Teaching video neuroimages: trapezius myotonia percussion sign in myotonic dystrophy type 2.

Abstract

Myotonic dystrophy type 2 (DM2) is an autosomal dominant disorder with proximal weakness, muscle pain, and early-onset cataracts.¹ In comparison with myotonic dystrophy type 1 (DM1), myotonia is less symptomatic, more proximal, and harder to detect during clinical and electrodiagnostic testing.² Here we document the presence of trapezius myotonia in patients with DM2 (video on the <i>Neurology</i>® Web site at www.neurology.org). In our experience, similar proximal percussion does not produce as marked a response in DM1 or nondystrophic myotonic disorders. This sign demonstrates a mechanism to test for proximal myotonia, and in at-risk patients, may be suggestive of an underlying diagnosis of DM2.