Mild Parkinsonian signs: An overview of an emerging concept.

Mild Parkinsonian signs (MPS) include gait and balance changes, rigidity, bradykinesia, and tremor. MPS can occur commonly during the clinical examination of older people who do not have known neurological disease, with prevalence estimates for MPS as a whole ranging from 15% to 95%. MPS are generally progressive and they are coupled with functional difficulties, impaired gait and balance, and increased risks of mild cognitive impairment, dementia, and mortality. The mechanistic basis for these signs is unclear, but is likely to be multifactorial, with possible factors including an age-associated decline in dopaminergic nigrostriatal activity, the early development of neurodegenerative (Lewy body or Alzheimer's type) pathologies in the basal ganglia, or the accumulation of vascular pathology in the brain. It would be valuable to identify those individuals with MPS who are at increased risk for the development of future Alzheimer's disease, full-blown Parkinson's disease, or strokes, and to develop therapeutic strategies to intervene to lessen the likelihood of MPS-related morbidity and mortality.