Teaching Video NeuroImages: Slow periodic myoclonus in subacute sclerosing panencephalitis and fulminant Wilson disease

Abstract

Slow periodic myoclonus is a well-recognized phenotype of fulminant subacute sclerosing panencephalitis (video 1).1 This distinctive phenotype has not been previously recognized in another rapidly progressive disorder, fulminant Wilson disease. We documented slow periodic myoclonus in a 34-year-old Peruvian man who developed paranoid schizophrenia and, 6 months later, levodopa-unresponsive parkinsonism and falls, progressing into akinetic mutism (video 2). Prior to death, the diagnosis of Wilson disease was supported by ocular and neuroimaging features (figure), low ceruloplasmin (5.3 U/L), high urinary copper, and diffuse hepatopathy on echography. Slow periodic flexor myoclonus reflects cortical excitability and bears a poor prognosis.2 The EEG correlates are generalized, high-amplitude, quasiperiodic complexes.