are unimpaired. Clinicians also note that people who have received excessive cosmetic botulinum toxin, or Botox, treatment can sometimes be mistakenly thought to show hypomimia, because the treatment itself limits the movement of the facial muscles and produces a similarly diminished range of expression without an underlying motor or psychiatric cause.