Phasic dysfunction of dopamine transmission in Tourette's syndrome evaluated with 99mTc TRODAT-1 imaging

Pharmacological treatment of Tourette's syndrome: from the past to the future

Tourette's syndrome (TS) is a neuropsychiatric disease featuring tics and vocal tics, with a prevalence of approximately 1%, including 75% of the total number of male patients. TS seriously disturbs the patients' career, education, and life and brings a serious and unbearable psychological burden to the patients themselves and their families. At present, there are no specific clinical medications recommended for treating TS. Therefore, it is necessary to select the appropriate medication for symptomatic treatment based on the doctor's personal experience and the patient's symptoms, with the main goal of relieving symptoms, thus improving the patient's social skills and psychological problems. Here we conducted a comprehensive search on PubMed to review and organize the history and current status of the development of drug therapy for TS through a timeline format. We also systematically evaluated the effects of each drug for TS treatment to summarize the current problems and new research directions and to provide some ideas for clinical treatment.

The multimodality neuroimage findings in individuals with Tourette syndrome

Chronic tic disorder and Gilles de la Tourette syndrome are very common childhood-onset diseases. However, the pathophysiology underlying these disorders is not yet clear and most studies focus on the disinhibition of the cortico-striatal-thalamo-cortical circuit. Although dysfunction of this circuit is possible, routine clinical neuroimaging studies such as T1-weighted or T2-weighted MRI usually reveal normal results. Therefore, special neuroimaging techniques may be needed to investigate the possible microstructural or functional changes in the brain. Previous structural studies, such as those using diffusion tensor imaging, and volumetric MRI studies, revealed the main abnormalities to be located in the cortico-striatal-thalamo-cortical circuit and to be related to brain regions such as basal ganglion, thalamus, frontal cortex, and motor cortex. Some other potential regions, such as the amygdala, hippocampus or cerebellum, are also occasionally reported. Perfusion studies, such as those using positron emission tomography or functional MRI, also suggest hemodynamic changes over those brain regions related to the cortico-striatal-thalamo-cortical circuit. However, the results can be different in adult and pediatric groups, and neuroimaging findings are also inconsistent between different studies, which may reflect the high diversity of this disease or differences in enrolled patient groups with different comorbidities. Therefore, in this review article, we will focus on the neuroimaging findings relating to Tourette syndrome in different age groups using different imaging techniques.

Drug and Non-drug Treatment of Tourette Syndrome

Background:

Tourette Syndrome (TS) is a neurodevelopmental disorder characterized by multiple repetitive motor and vocal tics. In most patients, its clinical course has a waxing and waning nature and most patients, usually children, will benefit from tolerant environmental and psychoeducation. Patients with more complicated tics, in particular, those with significant comorbidities will require drug therapy.

Objective:

The present paper is a mini-review of the current therapeutic arsenal for TS with reference to drug and non-drug management approach.

Methods:

A systematic survey of medical literature regarding the treatment decision making and the reported clinical trials or accumulating experience with different medications or other therapeutic modalities which were proven beneficial over the years.

Results:

Reviewing the literature indicates that dopamine antagonists, such as haloperidol and pimozoide, are the most reliable agents in terms of treatment response. Due to numerous adverse effects, newer atypical anti-psychotic drugs have been shown effective. Other widely accepted medications include alpha-2 adrenergic agonists, benzamides, dopamine depleting agents, benzodiazepines and dopamine depleting agents. In more selective and intractable cases botulinum toxin, dopamine agonists and cannabinoids should be also considered. Non-pharmacologic therapies reported beneficial effects, which include on the one hand, non-invasive behavioral techniques, such as comprehensive behavior therapy for tics. While on the other hand, in cases with particular protracted pharmaco-resistant tics electric stimulation techniques, such as deep brain stimulation, have been shown to be successful.

Conclusion:

Currently, there are numerous multifarious options for treatment of tics and other comorbid symptoms of TS. Nevertheless, treatment options and decision-making algorithms are still a clinical challenge.

Area Covered:

A step by step decision-making and various drugs and non-pharmacologic modalities appropriate for the management of TS.

Dopaminergic Disturbances in Tourette Syndrome: An Integrative Account

Tourette syndrome (TS) is thought to involve dopaminergic disturbances, but the nature of those disturbances remains controversial. Existing hypotheses suggest that TS involves 1) supersensitive dopamine receptors, 2) overactive dopamine transporters that cause low tonic but high phasic dopamine, 3) presynaptic dysfunction in dopamine neurons, or 4) dopaminergic hyperinnervation. We review evidence that contradicts the first two hypotheses; we also note that the last two hypotheses have traditionally been considered too narrowly, explaining only small subsets of findings. We review all studies that have used positron emission tomography and single-photon emission computerized tomography to investigate the dopaminergic system in TS. The seemingly diverse findings from those studies have typically been interpreted as pointing to distinct mechanisms, as evidenced by the various hypotheses concerning the nature of dopaminergic disturbances in TS. We show, however, that the hyperinnervation hypothesis provides a simple, parsimonious explanation for all such seemingly diverse findings. Dopaminergic hyperinnervation likely causes increased tonic and phasic dopamine. We have previously shown, using a computational model of the role of dopamine in basal ganglia, that increased tonic dopamine and increased phasic dopamine likely increase the propensities to express and learn tics, respectively. There is therefore a plausible mechanistic link between dopaminergic hyperinnervation and TS via increased tonic and phasic dopamine. To further bolster this argument, we review evidence showing that all medications that are effective for TS reduce signaling by tonic dopamine, phasic dopamine, or both.

The relationship between the striatal dopamine transporter and novelty seeking and cognitive flexibility in opioid dependence

Novelty seeking (NS) is a core personality trait that primes the susceptibility to drug addiction. Striatal dopamine activity contributes to cognitive flexibility, an important cognitive strategy to inhibit impulsivity and compulsive drug-seeking behavior. Evidence supports the association between dopamine and NS. Opioid-dependent patients show higher levels of NS, and repeated opioid exposure can cause cognitive deficits including poor cognitive flexibility and impaired impulse control. However, in opioid-dependent patients, the link between NS, striatal dopamine activity, and cognitive flexibility is still unclear. We recruited 22 opioid-dependent individuals and 30 age- and sex-matched healthy controls. Single-photon emission computed tomography with [^99mTc]TRODAT-1 as a ligand was used to measure the striatal dopamine transporter (DAT) availability. The Trail Making Test (TMT) was performed to assess cognitive flexibility. Cloninger's Tridimensional Personality Questionnaire (TPQ) was used to measure NS. We found that in opioid-dependent patients, the striatal DAT availability was lower and negatively associated with TMT Part B÷Part A. Moreover, an inverted-U shape significantly matched the scores of NS as a function of the striatal DAT availability, with maximum NS potential in the midrange of the DAT availability. An extra sum-of-squares F test was conducted, indicating that a quadratic model fitted the association between the DAT and NS better than a linear model did. In brief, in opioid-dependent patients, the striatal DAT availability is nonlinearly linked to NS and linearly linked to cognitive flexibility. The role of the striatal DAT in the transition from controlled to compulsive opioid use warrants further research.

Reduced striatal dopamine transporter density associated with working memory deficits in opioid-dependent male subjects: a SPECT study

Research on the effects of repeated opioid use on striatal dopamine transporters has yielded inconsistent results, possibly confounded by a history of methamphetamine or methadone exposure in opioid-dependent individuals. Previous studies have shown that striatal dopamine transporter density is positively correlated with the cognitive performance of healthy volunteers. This study aimed to investigate changes in striatal dopamine transporter density and their functional significance in opioid-dependent individuals. Single-photon emission computed tomography with [(99m) Tc]TRODAT-1 as a ligand was used to measure striatal dopamine transporter levels in 20 opioid-dependent individuals and 20 age- and sex-matched healthy controls. Opioid-dependent individuals had no history of methamphetamine or methadone use. The Wisconsin Card Sorting Test (WCST) was performed to assess neurocognitive function. We found that compared with healthy controls, opioid-dependent individuals showed a significant reduction in striatal dopamine transporter density. They also showed poorer performance on the WCST in terms of the trials administered, total errors, perseverative responses, perseverative errors, and non-perseverative errors. Striatal dopamine transporter levels negatively correlated with non-perseverative errors not only in opioid-dependent individuals but also in healthy controls. These findings suggest that in human, repeated opioid exposure reduces striatal dopamine transporter density, which can be associated with non-perseverative errors. Non-perseverative errors may be one of the more sensitive parameters in WCST to identify working memory deficits associated with striatal dopamine transporter reduction. Moreover, we suggest that whether opioid-associated neurotoxicity is reversible depends on the brain region.

Association between DRD2/ANKK1 TaqIA Polymorphism and Susceptibility with Tourette Syndrome: A Meta-Analysis

Background

Genetic factors are important in the pathogenesis of Tourette syndrome (TS). Notably, Dopamine receptor D2 (DRD2) gene has been suggested as a possible candidate gene for this disorder. Several studies have demonstrated that DRD2/ANKK1 TaqIA polymorphism is associated with an increased risk of developing TS. However, past results remain conflicting. We addressed this controversy by performing a meta-analysis of the relationship between DRD2/ANKK1 TaqIA polymorphism and TS.

Methods

Literature was searched in multiple databases including PUBMED, COCHRANE and WEB OF SCIENCE up to July 2014. The number of the genotypes for DRD2/ANKK1 TaqIA in the TS and control subjects was extracted and statistical analysis was performed using Review Manager 5.0.16 and Stata 12.0 software. Summary odds ratios (ORs) and 95% confidence intervals (95%CIs) were utilized to calculate the risk of TS with DRD2/ANKK1 TaqIA. Stratified analysis based on ethnicity was also conducted.

Results

523 patients with TS, 564 controls and 87 probands plus 152 relatives from five published studies were finally involved in this meta-analysis. Combined analysis revealed that the overall ORs for the DRD2/ANKK1 TaqIA A1 allele were 1.69 (95%CIs = 1.42-2.00) in the fixed-effect model and 1.66 (95%CIs = 1.33-2.08) in the random-effects model. Stratification by ethnicity indicated the TaqIA A1 allele was significantly associated with TS in Caucasians (fixed-effect model: OR=1.75, 95%CI = 1.43-2.16; random-effect model: OR=1.69, 95%CI = 1.25-2.28) and in Asians (OR=1.54, 95%CI = 1.12-2.10). Meta-analysis of the A1A1 vs. A2A2 (homozygous model), A1A2 vs. A2A2 (heterozygous model) and A1A1+A1A2 vs. A2A2 (dominant model) of this polymorphism revealed a significant association with TS in overall populations and Caucasians.

Conclusions

This meta-analysis suggested that the DRD2/ANKK1 TaqIA polymorphism might contribute to TS susceptibility, especially in Caucasian population. However, further investigation with a larger number of worldwide studies should be conducted to verify the association.

Levodopa effects on [ (11)C]raclopride binding in the resting human brain

Rationale: Synaptic dopamine (DA) release induced by amphetamine or other experimental manipulations can displace [ ¹¹C]raclopride (RAC*) from dopamine D2-like receptors. We hypothesized that exogenous levodopa might increase dopamine release at striatal synapses under some conditions but not others, allowing a more naturalistic assessment of presynaptic dopaminergic function. Presynaptic dopaminergic abnormalities have been reported in Tourette syndrome (TS).

Objective: Test whether levodopa induces measurable synaptic DA release in healthy people at rest, and gather pilot data in TS.

Methods: This double-blind crossover study used RAC* and positron emission tomography (PET) to measure synaptic dopamine release 4 times in each of 10 carbidopa-pretreated, neuroleptic-naïve adults: before and during an infusion of levodopa on one day and placebo on another (in random order). Five subjects had TS and 5 were matched controls. RAC* binding potential (BP _ND) was quantified in predefined anatomical volumes of interest (VOIs). A separate analysis compared BP _ND voxel by voxel over the entire brain.

Results: DA release declined between the first and second scan of each day (p=0.012), including on the placebo day. Levodopa did not significantly reduce striatal RAC* binding and striatal binding did not differ significantly between TS and control groups. However, levodopa’s effect on DA release differed significantly in a right midbrain region (p=0.002, corrected), where levodopa displaced RAC* by 59% in control subjects but increased BP _ND by 74% in TS subjects.

Discussion: Decreased DA release on the second scan of the day is consistent with the few previous studies with a similar design, and may indicate habituation to study procedures. We hypothesize that mesostriatal DA neurons fire relatively little while subjects rest, possibly explaining the non-significant effect of levodopa on striatal RAC* binding. The modest sample size argues for caution in interpreting the group difference in midbrain DA release with levodopa.

Emerging treatment strategies in Tourette syndrome: what's in the pipeline?

Tourette syndrome (TS) is a neurodevelopmental disorder characterized by multiple motor/phonic tics and a wide spectrum of behavioral problems (e.g., complex tic-like symptoms, attention deficit hyperactivity disorder, and obsessive-compulsive disorder). TS can be a challenging condition even for the specialists, because of the complexity of the clinical picture and the potential adverse effects of the most commonly prescribed medications. Expert opinions and consensus guidelines on the assessment and treatment of tic disorders have recently been published in Europe and Canada. All pharmacological treatment options are mere symptomatic treatments that alleviate, but do not cure, the tics. We still lack evidence of their effects on the natural long-term course and on the prognosis of TS and how these treatments may influence the natural course of brain development. The most commonly prescribed drugs are dopamine antagonists, such as typical (e.g., haloperidol, pimozide) and atypical neuroleptics (e.g., risperidone, aripiprazole), and α-2-adrenoreceptor agonists (e.g., clonidine). However, several studies have investigated the efficacy and tolerability of alternative pharmacological agents that may be efficacious, including the newest atypical antipsychotic agents (e.g., paliperidone, sertindole), tetrabenazine, drugs that modulate acetylcholine (e.g., nicotine) and GABA (e.g., baclofen, levetiracetam), tetrahydrocannabinol, botulinum toxin injections, anticonvulsant drugs (e.g., topiramate, carbamazepine), naloxone, lithium, norepinephrine, steroid 5α reductase, and other neuroactive agents (buspirone, metoclopramide, phytostigmine, and spiradoline mesylate). As regards nonpharmacological interventions, some of the more recent treatments that have been studied include electroconvulsive therapy and repetitive transcranial magnetic stimulation. This review focuses primarily on the efficacy and safety of these emerging treatment strategies in TS.

Tourette syndrome and other tic disorders in childhood, adolescence and adulthood

BACKGROUND

Tourette syndrome is a combined motor and vocal tic disorder that begins in childhood and takes a chronic course. It arises in about 1% of all children, with highly varying severity. Transient and usually mild tics are seen in as many as 15% of all children in elementary school. The diagnosis is often delayed by several years.

METHODS

We selectively reviewed the pertinent literature, including the guidelines of the European Society for the Study of Tourette Syndrome for the diagnosis and treatment of tic disorders.

RESULTS

Tic disorders usually take a benign course, with spontaneous improvement in adolescence in about 90% of patients. Psychoeducation is the basis of treatment in each case and almost always brings marked emotional relief. Specific treatment is needed only for more severe tics and those that cause evident psychosocial impairment. 80-90% of patients with Tourette syndrome have comorbidities (attention deficit-hyperactivity disorder, obsessive-compulsive disorder, depression, anxiety, emotional dysregulation, autoaggression), which often impair their quality of life more than the tics do and therefore become the main target of treatment. There is little evidence for the efficacy of treatment for tics. Small-scale controlled studies with a brief follow-up period have been carried out for some neuroleptic drugs. Behavior therapy should be tried before drug treatment. A further option for very severely affected adults is deep brain stimulation.

CONCLUSION

Because of the low level of the available evidence, no definitive recommendations can be made for the treatment of tics.

The rCBF brain mapping in adolescent ADHD comorbid developmental coordination disorder and its changes after MPH challenging

BACKGROUND

Comorbid developmental coordination disorder (DCD) in the patients with attention-deficit hyperactivity disorder (ADHD) often complicated the treatment strategy. Methylphenidate (MPH) improves the coordination problem in patients with ADHD.

AIM

The study intended to investigate the pathophysiology and the mechanisms of MPH in comorbid DCD of the adolescents with ADHD.

METHODS

Brain images using technetium-99m ethyl cysteinate dimmer ((99m)Tc-ECD) single photon emission computed tomography (SPECT) were done in 10 drug-naïve adolescents with ADHD without DCD and 5 adolescents with ADHD comorbid DCD. The baseline rCBF and changes of rCBF after 10 mg MPH challenge between two groups were compared using statistical parametric mapping (SPM99) analysis.

RESULTS

Lower rCBF of bilateral frontal lobe, inferior parental lobe, and increased rCBF of right posterior cingulate gyrus, anterior lobe of cerebellum were found in ADHD comorbid DCD group compared to ADHD without DCD group. Decreased rCBF in the right occipital, inferior temporal lobe was found in ADHD comorbid DCD group after MPH while ADHD alone group revealed increased rCBF in bilateral occipital lobe.

CONCLUSIONS

The results help us understand the pathophysiology of DCD in ADHD adolescents. The different rCBF response to MPH provides a clue for future intervention of DCD in ADHD adolescents.

Reward circuitry dysfunction in psychiatric and neurodevelopmental disorders and genetic syndromes: animal models and clinical findings

This review summarizes evidence of dysregulated reward circuitry function in a range of neurodevelopmental and psychiatric disorders and genetic syndromes. First, the contribution of identifying a core mechanistic process across disparate disorders to disease classification is discussed, followed by a review of the neurobiology of reward circuitry. We next consider preclinical animal models and clinical evidence of reward-pathway dysfunction in a range of disorders, including psychiatric disorders (i.e., substance-use disorders, affective disorders, eating disorders, and obsessive compulsive disorders), neurodevelopmental disorders (i.e., schizophrenia, attention-deficit/hyperactivity disorder, autism spectrum disorders, Tourette's syndrome, conduct disorder/oppositional defiant disorder), and genetic syndromes (i.e., Fragile X syndrome, Prader-Willi syndrome, Williams syndrome, Angelman syndrome, and Rett syndrome). We also provide brief overviews of effective psychopharmacologic agents that have an effect on the dopamine system in these disorders. This review concludes with methodological considerations for future research designed to more clearly probe reward-circuitry dysfunction, with the ultimate goal of improved intervention strategies.

Translating laboratory discovery to the clinic: from nicotine and mecamylamine to Tourette's, depression, and beyond

The early development of novel nicotinic drugs for Tourette's and depression was a very long journey in discovery, which began with basic behavioral neuroscience studies aimed at understanding how cholinergic and dopaminergic systems interact in the basal ganglia to control goal directed movement. These early rodent studies with nicotine and dopamine antagonists formed the basis for investigating a potentially improved treatment for children suffering from Tourette's syndrome (TS). Clinically, the research trajectory first focused on studies employing the use of nicotine gum to potentiate the therapeutic effect of the dopamine receptor antagonist, haloperidol, in patients with TS. These projects led to the discovery of a new use for a decades-old blood pressure medication, mecamylamine, a nicotine antagonist, which also appeared to provide symptomatic relief in some TS patients when used clinically and was found to reduce symptoms of mood instability and depression. This unexpected discovery led to a new hypothesis regarding the mechanism of action of antidepressants as well as a series of successful independent trials employing mecamylamine, and its active enantiomer, TC5214, as an augmenting agent in the treatment of major depression. This article is a chronological mini review of these basic and clinical translational studies on nicotinic therapeutics for Tourette's syndrome and depression over the past 25 years.

Pharmacological treatment of tic disorders and Tourette Syndrome

The present review gives an overview of current pharmacological treatment options of tic disorders and Tourette Syndrome (TS). After a short summary on phenomenology, clinical course and comorbid conditions we review indications for pharmacological treatment in detail. Unfortunately, standardized and large enough drug trials in TS patients fulfilling evidence based medicine standards are still scarce. Treatment decisions are often guided by individual needs and personal experience of treating clinicians. The present recommendations for pharmacological tic treatment are therefore based on both scientific evidence and expert opinion. As first-line treatment of tics risperidone (best evidence level for atypical antipsychotics) or tiapride (largest clinical experience in Europe and low rate of adverse reactions) are recommended. Aripiprazole (still limited but promising data with low risk for adverse reactions) and pimozide (best evidence of the typical antipsychotics) are agents of second choice. In TS patients with comorbid attention deficit hyperactivity disorder (ADHD) atomoxetine, stimulants or clonidine should be considered, or, if tics are severe, a combination of stimulants and risperidone. When mild to moderate tics are associated with obsessive-compulsive symptoms, depression or anxiety sulpiride monotherapy can be helpful. In more severe cases the combination of risperidone and a selective serotonin reuptake inhibitor should be given. In summary, further studies, particularly randomized, double-blind, placebo-controlled trials including larger and/or more homogenous patient groups over longer periods are urgently needed to enhance the scientific basis for drug treatment in tic disorders. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Update on the role of antipsychotics in the treatment of Tourette syndrome

Tourette syndrome (TS) is a neuropsychiatric disorder with typical onset in childhood and characterized by chronic occurrence of motor and vocal tics. The disorder can lead to serious impairments of both quality of life and psychosocial functioning, particularly for those individuals displaying complex tics. In such patients, drug treatment is recommended. The pathophysiology of TS is thought to involve a dysfunction of basal ganglia-related circuits and hyperactive dopaminergic innervations. Congruently, dopamine receptor antagonism of neuroleptics appears to be the most efficacious approach for pharmacological intervention. To assess the efficacy of the different neuroleptics available, a systematic, keyword-related search in PubMed (National Library of Medicine, Washington, DC) was undertaken. Much information on the use of antipsychotics in the treatment of TS is based on older data. Our objective was to give an update and therefore we focused on papers published in the last decade (between 2001 and 2011). Accordingly, the present review aims to summarize the current and evidence-based knowledge on the risk-benefit ratio of both first and second generation neuroleptics in TS.

Striatal dopamine transporter binding for predicting the development of delayed neuropsychological sequelae in suicide attempters by carbon monoxide poisoning: A SPECT study

Carbon monoxide poisoning (COP) after charcoal burning results in delayed neuropsychological sequelae (DNS), which show clinical resemblance to Parkinson's disease, without adequate predictors at present. This study examined the role of dopamine transporter (DAT) binding for the prediction of DNS. Twenty-seven suicide attempters with COP were recruited. Seven of them developed DNS, while the remainder did not. The striatal DAT binding was measured by single photon emission computed tomography with (99m)Tc-TRODAT. The specific uptake ratio was derived based on a ratio equilibrium model. Using a logistic regression model, multiple clinical variables were examined as potential predictors for DNS. COP patients with DNS had a lower binding on left striatal DAT binding than patients without DNS. Logistic regression analysis showed that a combination of initial loss of consciousness and lower left striatal DAT binding predicted the development of DNS. Our data indicate that the left striatal DAT binding could help to predict the development of DNS. This finding not only demonstrates the feasibility of brain imaging techniques for predicting the development of DNS but will also help clinicians to improve the quality of care for COP patients.

European clinical guidelines for Tourette syndrome and other tic disorders. Part II: pharmacological treatment

To develop a European guideline on pharmacologic treatment of Tourette syndrome (TS) the available literature was thoroughly screened and extensively discussed by a working group of the European Society for the Study of Tourette syndrome (ESSTS). Although there are many more studies on pharmacotherapy of TS than on behavioral treatment options, only a limited number of studies meets rigorous quality criteria. Therefore, we have devised a two-stage approach. First, we present the highest level of evidence by reporting the findings of existing Cochrane reviews in this field. Subsequently, we provide the first comprehensive overview of all reports on pharmacological treatment options for TS through a MEDLINE, PubMed, and EMBASE search for all studies that document the effect of pharmacological treatment of TS and other tic disorders between 1970 and November 2010. We present a summary of the current consensus on pharmacological treatment options for TS in Europe to guide the clinician in daily practice. This summary is, however, rather a status quo of a clinically helpful but merely low evidence guideline, mainly driven by expert experience and opinion, since rigorous experimental studies are scarce.

Functional neuroimaging in Tourette syndrome

Functional neuroimaging of neuropsychiatric disorders is a complex discipline requiring skills in medical science, philosophy, and technical physics. This review first examines the broad categories of functional imaging studies that have been utilized in this area, comparing the strengths and weaknesses of each approach. This review then looks at much of the available literature on functional imaging in Tourette syndrome (TS) and provides a synthesis of data. The review will also examine the different methodologies employed and will suggest which methodologies are most likely to lead to elucidation of the pathophysiology of TS and related conditions.

Involvement of nigrostriatal pathway in Japanese encephalitis with movement disorders: evidence from 99mTc-TRODAT-1 and 123I-IBZM SPECT imagings

PURPOSE

The purpose of this study was to evaluate molecular evidence of nigrostriatal pathway involvement in Japanese encephalitis (JE) survivors with movement complications.

METHODS

Three JE patients were recruited. All had cranial magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) studies with (99m)Tc-TRODAT-1 and (123)I-IBZM.

RESULTS

Cranial MRI revealed involvement of bilateral thalami, substantia nigra, and medial temporal lobes in all three patients, but only case 1 had additional bilateral basal ganglia involvement. The (99m)Tc-TRODAT-1 SPECT for presynaptic dopamine transporter imaging disclosed asymmetrical decreases in bilateral striatal uptake in all three patients. However, the (123)I-IBZM SPECT imaging for postsynaptic D2 dopamine receptors (D2Rs) revealed inconsistent abnormalities including asymmetrical bilateral decreases (case 1), unilateral decrease (case 2), and bilateral increases (case 3) in striatal uptakes.

CONCLUSION

Data have suggested that presynaptic dopaminergic neurons in JE patients are more susceptible to JE virus than postsynaptic striatal neurons. The degree of movement impairment was more closely correlated to the degree of D2Rs disruption seen in (123)I-IBZM SPECT imaging.