Abstract
BACKGROUND: Parkinson's disease (PD) is a condition that affects movement and is usually seen in those over the age of 50. It is caused by the death of dopaminergic neurons, particularly in the substantia nigra. PD has shifted from being perceived as an uncommon condition to a significant neurological illness, mostly due to the increasing number of elderly individuals and the impact of environmental factors. Parkinson's plus syndromes, such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal degeneration (CBD), and vascular Parkinsonism (VaP), provide difficulties in distinguishing them clinically from PD since they have similar characteristics. METHODOLOGY: A thorough examination was performed utilizing the PubMed, Medline, Scopus, and Web of Science databases. The search utilized specific keywords like "Parkinson's disease," "Parkinson's plus syndrome," "Lewy body dementia," "Alzheimer's dementia," "progressive supranuclear palsy," and "multiple system atrophy." The selection criteria were aimed at English-language literature, with a particular focus on examining the connection between PD and associated disorders or dementias. RESULTS AND DISCUSSION: Parkinson's plus syndromes, such as PSP, MSA, CBD, and VaP, exhibit unique clinical characteristics, imaging results, and diverse reactions to levodopa. This makes it difficult to distinguish them from PD. LBD is characterized by Lewy bodies containing α-synuclein, which leads to both motor and cognitive deficits. PD and Alzheimer's disease (AD) exhibit a complex interaction, including common pathogenic processes, genetic predispositions, and clinical characteristics of dementia. CONCLUSION: The interrelatedness of PD, Parkinson's plus syndromes, LBD, and AD highlights the significance of comprehending shared disease-causing processes. Aberrant protein clumping, impaired functioning of mitochondria, increased oxidative stress, and inflammation in the brain are common factors which can be addressed for specific treatments. More research is essential for understanding complicated connections and developing effective therapies for these sophisticated neurological illnesses.