Management of Psychosis in Parkinson’s Disease: Emphasizing Clinical Subtypes and Pathophysiological Mechanisms of the Condition

Hindawi Parkinson’s Disease Volume 2017, Article ID 3256542, 18 pages https://doi.org/10.1155/2017/3256542 Review Article Management of Psychosis in Parkinson’s Disease: Emphasizing Clinical Subtypes and Pathophysiological Mechanisms of the Condition Raquel N. Taddei, Seyda Cankaya, Sandeep Dhaliwal, and K. Ray Chaudhuri Maurice Wohl Clinical Neuroscience Institute and NIHR Biomedical Research Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College Hospital, London, UK Correspondence should be addressed to Raquel N. Taddei; Received 26 May 2017; Accepted 6 August 2017; Published 12 September 2017 Academic Editor: Giovanni Mirabella Copyright © 2017 Raquel N. Taddei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Investigation into neuropsychiatric symptoms in Parkinson’s disease (PD) is sparse and current drug development is mainly focused on the motor aspect of PD. The tight association of psychosis with an impaired quality of life in PD, together with an important underreporting of this comorbid condition, contributes to its actual insufficient assessment and management. Furthermore, the withdrawal from access to readily available treatment interventions is unacceptable and has an impact on PD prognosis. Despite its impact, to date no standardized guidelines to the adequate management of PD psychosis are available and they are therefore highly needed. Readily available knowledge on distinct clinical features as well as early biomarkers of psychosis in PD justifies the potential for its timely diagnosis and for early intervention strategies. Also, its specific characterisation opens up the possibility of further understanding the underlying pathophysiological mechanisms giving rise to more targeted therapeutic developments in the nearer future. A literature review on the most recent knowledge with special focus on specific clinical subtypes and pathophysiological mechanisms will not only contribute to an up to date practical approach of this condition for the health care providers, but furthermore open up new ideas for research in the near future. 1. Introduction 2. Defining PD Psychosis Nonmotor symptoms have an important impact on quality of life in PD patients and their caregivers and are largely recognized as such by a growing number of health care providers [1, 2]. Psychosis is recognized as one of the most frequent and disabling nonmotor symptoms in PD with prevalences of 20% up to 70% in advanced stages of the condition [3]. Its relevance is such that it has even been named as the main feature of one of the seven proposed nonmotor subtypes of PD described by Sauerbier et al. [4]. In this review we aim at providing an up to date practical approach to psychosis in PD, with especial emphasis on clinical subtypes and pathophysiological mechanisms underlying this condition with the aim of leading to better intervention strategies in the nearer future. 2.1. History. The history of psychosis in PD goes back to the early 19th century, where the presence of mental disturbances among PD patients was described as being rare and was accounted for as either a consequence of a chronic disease evolution or regarded as coincidental [5]. After an outbreak of encephalitis lethargica between 1915 and 1926, a condition of unknown origin with acute onset and often chronic persistence of various neurological symptoms, including headache, lethargy, catatonia, parkinsonism, and tremor, a potential link between an altered mental state and parkinsonism was proposed and the first idea of complex psychotic symptoms in postencephalitic parkinsonism (PEP) cases was described [6, 7]. In more recent years however, the etiologic relationship between the encephalitis outbreak and the 2 Parkinson’s Disease (G1) An acute onset of delusions, hallucinations, incomprehensible or incoherent speech, or any combination of these. The time interval between the first appearance of any psychotic symptoms and the presentation of the fully developed disorder should not exceed two weeks. (G2) If transient states of perplexity, misidentification, or impairment of attention and concentration are present, they do not fulfill the criteria for organically caused clouding of consciousness. (G3) The disorder does not meet the symptomatic criteria for manic episode (F30), depressive episode (F32), or recurrent depressive disorder. (G4) No evidence of recent psychoactive substance use sufficient to fulfil the criteria of intoxication, harmful use, dependence, or withdrawal states. The continued moderate and largely unchanged use of alcohol or drugs in amounts or frequencies to which the subject is accustomed does not necessarily rule out the use of F23; this must be decided by clinical judgement and the requirements of the research project in question. (G5) Most commonly used exclusion criteria: absence of organic brain disease or serious metabolic disturbances affecting the central nervous system (this does not include childbirth). Box 1: The ICD-10 classification of mental and behavioural disorders: definition criteria for acute and transient psychosis. F23, F30, F32: diagnosis codes of psychotic (F23) and mood disorders (F30 and F32) taken from ICD-10 guidelines; reference: taken from WHO International classifications, ICD-10 guidelines [15]. alleged PEP has been discussed as controversial due to a lack of consistency in clinical features and in the onset of symptoms and the possibility of other causes of parkinsonism has been postulated [7, 8]. Moreover, in subsequent years, confusional states were reported under treatment with L-Dopa and later under dopamine agonist therapy in PD patients, giving rise to this new core feature in PD. In 1995 the first review on drug-induced psychosis in PD was published by Factor et al., leading to the first international awareness of this PD complication [9]. Currently, under various searching terms on psychotic symptoms in PD, including the terms hallucinations, psychotic symptoms, illusions, delusions, and misperceptions among others, over 4000 articles and reviews can be found, dated back as far as 1945 in the current literature (PubMed), being the first description found in a book published in 1921. 2.2. General Psychosis and PD Psychosis. With regard to the clinical definition of the main features of psychosis, which include hallucinations, illusions, and delusions, current ICD10 guidelines define hallucinations as a disorder characterised by a false sensory perception in the absence of an external stimulus, whereas an illusion is regarded as a misperception of an externally present stimulus. In contrast to classical hallucinations and illusions, delusions are a false interpretation of the experienced misperceptions, often involving topics of persecution, imposters, or gr (...truncated)