Customized FreeSurfer-based brain atlas for diffeomorphic anatomical registration through exponentiated lie algebra tool

Parkinson's disease with hyposmia and dysautonomia: does it represent a distinct subtype?

BACKGROUND AND PURPOSE

Olfactory dysfunction or dysautonomia is one of the earliest prodromal nonmotor symptoms of Parkinson's disease (PD). We aimed to investigate whether PD patients with dysautonomia and hyposmia at the de novo stage present different prognoses regarding PD dementia (PDD) conversion, motor complication development, and change in levodopa-equivalent doses (LED).

METHODS

In this retrograde cohort study, we included 105 patients with newly diagnosed PD patients who underwent cross-cultural smell identification test (CC-SIT), autonomic function tests (AFT), and dopamine transporter (DAT) scan at the de novo stage. PD patients were divided into Hyposmia + /Dysautonomia + (H + /D +) and Hyposmia - /Dysautonomia - (H - /D -) groups depending on the result of AFT and CC-SIT. Baseline clinical, cognitive, imaging characteristics, longitudinal risks of PDD development and motor complication occurrence, and longitudinal LED changes were compared between the two groups.

RESULTS

When compared with the H - /D - group, the H + /D + group showed lower standardized uptake value ratios in all subregions, lower asymmetry index, and steeper ventral - dorsal gradient in the DAT scan. The H + /D + group exhibited poorer performance in frontal/executive function and a higher risk of PDD development. The risk of motor complications including levodopa-induced dyskinesia, wearing off, and freezing of gait, was comparable between the two groups. The analysis of longitudinal changes in LED using a linear mixed model showed that the increase of LED in the H + /D + group was more rapid.

CONCLUSIONS

Our results suggest that PD patients with dysautonomia and hyposmia at the de novo stage show a higher risk of PD dementia conversion and rapid progression of motor symptoms.

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)-2β-carbon ethoxy-3β-(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.

Role of Enlarged Perivascular Space in the Temporal Lobe in Cerebral Amyloidosis

OBJECTIVE

Although growing evidence suggests that perivascular space (PVS) serves as a clearance route for amyloid and tau, the association between enlarged PVS (EPVS) and Alzheimer disease is highly inconsistent across studies. As the conventional visual rating systems for EPVS were insufficient to predict amyloid/tau/neurodegeneration (A/T/N) status, we developed a new rating scale for EPVS located in the temporal lobe (T-EPVS).

METHODS

EPVS located in the basal ganglia (BG-EPVS), centrum semiovale (CS-EPVS), and T-EPVS was visually rated in 272 individuals (healthy controls, n = 96; mild cognitive impairment, n = 106; dementia, n = 70) who underwent structural magnetic resonance imaging (MRI) and dual positron emission tomography scans (¹⁸ F-flortaucipir and ¹⁸ F-florbetaben). T-EPVS and BG-EPVS were defined as high degree when the counts in any hemisphere were >10, and the CS-EPVS cutoff was >20. Logistic regression models were constructed to investigate whether the regional EPVS burden was predictive of A/T/N status. The derived models were externally validated in a temporal validation cohort (n = 195) that underwent MRI studies using a different scanner.

RESULTS

Compared with those with low-degree T-EPVS (23/136, 16.9%), individuals with high-degree T-EPVS/CS-EPVS but low-degree BG-EPVS were more likely to exhibit amyloid positivity (46/56, 82.1%). High-degree T-EPVS burden (odds ratio [OR] = 7.251, 95% confidence interval [CI] = 3.296-15.952) and low-degree BG-EPVS (OR = 0.241, 95% CI = 0.109-0.530) were predictive of amyloid positivity. Although high-degree T-EPVS was associated with tau positivity, the association was no longer significant after adjusting for amyloid and neurodegeneration status.

INTERPRETATION

Investigating the burden and topographic distribution of EPVS including T-EPVS may be useful for predicting amyloid status, indicating that impaired perivascular drainage may contribute to cerebral amyloidosis. ANN NEUROL 2023.

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.

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.

Genetic factors affecting dopaminergic deterioration during the premotor stage of Parkinson disease

To estimate dopaminergic dysfunction in patients with Parkinson disease (PD) during the premotor stage and to investigate the effect of genetic factors on the trajectories. Using longitudinal dopamine transporter single-photon emission computed tomography data from 367 sporadic PD (sPD), 72 LRRK2 (G2019S), and 39 GBA (N370S) PD patients in the Parkinson's Progression Markers Initiative (PPMI) study, we estimated the temporal trajectories of putaminal-specific binding ratios using an integrating function between baseline values and their annual change rates. In order to test reproducibility, we computed another trajectory for sPD using positron emission tomography data of 38 sPD patients at Gangnam Severance Hospital (GSH). Temporal trajectories of sPD were compared between the groups separated by age at onset (AAO) and polygenic load for common PD risk variants, and also compared with genetic PD. sPD patients in both the PPMI and GSH cohorts showed similar onset of dopaminergic degeneration around 10 years before motor onset. Early-onset PD patients exhibited later onset of degeneration and a faster decline in dopaminergic activity during the premotor period than late-onset patients. sPD patients with high polygenic load were associated with earlier onset and slower progression of dopaminergic dysfunction. Compared to the sPD and LRRK2 PD groups, GBA PD patients exhibited faster deterioration of dopaminergic function during the premotor stage. Dopaminergic dysfunction in PD appears to start about 10 years before motor onset. Genetic factors may be contributing to the heterogeneity of dopaminergic deterioration during the premotor stage.

Principal components of tau positron emission tomography and longitudinal tau accumulation in Alzheimer's disease

Background

We aimed to investigate the clinical correlates of principal components (PCs) of tau positron emission tomography (PET) and their predictability for longitudinal changes in tau accumulation in Alzheimer’s disease (AD).

Methods

We enrolled 272 participants who underwent two PET scans [¹⁸F-flortaucipir for tau and ¹⁸F-florbetaben for amyloid-β (Aβ)], brain magnetic resonance imaging, and neuropsychological tests as baseline assessments. Among them, 187 participants underwent the same follow-up assessments after an average of 2 years. Using Aβ-positive AD dementia-specific PCs obtained from the baseline scans of 56 Aβ-positive patients with AD dementia, we determined the expression of the first two PCs (PC1 and PC2) in all participants. We assessed the correlation of PC expression with baseline clinical characteristics and tau accumulation rates. Moreover, we investigated the predictability of PCs for the longitudinal tau accumulation in training and test sets.

Results

PC1 corresponded to the tau distribution pattern in AD, while the two PC2 extremes reflected the parietal or temporal predominance of tau distribution. PC1 expression increased with tau burden and decreased with cognitive impairment, while PC2 expression decreased with advanced age and visuospatial and attention function deterioration. The tau accumulation rate was positively correlated with PC1 expression (greater tau burden) and negatively correlated with PC2 expression (temporal predominance). A regression model using both PCs could predict longitudinal changes in the tau burden (intraclass correlation coefficient = 0.775, R² = 0.456 in test set).

Conclusions

PC analysis of tau PET could be useful for evaluating disease progression, characterizing the tau distribution pattern, and predicting longitudinal tau accumulation.