Precuneus degeneration and isolated apathy in patients with Parkinson's disease

•PD patients with isolated apathy showed attentive and working memory dysfunctions.•Hypometabolism and atrophy in the Precuneus is correlated with apathy severity.•Precuneus degeneration can be one of neural substrates to isolated apathy in PD.

IntroductionTo investigate isolated apathy in a set of consecutively enrolled Parkinson's disease (PD) patients without dementia, depression, and significant motor response fluctuations, by conducting neuropsychological and neuroimaging analyses.MethodsOne hundred twenty-four patients were eligible for inclusion in this study. Clinical information and data were collected from a predefined neuropsychological test battery, including the mini-mental status examination, apathy scale, geriatric depression scale, digit span test, Boston naming test, Seoul verbal learning test, controlled oral word association test, go-no-go test, and the Rey figure copy test. From matched groups of 10 non-apathetic and 12 apathetic patients in the initial cohort and 9 healthy controls, [18F]fluorodeoxyglucose positron emission tomography and volumetric magnetic resonance images were acquired.ResultsApathy was detected in 59.7% of the initial cohort. Apathetic patients had lower scores in the digit span forward, digit span backward, and immediate recall of verbal learning tests than did those without apathy (p < 0.05). The results were unaffected by parkinsonian motor severity and medication dose. Neuroimaging analyses revealed precuneus atrophy and hypometabolism in patients with isolated apathy. These precuneus changes were well-correlated with apathy severity (p < 0.001). Apathy severity was also positively correlated with gray matter volume in the superior frontal gyrus and cerebellar vermis, and with metabolism in the medial frontal and anterior cingulate regions (p < 0.001).ConclusionsPD patients with isolated apathy showed attention and working memory dysfunction, and precuneus degeneration might be related to this distinctive nonmotor symptom in PD.