Dopaminergic dysregulation syndrome in Parkinson's disease

Dementia-Associated Compulsive Singing (DACS): Presentation of Unpublished Clinical Cases Miniseries

Dementia-associated compulsive singing (DACS) is a neurotransmettitorial-based behavioral disturbance, characterized by an unabating melodic expression, occurring in patients that suffer from evolved dementia. Previously described only as a "punding" aspect of the dopamine dysregulation syndrome (DDS) in the Parkinson's disease (PD), compulsive singing has now been described, for the first time, in four non-PD patients effectively treated with Haloperidol or Quetiapine. Unlike the DDS-associated conditions, in our cases DACS is not pharmacologically induced, being that all patients were L-dopa-free. We detected a diffuse hyperintensity of the white matter and brain atrophy, with insular shrinkage as well as ventricular system and/or sub-arachnoid space enlargement in our DACS patients. Furthermore, similarly to the other behavioral symptoms of dementia, DACS also seems to be correlated to the degree of cognitive and functional impairment, rather than its subtype. In conclusion, DACS is a non-cognitive, unpublished clinical aspect of evolved dementia, which is interesting due to the involvement of the extra-nigral dopaminergic system, resulting in an unabating altered behavior, but also to the enrichment of our knowledge in the involutional diseases of the central nervous system and their physiopathological manifestations.

New pharmacological and neuromodulation approaches for impulsive-compulsive behaviors in Parkinson's disease

INTRODUCTION

A significant proportion of patients with Parkinson's disease (PD) display a set of impulsive-compulsive behaviors at some point during the course of illness. These behaviors range from the so-called behavioral addictions to dopamine dysregulation syndrome, punding and hoarding disorders. These behaviors have been consistently linked to the use of dopaminergic medications used to treat PD motor symptoms (dopamine agonists, levodopa, and other agents) and less consistently to neuromodulation techniques such as deep brain stimulation (DBS). Since there are still no approved treatments for these conditions, their pharmacological management is still a big challenge for clinicians.

METHODS

We conducted an extensive review of current pharmacological and neuromodulation literature for the management of impulsive-compulsive disorders in PD patients.

RESULTS

Pharmacological treatment approaches for impulsive-compulsive behaviors and DDS in PD patients include reduction of levodopa (LD), reduction/cessation of dopamine agonist (DA), and initiation of infusion therapies (apomorphine infusion and duodopa). Also, atomoxetine, a noradrenergic agent approved for the treatment of attention deficit hyperactivity disorder, showed some interesting preliminary results but there is still a lack of controlled longitudinal studies. Finally, while DBS effects on impulsive-compulsive disorders are still controversial, non-invasive techniques (such as transcranial magnetic stimulation and transcranial direct current stimulation) could have a potential positive effect but, again, there is still a lack of controlled trials.

CONCLUSION

Managing impulsivity and compulsivity in PD patients is still a non-evidence-based challenge for clinicians. Controlled trials on promising approaches such as atomoxetine and non-invasive neuromodulation techniques are needed.

Advanced Therapies for the Management of Dopamine Dysregulation Syndrome in Parkinson's Disease

Background

Dopamine Dysregulation Syndrome (DDS) is an adverse non-motor complication of dopamine replacement therapy in Parkinson's disease. The current literature on this syndrome is limited, and it remains underdiagnosed and challenging to manage.

Objective

To assess the role of advanced therapies in the management of DDS.

Methods

We performed a retrospective chart review and identified patients who fit the inclusion criteria for DDS. They were classified according to risk factors that have been identified in the literature, motor and complication scores, intervention (medical or surgical) and outcome. Multivariate analyses were performed to analyze these characteristics.

Results

Twenty-seven patients were identified (23 males, mean age of onset: 49 ± 8.8 years). Average levodopa equivalent daily dose was 1916.7 ± 804 mg and a history of impulse control disorders, psychiatric illness, and substance abuse was present in 89%, 70% and 3.7% of the patients, respectively. Overall 81.5% of patients had symptom resolution at follow up, on average 4.8 ± 3.5 years after management, with medication only (7/9), levodopa-carbidopa intestinal gel (1/3), deep brain stimulation of subthalamic nucleus (10/13), or globus pallidus pars interna (2/2). Reduction of medications occurred with deep brain stimulation of subthalamic nucleus (P = 0.01) but was associated with a relapse in two patients.

Conclusion

Although the small sample size of some subgroups limits our ability to draw meaningful conclusions, our results did not suggest superiority of a single treatment option. Advanced therapies including deep brain stimulation can be considered in patients with DDS refractory to conservative measures, but outcome is variable and relapse is possible.

Attentional dysfunction and the punding spectrum in Parkinson's disease

BACKGROUND

Punding is a complication of Parkinson's disease (PD) treatment and stimulant abuse that features excessive preoccupation with repetitive and/or aimless behaviors. We hypothesized that cognitive impairment and functional limitations influence how punding behaviors manifest in PD.

METHODS

We extracted data on punding, hobbyism, and cognition from the Parkinson's Progression Marker Initiative (PPMI). Punding and hobbyism were measured with the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP) scale. We determined how cognition predicted punding and hobbyism behaviors-adjusting for levodopa dose, Hoehn & Yahr stage, disease duration, and age-using generalized estimating equation (GEE) logistic regression. Activities of daily living (ADL) and motor impairment were measured with the MDS-UPDRS scale.

RESULTS

In GEE logistic regression models, punding was selectively associated with lower scores on the Letter Number Sequencing test (LNS), the primary attention test in PPMI (Odds ratio: 0.87 (95% CI: 0.79-0.96); p = 0.022). This was corroborated by a subscale-analysis of Montreal Cognitive Assessment (MoCA) scores, as only the attention subscale was significantly associated with punding (OR: 0.59 (0.45-0.77); p < 0.001). Baseline impairment in LNS (Hazard ratio: 2.52 (1.22-5.20); p = 0.012) and MoCA attention (HR: 2.68 (1.32-5.42); p = 0.006) predicted earlier punding in Cox regression. In turn, ADL dysfunction predicted punding (OR: 1.55 (1.20-2.00); p < 0.001), but not hobbyism.

CONCLUSION

Attentional dysfunction is a domain-specific cognitive biomarker of punding risk in PD. Further, attentional capacity and functional impairment may determine the complexity of perseverative behaviors on the continuum from rudimentary punding to semi-purposeful hobbyism.

Ultrasonic stimulation of the brain to enhance the release of dopamine - A potential novel treatment for Parkinson's disease

Parkinson's disease (PD) is characterized by the decrease of dopamine (DA) production and release in the substantia nigra and striatum regions of the brain. Transcranial ultrasound has been exploited recently for neuromodulation of the brain in a number of fields. We have stimulated DA release in PC12 cells using low-intensity continuous ultrasound (0.1 W/cm² - 0.3 W/cm², 1 MHz), 12 h after exposure at 0.2 W/cm², 40 s, the amount of DA content eventually increased 78.5% (p = 0.004). After 10-day ultrasonic treatment (0.3 W/cm², 5 min/d), the DA content in the striatum of PD mice model restored to 81.07% of the control (vs 43.42% in the untreated PD mice model). In addition to this the locomotion activity was restored to the normal level after treatment. We suggest that the low intensity ultrasound-induced DA release can be attributed to a combination of neuron regeneration and improved membrane permeability produced by the mechanical force of ultrasound. Our study indicates that the application of transcranial ultrasound applied below FDA limits, could provide a candidate for relatively safe and noninvasive PD therapy through an amplification of DA levels and the stimulation of dopaminergic neuron regeneration without contrast agents.

Dopamine Agonists and Impulse Control Disorders: A Complex Association

Impulse control disorders (ICDs) are a well-known adverse effect of dopamine agonists (DAAs). This critical review aims to summarize data on the prevalence and factors associated with the development of an ICD simultaneous to DAA use. A search of two electronic databases was completed from inception to July 2017. The search terms were medical subject headings (MeSH) terms including “dopamine agonists” AND “disruptive disorders”, “impulse control disorders”, or “conduct disorders”. Articles had to fulfill the following criteria to be included: (i) the target problem was an ICD; (ii) the medication was a dopaminergic drug; and (iii) the article was an original article. Of the potential 584 articles, 90 met the criteria for inclusion. DAAs were used in Parkinson’s disease (PD), restless legs syndrome (RLS) or prolactinoma. The prevalence of ICDs ranged from 2.6 to 34.8% in PD patients, reaching higher rates in specific PD populations; a lower prevalence was found in RLS patients. We found only two studies about prolactinoma. The most robust findings relative to the factors associated with the development of an ICD included the type of DAA, the dosage, male gender, a younger age, a history of psychiatric symptoms, an earlier onset of disease, a longer disease duration, and motor complications in PD. This review suggests that DAA use is associated with an increased risk in the occurrence of an ICD, under the combined influence of various factors. Guidelines to help prevent and to treat ICDs when required do exist, although further studies are required to better identify patients with a predisposition.

The Outcome of Dopamine Dysregulation Syndrome in Parkinson's Disease: A Retrospective Postmortem Study

Introduction

We have performed a retrospective analysis of the frequency and relation to treatment of dopamine dysregulation syndrome (DDS) using the Queen Square Brain Bank (QSBB) database.

Methods

A search of the QSBB database for consecutive cases donated between 2005 and 2016 with a pathological diagnosis of Parkinson's disease was performed.

Results

DDS was present in 8.8% of cases, was more prevalent in males, and was associated with younger age of onset, longer disease duration, and more dopa-induced dyskinesias. Treatment approaches for DDS included: reduction of levodopa, reduction/cessation of dopamine agonist (DA), and initiation of infusion therapies. DDS had completely resolved in just over half the patients. DA peak l-dopa equivalent daily dose (LEDD) was higher in patients who failed to achieve remission.

Conclusion

This is the first study to provide data on the course of DDS until death. Treatment strategies consisted mainly of reduction of dopaminergic treatment, and, despite the majority of patients showing some improvement, half remained symptomatic. Successful treatment was associated with a lower l-dopa dosage at death.

Markers of impaired motor and cognitive volition in Parkinson's disease: Correlates of dopamine dysregulation syndrome, impulse control disorder, and dyskinesias

INTRODUCTION

Dopaminergic therapy in Parkinson's disease (PD) can be associated with both motoric (e.g., dyskinesias) and neuropsychiatric adverse effects. Examples of the latter include Dopamine Dysregulation Syndrome (DDS) and impulse control disorder (ICD), which are separate but related behavioral/psychiatric complications of treatment in PD. Dysregulation of volition characterizes both dyskinesias and DDS/ICD; thus, we analyzed potential disease-related correlates in a large PD cohort.

METHODS

We analyzed cross-sectional data from 654 participants collected through the NINDS Parkinson's Disease Biomarkers Program. DDS/ICD symptoms and dyskinesias were assessed using the Movement Disorders Society (revised) Unified Parkinson's Disease Rating Scale. Potential associated variables were selected from PD-validated or PD-specific scales of neuropsychiatric or motoric status. Multivariable models with DDS/ICD or dyskinesia presence outcomes were produced with backward stepwise regression to identify factors independently associated with DDS/ICD and/or dyskinesias.

RESULTS

Fifty-three (8.1%) participants endorsed DDS and/or ICD symptoms and 150 (22.9%) were dyskinetic. In multivariable analysis, psychosis was independently associated with both dyskinesias (p = 0.006) and DDS/ICD (p < 0.001). Unpredictable motor fluctuations (p = 0.026) and depression (p = 0.023) were also associated with DDS/ICD; female sex (p = 0.025), low tremor score (p = 0.001) and high akinesia-rigidity score (p < 0.001) were associated with dyskinesias.

CONCLUSIONS

Our findings suggest that psychosis may be an important marker of impaired volition across motor and cognitive domains. Unpredictable motor fluctuations, psychosis, and depression may together comprise a phenotypic profile of patients at increased risk for DDS/ICD. Similarly, dyskinetic PD patients should be closely monitored for psychotic symptoms and treated appropriately.

[Syndrome dopamine dysregulation and deep brain stimulation of the subthalamic nucleus in Parkinson's disease]

AIM

Dopamine dysregulation syndrome (DDS) is a complication of the dopaminergic therapy in Parkinson's disease (PD); it is manifested as a compulsive medication use and may have negative impact on patients' social, psychological, and physical functioning. An effect of deep brain stimulation in the subthalamic nucleus (DBS STN) on DDS is not fully understood. Therefore, the degree of DDS during DBS STN in PD patients was evaluated in the study.

MATERIAL AND METHODS

The main group included 15 patients with DDS symptoms in the preoperative period. The comparison group consisted of 15 patients without DDS symptoms and the control group consisted of 15 patients who did not undergo surgery.

RESULTS AND CONCLUSION

The severity of motor disturbances in the surgery groups has decreased significantly (by 45%). Motor complications during DBS STN in patients with DDS have decreased by 50%; a decrease in the reduction of doses of dopaminergic preparations was noted as well.

Dopamine dysregulation syndrome in Parkinson's disease: a systematic review of published cases

OBJECTIVES

Dopamine dysregulation syndrome (DDS) is an uncommon complication of the treatment of Parkinson's disease, characterised by addictive behaviour and excessive use of dopaminergic medication. DDS may frequently go unrecognised or misdiagnosed. We aimed to clarify current understanding of presentation, risk factors, comorbidities and management of DDS.

METHODS

Case reports were identified through a systematic search of databases (PubMed, Embase) with the following terms: dopaminergic dysregulation syndrome, hedonistic homeostatic dysregulation, dopamine/levodopa addiction.

RESULTS

We reviewed 390 articles, identifying 98 cases of DDS. Early-onset Parkinson's disease (67%) and male gender (83%) were common. DDS presented with significant physical and social impairment, actions to enable or prevent detection of overuse, as well as mood, anxiety and motor fluctuations. All DDS cases met DSM-V (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) substance use disorder criteria. Past substance and psychiatric history was present in 15.3% and 10.2% of cases. Comorbid impulse control disorders (61%), psychosis (32%) and panic attacks (14%) were common. A large variety of management strategies were used; only 56% of cases resolving. Sodium valproate was successful in 5/5 cases. The response to deep brain stimulation varied.

CONCLUSIONS

Given the functional impairment, medical and psychiatric consequences and the difficulties of treatment, early identification of DDS should be a priority.

Autonomy in Depressive Patients Undergoing DBS-Treatment: Informed Consent, Freedom of Will and DBS' Potential to Restore It

According to the World Health Organization, depression is one of the most common and most disabling psychiatric disorders, affecting at any given time approximately 325 million people worldwide. As there is strong evidence that depressive disorders are associated with a dynamic dysregulation of neural circuits involved in emotional processing, recently several attempts have been made to intervene directly in these circuits via deep brain stimulation (DBS) in patients with treatment-resistant major depressive disorder (MDD). Given the promising results of most of these studies, the rising medical interest in this new treatment correlates with a growing sensitivity to ethical questions. One of the most crucial concerns is that DBS might interfere with patients' ability to make autonomous decisions. Thus, the goal of this article is to evaluate the impact DBS presumably has on the capacity to decide and act autonomously in patients with MDD in the light of the autonomy-undermining effects depression has itself. Following the chronological order of the procedure, special attention will first be paid to depression's effects on patients' capacity to make use of their free will in giving valid Informed Consent. We suggest that while the majority of patients with MDD appear capable of autonomous choices, as it is required for Informed Consent, they might still be unable to effectively act according to their own will whenever acting includes significant personal effort. In reducing disabling depressive symptoms like anhedonia and decrease of energy, DBS for treatment resistant MDD thus rather seems to be an opportunity to substantially increase autonomy than a threat to it.

Impulsive and compulsive behaviors in Parkinson's disease

BACKGROUND

Impulsive and compulsive behaviors (ICBs) are a heterogeneous group of conditions that may be caused by long-term dopaminergic replacement therapy (DRT) of Parkinson's disease (PD). The spectrum of ICBs includes dopamine dysregulation syndrome (DDS), punding, and impulse control disorders (ICDs).

CONTENTS

We made a detailed review regarding the epidemiology, pathology, clinical characteristics, risk factors, diagnosis as well as treatment of ICBs.

RESULTS

The prevalence of ICBs in PD patients is approximately 3-4% for DDS, 0.34-4.2% for punding, and 6-14% for ICDs, with higher prevalence in Western populations than in Asian. Those who take high dose of levodopa are more prone to have DDS, whereas, ICDs are markedly associated with dopamine agonists. Different subtypes of ICBs share many risk factors such as male gender, higher levodopa equivalent daily dose, younger age at PD onset, history of alcoholism, impulsive, or novelty-seeking personality. The Questionnaire for Impulsive-Compulsive Disorder in Parkinson's Disease-Rating Scale seems to be a rather efficacious instrument to obtain relevant information from patients and caregivers. Treatment of ICBs is still a great challenge for clinicians. Readjustment of DRT remains the primary method. Atypical antipsychotics, antidepressants, amantadine, and psychosocial interventions are also prescribed in controlling episodes of psychosis caused by compulsive DRT, but attention should be drawn to balance ICBs symptoms and motor disorders. Moreover, deep brain stimulation of the subthalamic nucleus might be a potential method in controlling ICBs.

CONCLUSION

The exact pathophysiological mechanisms of ICBs in PD remains poorly understood. Further researches are needed not only to study the pathogenesis, prevalence, features, and risk factors of ICBs, but to find efficacious therapy for patients with these devastating consequences.

Impulse control disorder in patients with Parkinson's disease under dopamine agonist therapy: a multicentre study

BACKGROUND

Impulse control disorders (ICDs) encompass a wide spectrum of abnormal behaviour frequently found in cases of Parkinson's disease (PD) treated with dopamine agonists (DAs). The main aim of this study was to analyse ICD prevalence with different DAs.

METHODS

We carried out a multicentre transversal study to evaluate the presence of ICDs in patients with PD chronically treated (>6 months) with a single non-ergolinic DA (pramipexole, ropinirole, or rotigotine). Clinical assessment of ICD was performed using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease.

RESULTS

Thirty-nine per cent of patients (91/233) fulfilled the clinical criteria for ICD. The group of patients with ICD symptoms (ICD+) differed from those without ICD symptoms (ICD-) in younger age and type of DA intake. Oral DA treatment (pramipexole and ropinirole) was associated with higher risk of ICDs compared with transdermal DA (rotigotine): 84/197 (42%) patients treated with oral DA developed ICD, versus 7/36 (19%) patients treated with transdermal DA (Fisher's exact text <0.01). In univariate analysis, a younger age (p<0.01), treatment with rasagiline (p<0.05), and especially treatment with an oral DA (pramipexole or ropinirole) (p<0.01) were significantly associated with ICD. Multivariate analysis confirmed that oral DA remained significantly associated with ICD (p: 0.014, OR: 3.14; 1.26-7.83).

CONCLUSIONS

ICD was significantly associated with the use of the non-ergolinic oral DA (pramipexole and ropinirole) when compared with transdermal non-ergolinic DA (rotigotine). Since pramipexole, ropinirole and rotigotine are non-ergolinic DAs with very similar pharmacodynamic profiles, it is likely that other factors including route of administration (transdermal vs oral) explain the difference in risk of ICD development.

Dopamine dysregulation syndrome in Parkinson's disease: from clinical and neuropsychological characterisation to management and long-term outcome

OBJECTIVE

Dopamine dysregulation syndrome (DDS) refers to a compulsive pattern of dopaminergic drug misuse complicating Parkinson's disease (PD). To date, few data are available on DDS risk factors, cognitive profile and long-term outcome.

METHODS

In this retrospective case-control study, consecutive PD outpatients fulfilling criteria for DDS were assessed over a 6-year period (2005-2011). They were compared with 70 PD cases matched for age at onset, gender and disease duration, and with 1281 subjects with motor fluctuations and dyskinesias. DDS patients and matched controls underwent extensive neuropsychological assessment. Strategies for DDS patients management and the outcome at the last follow-up visit were recorded.

RESULTS

Thirty-five patients with DDS were identified, reporting history of depression, family history of PD and drug abuse, greater difference between 'Off' versus 'On' motor symptoms compared to age-matched controls. They had younger age at onset (but not any gender difference) compared to general PD population. Cognitive profile of DDS did not show major abnormalities, including executive functions. DDS patients have been followed up for 3.2±2.1 years and remission was recorded in 40% of cases. Negative DDS outcome was significantly associated with poor caregiver supervision. Sustained remission occurred more commonly on clozapine and on duodenal levodopa infusion and subthalamic nucleus deep brain stimulation (STN-DBS) than on apomorphine pump treatment.

CONCLUSIONS

Clinicians should be aware of risk factors predisposing to DDS. Duodenal levodopa infusion and, less consistently, STN-DBS were more commonly associated with DDS remission. Effective caregiving plays a key role in long-term behavioural outcome.

Biomarkers in Parkinson's disease (recent update)

Parkinson's disease (PD) is the second most common neurodegenerative disorder mostly affecting the aging population over sixty. Cardinal symptoms including, tremors, muscle rigidity, drooping posture, drooling, walking difficulty, and autonomic symptoms appear when a significant number of nigrostriatal dopaminergic neurons are already destroyed. Hence we need early, sensitive, specific, and economical peripheral and/or central biomarker(s) for the differential diagnosis, prognosis, and treatment of PD. These can be classified as clinical, biochemical, genetic, proteomic, and neuroimaging biomarkers. Novel discoveries of genetic as well as nongenetic biomarkers may be utilized for the personalized treatment of PD during preclinical (premotor) and clinical (motor) stages. Premotor biomarkers including hyper-echogenicity of substantia nigra, olfactory and autonomic dysfunction, depression, hyposmia, deafness, REM sleep disorder, and impulsive behavior may be noticed during preclinical stage. Neuroimaging biomarkers (PET, SPECT, MRI), and neuropsychological deficits can facilitate differential diagnosis. Single-cell profiling of dopaminergic neurons has identified pyridoxal kinase and lysosomal ATPase as biomarker genes for PD prognosis. Promising biomarkers include: fluid biomarkers, neuromelanin antibodies, pathological forms of α-Syn, DJ-1, amyloid β and tau in the CSF, patterns of gene expression, metabolomics, urate, as well as protein profiling in the blood and CSF samples. Reduced brain regional N-acetyl-aspartate is a biomarker for the in vivo assessment of neuronal loss using magnetic resonance spectroscopy and T2 relaxation time with MRI. To confirm PD diagnosis, the PET biomarkers include [(18)F]-DOPA for estimating dopaminergic neurotransmission, [(18)F]dG for mitochondrial bioenergetics, [(18)F]BMS for mitochondrial complex-1, [(11)C](R)-PK11195 for microglial activation, SPECT imaging with (123)Iflupane and βCIT for dopamine transporter, and urinary salsolinol and 8-hydroxy, 2-deoxyguanosine for neuronal loss. This brief review describes the merits and limitations of recently discovered biomarkers and proposes coenzyme Q10, mitochondrial ubiquinone-NADH oxidoreductase, melatonin, α-synculein index, Charnoly body, and metallothioneins as novel biomarkers to confirm PD diagnosis for early and effective treatment of PD.

Valproate as a treatment for dopamine dysregulation syndrome (DDS) in Parkinson's disease

It has been previously well established that the use of dopaminergic agents in Parkinson's disease may contribute to behavioral disturbances such as dopamine dysregulation syndrome (DDS), impulse control disorders (ICD), and punding. ICD and punding have been most commonly addressed by reducing dose or by discontinuing the use of a dopamine agonist. Treatment of DDS has proven more challenging, and to date there has been no standard approach. In this paper, we review a series of four patients who met criteria for DDS, who were all refractory to medication adjustments. The DDS symptoms responded by the addition of valproic acid in all cases.

An update on the management of juvenile and young-onset Parkinson’s disease

Early-onset Parkinson’s disease (PD) denotes onset of the disease below the age of 40 years. Patients tend to have a slower disease progression, an increased rate of dystonia, an increased rate of dyskinesias in response to L-3,4-dihydroxyphenylalanine and a lower rate of dementia compared with those in late-onset PD. Early-onset PD patients may experience more social and psychosocial conflict compared with late-onset patients and these factors would contribute to greater impairment of quality of life. Unemployment due to disability or early retirement may be causes for these conflicts. We have to take these factors into account whenever we institute drug therapy in early-onset PD. There is no randomized controlled study on early-onset PD; however, we may make a reasonable decision by considering the data on PD in general and clinical characteristics of early-onset patients. The management of motor and non-motor symptoms of early-onset PD patients is reviewed here.

Dopamine dysregulation syndrome and deep brain stimulation of the subthalamic nucleus in Parkinson's disease

Dopamine dysregulation syndrome is a complication of the dopaminergic treatment in Parkinson's disease that may be very disabling due to the negative impact that compulsive medication use may have on patients' social, psychological, and physical functioning. The relationship between subthalamic nucleus deep brain stimulation and dopamine dysregulation syndrome in patients with Parkinson's disease remains unclear. Deep brain stimulation may improve, worsen, or have no effect on preoperative dopamine dysregulation syndrome. Moreover, dopamine dysregulation syndrome may appear for the first time after deep brain stimulation of the subthalamic nucleus. The outcome of postoperative dopamine dysregulation syndrome is poor despite stimulation and medication adjustments. Here we review the phenomenology and neurobiology of this disorder, discuss possible mechanisms that may underlie the diverse outcomes of dopamine dysregulation syndrome after subthalamic nucleus deep brain stimulation, and propose management strategies.