SCN8A and Myoclonus: Neurometabolic conditions being ruled out, hyperkinetic neonatal-onset MD should first raise suspicion of an SCN8A or STXBP1-related disorder, as these are associated with myoclonus/myoclonus-like dyskinesia (STXBP1, but also reported in KCNQ2), dystonia and/or opistotonus (SCN8A, although also described in PCDH12), tremors (both conditions), and startles (both, plus GRIA2).