Riassunto analitico
Background. Anosognosia, the lack of awareness of disease, is a common phenomenon in neurodegenerative disorders such as Huntington's disease (HD) and Parkinson's disease (PD). Clinical observations suggest that individuals may paradoxically show signs of understanding or recognition of their deficits without explicitly expressing this awareness: this is defined as “implicit awareness”. Explicit awareness has previously been investigated using questionnaires, whereas implicit awareness has not been extensively studied in HD and PD. This study aimed to investigate explicit and implicit anosognosia in patients with HD and PD.
Methods. We performed: i) a scoping review to investigate in detail motor, cognitive, behavioral, and neuroimaging correlates of unawareness in PD and HD across different cognitive and motor domains; literature searches were performed using PubMed Medline and we retrieved research studies published from inception to 31 December 2023. ii) an experimental study to investigate explicit and implicit awareness in PD and HD in comparison to healthy control subjects. The study included five patients (four with HD and one with PD) and twenty-seven healthy controls. Demographic and clinical characteristics of the participants were collected, including the Mini-Mental State Examination (MMSE). Explicit awareness was assessed using the AQ-D for controls, and the Self-Assessment Parkinson's Disease Disability Scale (SPDDS) and Global Awareness of Movement (GAM) for patients. Implicit awareness was measured by reaction times (RTs) to disease-related, negative, and neutral words presented in a modified emotional Stroop test.
Results. Scoping Review. Findings from the literature review investigating awareness of cognitive and motor symptoms in people with PD and HD are mixed, limited, and influenced by methodological heterogeneity. The clinical characteristics of the study participants, awareness domain investigated, measurement of awareness used, and in vivo neuroimaging technique applied are different across the studies and should be accurately considered when interpreting the results. Experimental study. Significant differences in age, education, and MMSE scores were observed between HD patients and controls, with HD patients having higher neuropsychiatric symptom scores. HD patients showed longer reaction times for disease-related words compared to neutral and negative words, suggesting preserved implicit awareness.
Conclusions. Impaired self-awareness in PD and HD is still poorly understood, and there are no homogeneous results in terms of its brain correlates, therefore, solid inference about neuropsychological or brain mechanisms cannot be achieved due to a lack of sufficient data. Our experimental data suggest that implicit awareness may remain intact, particularly in the early stages of the disease. It is therefore possible that a potential dissociation between implicit and explicit awareness mechanisms, like that observed in Alzheimer's disease, may also occur in HD patients. Further research with larger cohorts is needed to better understand this phenomenon and to identify the neural basis and clinical implications of these findings.
Keywords: Anosognosia, Implicit Awareness, Emotional Stroop Test, Parkinson's Disease, Huntington's Disease.
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