Introduction: In Parkinson's disease there are patients with isolated and multiple cognitive impairment, and their cognitive performance ranges from normal to an advanced degree of dementia. Most patients present an executive deficit, either in isolation or combined with other cognitive disorders, which is considered to be the most characteristic aspect of the disease, and 30-40% of those affected will end up with a clinically-defined dementia.
Development: The presence of a mild cognitive disorder in patients with Parkinson means that the risk of dementia appearing at some time during the development of the disease is high. The dementia associated with Parkinson's disease is specifically related with neuropsychiatric signs and symptoms, which may have three possible explanations: disorders affecting the mesolimbic pathways, diffuse limbic and cortical compromise, or associated Alzheimer-type phenomenology. Psychotic episodes tend to present more often in patients with dopaminergic treatment and the clinical spectrum of Parkinson-related psychosis covers visual illusions, visual-audio-olfactory hallucinations, delirium and severe paranoid hallucinatory psychosis. All the antiparkinsonian drugs can give rise to hallucinations and psychosis, but the dopamine agonists are the ones with the greatest capacity to do so.
Conclusions: In managing these problems, it is crucial for prevention as well as diagnosis and treatment to be carried out as soon as they are detected. Doses of antiparkinsonian drugs must be reduced, although this is not usually enough, and so it will be necessary to associate atypical antipsychotics, which act mainly on 5-HT receptors and, in most cases, do not produce D2 blockage.