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Chapter 116in amplitude or speed) with either rigidity (resistance to passive movement, also called “muscle stiffness”), rest tremor in a limb, or both.44 These motor symptoms are caused by loss of dopaminergic neurons in the substantia nigra pars compacta, resulting in dopamine depletion in the striatum.42Therefore, treatment of Parkinson’s disease includes substitution of dopamine by a dopamine precursor, such as levodopa. The pathophysiology of Parkinson’s disease is not completely understood, but seems to result from an interplay of different factors including aberrant a-synuclein (protein) aggregation, mitochondrial dysfunction, lysosomal-autophagic dysfunction and disturbed endosomal trafficking.42, 43 Genetic, epigenetic as well as environmental factors may contribute to the vulnerability of dopaminergic neurons to develop Parkinson’s disease.43 Several monogenetic variants have been associated with Parkinson’s disease, such as SNCA,45 as well as the 22q11.2 deletion.46In addition to Parkinson’s disease, causes of parkinsonism include vascular pathology, trauma, and medication that negatively affects dopaminergic neurotransmission (in particular anti-psychotics). It is important to differentiate these forms of parkinsonism from neurodegenerative parkinsonism for patient follow-up and treatment. This differentiation may be challenging in individuals with a GND, because of higher prevalence rates of co-morbidities, including additional movement or neuropsychiatric disorders, and polypharmacy.37, 47, 48A previous study in a large population-based sample of adults with an intellectual disability indicated a prevalence of Parkinson’s disease and parkinsonism of 0.4%, two times higher compared to their control group without intellectual disabilities.49 For adults with 22q11.2DS, there has been one mono-center study that indicated a 20-70 fold increased risk of Parkinson’s disease compared to the general population, although in relatively small sample of adults.46The sensory systemThe sensory system includes visual, auditory, gustatory, olfactory, tactile, vestibular, proprioceptive and interoceptive systems. Stimuli such as light or noise are transformed into patterns of neural activity that are centrally