GBA1 and Parkinson disease: Utilising fluorodopa PET and transcranial sonography, no significant difference in nigrostriatal imaging has been reported between iPD and GBA1-PD patients (Kono et al. 2007; Kraoua et al. 2009; Goker-Alpan et al. 2012; Barrett et al. 2013; Lopez et al. 2020).