Comparative Analysis of Deutetrabenazine and Valbenazine as VMAT2 Inhibitors for Tardive Dyskinesia: A Systematic Review.

Background: Tardive Dyskinesia (TD) is a neurological disorder characterized by involuntary movements, often caused by dopamine receptor antagonists. Vesicular Monoamine Transporter 2 (VMAT2) inhibitors, such as valbenazine and deutetrabenazine, have emerged as promising therapies for TD and several clinical trials have shown their efficacy. This study aims to compare the efficacy and safety profile of VMAT2 inhibitors, focusing on a recent trial conducted in the Asian population. Methods: We reviewed the PubMed, Cochrane Library, Embase database, and clinicaltrials.gov between January 2017 and October 2023, using the keywords "tardive dyskinesia" AND ("valbenazine" [all fields] OR " deutetrabenazine " [all fields]) AND "clinical trial". The reviewed articles were studied for efficacy and side effects. Results: An initial search yielded 230 articles, of which 104 were duplicates. Following the title and abstract screening, 25 additional articles were excluded. A full-text review resulted in the exclusion of 96 more articles. Ultimately, four double-blind clinical trials met the inclusion criteria. The deutetrabenazine studies demonstrated significant improvements in Abnormal Involuntary Movement Scale (AIMS) scores compared to placebo, with no difference in adverse events. The valbenazine studies showed favorable results in reducing TD symptoms and were well-tolerated. Discussion: The studies reviewed in this analysis underscore the potential of deutetrabenazine and valbenazine as valuable treatment options for TD in diverse populations. Both medications demonstrated significant improvements in AIMS scores, suggesting their effectiveness in managing TD symptoms. Additionally, they exhibited favorable safety profiles, with low rates of serious adverse events and no significant increase in QT prolongation, parkinsonism, suicidal ideation, or mortality. Conclusion: The studies reviewed highlight the promising efficacy and tolerability of deutetrabenazine and valbenazine as treatments for Tardive Dyskinesia, providing new hope for individuals affected by this challenging condition.

An Evidence-Based Update on Anticholinergic Use for Drug-Induced Movement Disorders.

Drug-induced movement disorders (DIMDs) are associated with use of dopamine receptor blocking agents (DRBAs), including antipsychotics. The most common forms are drug-induced parkinsonism (DIP), dystonia, akathisia, and tardive dyskinesia (TD). Although rare, neuroleptic malignant syndrome (NMS) is a potentially life-threatening consequence of DRBA exposure. Recommendations for anticholinergic use in patients with DIMDs were developed on the basis of a roundtable discussion with healthcare professionals with extensive expertise in DIMD management, along with a comprehensive literature review. The roundtable agreed that "extrapyramidal symptoms" is a non-specific term that encompasses a range of abnormal movements. As such, it contributes to a misconception that all DIMDs can be treated in the same way, potentially leading to the misuse and overprescribing of anticholinergics. DIMDs are neurobiologically and clinically distinct, with different treatment paradigms and varying levels of evidence for anticholinergic use. Whereas evidence indicates anticholinergics can be effective for DIP and dystonia, they are not recommended for TD, akathisia, or NMS; nor are they supported for preventing DIMDs except in individuals at high risk for acute dystonia. Anticholinergics may induce serious peripheral adverse effects (e.g., urinary retention) and central effects (e.g., impaired cognition), all of which can be highly concerning especially in older adults. Appropriate use of anticholinergics therefore requires careful consideration of the evidence for efficacy (e.g., supportive for DIP but not TD) and the risks for serious adverse events. If used, anticholinergic medications should be prescribed at the lowest effective dose and for limited periods of time. When discontinued, they should be tapered gradually.

Meta-analysis and systematic review of vesicular monoamine transporter (VMAT-2) inhibitors in schizophrenia and psychosis.

RATIONALE: Dopamine antagonists induce dopamine receptor supersensitivity. This may manifest in late-appearing movement disorders (tardive dyskinesia (TD). VMAT-2 inhibitors reduce dopaminergic transmission but have limited activity at postsynaptic receptors and so may have antipsychotic activity with lower risk of tardive dyskinesia. METHODS: We conducted a systematic database search from inception to September 2022 for articles describing the use of VMAT-2 inhibitors in psychosis. Inclusion criteria were as follows: Population: adults diagnosed with psychosis or schizophrenia; Intervention: treatment with tetrabenazine, deutetrabenazine or valbenazine; Comparison: comparison with placebo or/and antipsychotic drug; Outcomes: with efficacy outcomes (e.g. Brief Psychiatric Rating Scale (BPRS) change or clinician assessment) and adverse effects ratings (e.g. rating scale or clinician assessment or dropouts); and Studies: in randomised controlled trials and non-randomised studies. RESULTS: We identified 4892 records relating to VMAT-2 inhibitor use of which 5 (173 participants) met our a priori meta-analysis inclusion criteria. VMAT-2 inhibitors were more effective than placebo for the outcome 'slight improvement' (risk ratio (RR) = 1.77 (95% CI 1.03, 3.04)) but not for 'moderate improvement' (RR 2.81 (95% CI 0.27, 29.17). VMAT-2 inhibitors were as effective as active comparators on both measures for-'slight improvement' (RR 1.05 (95% CI 0.6, 1.81)) and 'moderate improvement' (RR 1.11 (95% CI 0.51, 2.42). Antipsychotic efficacy was also suggested by a narrative review of 37 studies excluded from the meta-analysis. CONCLUSIONS: VMAT-2 inhibitors may have antipsychotic activity and may offer promise for treatment of psychosis with the potential for a reduced risk of TD.

A descriptive analysis of spontaneous reports of antipsychotic-induced tardive dyskinesia and other extrapyramidal symptoms in the Japanese Adverse Drug Event Report database.

AimThe aim of this study is to summarize the spontaneous reports of tardive dyskinesia (TD) and extrapyramidal symptoms (EPSs) that occurred in Japan over the past decade. MethodsThe study analyzed TD and EPS cases reported in the Japanese Adverse Drug Event Report database between April 2011 and March 2021. The cases were stratified by the diagnoses of schizophrenia, bipolar disorders, and depressive disorders. ResultsIn total, 800 patients including a total of 171 TD cases and 682 EPS cases were reported in the JADER database across psychiatric diagnosis. The cases were caused by first-generation antipsychotics (FGA, TD: n = 105, EPS: n = 245) and second-generation antipsychotics (SGA, TD: n = 144, EPS: n = 598). The SGA were categorized based on Neuroscience-based Nomenclature (NbN) regarding pharmacological domain and mode of action, which were reported evenly as the offending agents. Among reported treatment and outcome in TD cases (n = 67, 37.6%) and EPS cases (n = 405, 59.3%), the relatively limited number of TD cases were reported as recovered/improved was also limited (n = 32, 47.8%) compared to those of EPS cases (n = 266, 65.7%). Some cases still had residual symptoms or did not recover fully (TD: n = 21, 31.3%, EPS: n = 77, 19.0%). CONCLUSION: Tardive dyskinesia and EPS have been widely reported in Japan over the past decade across psychiatric diagnoses and antipsychotic classes. LIMITATIONS: It is important to acknowledge the presence of reporting bias and the lack of comparators to accurately assess risks. Owing to the nature of spontaneous reporting, the estimation of prevalence is not feasible.

The Extrapyramidal Symptom Rating Scale and Its Abbreviated Version: A Critical Review of Clinimetric Properties.

BACKGROUND: The Extrapyramidal Symptom Rating Scale - Abbreviated (ESRS-A) is an abbreviated version of the Extrapyramidal Symptom Rating Scale (ESRS) with instructions, definitions, and a semi-structured interview that follows clinimetric concepts of measuring clinical symptoms. Similar to the ESRS, the ESRS-A was developed to assess four types of drug-induced movement disorders (DIMD): parkinsonism, akathisia, dystonia, and tardive dyskinesia (TD). SUMMARY: The present review of the literature provides the most relevant clinimetric properties displayed by the ESRS and ESRS-A in clinical studies. Comprehensive ESRS-A definitions, official scale, and basic instructions are provided. ESRS inter-rater reliability was evaluated in two pivotal studies and in multicenter international studies. Inter-rater reliability was high for assessing both antipsychotic-induced movement disorders and idiopathic Parkinson's disease. Guidelines were also established for inter-rater reliability and the rater certification processes. The ESRS showed good concurrent validity with 96% agreement between Abnormal Involuntary Movement Scale (AIMS) for TD-defined cases and ESRS-defined cases. Similarly, concurrent validity for ESRS-A total and subscores for parkinsonism, akathisia, dystonia, and dyskinesia ranged from good to very good. The ESRS was particularly sensitive for detecting DIMD-related movement differences following treatment with placebo, antipsychotics, and antiparkinsonian and antidyskinetic medications. ESRS measurement of drug-induced extrapyramidal symptoms was shown to discriminate extrapyramidal symptoms from psychiatric symptoms. KEY MESSAGES: The ESRS and ESRS-A are valid clinimetric indices for measuring DIMD. They can be valuably implemented in clinical research, particularly in trials testing antipsychotic medications, and in clinics to detect the presence, severity, and response to treatment of movement disorders.

Bacillus Calmette-Guérin Vaccine Attenuates Haloperidol-Induced TD-like Behavioral and Neurochemical Alteration in Experimental Rats.

Tardive dyskinesia (TD) is a hyperkinetic movement disorder that displays unusual involuntary movement along with orofacial dysfunction. It is predominantly associated with the long-term use of antipsychotic medications, particularly typical or first-generation antipsychotic drugs such as haloperidol. Oxidative stress, mitochondrial dysfunction, neuroinflammation, and apoptosis are major pathophysiological mechanisms of TD. The BCG vaccine has been reported to suppress inflammation, oxidative stress, and apoptosis and exert neuroprotection via several mechanisms. Our study aimed to confirm the neuroprotective effect of the BCG vaccine against haloperidol-induced TD-like symptoms in rats. The rats were given haloperidol (1 mg/kg, i.p.) for 21 days after 1 h single administration of the BCG vaccine (2 × 107 cfu). Various behavioral parameters for orofacial dyskinesia and locomotor activity were assessed on the 14th and 21st days after haloperidol injection. On the 22nd day, all rats were euthanized, and the striatum was isolated to estimate the biochemical, apoptotic, inflammatory, and neurotransmitter levels. The administration of the BCG vaccine reversed orofacial dyskinesia and improved motor function in regard to haloperidol-induced TD-like symptoms in rats. The BCG vaccine also enhanced the levels of antioxidant enzymes (SOD, GSH) and reduced prooxidants (MDA, nitrite) and pro-apoptotic markers (Cas-3, Cas-6, Cas-9) in rat brains. Besides this, BCG treatment also restored the neurotransmitter (DA, NE, 5-HT) levels and decreased the levels of HVA in the striatum. The study findings suggest that the BCG vaccine has antioxidant, antiapoptotic, and neuromodulatory properties that could be relevant in the management of TD.

Treatment of severe tardive dyskinesia with concurrent administration of olanzapine, clonazepam, baclofen, and gabapentin: a case report.

BACKGROUND: Long-term use of antipsychotics or other dopamine antagonists can result in the extrapyramidal side effect of tardive dyskinesia (TD).Case presentation: An 18-year-old female patient experienced abnormal speech and behavior and because of an equivocal diagnosis, she was given daily doses of 300 mg of quetiapine and 60 mg of ziprasidone. She had used these medications for 2 years before the appearance of involuntary abnormal movements. These movements, which were classified as TD, steadily worsened and markedly interfered with her daily life. Following a trial-and-error course of therapy with vitamin E, vitamin B6, amantadine, valproic acid sodium, lorazepam, and diazepam, the drugs were gradually reduced and stopped, yet the aberrant movements persisted. Finally, the patient was given olanzapine, clonazepam, baclofen, and gabapentin. The Abnormal Involuntary Movement Scale was used to assess changes in the patient's condition. Her TD was efficiently managed through co-administration of olanzapine, clonazepam, baclofen, and gabapentin. CONCLUSIONS: The possibility of TD inducing by antipsychotic use is a clinical concern, even though atypical antipsychotics decrease the incidence of extrapyramidal side effects, and it cannot be entirely excluded. This report provides useful insights into the management of TD and will help clinicians manage similar cases.

Associations between polymorphisms in the cannabinoid receptor 1 gene, cognitive impairments and tardive dyskinesia in a Chinese population with schizophrenia.

OBJECTIVE: Tardive dyskinesia (TD) is a medically induced movement disorder that occurs as a result of long-term use of antipsychotic medications, commonly seen in patients with schizophrenia (SCZ). The study aimed to investigate the relationship between single nucleotide polymorphisms (SNPs) of the CNR1 gene, TD and cognitive impairments in a Chinese population with SCZ. METHODS: A total of 216 SCZ patients were recruited. The participants were divided into TD and without TD (WTD) groups using the Schooler-Kane International Diagnostic Criteria. The severity of TD was assessed using the Abnormal Involuntary Movement Scale (AIMS). Cognitive function was assessed using the Repeatable Battery for Assessment of Neuropsychological Status (RBANS) scale. Hardy-Weinberg equilibrium tests, chained disequilibrium analyses and haplotype analyses were performed using SHE-sis software. To explore the main effects of TD diagnosis, genotype and cognitive function, as well as interaction effects, analysis of covariance (ANCOVA) was employed. RESULTS: The prevalence of TD was approximately 27.3%. Significant differences were observed in the rs806368 CT genotype and rs806370 TC genotype within the hypercongenic pattern between the male TD and WTD groups (OR = 2.508, 95% CI: 1.055-5.961, p = 0.037; OR = 2.552, 95% CI: 1.073-6.069, p = 0.034). Among TD patients, those carrying the rs806368 CC genotype exhibited higher limb trunk scores (p < 0.05). Moreover, there was a statistically significant difference in visuospatial/construction between the TD and WTD groups (p = 0.04), and a borderline significant difference in visuospatial/construction when considering the interaction between TD diagnosis and genotype at the rs806368 locus (p = 0.05). CONCLUSION: CNR1 rs806368 and rs806370 polymorphisms may play a role in TD susceptibility. Additionally, CNR1 gene polymorphisms were associated with the severity of involuntary movements and cognitive impairments in TD patients.

Levodopa/Carbidopa to Augment the Treatment of Amblyopia: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the published literature on the use of levodopa/carbidopa to augment the treatment of amblyopia. METHODS: Literature searches for English language studies were last conducted in October 2022 in the PubMed database with no date restrictions. The combined searches yielded 55 articles, of which 23 were reviewed in full text. Twelve of these were considered appropriate for inclusion in this assessment and were assigned a level of evidence rating by the panel methodologist. Nine studies were rated level I, and 3 studies were rated level II; there were no level III studies. RESULTS: The duration of treatment was limited to 3 to 16 weeks because of concern about long-term adverse effects such as tardive dyskinesia. This complication was not reported in any of the study participants. The dose of levodopa ranged from 1.5 to 8.3 mg/kg/day, generally divided into 3 daily doses. The carbidopa dose was approximately 25% of the levodopa dose in all treatments. Evidence from these studies indicates that augmenting traditional patch occlusion therapy with the oral administration of levodopa/carbidopa can improve the vision of amblyopic children, but the effect was small (0.17-0.3 logarithm of the minimum angle of resolution [logMAR] units) and only statistically significant when compared with patching alone in 2 of the 12 studies cited. Regression of vision was reported in the majority of studies (9 of 12 reported; range, 0-0.17 logMAR unit regression) after discontinuation of therapy. Short-term side effects of the medications were not consistently reported but were most frequently mild and included headache and nausea. CONCLUSIONS: The best available evidence is currently insufficient to show that augmenting amblyopia therapy using up to 16 weeks of levodopa/carbidopa will result in meaningful improvement in visual acuity. Given the potential for significant side effects such as tardive dyskinesia with long-term therapy, levodopa/carbidopa does not appear to be a viable option for amblyopia therapy FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

[Tardive dyskinesia]. / Tardivnaya diskineziya.

Tardive dyskinesia (TD) is a delayed, often irreversible iatrogenic movement disorder caused by long-term use of that dopamine receptors blocking drugs. Prevention of TD is paramount, and clinicians should follow best practice recommendations for prescribing antipsychotics, as well as reduction the using of dopamine receptor blocking drugs for non-psychiatric prescriptions. Replacement of antipsychotics with lower affinity for D2 receptors drugs, addition of VMAT2 (tetrabenazine), botulinum therapy, amantadine may be effective. In detection and incurable cases, the possibility of neuromodulation of brain structures should be considered. Most methods for testing TD currently have an insufficient level of evidence, although they include recommendations from professional communities. There is a great need for new clinical trials.

The effects of sigma-1 agonist fluvoxamine on experimental induced tardive dyskinesia model in rats.

Tardive dyskinesia (TD) is a persistent involuntary complex movement disorder that is known to occur with long-term antipsychotic treatment. Despite being a well-recognized complication of this treatment, its symptoms are often masked by the antipsychotic agents, only to become apparent upon reducing or terminating the treatment. In an effort to advance our understanding of TD pathophysiology and to identify potential therapies, the current study aimed to establish an animal model of TD by administering haloperidol to rats and to evaluate the efficacy of fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), in ameliorating TD symptoms. The study compared the behavioral and biochemical parameters of rats that were treated with either fluvoxamine, tetrabenazine, haloperidol, or saline (control group). The biochemical parameters of interest included the brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), superoxide dismutase (SOD), and malondialdehyde (MDA). To achieve the study objectives, 32 male Wistar Albino rats were assigned to four different groups. The control group received physiological saline for six weeks. The haloperidol group received 1 mg/kg/ip haloperidol for the first three weeks, followed by two weeks of saline. The haloperidol+fluvoxamine group received 1 mg/kg/ip haloperidol for the first three weeks, followed by 30 mg/kg/ip fluvoxamine. The haloperidol+tetrabenazine group was administered 1 mg/kg/ip haloperidol for the first three weeks, followed by 5 mg/kg/ip tetrabenazine. Behavioral assessments of the rats were performed by measuring vacuous chewing movements. Subsequently, samples were collected from the hippocampus, striatum, and frontal lobe tissues of the rats, and BDNF, NGF, SOD, and MDA levels were measured. The results of the study demonstrated significant differences between the groups with respect to behavioral observations. Furthermore, SOD levels in the hippocampus, as well as BDNF, NGF, and SOD levels in the striatum of the haloperidol+fluvoxamine group were significantly higher than those observed in the haloperidol group. Conversely, MDA levels in the hippocampus were significantly lower in the haloperidol+fluvoxamine group than in the haloperidol group. These findings provide evidence of the beneficial effects of fluvoxamine, acting as a sigma-1 agonist, in treating TD symptoms induced experimentally. The observed benefits were supported by the biochemical investigations performed on brain tissue samples. Therefore, fluvoxamine may be considered as a potential alternative treatment for TD in clinical practice, although further research is needed to corroborate these findings.

Integrative approach for managing tardive dyskinesia: A case report.

Tardive dyskinesia (TD) is a debilitating condition characterized by involuntary movements, often resulting from long-term use of antipsychotic medications. Conventional treatment options for TD are limited, expensive, and show mixed effectiveness. This case report presents successful integrative treatment of TD in a patient with mood disorder using Ayurveda and Yoga therapies. The patient showed significant symptom improvement, with sustained benefits at 8-month follow-up, and without any notable adverse effects. This case highlights the potential of integrative approaches in TD management and emphasizes the need for further research to better understand the underlying mechanisms of such therapies.

[Pharmacological Treatment of Tardive Dyskinesia].

Tardive dyskinesia (TD) is a serious, intractable, and potentially disabling side effect. Adjunctive drug treatment is used after optimizing the causative drugs. This article describes valbenazine, the first drug for treating TD that was recently approved in Japan, clonazepam, and vitamin E.

Withdrawal-Emergent Dyskinesia Related to Benztropine: A Case Report.

INTRODUCTION: Benztropine is an anticholinergic drug used as a therapy for Parkinson's disease and treatment for extrapyramidal side effects. While tardive dyskinesia is an involuntary movement disorder that often occurs gradually after long-term use of medications, it does not commonly present acutely. CASE PRESENTATION: A 31-year-old White woman experiencing psychosis presented with spontaneous, acute-onset dyskinesia induced with the withdrawal of benztropine. She had been followed in our academic outpatient clinic for medication management and intermittent psychotherapy. DISCUSSION: The pathophysiology of tardive dyskinesia is not fully understood, but several hypotheses exist, including the involvement of changes in basal ganglia neuronal systems. To our knowledge, this is the first case report to document acute-onset dyskinesia associated with the withdrawal of benztropine. CONCLUSION: his case report, which describes an atypical response to discontinuing benztropine, might offer the scientific community potential clues to better understand the pathophysiology of tardive dyskinesia.

Impact of Tardive Dyskinesia on Physical, Psychological, Social, and Professional Domains of Patient Lives: A Survey of Patients in the United States.

Objective: To assess the physical, psychological, social, and professional impact of tardive dyskinesia (TD) on patients in the United States.Methods: An online survey (April 2020-June 2021) to assess patient burden of TD was developed using targeted literature review and interviews with clinicians, patients, and caregivers. Survey participants (aged ≥ 18 years) with current diagnoses of TD and schizophrenia, bipolar disorder, or major depressive disorder rated the 7-day impact of TD on their physical, psychological, and social functioning via Likert scales (scored from 1 [least impact] to 5 [most impact]). Impact scores were calculated and summarized descriptively overall by self-reported disease severity and underlying disease. Participants also completed the Work Productivity and Activity Impairment Questionnaire and reported the impact of TD on their underlying psychiatric condition.Results: Overall, 269 patients (mean [SD] age = 40.6 years [9.9]; 74.7% employed) responded to the survey. Mean (SD) impact scores of 3.1 (0.9), 3.5 (1.0), and 3.2 (1.1) were reported in the physical, psychological, and social domains, respectively, and scores increased with reported TD symptom severity. Patients with underlying schizophrenia reported the highest burden for all domains. Patients reported 66.2% activity impairment because of TD. Employed patients (n = 193) indicated 29.1% absenteeism, 68.4% presenteeism, and 73.5% overall work impairment. Over one-third of patients reported skipping/reducing (48.4%) or stopping (39.3%) their antipsychotic medication and stopping visits to clinicians treating their underlying condition (35.7%) because of TD.Conclusion: TD imposes a substantial burden on patients' physical, psychological, social, and professional lives and impacts management of their underlying condition.

Telehealth for Assessing and Managing Tardive Dyskinesia: Expert Insights from a Cross-Disciplinary Virtual Treatment Panel.

Introduction: Publications on the integration of telehealth in the care of patients with movement disorders are increasing, but little has been presented regarding its use in tardive dyskinesia (TD), a drug-induced movement disorder associated with prolonged exposure to dopamine receptor blocking agents. This study was conducted to address that knowledge gap, based on insights from a panel of TD experts. Methods: In 2020, six neurologists, three psychiatrists, and three psychiatric nurse practitioners participated in individual semistructured interviews about in-person and virtual TD assessment and management in their practices. Two virtual roundtables were then conducted to consolidate findings from these interviews. Results: The panel agreed that despite the challenges of virtual TD assessment (e.g., technology issues, difficulty observing entire body, inability to conduct thorough neurological examinations), telehealth can offer benefits (e.g., fewer missed appointments, reduced time/cost, easier access to family/caregiver feedback). The panel also agreed that telehealth should be combined with periodic in-person visits, and they recommended an in-person TD assessment within 6 months before the first virtual visit and at least one in-person assessment every 6 months thereafter. Additional best practices for TD telehealth included implementing video, involving family/caregivers, and providing preappointment instructions to help patients prepare their technology and environment. Conclusions: Telehealth is not a substitute for in-person visits but can be a helpful complement to in-person clinical care. Clinicians can optimize virtual visits in patients at risk of TD by using targeted questions to identify TD and evaluate its impact and by providing education about approved TD treatments.

Tardive Dyskinesia Development, Superoxide Dismutase Levels, and Relevant Genetic Polymorphisms.

Tardive dyskinesia (TD) is a prevalent movement disorder that significantly impacts patients with schizophrenia (SCZ) due to extended exposure to antipsychotics (AP). Several genetic polymorphisms, including superoxide dismutase (SOD) and DRD3 9ser, have been suggested as explanations why some patients suffer from TD. Methods. A PubMed search was used to search relevant articles using the following keywords: "Tardive Dyskinesia and Superoxide Dismutase". Fifty-eight articles were retrieved. Among them, 16 were included in this review. Results. Overall, 58 studies were retrieved from PubMed. Most studies investigated the association between TD and the SOD-related polymorphisms. In addition, previous studies reported an association between TD occurrence and other genetic polymorphisms. Conclusion. This study found that the risk of TD is associated with altered SOD levels and several genetic polymorphisms, including VAL 66 Met and DRD3 9ser.