Parkinson's disease (PD), is one of the commonest neurodegenerative disorders with a severe progressive course and major impact on patients' quality of life. The development of late-onset PD likely results from the interaction of genetic and environmental factors in the context of brain aging.~Although several environmental exposures have been implicated, evidence for their causal contributions is limited.~PD in Egypt is a rapidly emerging concern as prevalence rose by 40.7% between 1990 and 2016, one of the highest increases in the world. which influences us to dig further in the genetic basis behind the scenes leading to that leap.~Cognitive impairment in PD constitutes a major source of disease burden for patients and families, and has a significant negative effect on patients' quality of life. Cognitive impairment without dementia is designated as mild cognitive impairment of PD (PD-MCI), where the activities of daily living are grossly preserved, whereas dementia associated with PD is designated as PD-D.~Parkinson's disease dementia is a neurofibrillary tangle degeneration involving the deposition of Alzheimer-type tau, predominantly in the mesial temporal cortex, brainstem, and basal ganglia.~The prevalence of Parkinson's Disease Dementia (PD-D) in the general population aged 65 years and over was 0.3 to 0.5%, and 3 to 4% of patients with dementia in the general population were estimated to be due to PD-D.~Transcranial magnetic stimulation (TMS) is a noninvasive neurophysiological technique for assessing human motor cortical function. With TMS, the underlying motor cortex is stimulated by an electric current induced by a transient magnetic field, generated in response to the passage of a large current through the stimulating coil located on the patient's scalp.
To compare between Idiopathic PD versus Parkinson-Dementia complex using different modalities: Demographic, Clinical, genetic, Psychometric and electrophysiologically