Shen-Yang Lim

Dopamine dysregulation syndrome, impulse control disorders and punding after deep brain stimulation surgery for Parkinson's disease

Data regarding the effect of deep brain stimulation (DBS) surgery on the dopamine dysregulation syndrome (DDS), impulse control disorders (ICDs) and punding in Parkinsons disease (PD) are limited. We present a case series of 21 operated PD patients who had exhibited DDS, ICDs or punding at some stage during the disease. DDS remained unimproved or worsened post-operatively in 12/17 patients with pre-operative DDS (71%) (nine bilateral subthalamic nucleus [STN], one right-sided STN, two bilateral globus pallidus internus [GPi] DBS). DDS improved or resolved after bilateral STN DBS in 5/17 patients with pre-operative DDS. DDS apparently developed for the first time after bilateral STN DBS in two patients, although only after a latency of eight years in one case. One patient without reported pre-operative DDS or ICDs developed pathological gambling post-STN DBS. One patient had pathological gambling which resolved pre-operatively, and did not recur post-DBS. Thus, DDS, ICDs and punding may persist, worsen or develop for the first time after DBS surgery, although a minority of patients improved dramatically. Predictive factors may include physician vigilance, motor outcome and patient compliance.

Overview of the Extranigral Aspects of Parkinson Disease

In recent years, there has been increasing recognition of the features of Parkinson disease that are not related to nigrostriatal dopamine deficiency. This review addresses selected clinical, anatomic, pathologic, and biochemical correlates of the early premotor symptoms of Parkinson disease, later nonmotor fluctuations, and advanced dopa-unresponsive motor and nonmotor features. The recognition of early features that predate classic motor symptoms will be important as effective neuroprotective therapy becomes available. Later-stage features often contribute markedly to disability and impaired quality of life and, therefore, represent an important future therapeutic challenge.

Phenotype in parkinsonian and nonparkinsonian LRRK2 G2019S mutation carriers

Objectives: Using a family study design, we describe the motor and nonmotor phenotype in probands with LRRK2 G2019S mutations and family members and compare these individuals to patients with idiopathic Parkinson disease (iPD) and unrelated controls. Methods: Probands with G2019S mutations and their first-degree relatives, subjects with iPD, and unrelated control subjects were identified from 4 movement disorders centers. All underwent neurologic examinations and tests of olfaction, color vision, anxiety, and depression inventories. Results: Tremor was more often a presenting feature among 25 individuals with LRRK2-associated PD than among 84 individuals with iPD. Subjects with LRRK2-PD had better olfactory identification compared with subjects with iPD, higher Beck Depression Inventory scores, and higher error scores on Farnsworth-Munsell 100-Hue test of color discrimination. Postural or action tremor was more common among 29 nonmanifesting mutation carriers compared with 53 noncarriers within the families. Nonparkinsonian family members had higher Unified Parkinsons Disease Rating Scale motor scores, more constipation, and worse color discrimination than controls, regardless of mutation status. Conclusions: Although tremor is a more common presenting feature of LRRK2-PD than iPD and some nonmotor features differed in degree, the phenotype is largely overlapping. Postural or action tremor may represent an early sign. Longitudinal evaluation of a large sample of nonmanifesting carriers will be required to describe any premotor phenotype that may allow early diagnosis.

The nonmotor symptoms of Parkinson's disease—An overview†

Nonmotor symptoms (NMS) are very common in Parkinsons disease (PD) and may result in significant disability. The increased focus on these important clinical features represents a major advance in the care of PD patients. In this article, we provide an overview of recent developments in the field.

Impulse Control and Related Disorders in Parkinson's Disease

In the past decade, impulse control disorders, punding, and dopamine dysregulation syndrome (which we refer to collectively as disinhibitory psychopathologies) have been increasingly recognized in treated patients with Parkinsons disease. Practicing neurologists must understand these problems to limit potential harm. In this article, we summarize current knowledge regarding these behavioral disorders, including phenomenology, epidemiology, pathophysiology, and treatment.

Do dyskinesia and pain share common pathophysiological mechanisms in Parkinson's disease?†

Plastic changes within the striatum resulting from pulsatile dopaminergic stimulation are thought to lead to dyskinesia in patients with Parkinsons disease (PD). The basal ganglia play a role in processing pain. We hypothesized that the plastic changes that lead to dyskinesia may also mediate pain responses. Our objective was to compare the change in pain sensitivity after levodopa administration between stable responders, fluctuators without dyskinesia, and dyskinetic patients, and to compare pain sensitivity between PD and healthy subjects. Fifty patients with PD were assessed with cold water immersion after overnight withdrawal of dopaminergic medications and again after a standard levodopa challenge, and carefully classified into stable responder (n = 12), fluctuator (n = 15), and dyskinetic (n = 23) groups. Twenty age‐matched controls were also tested. PD patients “off”‐medication had a lower threshold (P = 0.016) and tolerance (P < 0.0001) to cold pain compared to controls. After levodopa administration, dyskinetic patients experienced a large increase in cold pain threshold (48%) and tolerance (66%) that was absent in stable responders (P = 0.038 and P = 0.015); there was no significant difference in pain sensitivity change scores between the fluctuator and either the stable responder or dyskinetic groups. Our results suggest that dyskinesia and pain may share common pathophysiological mechanisms in PD.

Subthalamic deep brain stimulation at individualized frequencies for Parkinson disease

Objectives: The oscillation model of Parkinson disease (PD) states that, in the subthalamic nucleus (STN), increased θ (4–10 Hz) and β (11–30 Hz) frequencies were associated with worsening whereas γ frequencies (31–100 Hz) were associated with improvement of motor symptoms. However, the peak STN frequency in each band varied widely from subject to subject. We hypothesized that STN deep brain stimulation (DBS) at individualized γ frequencies would improve whereas θ or β frequencies would worsen PD motor signs. Methods: We prospectively studied 13 patients with PD. STN local field potential (LFP) was recorded after electrode implantations, in the OFF and then in ON dopaminergic medication states while patients performed wrist movements. Six individual peak frequencies of the STN LFP power spectra were obtained: the greatest decrease in θ and β and greatest increase in γ frequencies in the ON state (MED) and during movements (MOVE). Eight DBS frequencies were applied including 6 MED and MOVE frequencies, high frequency (HF) used for chronic stimulation, and no stimulation. The patients were assessed using the motor Unified Parkinsons Disease Rating Scale (mUPDRS). Results: STN DBS at γ frequencies (MED and MOVE) and HF significantly improved mUPDRS scores compared to no stimulation and both γ frequencies were not different from HF. DBS at θ and β frequencies did not worsen mUPDRS scores compared to no stimulation. Conclusion: Short-term administration of STN DBS at peak dopamine-dependent or movement-related γ frequencies were as effective as HF for reducing parkinsonian motor signs but DBS at θ and β frequencies did not worsen PD motor signs. Classification of evidence: This study provides Class III evidence that STN DBS at patient-specific γ frequencies and at usual high frequencies both improved mUPDRS scores compared to no stimulation and did not differ in effect.

Bilateral Pallidal Stimulation for X-Linked Dystonia Parkinsonism

OBJECTIVE To report the clinical benefits of bilateral deep brain stimulation (DBS) of the globus pallidus internus (GPi) in a patient with X-linked dystonia parkinsonism (XDP). DESIGN Case report. SETTING Tertiary referral center. Patient A 40-year-old Filipino man with genetically confirmed XDP and severely disabling generalized dystonia. Intervention Bilateral GPi DBS. MAIN OUTCOME MEASURES The primary outcome measures were the Burke-Fahn-Marsden Dystonia Scale (BFMDS) severity and disability scores, and the secondary outcome measure was the Unified Parkinson Disease Rating Scores. RESULTS At the 1-year postoperative follow-up, there was 80.4% improvement in the BFMDS severity score and 66.7% improvement in the BFMDS disability score. CONCLUSION Bilateral GPi DBS seems to be very effective in improving dystonia in XDP.

DRD and GRIN2B polymorphisms and their association with the development of impulse control behaviour among Malaysian Parkinson’s disease patients

BackgroundImpulse control disorder (ICD) and behaviours (ICB) represent a group of behavioural disorders that have become increasingly recognised in Parkinson’s disease (PD) patients who previously used dopaminergic medications, particularly dopamine agonists and levodopa. It has been suggested that these medications can lead to the development of ICB through the abnormal modulation of dopaminergic transmission and signalling in the mesocorticolimbic dopaminergic system. Several studies have reported an association between polymorphisms in the dopamine receptor (DRD) and N-methyl-D-aspartate 2B (GRIN2B) genes with the development of ICB in PD (PD-ICB) patients. Thus, this study aimed to investigate the association of selected polymorphisms within the DRD and GRIN2B genes with the development of ICB among PD patients using high resolution melt (HRM) analysis.MethodWe used high resolution melt (HRM) analysis to genotype 11 polymorphisms in 5 DRD genes [DRD1 (rs4532, rs4867798 and rs265981), DRD2 (ANKK1 rs1800497, rs104894220 and rs144999500), DRD3 (rs3732783 and rs6280), DRD4 (rs1800443), and DRD5 (rs144132215)] and 1 polymorphism in GRIN2B (rs7301328) in PD patients with (cases, n = 52) and without (controls, n = 39) ICB. Cases were obtained from two tertiary movement disorder centres [UKMMC (n = 9) and UMMC (n = 43)]. At both centres, the diagnosis of ICB was made using the QUIP questionnaire. Controls were recruited from PD patients who attended UKMMC and were found to be negative for ICB using the QUIP questionnaire.ResultsThe HRM analysis showed that 7 of 11 polymorphisms [DRD1 (rs4532, rs4867798, and rs265981), DRD2 (ANKK1 rs1800497), DRD3 (rs3732783 and rs6280), and GRIN2B (rs7301328)] exhibited a clear distinction between wild-type and variant alleles. Variants of DRD2/ANKK1 rs1800497 (OR = 3.77; 95% CI, 1.38-10.30; p = 0.0044), DRD1 rs4867798 (OR = 24.53; 95% CI, 1.68-357.28; p = 0.0054), DRD1 rs4532 (OR = 21.33; 95% CI, 1.97-230.64; p = 0.0024), and GRIN2B rs7301328 (OR = 25.07; 95% CI, 1.30-483.41; p = 0.0097) were found to be associated with an increased risk of developing ICB among PD patients.ConclusionOur findings suggest that polymorphisms in dopamine [DRD1 (rs4532 and rs4867798) and DRD2/ANKK1 rs1800497] and glutamate (GRIN2B rs7301328) receptor genes confer increased risk of ICB development among PD patients.

Analysis of non-synonymous-coding variants of Parkinson's disease-related pathogenic and susceptibility genes in East Asian populations

To evaluate the contribution of non-synonymous-coding variants of known familial and genome-wide association studies (GWAS)-linked genes for Parkinsons disease (PD) to PD risk in the East Asian population, we sequenced all the coding exons of 39 PD-related disease genes and evaluated the accumulation of rare non-synonymous-coding variants in 375 early-onset PD cases and 399 controls. We also genotyped 782 non-synonymous-coding variants of these genes in 710 late-onset PD cases and 9046 population controls. Significant enrichment of LRRK2 variants was observed in both early- and late-onset PD (odds ratio = 1.58; 95% confidence interval = 1.29-1.93; P = 8.05 × 10(-6)). Moderate enrichment was also observed in FGF20, MCCC1, GBA and ITGA8. Half of the rare variants anticipated to cause loss of function of these genes were present in healthy controls. Overall, non-synonymous-coding variants of known familial and GWAS-linked genes appear to make a limited contribution to PD risk, suggesting that clinical sequencing of these genes will provide limited information for risk prediction and molecular diagnosis.