Spatiotemporal Progression Patterns of Dopamine Availability and Deep Gray Matter Volume in Parkinson Disease-Related Cognitive Impairment.

BACKGROUND AND OBJECTIVES: Cognitive impairment is a frequent nonmotor symptom in patients with Parkinson disease (PD), and early cognitive decline is often attributed to dopaminergic system dysfunction. We aimed to explore spatiotemporal progression patterns of striatal dopamine availability and regional brain volume based on cognitive status among patients with PD. METHODS: This retrospective, cross-sectional study included patients with newly diagnosed PD who were not taking medication for this condition who visited a university-affiliated hospital in Seoul between January 2018 and December 2020. Patients were classified as having normal cognition (PD-NC), mild cognitive impairment (PD-MCI), or PD dementia (PDD) based on Seoul Neuropsychological Screening Battery-II, which includes 31 subsets covering activities of daily living and 5 cognitive domains. They all had brain imaging with MRI and PET with 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane at baseline. Subsequently, standardized uptake value ratios (SUVRs) for regional dopamine availability and regional gray matter volumes were obtained using automated segmentation. These metrics were compared across cognitive status groups, and spatiotemporal progression patterns were analyzed using the Subtype and Stage Inference machine learning technique. RESULTS: Among 168 patients (mean age, 73.3 ± 6.1 years; 81 [48.2%] women), 65 had PD-NC, 65 had PD-MCI, and 38 had PDD. Patients with PD-MCI exhibited lower SUVRs (3.61 ± 1.31, p < 0.001) in the caudate than patients with PD-NC (4.43 ± 1.21) but higher SUVRs than patients with PDD (2.39 ± 1.06). Patients with PD-NC had higher thalamic SUVRs (1.55 ± 0.16, p < 0.001) than patients with both PD-MCI (1.45 ± 0.16) and PDD (1.38 ± 0.19). Regional deep gray matter volumes of the caudate (p = 0.015), putamen (p = 0.012), globus pallidus (p < 0.001), thalamus (p < 0.001), hippocampus (p < 0.001), and amygdala (p < 0.001) were more reduced in patients with PD-MCI or PDD than in patients with PD-NC, and the SUVR of the caudate correlated with caudate volume (r = 0.187, p = 0.015). Hippocampal atrophy was the initial change influencing cognitive impairment. The reduced dopamine availability of the thalamus preceded reductions in volume across most deep gray matter regions. DISCUSSION: Our finding underscores the association between decreased dopamine availability and volume of the caudate and thalamus with cognitive dysfunction in PD. The dopamine availability of the caudate and thalamus was reduced before the volume of the caudate and thalamus was decreased, highlighting the spatiotemporal association between dopaminergic and structural pathology in cognitive impairment in PD.

Evaluating the validity and reliability of the Korean version of Scales for Outcomes in Parkinson's Disease-Cognition.

Objective: The Scales for Outcomes in Parkinson's Disease-Cognition (SCOPA-Cog) was developed to screen for cognition in PD. In this study, we aimed to evaluate the validity and reliability of the Korean version of the SCOPA-cog. Methods: We recruited 129 PD patients from 31 clinics with movement disorders in South Korea. The original version of the SCOPA-cognition was translated into Korean using the translation-retranslation method. The test-rest method with an intraclass correlation coefficient (ICC) and Cronbach's alpha coefficient were used to assess reliability. The Spearman's Rank correlation analysis with Montreal Cognitive Assessment-Korean version (MOCA-K) and Korean Mini-Mental State Examination (K-MMSE) were used to assess concurrent validity. Results: The Cronbach's alpha coefficient was 0.797, and the ICC was 0.887. Spearman's rank correlation analysis showed a significant correlation with the K-MMSE and MOCA-K scores (r = 0.546 and r = 0.683, respectively). Conclusions: Our results demonstrate that K-SCOPA-Cog exhibits good reliability and validity.

Fasting Plasma Glucose Levels and Longitudinal Motor and Cognitive Outcomes in Parkinson's Disease Patients.

OBJECTIVE: Hyperglycemia and diabetes mellitus have been identified as poor prognostic factors for motor and nonmotor outcomes in patients with Parkinson's disease (PD), although there is some controversy with this finding. In the present study, we investigated the effects of fasting plasma glucose (FPG) levels on longitudinal motor and cognitive outcomes in PD patients. METHODS: We included a total of 201 patients who were diagnosed with PD between January 2015 and January 2020. The patients were categorized based on FPG level into euglycemia (70 mg/dL < FPG < 100 mg/dL), intermediate glycemia (100 mg/dL ≤ FPG < 126 mg/dL), and hyperglycemia (FPG ≥ 126 mg/dL), and longitudinal FPG trajectories were analyzed using group-based trajectory modeling. Survival analysis was conducted to determine the time until motor outcome (Hoehn and Yahr stage ≥ 2) and the conversion from normal cognition to mild cognitive impairment. RESULTS: Among the patient cohort, 82 had euglycemia, 93 had intermediate glycemia, and 26 had hyperglycemia. Intermediate glycemia (hazard ratio 1.747, 95% confidence interval [CI] 1.083-2.816, p = 0.0221) and hyperglycemia (hazard ratio 3.864, 95% CI 1.996-7.481, p < 0.0001) were found to be significant predictors of worsening motor symptoms. However, neither intermediate glycemia (hazard ratio 1.183, 95% CI 0.697-2.009, p = 0.5339) nor hyperglycemia (hazard ratio 1.297, 95% CI 0.601-2.800, p = 0.5078) demonstrated associations with the longitudinal progression of cognitive impairment. Diabetes mellitus, defined by self-reported medical history, was not related to poor motor or cognitive impairment outcomes. CONCLUSION: Our. RESULTS: suggest that both impaired glucose tolerance and hyperglycemia could be associated with motor progression in PD patients.

Generation of an induced pluripotent stem cell line (KNIHi001-A) by reprogramming peripheral blood mononuclear cells isolated from a patient with Parkinson's disease.

Parkinson's disease is a degenerative brain disorder characterized by dopamine neuronal degeneration and dopamine transporter loss. In this study, we generated an induced pluripotent stem cell (iPSC) line, KNIHi001-A, from the peripheral blood mononuclear cells (PBMCs) of a 76-year-old man with Parkinson's disease. The non-integrating Sendai virus was used to reprogram iPSCs. iPSCs exhibit pluripotent markers, a normal karyotype, viral clearance, and the ability to differentiate into the three germ layers.

Estimating motor progression trajectory pursuant to temporal dynamic status of cardiac denervation in Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) is a multifaceted disease that encompasses diverse clinical phenotypes. The diversity of PD could be subtyped based on the temporal dynamic status of cardiac sympathetic innervation; (1) initially, denervated myocardium (peripheral nervous system-predominant; PNS-predominant), (2) preserved myocardium (central nervous system-predominant; CNS-predominant), and (3) preserved myocardium who developed cardiac sympathetic denervation (CSD) on the subsequent imaging (Converter; delayed cardiac denervation). This study assessed how the cardiac denervation could reflect the pathobiology. We investigated whether this phenotyping could help predict the motor progression trajectory of PD. METHODS: Cardiac sympathetic innervation was evaluated using initial and sequential 123I-meta-iodobenzylguanidine myocardial scintigraphy and patients were stratified into three groups as above. Motor severity and progression were evaluated in each patient. The association between subtypes and dopaminergic nigrostriatal degeneration was analyzed. The influence of cardiac denervation on motor progression was also investigated. RESULTS: Among the enrolled 195 patients, 144 PD subjects were defined as PNS-predominant, 16 as Converter, and 35 as CNS-predominant. The most severe nigrostriatal degeneration was observed in the PNS-predominant group and the dopaminergic degeneration was the most asymmetric in the CNS-predominant group. Positive linear trends of nigrostriatal degeneration and its asymmetric degeneration of striatum and globus pallidus were found across the patterns of cardiac sympathetic innervation (PNS-predominant vs. Converter vs. CNS-predominant). It indicated an increasing degree of asymmetric degeneration among the groups. A longitudinal estimation of motor progression revealed distinct cardiac denervation trajectories for each subtype. CONCLUSIONS: These results implicated that the subtypes of CSD might indicate a predominant origin and spreading pattern of pathobiology.

Correlation of olfactory function factors with cardiac sympathetic denervation in Parkinson's disease.

BACKGROUND: Hyposmia is a common nonmotor symptom of Parkinson's disease (PD) and reportedly associated with dysautonomia in PD. The smell identification test for measuring olfactory function consists of multiple items to discriminate specific scents. In the present study, factor analysis of the smell identification test was performed, and the correlation of extracted factors with cardiac sympathetic denervation (CSD) in patients with PD was investigated. METHODS: The present study included 183 early PD patients who underwent the Cross-Cultural Smell Identification Test (CC-SIT) and 123I-meta-iodobenzylguanidine (123I-MIBG) myocardial scintigraphy. Factor analysis of 12 items on the CC-SIT was performed using the computed correlation matrix for the binary items, and five smell factors were extracted. Multiple linear regression was performed to determine the correlation of olfactory function with late heart-to-mediastinum (H/M) ratio of 123I-MIBG uptake. RESULTS: The mean CC-SIT score was 6.1 ± 2.6, and 133 patients (72.7%) had CSD. The CC-SIT score and five smell factors were not associated with dopamine transporter uptake or cognitive functions. However, the CC-SIT score significantly correlated with age (P < 0.001) and late H/M ratio (P < 0.001). Factors 1 and 5 showed an increasing trend with larger H/M ratio, although it was not statistically significant (ß = 0.203, P = 0.085 and ß = 0.230, P = 0.085, respectively). Factor 5 significantly correlated with the H/M ratio in PD patients with CSD (ß = 0.676, P = 0.036). DISCUSSION: The results showed olfactory dysfunction to be selectively associated with cardiac sympathetic burden in PD. The correlation of certain factors with CSD indicates the possibility of selective hyposmia in PD patients.

Cardiac sympathetic "morbidity" might reflect the neurobiology of early Parkinson's disease.

BACKGROUND: An appropriate extracranial biomarker that delineates endophenotypes of Parkinson's disease (PD) at an early stage and reflects the neurodegenerative process is lacking. An evaluation of myocardial sympathetic nerve terminals could be a good candidate. This study aimed to explore subtypes of PD patients that showed cardiac catecholaminergic vesicular defect and their characteristics. METHODS: This study included 122 early drug-naïve PD patients who were followed for approximately 4-5 years. All patients were examined with 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane positron-emission tomography and 123I-meta-iodobenzylguanidine myocardial scintigraphy. Cardiac scans were reexamined two or three times. Patients were subgrouped into the sympathetic denervated group at the initial scan, those without evidence of denervated myocardium in the first and subsequent scans, and the converters whose myocardium was initially normal but became impaired in the subsequent scans. Cognition in 99 patients was initially assessed with neuropsychological tests. Any associations between cardiac denervation subtypes and presynaptic dopamine transporter densities were investigated. Cognitive status relevant to cardiac sympathetic denervation status was evaluated. RESULTS: This study found that cross-sectional comparisons of presynaptic monoamine transporter availability with a predefined order of cardiac denervation groups revealed parallel degeneration. A quadratic correlation between cardiac catecholamine capacity and cognition was observed. This association was interpreted to reflect the early neurobiology of PD. CONCLUSION: An observed cardiac catecholaminergic gradient was to mirror the central neurobiology of early PD.

Exploring the link between essential tremor and Parkinson's disease.

Epidemiological studies have reported a link between essential tremor (ET) and Parkinson's disease (PD). Recent studies have suggested ET as a possible neurodegenerative disease whose subgroup contained Lewy bodies in the brainstem, as in PD. PD with antedated ET (PDconv) might exhibit traits different from those of the pure form of ET or PD. This study aimed to unveil the interplay between PD and premorbid ET, which might be the core pathobiology that differentiates PDconv from PD. The study included 51 ET, 32 PDconv, and 95 PD patients who underwent positron emission tomography using 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane and 123I-meta-iodobenzylguanidine myocardial scintigraphy to analyze central dopaminergic and peripheral noradrenergic integrity. The results show that PDconv group followed the typical striatal pathology of PD but with a delay in noradrenergic impairment as it caught up with the denervating status of PD a few years after PD diagnosis. Whereas the two PD subtypes displayed similar patterns of presynaptic dopamine transporter deficits, ET patients maintained high densities in all subregions except thalamus. Presynaptic dopaminergic availability decreased in a linear or quadratic fashion across the three groups (ET vs. PDconv vs. PD). The age at onset and duration of ET did not differ between pure ET and PDconv patients and did not influence the striatal monoamine status. The myocardium in PDconv patients was initially less denervated than in PD patients, but it degenerated more rapidly. These findings suggest that PDconv could be a distinctive subclass in which the pathobiology of PD interacts with that of ET in the early phase of the disease.

A 3-year natural history of orthostatic blood pressure dysregulation in early Parkinson's disease.

In Parkinson's disease (PD), cardiovascular dysautonomia accumulates with disease progression, but studies are lacking on the natural history behind each subtype except orthostatic hypotension. This study investigated the early natural history of orthostatic blood pressure (BP) subtypes in PD. Two hundred sixty-seven early PD patients were included. Their cardiovascular functions were assessed by head-up tilt-test and 123I-metaiodobenzylguanidine scintigraphy. All patients were classified as having supine hypertension (SH), orthostatic hypertension (OHT), delayed orthostatic hypotension (dOH), or orthostatic hypotension (OH) according to consensus criteria. The patients were assigned to one of three groups: extreme BP dysregulation (BPextreme), mild BP dysregulation (BPmild), and no BP dysregulation (BPnone) according to their orthostatic BP subtypes. The autonomic functions of 237 patients were re-assessed after approximately 3 years. Among initially enrolled subjects, 61.8% of the patients showed orthostatic BP dysregulation: 29.6% in the BPextreme group and 32.2% in the BPmild group. At follow-up, the BPextreme group increased in number, while the BPmild group diminished. Two-thirds of the initial BPextreme patients maintained their initial subtype at follow-up. In comparison, 40.7% of the initial BPmild patients progressed to the BPextreme group, and 32.4% and 14.7% of the initial BPnone group progressed to BPextreme and BPmild groups, respectively. Cardiac denervation was most severe in the BPextreme group, and a linear gradient of impairment was observed across the subtypes. In conclusion, various forms of positional BP dysregulation were observed during the early disease stage. SH and OH increased with disease progression, while OHT and dOH decreased, converting primarily to SH and/or OH.

Obstructive Sleep Apnea and Striatal Dopamine Availability in Parkinson's Disease.

BACKGROUND: Sleep disorders are frequently associated with Parkinson's disease. Obstructive sleep apnea syndrome is one of these sleep disorders and is associated with the severity of motor symptoms in Parkinson's disease. Obstructive sleep apnea can lead to dopaminergic neuronal cell degeneration and may impair the clearance of α-synuclein in Parkinson's disease. Striatal dopamine uptake is a surrogate marker of nigral dopaminergic cell damage. OBJECTIVE: We aimed to investigate the differences in striatal dopamine availability between Parkinson's disease patients with or without obstructive sleep apnea. METHODS: A total of 85 de novo and nonmedicated Parkinson's disease patients were enrolled. Full-night polysomnography was performed for all patients, and obstructive sleep apnea was diagnosed as apnea/hypopnea index ≥5. Positron emission tomography was performed with 18 F-N-(3-fluoropropyl)-2ß-carbon ethoxy-3ß-(4-iodophenyl) nortropane, and the regional standardized-uptake values were analyzed using a volume-of-interest template and compared between groups with or without obstructive sleep apnea. RESULTS: Dopamine availability in the caudate nucleus of the obstructive sleep apnea group was significantly lower than that of the nonobstructive sleep apnea group. On subgroup analysis, such association was found in female but not in male patients. In other structures (putamen, globus pallidus, and thalamus), dopamine availability did not differ between the two groups. CONCLUSION: This study supports the proposition that obstructive sleep apnea can contribute to reduced striatal dopamine transporter availability in Parkinson's disease. Additional studies are needed to assess the causal association between obstructive sleep apnea and the neurodegenerative process in Parkinson's disease. © 2023 International Parkinson and Movement Disorder Society.

Unilateral Myoclonus as an initial manifestation in Moyamoya disease with asymmetric vasculature.

Movement disorders have been identified as a rare early manifestation of the Moyamoya disease. Herein, we present a case of a 34-year-old man with a genetically confirmed Moyamoya disease who showed unilateral myoclonus as an initial manifestation. Neuroimaging studies showed prominent asymmetrically developed Moyamoya disease on the right hemisphere with near-complete loss of normal vessels while the left hemisphere was adjunctively fed with extension of posterior cerebral artery: uneven progression of vasculature. 99mTc-hexamethylpropylene amine oxime single-photon emission computed tomography demonstrated impaired vascular reserve. Electroencephalography showed occasional sharp waves on right temporal area. The phenomenon of this patient could be explained in the context of excitable cortex and hypoactive subcortical substrate that might imply putative contradictory neurobiology in Moyamoya disease.

Validity and Reliability of the Korean-Translated Version of the International Cooperative Ataxia Rating Scale in Cerebellar Ataxia.

OBJECTIVE: The International Cooperative Ataxia Rating Scale (ICARS) is a semiquantitative clinical scale for ataxia that is widely used in numerous countries. The purpose of this study was to investigate the validity and reliability of the Korean-translated version of the ICARS. METHODS: Eighty-eight patients who presented with cerebellar ataxia were enrolled. We investigated the construct validity using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). We also investigated the internal consistency using Cronbach's α and intrarater and interrater reliability using intraclass correlation coefficients. RESULTS: The Korean-translated ICARS showed satisfactory construct validity using EFA and CFA. It also revealed good interrater and intrarater reliability and showed acceptable internal consistency. However, subscale 4 for assessing oculomotor disorder showed moderate internal consistency. CONCLUSION: This is the first report to investigate the validity and reliability of the Korean-translated ICARS. Our results showed excellent construct and convergent validity. The reliability is also acceptable.

Caudate-anchored cognitive connectivity pursuant to orthostatic hypotension in early Parkinson's disease.

18F-Florbetaben is a tracer used to evaluate the metabolic activity of and amyloid accumulation in the brain when measured in early- and late-phase, respectively. The metabolism of neural substrates could be viewed as a network and might be an important factor in cognition. Orthostatic hypotension (OH) might play an indirect moderating role in cognition, and its latent influence could modify the inherent cognitive network. This study aimed to identify changes of cognitive connectivity according to orthostatic stress in patients with early Parkinson's disease (PD). This study included 104 early PD patients who were evaluated with a head-up tilt-test and18F-Florbetaben positron emission tomography (PET). Cognition was assessed with a comprehensive neuropsychological battery that gauged attention/working memory, language, visuospatial, memory, and executive functions. PET images were analyzed visually for amyloid deposits, and early-phase images were normalized to obtain standardized uptake ratios (SUVRs) of pre-specified subregions relevant to specific cognitive domains. The caudate nucleus was referenced and paired to these pre-specified regions. The correlations between SUVRs of these regions were assessed and stratified according to presence of orthostatic hypotension. Among the patients studied, 22 (21.2%) participants had orthostatic hypotension. Nineteen patients (18.3%) were positive for amyloid-ß accumulation upon visual analysis. Moderate correlations between the caudate and pre-specified subregions were observed (Spearman's rho, range [0.331-0.545]). Cognition did not differ, but the patterns of correlation were altered when the disease was stratified by presence of orthostatic stress. In conclusion, cognition in early PD responds to hemodynamic stress by adapting its neural connections between regions relevant to cognitive functions.

Comparison of disease progression between brain-predominant Parkinson's disease versus Parkinson's disease with body-involvement phenotypes.

Recently, new disease phenotyping has been proposed based on the origin site of α-synuclein pathology in Parkinson's disease (PD). In addition, a great deal of evidences suggested of parallel degeneration in the central nervous system and peripheral nervous system in PD. The myocardial uptake pattern of 123I-meta-iodobenzylguanidine can be a surrogate imaging biomarker for the peripheral nervous system involvement in PD. This study aimed to compare the clinical progression between brain-predominant PD (br-PD) and PD with body-involvement (bo-PD) phenotypes according to the onset of cardiac sympathetic denervation (CSD); the bo-PD group was defined as having the early onset of CSD and the br-PD phenotype was defined as those without initial CSD but later developed CSD in subsequent scans (the delayed onset of CSD). Clinical chracteristics, dopamine transporter activity, and non-motor manifestations were compared between the groups. Motor symptoms and cognitive functions at the initial and follow-up tests [3.1 (±1.4) years interval] were compared between the groups. This study included 29 br-PD and 103 bo-PD patients. Symptoms of rapid-eye-movement sleep behavior disorder, excessive daytime sleepiness, constipation, and orthostatic hypotension were more frequent in the bo-PD than in the br-PD group. The Unified Parkinson's Disease Rating Scale part III score was higher at the initial and increased more steeply during the follow-up period in the bo-PD patients than in the br-PD patients. Although the general cognitive status was not much different between the groups at initial and follow-up, each group showed statistically different cognitive domain profiles and progression patterns. The results demonstrated that the bo-PD group had more severe initial symptoms and steeper motor deterioration than the br-PD group, which indicated that there may be the more pathological involvements of central and peripheral nervous systems in the bo-PD group.

Premorbid cancer and motor reserve in patients with Parkinson's disease.

Decreased cancer risk has been reported in patients with Parkinson's disease (PD), and cancer prior to PD can have a protective effect on PD risk. We investigated cancer history prior to PD diagnosis to determine if such history can enhance motor reserve in PD by assessing the association between motor deficits and striatal subregional dopamine depletion. A total of 428 newly diagnosed, drug-naïve PD patients was included in the study. PD patients were categorized into three groups of no prior neoplasia, premorbid precancerous condition, and premorbid malignant cancer before PD diagnosis. Parkinsonian motor status was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) motor score and modified Hoehn and Yahr stage score. All patients underwent positron emission tomography (PET) with 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane (18F-FP-CIT), and the regional standardized uptake value ratios (SUVRs) were analyzed with a volume-of-interest template among the groups. The UPDRS motor score negatively correlated with SUVRs in the posterior putamen for all patient groups. Groups with neoplasia, especially those with premorbid cancer, showed lower motor scores despite similar levels of dopamine depletion in the posterior putamen relative to those without neoplasia. These results suggest that premorbid cancer acts as a surrogate for motor reserve in patients with PD and provide imaging evidence that history of cancer has a protective effect on PD.

Simulating the progression of brain structural alterations in Parkinson's disease.

Considering brain structural alterations as neurodegenerative consequences of Parkinson's disease (PD), we sought to infer the progression of PD via the ordering of brain structural alterations from cross-sectional MRI observations. Having measured cortical thinning in gray matter (GM) regions and disintegrity in white matter (WM) regions as MRI markers of structural alterations for 130 patients with PD (69 ± 10 years, 72 men), stochastic simulation based on the probabilistic relationship between the brain regions was conducted to infer the ordering of structural alterations across all brain regions and the staging of structural alterations according to changes in clinical status. The ordering of structural alterations represented WM disintegrity tending to occur earlier than cortical thinning. The staging of structural alterations indicated structural alterations happening mostly before major disease complications such as postural instability and dementia. Later disease states predicted by the sequence of structural alterations were significantly related to more severe clinical symptoms. The relevance of the ordering of brain structural alterations to the severity of clinical symptoms suggests the clinical feasibility of predicting PD progression states.

Decreased thalamic monoamine availability in drug-induced parkinsonism.

Drug-induced parkinsonism (DIP) is caused by a dopamine receptor blockade and is a major cause of misleading diagnosis of Parkinson's disease (PD). Striatal dopamine activity has been investigated widely in DIP; however, most studies with dopamine transporter imaging have focused on the clinical characteristics and prognosis. This study investigated differences in striatal subregional monoamine availability among patients with DIP, normal controls, and patients with early PD. Thirty-five DIP patients, the same number of age-matched PD patients, and 46 healthy controls were selected for this study. Parkinsonian motor status was examined. Brain magnetic resonance imaging and positron emission tomography with 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane were performed, and the regional standardized uptake values were analyzed with a volume-of-interest template and compared among the groups. The groups were evenly matched for age, but there were numerically more females in the DIP group. Parkinsonian motor symptoms were similar in the DIP and PD groups. Monoamine availability in the thalamus of the DIP group was lower than that of the normal controls and similar to that of the PD group. In other subregions (putamen, globus pallidus, and ventral striatum), monoamine availability in the DIP group and normal controls did not differ and was higher than that in the PD group. This difference compared to healthy subject suggests that low monoamine availability in the thalamus could be an imaging biomarker of DIP.