Parkinson's Disease Tremor Differentially Responds to Levodopa and Subthalamic Stimulation

Background

Tremor in Parkinson's disease (PD) has an inconsistent response to levodopa and subthalamic deep brain stimulation (STN-DBS).

Objectives

To identify predictive factors of PD tremor responsiveness to levodopa and STN-DBS.

Material and Methods

PD patients with upper limb tremor who underwent STN-DBS were included. The levodopa responsiveness of tremor (overall, postural, and rest sub-components), was assessed using the relevant Unified Parkinson's Disease Rating Scale-III items performed during the preoperative assessment. Post-surgical outcomes were similarly assessed ON and OFF stimulation. A score for the rest/postural tremor ratio was used to determine the influence of rest and postural tremor severity on STN-DBS outcome. Factors predictive of tremor responsiveness were determined using multiple linear regression modeling. Volume of tissue activated measurement coupled to voxel-based analysis was performed to identify anatomical clusters associated with motor symptoms improvement.

Results

One hundred and sixty five patients were included in this study. Male gender was negatively correlated with tremor responsiveness to levodopa, whereas the ratio of rest/postural tremor was positively correlated with both levodopa responsiveness and STN-DBS tremor outcome. Clusters corresponding to improvement of tremor were in the subthalamic nucleus, the zona incerta and the thalamus, whereas clusters corresponding to improvement for akinesia and rigidity were located within the subthalamic nucleus.

Conclusion

More severe postural tremor and less severe rest tremor were associated with both poorer levodopa and STN-DBS response. The different locations of clusters associated with best correction of tremor and other parkinsonian features suggest that STN-DBS effect on PD symptoms is underpinned by the modulation of different networks.

Long-Term Effects of Subthalamic Stimulation on Motor Symptoms and Quality of Life in Patients with Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting both motor functions and quality of life (QoL). This study compared motor symptoms and QoL in patients with PD before and at 1 and 5 years after subthalamic nucleus deep brain stimulation (STN-DBS) surgery in Taiwan. This study included 53 patients with PD undergoing STN-DBS. The motor symptoms improved by 39.71 ± 26.52% and 18.83 ± 37.15% in the Unified Parkinson's Disease Rating Scale (UPDRS) part II and by 36.83 ± 22.51% and 22.75 ± 36.32% in the UPDRS part III at 1 and 5 years after STN-DBS in the off-medication/on-stimulation state, respectively. The Hoehn and Yahr stage significantly improved at the 1-year follow-up but declined progressively and returned to the baseline stage 5 years post-surgery. The Schwab and England Activities of Daily Living improved and sustained for 5 years following STN-DBS. Levodopa equivalent daily dose decreased by 35.32 ± 35.87% and 15.26 ± 65.76% at 1 and 5 years post-surgery, respectively. The QoL revealed significant improvement at 1 year post-surgery; however, patients regressed to near baseline levels 5 years post-surgery. The long-term effects of STN-DBS on motor symptoms were maintained over 5 years after STN-DBS surgery. At the same time, STN-DBS had no long-lasting effect on QoL. The study findings will enable clinicians to become more aware of visible and invisible manifestations of PD.

l-Dopa/carbidopa intestinal gel and subthalamic nucleus stimulation: Effects on cognition and behavior

OBJECTIVE

In Parkinson's disease (PD), effects on behavior and cognition of levodopa/carbidopa intestinal gel (LCIG) and subthalamic stimulation (STN-DBS) and their practical consequences remain controversial. This study was designed to analyze the possible effects of these therapies on cognition and behavior after 1 year follow-up.

METHODS

This was an open-label, nonrandomized prospective study for pre- and postintervention analyses. Twenty-four patients were considered eligible to be candidates for complex therapies such as STN-DBS or LCIG; 23 patients treated with standard medication were included as controls. Several cognitive, behavioral, and motor scales were administered before and at 6 and 12 months after the intervention.

RESULTS

Patients treated with LCIG experienced significant improvement in specific neuropsychological functions when compared with patients receiving STN-DBS and conventional medical treatment after 1 year from the onset of the intervention. In this study, no significant cognitive or behavioral changes occurred in patients treated with subthalamic stimulation when compared to patients receiving conventional medical treatment at 1 year follow-up.

CONCLUSIONS

Patients treated with LCIG may significantly improve some specific neuropsychological functions when compared with patients receiving STN-DBS and with patients receiving conventional medical treatment after 1 year from the intervention; there are not significant cognitive or behavioral changes in patients treated with STN-DBS when compared to PD patients receiving conventional medical treatment after 1 year from the intervention. The outcomes showed in the study can help to the selection of the appropriate candidates for STN-DBS and LCIG.

Personality, dopamine, and Parkinson's disease: Insights from subthalamic stimulation

BACKGROUND

Subthalamic stimulation improves the motor and neuropsychiatric symptoms of Parkinson's disease. However, the impact of this treatment on impulse control and personality is the subject of heavy debate. The objective of this study was to investigate personality changes after subthalamic stimulation.

METHODS

Using Cloninger's biosocial model, we assessed personality in 73 Parkinson's disease patients before and 12 months after subthalamic stimulation accompanied by a drastic reduction in dopaminergic medication. Changes in psychobehavioral symptoms were measured using a battery of validated clinical scales (apathy, depression, anxiety, hyperemotionality, mania, psychosis, punding, and impulse control behaviors).

RESULTS

One year after surgery, the harm avoidance personality domain total score increased compared with the baseline (+2.8; 34 patients; P < 0.001), as did 3 of its 4 subdomains: anticipatory worry (+0.7; 10 patients; P = 0.005), shyness (+0.6; 7 patients; P = 0.03), and fatigability (+1.1; 10 patients; P = 0.0014). Evolution of the shyness personality trait correlated with the decrease in dopaminergic medication. Total scores in the other personality domains remained unchanged, except for extravagance, a subdomain of novelty seeking, and persistence, a subdomain of reward dependence, which both decreased following surgery (-0.3; 7 patients; and -0.6; 9 patients; P = 0.03 and P = 0.0019, respectively). Although apathy increased, other psychobehavioral symptoms, including impulse control behaviors and neuropsychiatric nonmotor fluctuations, improved. Depression and anhedonia remained stable. Scores in hypodopaminergia and neuropsychiatric nonmotor OFF correlated with harm avoidance. Scores in hyperdopaminergia and neuropsychiatric nonmotor ON correlated with novelty seeking.

CONCLUSIONS

When subthalamic stimulation is applied in Parkinson's disease, significant changes in personality traits are observed, which may be related to postoperative tapering of dopaminergic treatment. © 2017 International Parkinson and Movement Disorder Society.

Dissociable dorsal and ventral frontostriatal working memory circuits: evidence from subthalamic stimulation in Parkinson's disease

In this study, we investigated the neural substrates involved in visual working memory (WM) and the resulting effects of subthalamic nucleus (STN) stimulation in Parkinson's disease (PD). Cerebral activation revealed by positron emission tomography was compared among Parkinson patients with (PD-ON) or without (PD-OFF) STN stimulation, and a group of control subjects (CT) in two visual WM tasks with spatial (SP) and nonspatial (NSP) components. PD-OFF patients displayed significant reaction time (RT) deficits for both memory tasks. Although there were no significant differences in RT between patients with PD-ON and -OFF stimulation, patients with PD-ON stimulation performed comparably to controls. The memory tasks were executed with normal error rates in PD-ON and -OFF stimulation. In contrast to these behavioral results, whether the corresponding prefrontal activation was differentially affected by deep brain stimulation status in patients depended on whether the WM modality was SP versus NSP. Thus, SP WM was associated with (1) abnormal reduction in dorsolateral prefrontal activity in PD-OFF and -ON stimulation and (2) abnormal overactivation in parieto-temporal cortex in PD-OFF and in limbic circuits in PD-ON stimulation. In NSP WM, normal activation of the ventral prefrontal cortex was restored in PD-ON stimulation. In both visual modalities the posterior cerebral regions including fusiform cortex and cerebellum, displayed abnormally reduced activity in PD. These results indicate that PD induces a prefrontal hypoactivation that STN stimulation can partially restore in a modality selective manner by additional recruitment of limbic structures in SP WM or by recovery of the ventral prefrontal activation in NSP WM.