Early-onset drug-induced parkinsonism after exposure to offenders implies nigrostriatal dopaminergic dysfunction

Predictors associated with the rate of progression of nigrostriatal degeneration in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) manifests as a wide variety of clinical phenotypes and its progression varies greatly. However, the factors associated with different disease progression remain largely unknown.

METHODS

In this retrospective cohort study, we enrolled 113 patients who underwent 18F-FP-CIT PET scan twice. Given the negative exponential progression pattern of dopamine loss in PD, we applied the natural logarithm to the specific binding ratio (SBR) of two consecutive 18F-FP-CIT PET scans and conducted linear mixed model to calculate individual slope to define the progression rate of nigrostriatal degeneration. We investigated the clinical and dopamine transporter (DAT) availability patterns associated with the progression rate of dopamine depletion in each striatal sub-region.

RESULTS

More symmetric parkinsonism, the presence of dyslipidemia, lower K-MMSE total score, and lower anteroposterior gradient of the mean putaminal SBR were associated with faster progression rate of dopamine depletion in the caudate nucleus. More symmetric parkinsonism and lower anteroposterior gradient of the mean putaminal SBR were associated with faster depletion of dopamine in the anterior putamen. Older age at onset, more symmetric parkinsonism, the presence of dyslipidemia, and lower anteroposterior gradient of the mean putaminal SBR were associated with faster progression rate of dopamine depletion in the posterior putamen. Lower striatal mean SBR predicted the development of LID, while lower mean SBR in the caudate nuclei predicted the development of dementia.

DISCUSSION

Our results suggest that the evaluation of baseline clinical features and patterns of DAT availability can predict the progression of PD and its prognosis.

Drug-Induced Movement Disorders

Drug-induced movement disorders (DIMDs) are most commonly associated with typical and atypical antipsychotics. However, other drugs such as antidepressants, antihistamines, antiepileptics, antiarrhythmics, and gastrointestinal drugs can also cause abnormal involuntary movements. Different types of movement disorders can also occur because of adverse drug reactions. Therefore, the important key to diagnosing DIMDs is a causal relationship between potential offending drugs and the occurrence of abnormal movements. The pathophysiology of DIMDs is not clearly understood; however, many cases of DIMDs are thought to exert adverse mechanisms of action in the basal ganglia. The treatment of some DIMDs is quite challenging, and removing the offending drugs may not be possible in some conditions such as withdrawing antipsychotics in the patient with partially or uncontrollable neuropsychiatric conditions. Future research is needed to understand the mechanism of DIMDs and the development of drugs with better side-effect profiles. This article reviews the phenomenology, diagnostic criteria, pathophysiology, and management of DIMDs.

Updated Perspectives on the Management of Drug-Induced Parkinsonism (DIP): Insights from the Clinic

Parkinsonism refers to the clinical combination of bradykinesia, rigidity, tremor, and postural instability. Parkinsonism is often neurodegenerative, but it can be secondary or iatrogenic, as in drug-induced parkinsonism (DIP), which is the topic of this review. We review the pathophysiology of DIP, differentiate DIP and idiopathic Parkinson's disease (PD), list culprit medications in the development of DIP, discuss the diagnosis of DIP as well as the motor and nonmotor signs and symptoms that can help with differentiation of DIP and PD, and detail the management of DIP.

Dopamine Transporter Imaging, Current Status of a Potential Biomarker: A Comprehensive Review

A major goal of current clinical research in Parkinson's disease (PD) is the validation and standardization of biomarkers enabling early diagnosis, predicting outcomes, understanding PD pathophysiology, and demonstrating target engagement in clinical trials. Molecular imaging with specific dopamine-related tracers offers a practical indirect imaging biomarker of PD, serving as a powerful tool to assess the status of presynaptic nigrostriatal terminals. In this review we provide an update on the dopamine transporter (DAT) imaging in PD and translate recent findings to potentially valuable clinical practice applications. The role of DAT imaging as diagnostic, preclinical and predictive biomarker is discussed, especially in view of recent evidence questioning the incontrovertible correlation between striatal DAT binding and nigral cell or axon counts.

Recognition and Management of Antipsychotic-Induced Parkinsonism in Older Adults: A Narrative Review

Background: Parkinsonism is a common side-effect of antipsychotic drugs especially in older adults, who also present with a higher frequency of neurodegenerative disorders like Idiopathic Parkinson’s disease (IPD). Distinguishing between antipsychotic-induced parkinsonism (AIP) and IPD is challenging due to clinical similarities. Up to 20% of older adults may suffer from persisting parkinsonism months after discontinuation of antipsychotics, suggesting underlying neurodegeneration. A review of the literature on AIP in older adults is presented, focusing on epidemiology, clinical aspects, and management. Methods: A literature search was undertaken on EMBASE, MEDLINE and PsycINFO, for articles on parkinsonism induced by antipsychotic drugs or other dopamine 2 receptor antagonists in subjects aged 65 or older. Results: AIP in older adults is the second most common cause of parkinsonism after IPD. Older age, female gender, exposure to high-potency first generation antipsychotics, and antipsychotic dosage are the main risk factors. The clinical presentation of AIP resembles that of IPD, but is more symmetrical, affects upper limbs more, and tends to have associated motor phenomena such as orofacial dyskinesias and akathisia. Presence of olfactory dysfunction in AIP suggests neurodegeneration. Imaging of striatal dopamine transporters is widely used in IPD diagnosis and could help to distinguish it from AIP. There is little evidence base for recommending pharmacological interventions for AIP, the best options being dose-reduction/withdrawal, or switching to a second-generation drug. Conclusions: AIP is a common occurrence in older adults and it is possible to differentiate it from IPD. Further research is needed into its pathophysiology and on its treatment.

Impaired functional connectivity of sensorimotor network predicts recovery in drug-induced parkinsonism

OBJECTIVE

In a substantial portion of patients with drug-induced parkinsonism (DIP), parkinsonism may persist for long periods after discontinuation of offending drugs, suggesting subtle underlying neurodegeneration. We hypothesized that patients with DIP have impaired functional connectivity (FC) of brain networks, which may determine the reversibility of parkinsonism.

METHODS

In this case-control study, we consecutively recruited 60 patients with DIP and 32 healthy controls. We used independent component analysis and dual regression of functional magnetic resonance imaging data to identify seven resting-state networks and compared FC of the networks between the DIP and control groups. Among regions where the two groups showed a significant difference in the FC with sensorimotor network, we compared the FC between patients who had completely recovered (n = 21) and those who had partially recovered (n = 39) within 3 months of cessation of the offending drugs.

RESULTS

Patients with DIP had decreased FC between the sensorimotor network and widespread brain regions, when compared to healthy controls. FC in the prefrontal regions was negatively correlated with parkinsonian motor score. Patients who partially recovered had a significantly lower FC in the prefrontal and cerebellar regions than those who recovered completely, providing a useful predictor of recovery status.

CONCLUSIONS

Patients with DIP had decreased FC of the sensorimotor network, which correlated with the severity of parkinsonism and predicted the recovery status after cessation of offending drugs. Impaired FC of the sensorimotor network can be used as a biomarker to evaluate the severity and prognosis of DIP.

Recent developments in drug-induced movement disorders: a mixed picture

A large and ever-growing number of medications can induce various movement disorders. Drug-induced movement disorders are disabling but are often under-recognised and inappropriately managed. In particular, second generation antipsychotics, like first generation agents, are associated with potentially debilitating side-effects, most notably tardive syndromes and parkinsonism, as well as potentially fatal acute syndromes. Appropriate, evidence-based management is essential as these drugs are being prescribed to a growing population vulnerable to these side-effects, including children and elderly people. Prevention of the development of drug-induced movement disorders is an important consideration when prescribing medications that can induce movement disorders. Recent developments in diagnosis, such as the use of dopamine transporter imaging for drug-induced parkinsonism, and treatment, with the approval of valbenazine and deutetrabenazine, the first drugs indicated for tardive syndromes, have improved outcomes for many patients with drug-induced movement disorders. Future research should focus on development of safer antipsychotics and specific therapies for the different tardive syndromes and the treatment of drug-induced parkinsonism.

Distinct FP-CIT PET patterns of Alzheimer's disease with parkinsonism and dementia with Lewy bodies

PURPOSE

Little is known regarding the clinical relevance or neurobiology of subtle motor disturbance in Alzheimer's disease (AD). This study aims to investigate the patterns of striatal ¹⁸F-FP-CIT uptake in patients with AD-related cognitive impairment (ADCI) with mild parkinsonism.

METHODS

We recruited 29 consecutive patients with ADCI with mild parkinsonism. All patients underwent ¹⁸F-FP-CIT PET scans and dopamine transporter (DAT) availability in striatal subregions (anterior/posterior caudate, anterior/posterior putamen, ventral putamen, ventral striatum) was quantified. Additionally, 32 patients with dementia with Lewy bodies (DLB) and 21 healthy controls were included to perform inter-group comparative analyses of the striatal DAT availability. The discriminatory power of striatal DAT availability to differentiate ADCI from DLB was assessed using receiver operating characteristics (ROC) analyses. The Spearman's correlation coefficient was calculated to assess the relationship between motor severity and DAT availability in striatal subregions.

RESULTS

Patients with ADCI with mild parkinsonism exhibited decreased DAT availability in the caudate that was intermediate between healthy controls and patients with DLB. The DAT availability in other striatal subregions, including the posterior putamen, did not differ between the ADCI with parkinsonism and healthy control groups. The ROC analysis showed that DAT availability of all striatal subregions, especially the whole striatum, had a fair discriminatory power. Parkinsonian motor severity did not correlate with the striatal DAT availability in ADCI with parkinsonism.

CONCLUSIONS

The present study demonstrated that patients with ADCI with mild parkinsonism had distinct DAT scan patterns and suggests that parkinsonism is associated with the extranigral source of pathology.

Does Late Levodopa Administration Delay the Development of Dyskinesia in Patients with De Novo Parkinson's Disease?

BACKGROUND

It remains controversial whether late levodopa administration is a reasonable approach to reducing the risk of levodopa-induced dyskinesia in Parkinson's disease.

OBJECTIVE

This study aimed to investigate the effects of levodopa sparing on the development of levodopa-induced dyskinesia.

METHODS

We retrospectively reviewed medical records for patients with de novo Parkinson's disease who visited the Yonsei Parkinson Center between April 2009 and June 2015 and received at least 2 years of treatment. Among 657 patients with drug-naïve Parkinson's disease who met the study criteria, 90 were initially treated with dopamine agonists (levodopa-sparing group; levodopa supplementation after 2.15 years). Another 90 patients who were initially treated with levodopa (levodopa group) were matched to the 90 patients for age, sex, follow-up duration, Parkinson's disease duration, Unified Parkinson's Disease Rating Scale Part III scores, and baseline dopamine transporter availability in the posterior putamen. The effects of levodopa sparing on dyskinesia development were assessed with Kaplan-Meier estimates and a stratified Cox regression model adjusted for age of onset, sex, dopamine transporter availability, and daily levodopa dose per weight.

RESULTS

The levodopa-sparing group had a comparable age of onset (54.80 ± 7.36 years) to the levodopa group (56.53 ± 6.16 years). The Kaplan-Meier analysis revealed that the risk of levodopa-induced dyskinesia after treatment initiation was similar between the groups. Once the levodopa-sparing group started levodopa supplementation, they had a higher risk of developing levodopa-induced dyskinesia. However, a stratified Cox regression model indicated that hazard ratios for levodopa sparing to levodopa-induced dyskinesia development were 0.138 (95% confidence interval 0.024-0.785) after treatment initiation and 0.438 (95% confidence interval 0.105-1.832) after levodopa initiation.

CONCLUSION

Late levodopa administration was associated with a low risk of dyskinesia after adjusting for confounding effects and may be a reasonable strategy for prolonging the levodopa-induced dyskinesia-free period in Parkinson's disease.

Effect of striatal dopamine depletion on cognition in de novo Parkinson's disease

INTRODUCTION

To investigate the relationship between the sub-regional pattern of striatal dopamine depletion and cognitive impairment in early-stage Parkinson's disease (PD), and determine the effect of striatal dopamine density on cognitive prognosis.

METHODS

Patients with drug-naïve non-demented PD were divided into mild cognitive impairment (PD-MCI; n = 129) and cognitively normal (PD-CogN; n = 182) groups. Using quantification of the dopamine transporter (DAT) availability in each striatal sub-region with ¹⁸F-FP-CIT PET scans, we performed inter-group comparative analysis of DAT availability and multivariate linear regression analysis to assess the association between DAT availability and cognitive performance. Additionally, the effect of baseline DAT availability on the cognitive decline across time as well as on changes in the cognitive status was estimated.

RESULTS

The PD-MCI group exhibited more severely decreased DAT availability in all the striatal sub-regions compared to the PD-CogN group, although there was no significant difference in PD duration. The DAT availability in the caudate, anterior putamen, and ventral striatum was directly associated with attention/working memory, frontal/executive, and visuospatial functions, while the DAT availability of the posterior putamen was not. However, the baseline DAT availability of the striatal sub-regions did not influence the cognitive decline or cognitive status in the longitudinal cognitive assessment.

CONCLUSION

Our results suggest that striatal DAT availability may determine MCI in patients with de novo PD. Dopamine loss in the associative and limbic striatum is closely linked to cognitive deficits in early-stage PD, although it does not affect cognitive prognosis.