STXBP1 and Tremor: Older patients with Munc18-1 mutations also show signs of Parkinsonism including tremor and bradykinesia (Keogh et al., 2015; Álvarez Bravo and Yusta Izquierdo, 2018).Co-aggregation of mutant Munc18-1 with α-synuclein is thought to be the underlying mechanism of parkinsonian symptoms that are seen in older patients (reviewed in Lanoue et al., 2019).