The "Whack-a-Mole" Sign in Functional Movement Disorders.

Making the diagnosis of functional movement disorders can be challenging. Identifying positive physical signs and diagnostic maneuvers is critical to this process. Distractibility, entrainability, and variability are examples of classic physical findings in these patients. In this case series, we identify and characterize another phenomenon observed in some of these patients. In this phenomenon, movement suppression of one body part is followed by immediate reemergence of movement in another. We propose that this phenomenon be referred to as the "whack-a-mole" sign. This name is derived from the arcade game whack-a-mole, in which a mole, when hit into its original hole, re-emerges elsewhere. We present a case series of 4 patients with functional movement disorders who exhibit this sign.