A proposal for a semantic change in the current diagnostic criteria of Parkinson’s disease Psychosis

Editor

Psychosis may emerge as part of Parkinson’s disease (PD) process but is also associated with PD treatment. When the NINDS-NIMH criteria were applied to a cross-sectional PD cohort, the prevalence of PD psychosis in PD patients reached 60% [1].

The most frequent symptoms in PD-associated psychosis (PDAP) are related to sensory perception areas, especially hallucinations. Graham et al. [2], reported that 70% of their patients with hallucinations had retained insight. This seems a contradiction because psychosis is a mental disorder characterized by symptoms, such as delusions or hallucinations that indicate an impaired contact with reality [3]. If we adhere to this definition, which is in fact the common and accepted one, those patients who retained insight about abnormal sensory perceptive phenomena should not be diagnosed as “psychotic”. Moreover, Fénelon and Alves reviewed the epidemiology of psychosis across different centers worldwide, showing that although psychosis could be diagnosed at that point of time, visual hallucinations were not always present for diagnosis: other features were taken into account to make this diagnosis for example the presence of delusions or illusions [4].

According to a recent comprehensive review is more appropriate to consider that there is a spectrum of psychotic symptoms in the course of PD progression [5]. Early in the disease, symptoms experienced include passage hallucinations (where a person, animal or indefinite object is seen briefly passing in the peripheral visual field), illusions (for example, seeing the branch of a tree as a cat), and presence hallucinations (a feeling that someone is nearby). Later in PD, formed visual hallucinations, typically of animals or people, occur. Insight — that is, recognition that the experiences are hallucinations — is preserved at this stage, but becomes lost as PD progresses, with the onset of false beliefs (delusions) and hallucinations in other sensory modalities (multimodality hallucinations). Cognitive decline and loss of insight parallel symptom progression [5].

On the other hand, the term “hallucinosis” [6], first described by Karl Wernicke in 1905 (original reference), refers to a state characterized by a sensory phenomenon like a hallucination, but the subject is aware that the phenomenon is unreal. We suggest that those patients who are aware of the unreality of abnormal perceptions should not be diagnosed as psychotic, but with PD hallucinosis: a type of benign (may be not so benign!) perceptive disturbance. This is not only a semantic differentiation but has clinical and therapeutic implications. The diagnosis of psychosis should only be used in those patients who have lost contact with reality. In our opinion, NINDS criteria leads to a more frequent diagnosis of psychosis and the result could induce an indiscriminate use of neuroleptic medications with their well-known complications.

Conclusion

We propose a more selective criterion for PDPA, excluding those patients who retained insight about the unreality of the phenomena in order to have a more accurate diagnosis of PDPA. The term “PD related hallucinosis”, with or without associated medications, should be included in the current nomenclature for this disease, leaving the term “psychosis associated to PD” for those cases in which there is no insight of disease, plus other hallucinatory phenomena and neuropsychiatric symptoms.

1. Goldman JG, Vaughan C, Goetz CG (2011) An update expert opinion on management and research strategies in Parkinson's disease psychosis. Expert Opin Pharmacother 12: 2009-2024. Link: https://goo.gl/AW6aso
2. Graham JM, Grünewald RA, Sagar HJ (1997) Hallucinosis in idiopathic Parkinson's disease. J Neurol Neurosurg Psychiatry 63: 434-440. Link: https://goo.gl/XUZdgP
3. Yadad R, Kumar P (2004) Psychosis in Parkinson Disease. Textbook of movements disorders. Kumar A. Jaypee brothers medical publishers (p) Ltd Chapter 10: 76-83. Link: https://goo.gl/rLxhDp
4. Fénelon G, Alves G (2010) Epidemiology of psychosis in Parkinson's disease. Journal of the Neurological Sciences 289: 12-17 Link: https://goo.gl/ZSRCk4
5. Ffytche DH, Creese B, Politis M, Chaudhuri KR, Weintraub D, et al. (2017) The psychosis spectrum in Parkinson disease. Nat Rev Neurol 13: 81-95. Link: https://goo.gl/RxBLHM
6. Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. (2003). Link: https://goo.gl/oUbvKZ