Dopamine transporter imaging with [123I]-beta-CIT demonstrates presynaptic nigrostriatal dopaminergic damage in Wilson's disease

Defining Parkinson's Disease: Past and Future

Parkinson's disease (PD) is the second most common still relentlessly progressive neurodegenerative disorder with a long period in which the pathophysiological process is already spreading but cardinal motor symptoms are not present. This review outlines the major developments and milestones in our understanding of PD that have shaped the way we define this disorder. Past criteria and definitions of PD have been based on clinical motor manifestations enabling diagnosis of the disease only in later symptomatic stages. Nevertheless, with advancing knowledge of disease pathophysiology and aim of early disease detection, a major shift of the diagnostic paradigm is being advocated towards a biological definition similar to other neurodegenerative disorders including Alzheimer's disease and Huntington's disease, with the ultimate goal of an earlier, disease course modifying therapy. We summarize the major pillars of this possible approach including in vivo detection of neuronal α-synuclein aggregation, neurodegeneration and genetics and outline their possible application in different contexts of use in the frame of biological PD definition.

Distribution of non-ceruloplasmin-bound copper after i.v. 64Cu injection studied with PET/CT in patients with Wilson disease

Background & Aims

In Wilson disease (WD), copper accumulation and increased non-ceruloplasmin-bound copper in plasma lead to liver and brain pathology. To better understand the fate of non-ceruloplasmin-bound copper, we used PET/CT to examine the whole-body distribution of intravenously injected 64-copper (64Cu).

Methods

Eight patients with WD, five heterozygotes, and nine healthy controls were examined by dynamic PET/CT for 90 min and static PET/CT up to 20 h after injection. We measured 64Cu activity in blood and tissue and quantified the kinetics by compartmental analysis.

Results

Initially, a large fraction of injected 64Cu was distributed to extrahepatic tissues, especially skeletal muscle. Thus, across groups, extrahepatic tissues accounted for 45-58% of the injected dose (%ID) after 10 min, and 45-55% after 1 h. Kinetic analysis showed rapid exchange of 64Cu between blood and muscle as well as adipose tissue, with 64Cu retention in a secondary compartment, possibly mitochondria. This way, muscle and adipose tissue may protect the brain from spikes in non-ceruloplasmin-bound copper. Tiny amounts of cerebral 64Cu were detected (0.2%ID after 90 min and 0.3%ID after 6 h), suggesting tight control of cerebral copper in accordance with a cerebral clearance that is 2-3-fold lower than in muscle. Compared to controls, patients with WD accumulated more hepatic copper 6-20 h after injection, and also renal copper at 6 h.

Conclusion

Non-ceruloplasmin-bound copper is initially distributed into a number of tissues before being redistributed slowly to the eliminating organ, the liver. Cerebral uptake of copper is extremely slow and likely highly regulated. Our findings provide new insights into the mechanisms of copper control.

Impact and implications

Maintaining non-ceruloplasmin-bound copper within the normal range is an important treatment goal in WD as this "free" copper is considered toxic to the liver and brain. We found that intravenously injected non-ceruloplasmin-bound copper quickly distributed to a number of tissues, especially skeletal muscle, subcutaneous fat, and the liver, while uptake into the brain was slow. This study offers new insights into the mechanisms of copper control, which may encourage further research into potential new treatment targets.

Clinical trial number

2016-001975-59.

Decoding Neurodegeneration: A Comprehensive Review of Molecular Mechanisms, Genetic Influences, and Therapeutic Innovations

Neurodegenerative disorders often acquire due to genetic predispositions and genomic alterations after exposure to multiple risk factors. The most commonly found pathologies are variations of dementia, such as frontotemporal dementia and Lewy body dementia, as well as rare subtypes of cerebral and cerebellar atrophy-based syndromes. In an emerging era of biomedical advances, molecular-cellular studies offer an essential avenue for a thorough recognition of the underlying mechanisms and their possible implications in the patient's symptomatology. This comprehensive review is focused on deciphering molecular mechanisms and the implications regarding those pathologies' clinical advancement and provides an analytical overview of genetic mutations in the case of neurodegenerative disorders. With the help of well-developed modern genetic investigations, these clinically complex disturbances are highly understood nowadays, being an important step in establishing molecularly targeted therapies and implementing those approaches in the physician's practice.

Dystonia and Parkinson's disease: Do they have a shared biology?

Parkinsonism and dystonia co-occur across many movement disorders and are most encountered in the setting of Parkinson's disease. Here we aim to explore the shared neurobiological underpinnings of dystonia and parkinsonism through the clinical lens of the conditions in which these movement disorders can be seen together. Foregrounding the discussion, we briefly review the circuits of the motor system and the neuroanatomical and neurophysiological aspects of motor control and highlight their relevance to the proposed pathophysiology of parkinsonism and dystonia. Insight into shared biology is then sought from dystonia occurring in PD and other forms of parkinsonism including those disorders in which both can be co-expressed simultaneously. We organize these within a biological schema along with important questions to be addressed in this space.

Nuklearmedizinische Diagnostik beim Morbus Wilson

Wilson's disease is an autosomal recessive disorder of copper metabolism and is caused by a genetic defect on chromosome 13. Nuclear medicine methods can prove the metabolic defect and contribute to the assessment of central neurological deficits.With high specificity and sensitivity, the intravenous radiocopper test enables the diagnosis to be confirmed as the basis for initiating treatment. The oral radiocopper test is used to monitor zinc treatment.[¹²³I]β-CIT-SPECT and [¹²³I]IBZM-SPECT provide functional information of the nigrostriatal system.[¹²³I]β-CIT-SPECT also allows the determination of SERT availability in the hypothalamus/brain stem as a surrogate parameter of depression.Metabolic parameters of the cortex, basal ganglia and cerebellum can be assessed by [¹⁸F]FDG-PET studies.SPECT and [¹⁸F]FDG-PET studies show significant differences between neurological and non-neurological Wilson patients. Overall, only noninvasive in vivo nuclear medicine enables a deeper insight into the pathophysiology of neurological processes in Wilson's disease.

Dopamine transporter (DAT) imaging in Parkinson's disease and related disorders

This review gives an insight into the beginnings of dopamine transporter (DAT) imaging in the early 1990s, focussing on single photon emission tomography (SPECT). The development of the method and its consolidation as a now widely used clinical tool is described. The role of DAT-SPECT in the diagnosis and differential diagnosis of PD, atypical parkinsonian syndromes and several other different neurological disorders is reviewed. Finally the clinical research using DAT-SPECT as a biomarker for the progression of PD, for the detection of a preclinical dopaminergic lesion and its correlation with neuropathological findings is outlined.

Sleep disorders in Wilson disease: a systematic review and meta-analysis

STUDY OBJECTIVES

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism resulting in pathologic accumulation of copper in many organs and tissues. Sleep disorders are highly prevalent in patients with WD. However, both prevalence rates and severity of different sleep disorders in patients with WD vary widely. The aims of the current study were to systematically review and perform a meta-analysis of the association between WD and prevalent sleep disorders, including insomnia, rapid eye movement (REM) sleep behavior disorder (RBD), excessive daytime sleepiness (EDS), sleep-disordered breathing (SDB), restless legs syndrome (RLS), periodic limb movement in sleep (PLM), cataplexy-like episodes (CLEs) and sleep paralysis, and objective sleep characteristics.

METHODS

We performed a systematic search of PubMed, EMBase, the Cochrane Library, PsycINFO and ISI Web of Science for case-control studies. A total of 7 studies with 501 participants were included.

RESULTS

We found that 54.1% of patients with WD experience sleep disorders and up to 7.65-fold higher odds compared to control patients. Specifically, patients with WD had higher rates of RBD, insomnia, and EDS based on self-reported questionnaires. No differences were observed in terms of RLS, PLM, or SDB between patients with WD and control patients. Furthermore, objective sleep disruptions based on polysomnographic studies included prolonged sleep onset latency and REM sleep onset latency, reduced total sleep time and sleep efficiency, higher percentage of stage N1 sleep and lower percentage of stage N2 sleep were observed in patients with WD.

CONCLUSIONS

Our study indicates that sleep disorders are frequent in patients with WD. Future studies should examine the longitudinal association of WD with sleep disturbances.

Copper and the brain noradrenergic system

Copper (Cu) plays an essential role in the development and function of the brain. In humans, genetic disorders of Cu metabolism may cause either severe Cu deficiency (Menkes disease) or excessive Cu accumulation (Wilson disease) in the brain tissue. In either case, the loss of Cu homeostasis results in catecholamine misbalance, abnormal myelination of neurons, loss of normal brain architecture, and a spectrum of neurologic and/or psychiatric manifestations. Several metabolic processes have been identified as particularly sensitive to Cu dis-homeostasis. This review focuses on the role of Cu in noradrenergic neurons and summarizes the current knowledge of mechanisms that maintain Cu homeostasis in these cells. The impact of Cu misbalance on catecholamine metabolism and functioning of noradrenergic system is discussed.

Neurologic impairment in Wilson disease

Neurologic symptoms in Wilson disease (WD) appear at an older age compared to hepatic symptoms and manifest in patients with misdiagnosed liver disease, in patients when the hepatic stage is clinically silent, in the case of non-compliance with anti-copper treatment, or with treatment failure. Neurologic symptoms in WD are caused by nervous tissue damage that is primarily a consequence of extrahepatic copper toxicity. Copper levels in brain tissues as well as cerebrospinal fluid (CSF) are diffusely increased by a factor of 10 and its toxicity involves various mechanisms such as mitochondrial toxicity, oxidative stress, cell membrane damage, crosslinking of DNA, and inhibition of enzymes. Excess copper is initially taken-up and buffered by astrocytes and oligodendrocytes but ultimately causes dysfunction of blood-brain-barrier and demyelination. Most severe neuropathologic abnormalities, including tissue rarefaction, reactive astrogliosis, myelin palor, and presence of iron-laden macrophages, are typically present in the putamen while other basal ganglia, thalami, and brainstem are usually less affected. The most common neurologic symptoms of WD are movement disorders including tremor, dystonia, parkinsonism, ataxia and chorea which are associated with dysphagia, dysarthria and drooling. Patients usually manifest with various combinations of these symptoms while purely monosymptomatic presentation is rare. Neurologic symptoms are largely reversible with anti-copper treatment, but a significant number of patients are left with residual impairment. The approach for symptomatic treatment in WD is based on guidelines for management of common movement disorders. The vast majority of WD patients with neurologic symptoms have abnormalities on brain magnetic resonance imaging (MRI). Pathologic MRI changes include T2 hyperintensities in the basal ganglia, thalami and white matter, T2 hypointensities in the basal ganglia, and atrophy. Most importantly, brain damage and neurologic symptoms can be prevented with an early initiation of anti-copper treatment. Introducing population WD screening, e.g., by exome sequencing genetic methods, would allow early treatment and decrease the neurologic burden of WD.

Misidentification of Wilson Disease as Schizophrenia (1998-2013): Case Report and Review

Wilson's disease (WD) is a neurodegenerative disorder due to copper metabolism. Schizophrenia-like psychosis and delusional disorder are rare forms of psychiatric manifestations of WD. The lack of recognition of these signs and symptoms as being attributable to WD often leads to delays in diagnosis and management. Knowledge about relationship of the psychiatric manifestations to WD can help with the administration of adequate management aimed at both the psychiatric issues and underlying WD. The objectives of this article are to review case reports whose subject is the incorrect diagnosis of schizophrenia or schizophrenia-like syndrome in patients with WD and to detail one case of this mismanagement of the disease. A 35-year-old unmarried Iranian woman presented to the consulting psychiatrist in the emergency room after a suicide attempt due to commanding auditory hallucination. She had previous eleven admissions in psychiatric hospital with major depressive episode with psychotic features, schizoaffective disorders, and then schizophrenia diagnosis. Nineteen years after her first symptoms, it was discovered that the patient was suffering from WD. We searched Google Scholar, Ovid, PsycINFO, CINHAL, and PubMed databases from 1985 to 2015. Finally, 14 researches were entered into the study. Psychiatric manifestations may precede the diagnosis of WD and other symptoms related to neurological or hepatic impairment. Early detection of WD is important to prevent catastrophic outcome. Young patients presenting with psychiatric presentations along with abnormal movement disorder, seizure, or conversion-like symptoms should be evaluate for WD even if signs and symptoms are typically suggestive of schizophrenia or manic episode. An interdisciplinary approach with good collaboration of psychiatrists and neurologists is crucial for WD because early diagnosis and management without delay is an important for good prognosis.

Occupancy of the Zinc-binding Site by Transition Metals Decreases the Substrate Affinity of the Human Dopamine Transporter by an Allosteric Mechanism

The human dopamine transporter (DAT) has a tetrahedral Zn²⁺-binding site. Zn²⁺-binding sites are also recognized by other first-row transition metals. Excessive accumulation of manganese or of copper can lead to parkinsonism because of dopamine deficiency. Accordingly, we examined the effect of Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺ on transport-associated currents through DAT and DAT-H193K, a mutant with a disrupted Zn²⁺-binding site. All transition metals except Mn²⁺ modulated the transport cycle of wild-type DAT with affinities in the low micromolar range. In this concentration range, they were devoid of any action on DAT-H193K. The active transition metals reduced the affinity of DAT for dopamine. The affinity shift was most pronounced for Cu²⁺, followed by Ni²⁺ and Zn²⁺ (= Co²⁺). The extent of the affinity shift and the reciprocal effect of substrate on metal affinity accounted for the different modes of action: Ni²⁺ and Cu²⁺ uniformly stimulated and inhibited, respectively, the substrate-induced steady-state currents through DAT. In contrast, Zn²⁺ elicited biphasic effects on transport, i.e. stimulation at 1 μm and inhibition at 10 μm. A kinetic model that posited preferential binding of transition metal ions to the outward-facing apo state of DAT and a reciprocal interaction of dopamine and transition metals recapitulated all experimental findings. Allosteric activation of DAT via the Zn²⁺-binding site may be of interest to restore transport in loss-of-function mutants.

Brain MRI, Tc-99m HMPAO SPECT and F-18 FP-CIT PET/CT Findings in a Patient with Wilson Disease: A Case Report

A 34-year-old female had experienced head and hand tremors with a dystonic component for 8 months. Brain MRI showed T2 high signal intensity in the periaqueductal region, dorsal midbrain and dorsal upper pons. No abnormal uptake was noted on Tc-99m HMPAO SPECT or F-18 FP-CIT PET/CT. Wilson disease was diagnosed according to the 2008 consensus guideline from the American Association for the Study of Liver Disease and 2012 guideline from the European Association for the Study of the Liver. This case demonstrates T2 signal change in the basal ganglia, excluding the putamen, in a Wilson disease patient with relatively severe clinical findings, but normal Tc-99m HMPAO SPECT and F-18 FP-CIT PET/CT.

SLC transporters as therapeutic targets: emerging opportunities

Solute carrier (SLC) transporters - a family of more than 300 membrane-bound proteins that facilitate the transport of a wide array of substrates across biological membranes - have important roles in physiological processes ranging from the cellular uptake of nutrients to the absorption of drugs and other xenobiotics. Several classes of marketed drugs target well-known SLC transporters, such as neurotransmitter transporters, and human genetic studies have provided powerful insight into the roles of more-recently characterized SLC transporters in both rare and common diseases, indicating a wealth of new therapeutic opportunities. This Review summarizes knowledge on the roles of SLC transporters in human disease, describes strategies to target such transporters, and highlights current and investigational drugs that modulate SLC transporters, as well as promising drug targets.

The role of functional dopamine-transporter SPECT imaging in parkinsonian syndromes, part 2

SUMMARY

The functional imaging technique most widely used in European clinics to differentiate a true parkinsonian syndrome from vascular parkinsonism, drug-induced changes, or essential tremor is dopamine-transporter SPECT. This technique commonly reports dopamine-transporter function, with decreasing striatal uptake demonstrating increasingly severe disease. The strength of dopamine-transporter SPECT is that nigrostriatal degeneration is observed in both clinically inconclusive parkinsonism and early, even premotor, disease. In this clinical review (Part 2), we present the dopamine-transporter SPECT findings in a variety of neurodegenerative diseases, including multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, and dementia with Lewy bodies. The findings in vascular parkinsonism, drug-induced parkinsonism, and essential tremor are also described. It is hoped that this technique will be the forerunner of a range of routinely used, process-specific ligands that can identify early degenerative disease and subsequently guide disease-modifying interventions.

Automated Analysis of (123)I-beta-CIT SPECT Images with Statistical Probabilistic Anatomical Mapping

BACKGROUND

Population-based statistical probabilistic anatomical maps have been used to generate probabilistic volumes of interest for analyzing perfusion and metabolic brain imaging. We investigated the feasibility of automated analysis for dopamine transporter images using this technique and evaluated striatal binding potentials in Parkinson's disease and Wilson's disease.

MATERIALS AND METHODS

We analyzed 2β-Carbomethoxy-3β-(4-(123)I-iodophenyl)tropane ((123)I-beta-CIT) SPECT images acquired from 26 people with Parkinson's disease (M:F = 11:15, mean age = 49 ± 12 years), 9 people with Wilson's disease (M: F = 6:3, mean age = 26 ± 11 years) and 17 normal controls (M:F = 5:12, mean age = 39 ± 16 years). A SPECT template was created using striatal statistical probabilistic map images. All images were spatially normalized onto the template, and probability-weighted regional counts in striatal structures were estimated. The binding potential was calculated using the ratio of specific and nonspecific binding activities at equilibrium. Voxel-based comparisons between groups were also performed using statistical parametric mapping.

RESULTS

Qualitative assessment showed that spatial normalizations of the SPECT images were successful for all images. The striatal binding potentials of participants with Parkinson's disease and Wilson's disease were significantly lower than those of normal controls. Statistical parametric mapping analysis found statistically significant differences only in striatal regions in both disease groups compared to controls.

CONCLUSION

We successfully evaluated the regional (123)I-beta-CIT distribution using the SPECT template and probabilistic map data automatically. This procedure allows an objective and quantitative comparison of the binding potential, which in this case showed a significantly decreased binding potential in the striata of patients with Parkinson's disease or Wilson's disease.

Psychiatric aspects of Wilson disease: a review

OBJECTIVE

To review the current evidence about psychiatric symptoms in Wilson's disease (WD).

METHOD

We searched Ovid, PsychInfo, CINHAL and PubMed databases from May 1946 to May 2012 using the key words Wilson('s) disease in combination with psychiatry, psychiatric, psychosis, schizophrenia, depression, mania, bipolar, mood, anxiety, personality and behavior.

RESULTS

Psychiatric symptoms occur before, concurrent with or after the diagnosis and treatment for WD. Thirty to forty percent of patients have psychiatric manifestations at the time of diagnosis, and 20% had seen a psychiatrist prior to their WD diagnosis. When psychiatric symptoms preceded neurological or hepatic involvement, the average time between the psychiatric symptoms and the diagnosis of WD was 864.3 days. The prevalence of psychiatric disorders in WD patients varies wildly (major depressive disorder, 4-47%; psychosis, 1.4-11.3%). Certain gene mutations of ATP7B may correlate with specific personality traits.

CONCLUSIONS

Psychiatric manifestations represent a significant part of the clinical presentation of WD and can present at any point in the course of the illness. Psychiatric manifestations occurring without overt hepatic or neurologic involvement may lead to misdiagnosis. A better understanding of the psychiatric presentations in WD may provide insights into the underlying mechanisms of psychiatric disorders.

A second extracellular site is required for norepinephrine transport by the human norepinephrine transporter

The human norepinephrine transporter (NET) is implicated in many neurological disorders and is a target of tricyclic antidepressants and nisoxetine (NX). We used molecular docking simulations to guide the identification of residues likely to affect substrate transport and ligand interactions at NET. Mutations to alanine identified a hydrophobic pocket in the extracellular cavity of NET, comprising residues Thr80, Phe317, and Tyr317, which was critical for efficient norepinephrine (NE) transport. This secondary NE substrate site (NESS-2) overlapped the NX binding site, comprising Tyr84, Phe317, and Tyr317, and was positioned ∼11 Å extracellular to the primary site for NE (NESS-1). Thr80 in NESS-2 appeared to be critical in positioning NE for efficient translocation to NESS-1. Three residues identified as being involved in gating the reverse transport of NE (Arg81, Gln314, and Asp473) did not affect NE affinity for NESS-1. Mutating residues adjacent to NESS-2 abolished NET expression (D75A and L76A) or appeared to affect NET folding (S419A), suggesting important roles in stabilizing NET structure, whereas W308A and F388A at the top of NESS-2 abolished both NE transport and NX binding. Our findings are consistent with a multistep model of substrate transport by NET, for which a second, shallow extracellular NE substrate site (NESS-2) is required for efficient NE transport by NET.

Association of dopamine receptor gene polymorphisms with the clinical course of Wilson disease

BACKGROUND

Dopamine receptor D2 (DRD2) polymorphisms are proposed to be important factors in the presentation of neuropsychiatric symptoms in many disorders, including decreased striatum levels of dopamine D2 receptors in Wilson disease. The present study investigated the association between DRD2 gene polymorphisms and clinical manifestation of Wilson disease.

METHODS

Analyzing data from 97 symptomatic Wilson disease patients, we investigated the DRD2 gene polymorphisms rs1800497, rs1799732, and rs12364283. We assessed the polymorphisms impact on the phenotypic presentation of the disease.

RESULTS

Generally, the DRD2 gene polymorphisms had no impact on the hepatic or neuropsychiatric clinical presentation of Wilson disease. However, rs1799732 deletion allele carriers with neuropsychiatric symptoms had earlier onset of WD symptoms by almost 6 years compared with individuals without this allele (22.5 vs. 28.3 years; P < 0.05). This unfavorable effect of the rs1799732 polymorphism was even more pronounced among adenosine triphosphatase 7B gene (ATP7B) p.H1069Q homozygous patients, in whom carriership of the deletion allele was related to earlier initial neuropsychiatric manifestation by 14 years (18.4 vs. 32.2 years; P < 0.01).

CONCLUSIONS

Genetic variation of DRD2, specifically the rs1799732 polymorphism, may produce an earlier clinical presentation of Wilson disease neuropsychiatric symptoms and signs that occur in the course of dopaminergic system impairment due to copper accumulation in the brain. We speculate that this effect may be due to the impact of DRD2 polymorphism on dopamine D2 receptor density, but further studies are needed to understand the mechanisms of such phenotypic effects.

Role of neuroimaging in the evaluation of tremor

The role for neuroimaging in the management of patients with tremor is gradually increasing, particularly with respect to stereotactic neurosurgery and deep brain stimulation where less than 2-mm tolerance is required for accurate electrode placement. The routine use of single photon emission CT technology to image the nigrostriatal dopaminergic system is proving helpful in distinguishing essential and dystonic tremors from neurodegenerative forms of parkinsonism and in improving our understanding of the pathophysiology of rarer tremors.

Emerging structure-function relationships defining monoamine NSS transporter substrate and ligand affinity

Monoamine transporters are a group of transmembrane neurotransmitter sodium symporter (NSS) transporters that play a crucial role in regulating biogenic monoamine concentrations at peripheral and central synapses. Given the key role played by serotonin, dopamine and noradrenaline in addictive and disease states, structure-function studies have been conducted to help guide the development of improved central nervous system therapeutics. Extensive pharmacological, immunological and biochemical studies, in conjunction with three-dimensional homology modeling, have been performed to structurally and functionally characterise the monoamine transporter substrate permeation pathway, substrate selectivity, and binding sites for ions, substrates and inhibitors at the molecular level. However, only recently has it been possible to start to construct an accurate molecular interaction network for the monoamine transporters and their corresponding substrates and inhibitors. Crystal structures of Aquifex aeolicus leucine transporter (LeuT(Aa)), a homologous protein to monoamine transporters that has been experimentally demonstrated to share similar structural folds with monoamine transporters, have been determined in complex with amino acids and inhibitors. The molecular interactions of leucine and tricyclic antidepressants (TCA) has supported many of the predictions based on the mutational studies. Models constructed from LeuT(Aa) are now allowing a rational approach to further clarify the molecular determinants of NSS transporter-ligand complexes, and potentially the ability to better manipulate drug specificity and affinity. In this review, we compare the structure-function relationships of other SLC6 NSS family transporters with monoamine transporters, and discuss possible mechanisms involved in substrate binding and transport, and modes of inhibition by TCAs.

Psychopathology and personality traits in patients with treated Wilson disease grouped according to gene mutations

Wilson disease (WD) is a recessively inherited copper storage disorder mainly affecting liver and brain. Genotype/phenotype correlations have been report ed but as yet not regarding psychic symptoms. Our aim was to investigate if a correlation might exist between genotype and phenotype concerning psychopathology and/or personality traits in patients with treated WD. Nine homozygous and three compound heterozygous Swedish patients were retrospectively investigated, representing four different mutation settings. Psychopathological symptoms were studied using the Comprehensive Psychopathological Rating Scale (CPRS), personality traits using the Karolinska Scales of Personality (KSP) and mutations were analyzed by manifold sequencing. Psychopathological symptoms: Patients with the Trp779Stop mutation had the lowest scores on the total CPRS, due to less pronounced reported CPRS items, as compared to the other three groups of patients. Compound heterozygotes for the His1069Gln/Arg1319Stop mutation showed the highest total CPRS scores. Personality traits: Patients homozygous for the Trp779Stop and the Thr977Met mutations had high scores on Psychopathy related scales whereas patients with His1069Gln/Arg1319Stop mutations had the lowest scores on these scales. Serum ceruloplasmin levels were undetectable in all patients with the Trp779Stop and Thr977Met mutations. The results show a trend towards a genotype/phenotype correlation regarding psychopathological symptoms and personality traits in treated patients with WD. If replicable, these results might contribute to the elucidation of the possible clinical importance of functionally deleterious gene mutations in WD psychopathology and personality traits.

Manganese: recent advances in understanding its transport and neurotoxicity

The present review is based on presentations from the meeting of the Society of Toxicology in San Diego, CA (March 2006). It addresses recent developments in the understanding of the transport of manganese (Mn) into the central nervous system (CNS), as well as brain imaging and neurocognitive studies in non-human primates aimed at improving our understanding of the mechanisms of Mn neurotoxicity. Finally, we discuss potential therapeutic modalities for treating Mn intoxication in humans.

Wilson's disease

Progressive hepatolenticular degeneration, or Wilson's disease, is a genetic disorder of copper metabolism. Knowledge of the clinical presentations and treatment of the disease are important both to the generalist and to specialists in gastroenterology and hepatology, neurology, psychiatry, and paediatrics. Wilson's disease invariably results in severe disability and death if untreated. The diagnosis is easily overlooked but if discovered early, effective treatments are available that will prevent or reverse many manifestations of this disorder. Studies have identified the role of copper in disease pathogenesis and clinical, biochemical, and genetic markers that can be useful in diagnosis. There are several chelating agents and zinc salts for medical therapy. Liver transplantation corrects the underlying pathophysiology and can be lifesaving. The discovery of the Wilson's disease gene has opened up a new molecular diagnostic approach, and could form the basis of future gene therapy.

Wilson's disease: an update

Wilson's disease (WD) is an inborn error of copper metabolism caused by a mutation to the copper-transporting gene ATP7B. The disease has an autosomal recessive mode of inheritance, and is characterized by excessive copper deposition, predominantly in the liver and brain. Diagnosis of the condition depends primarily on clinical features, biochemical parameters and the presence of the Kayser-Fleischer ring, and a new diagnostic scoring system has recently been proposed. Mutations in ATP7B can occur anywhere along the entire 21 exons, which makes the identification of gene defects particularly challenging. Identification of carriers and presymptomatic family members of affected individuals is achieved by polymerase-chain-reaction-based marker analysis. The traditional treatment for WD is based on copper chelation with agents such as D-penicillamine, but use of this drug has been questioned because of reported side effects. The use of agents such as trientine and ammonium tetrathiomolybdate has been advocated, although results of long-term trials are awaited. In selected cases, orthotropic hepatic transplantation can reverse the basic metabolic abnormality in WD and improve both hepatic and neurological symptoms. Studies of the underlying defects in ATP7B and its suspected modifiers ATOX1 and COMMD1 are expected to unravel the disease's genotype-phenotype correlation, and should lead to the design of improved drugs for ameliorating the suffering of patients.

Neuroimaging in manganism

Neuroimaging such as magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) have been used in the last decade for investigating the neurotoxicolgy of manganese (Mn). Increased signal intensities on a T1-weighted image may reflect increased Mn deposits (e.g., due to exposure to Mn) but not necessarily manganism. In a biologically based dose-response model, our recent results strongly suggest that signal intensities in T1-weighted MRI reflect a target site dose. However, the threshold of signal intensity associated with clinical symptoms of manganism remains to be solved. Functional neuroimaging such as PET or SPECT examines the integrity of the nigrostriatal dopaminergic system, and thus is very important for the differential diagnosis of manganism. However, neuroimaging research should also aim at developing specific and sensitive parameters for manganism in Mn-exposed individuals.

Profound midbrain atrophy in patients with Wilson's disease and neurological symptoms?

Wilson's disease (WD) is characterized by impaired hepatic copper secretion and subsequent copper accumulation in many organs predominantly liver and brain, secondary to loss of function mutations in the copper transport protein ATP7B. If the disease is recognized too late or treatment is not adequate, brain copper accumulation leads to progressive neurodegeneration with a variety of clinical symptoms. The nigrostriatal dopaminergic system seems rather vulnerable. Midbrain atrophy, however, has not been recognized as one of the prime features of patients with WD. Here we report quantification of midbrain diameter in 41 patients with WD. Data were correlated to the severity of neurological symptoms and the integrity of dopaminergic neurons measured via dopamine transporter binding. For control, we measured midbrain diameter in 18 patients with no evidence for brainstem dysfunction and 5 patients with progressive supranuclear palsy (PSP). Patients with WD had a reduced midbrain diameter (15.5 +/- 0.4 mm) compared to controls (18.5 +/- 0.2 mm). WD patients without neurological symptoms had midbrain diameter that were not different from controls (18.0 +/- 0.3 mm), while patients with neurological symptoms showed midbrain atrophy similar to patients with PSP (14.4 +/- 0.3 mm versus 14.1 +/- 0.3). There was a strong and significant correlation between midbrain atrophy and the severity of neurological symptoms (r= -0.68, p < 0.001) while midbrain atrophy and dopamine transporter binding correlated significantly but was less pronounced (r=0.46, p < 0.001). In summary, we were able to show, that midbrain diameter is an easy to perform quantification of neurodegeneration induced by brain copper accumulation and that other structures than substantia nigra dopaminergic neurons seem to contribute to midbrain atrophy in WD.

Extrapyramidal symptoms in Wilson's disease are associated with olfactory dysfunction

Wilson's disease is a rare autosomal recessive disorder characterized by the accumulation of copper, mainly in the liver and the brain. As copper accumulation in the brain leads to disturbances in basal ganglia function, neurological-type patients typically present with hypo- and hyperkinetic extrapyramidal symptoms, with Parkinsonism being very common. Although there are numerous reports on olfactory deficits in primary neurodegenerative disorders, olfactory function has not been investigated in metabolic disorders presenting with extrapyramidal features. Twenty-four patients with Wilson's disease participated in the investigation. All patients were treated pharmacologically. They comprised patients with liver disease alone (including mild enzyme elevation in asymptomatic individuals; n = 11) and/or neurological symptoms (n = 13) at the time of testing. Twenty-one patients underwent both [18F]fluoro-2-deoxy-D-glucose positron emission tomography ([18F]FDG-PET) and magnetic resonance imaging (MRI). The severity of extrapyramidal symptoms was judged using a clinical score system ranging from 0 (no symptoms) to 3 (severe symptoms). In all patients, psychophysical testing was performed using the Sniffin' Sticks, which involved tests for odor threshold, discrimination, and identification. Results from the present study revealed that Wilson's disease patients with neurological symptoms show a significant olfactory dysfunction compared to hepatic-type patients. Individuals who are more severely neurologically affected also present with a more pronounced olfactory deficit. Of interest, there was no significant effect of long-term treatment with penicillamine on olfactory function. Olfactory function did not correlate significantly with the presence of MRI visible lesions in the basal ganglia or with any regional glucose metabolism as measured by [18]F-FDG-PET. In conclusion, these findings indicate that the underlying pathological alterations with degeneration in the basal ganglia and neuronal loss in association with a marked increase of the copper content in this brain region play a role in the olfactory deficit.

How useful is [123I]beta-CIT SPECT in clinical practice?

OBJECTIVE

To assess the accuracy and clinical usefulness of [(123)I]beta-CIT (2beta-carbomethoxy-3beta-(4-iodophenyl)tropane) SPECT in the differential diagnosis of Parkinson's disease.

SUBJECTS

185 consecutive patients with symptoms of movement disorder were studied. The diagnoses were Parkinson's disease (92), essential tremor (16), vascular parkinsonism (15), various Parkinson plus syndromes (P+) (12), dementia with Lewy bodies (DLB) (5), dystonia (5), drug induced movement disorder (12), and other diagnoses (8). A reference group (psychogenic parkinsonism) comprised 20 subjects with complaints suggesting extrapyramidal disease but with no unequivocal signs on clinical examination and no abnormalities on brain imaging.

RESULTS

beta-CIT uptake was significantly lower in the whole striatum as well as separately in the putamen and in the caudate nucleus in Parkinson's disease than in the reference group or in drug induced movement disorder, essential tremor, or dystonia. The uptake of beta-CIT in the vascular parkinsonism group was heterogeneous and mean beta-CIT uptake fell between the reference group and the Parkinson's disease group. In the P+ and DLB groups the striatal uptake ratios overlapped those of the Parkinson's disease group.

CONCLUSIONS

[(123)I]beta-CIT SPECT may not be as useful a tool in the clinical differential diagnosis of Parkinson's disease as was previously believed, but it was 100% sensitive and specific for the diagnosis in younger patients (age <55 years). In older patients (age >55 years) specificity was substantially lower (68.5%). This differential specificity reflected the different distribution of differential diagnostic disorders (P+, DLB, vascular parkinsonism) in the older and younger age groups.

Enhanced Mn-SOD immunoreactivity in the dopaminergic neurons of long-evans cinnamon rats

The abundance of cellular superoxide dismutase (Mn-SOD) was examined immunocytochemically in different regions of the brain of Long-Evans Cinnamon (LEC) rats at 4 and 50 weeks of age. When all animals develop chronic hepatitis, the substantia nigra and striatum showed a marked increase in Mn-SOD immunoreactivity versus Long-Evans agouti (LEA) rats of the same age. Mn-SOD was localized predominantly in dopaminergic neurons. The elevation of Mn-SOD level in the dopaminergic neurons of LEC rats may reflect the oxidative stress caused by copper accumulation in this brain area. Our data suggest that LEC rats may contribute to the mechanistic study of neurological manifestations in nigro-striatal dopaminergic system of Wilson's disease.

Absence of nigrostriatal degeneration in LEC rats up to 20 weeks of age

BACKGROUND

Long-Evans Cinnamon (LEC) rat has a genetic defect of copper metabolism that is similar to human Wilson's disease. We studied the pathological changes in the nigrostriatal system of the LEC rat to examine the feasibility of using the LEC rat as a model of neurological Wilson's disease.

METHODS

LEC and Long-Evans Agouti (LEA) rats were killed at 12 and 20 weeks of age. FluoroJade B staining and immunohistochemistry were performed and Western blot compared the amount of tyrosine hydroxylase (TH) protein.

RESULTS

Degenerating neurons were not found in the substantia nigra (SN) and striatum. Dopaminergic neurons were of the same number in the SN of both LEC and LEA rats. Gliosis was of a similar degree in both animals. Western blot showed the same amount of TH protein in both animals.

DISCUSSION

There was no evidence of neurodegeneration in the nigrostriatal system of the LEC rat up to developmental age 20 weeks. The LEC rat is not a suitable model for deposition of copper in the brain in human Wilson's disease.

Role of dopamine transporter imaging in routine clinical practice

Functional imaging of the dopamine transporter (DAT) defines integrity of the dopaminergic system and has its main clinical application in patients with mild, incomplete, or uncertain parkinsonism. Imaging with specific single positron emission computerised tomography ligands for DAT (FP-CIT, beta-CIT, IPT, TRODAT) provides a marker for presynaptic neuronal degeneration. Striatal uptake correlates with disease severity, in particular bradykinesia and rigidity, and monitoring of progression assists in clinical trials of potential neuroprotective drugs. DAT imaging is abnormal in idiopathic Parkinson's disease, multiple system atrophy and progressive supranuclear palsy and does not distinguish between these disorders. Dopamine loss is seen even in the earliest clinical presentations of true parkinsonism; a normal scan suggests an alternative diagnosis such as essential tremor, vascular parkinsonism (unless there is focal basal ganglia infarction), drug-induced parkinsonism, or psychogenic parkinsonism. Congruence between working clinical diagnosis and DAT imaging increases over time in favour of baseline DAT imaging results. Additional applications are characterising dementia with parkinsonian features (abnormal results in dementia with Lewy bodies, normal in Alzheimer's disease); and differentiating juvenile-onset Parkinson's disease (abnormal DAT) from dopa-responsive dystonia (normal DAT).

Neuroimaging in spasticity and movement disorders

Advances in neuroimaging provide unique opportunities to evaluate brain structure, biochemistry, and function. Although a number of imaging techniques have been used in newborns, cranial ultrasonography in premature infants and nuclear magnetic resonance modalities, including magnetic resonance imaging and diffusion-weighted imaging, in high-risk term infants are of foremost benefit. Interpretation is based on knowledge of characteristic imaging findings in specific childhood neurologic disorders and an understanding of differential diagnosis in cerebral palsy syndromes, such as spastic diplegia and various subtypes of extrapyramidal cerebral palsy. This review focuses on imaging studies that can be effectively used in at-risk infants and in children with spasticity and movement disorders to refine diagnosis and guide therapeutic interventions.

Dopamine transporter binding in Wilson's disease

INTRODUCTION

In Wilson's disease (WD), brain magnetic resonance images (MRI) show increased signal intensity in T2 weighted images in the lenticular nuclei, thalamus and brainstem, including the substantia nigra. A poor therapeutic response to levodopa in WD suggests the mechanism of a postsynaptic abnormality. However positron emission tomography studies show an involvement of the nigrostriatal presynaptic dopaminergic pathway.

CASE REPORT

We report the clinical manifestations in a case of WD with akinetic-rigid syndrome and initial hesitation. The brain MRI showed an increased signal intensity lesion in the substantia nigra region, in addition to basal ganglion and thalamic lesions. However, dopamine transporter (DAT) imaging with 99mTc-TRODAT-1 revealed a nonsignificantly increased DAT uptake, suggesting a normal presynaptic nigrostriatal dopaminergic terminal.

CONCLUSION

We suggest that significant heterogeneity can be found in WD patients and a normal presynaptic dopaminergic pathway may occur in some patients, even those with typical akinetic-rigid syndrome and evidence of substantia nigra involvement in the brain on MRI.

Concordant pre- and postsynaptic deficits of dopaminergic neurotransmission in neurologic Wilson disease

BACKGROUND AND PURPOSE

Although previous brain imaging studies of Wilson disease (WD) focused on the dopaminergic system, correlational data on the integrity of the pre- and postsynaptic compartments are lacking. The present study was initiated to intra-individually determine the integrity of these compartments in patients with WD.

METHODS

A total of 46 patients with WD and 10 matched control subjects underwent [(123)I]2beta-carbomethoxy-3beta-(4[(123)I]iodophenyl)tropane ([(123)I]beta-CIT) and [(123)I]iodobenzamide ([(123)I]IBZM) single photon emission CT (SPECT). For both radiotracers, specific striatal binding ratios (with the cerebellum as the reference region) were calculated after a standardized region-of-interest technique was applied. In addition, the severity of putative neurologic symptoms was evaluated by using a linear scoring system.

RESULTS

In patients without neurologic symptoms, striatal binding ratios of both radiotracers did not differ from those of the control group (13.8 +/- 3.1 vs 12.0 +/- 3.4 and 2.00 +/- 0.19 vs 1.90 +/- 0.27; n.s.). In symptomatic patients, however, striatal binding ratios for both [(123)I]beta-CIT and [(123)I]IBZM were significantly reduced (9.1 +/- 2.3 and 1.64 +/- 0.18; P <.001). In all patients with WD, the [(123)I]beta-CIT and [(123)I]IBZM binding ratios were significantly correlated (r = 0.65, P <.001), as were SPECT parameters and the severity of the neurologic symptoms (r = -0.60 and -0.62; P <.001).

CONCLUSION

These findings of a concordant bicompartmental dopaminergic deficit in neurologic WD provide in vivo evidence for assigning WD to the group of secondary Parkinsonian syndromes. These results could be relevant in therapeutic decision making in patients with this copper deposition disorder.

Dopamine transporter density is decreased in parkinsonian patients with a history of manganese exposure: what does it mean?

Manganese (Mn) exposure can cause parkinsonism. Pathological changes occur mostly in the pallidum and striatum. Two patients with a long history of occupational Mn exposure presented with Mn-induced parkinsonism. In one patient, magnetic resonance imaging (MRI) showed findings consistent with Mn exposure, and Mn concentration was increased in the blood and urine. However, this patient's clinical features were typical of idiopathic Parkinson disease (PD). Previous pathological and positron emission tomography studies indicate that striatal dopamine transporter density is normal in Mn-induced parkinsonism, whereas it is decreased in PD. Therefore, we performed [(123)I]-(1r)-2 beta-carboxymethoxy-3beta-(4-iodophenyl)tropane ([(123)I]-beta-CIT) single-photon emission computed tomography. Severe reduction of striatal beta-CIT binding was indicated, which is consistent with PD. We propose three interpretations: (1) the patients have PD, and Mn exposure is incidental; (2) Mn induces selective degeneration of presynaptic dopaminergic nerve terminals, thereby causing parkinsonism; or (3) Mn exposure acts as a risk of PD in these patients. Our results and careful review of previous studies indicate that the axiom that Mn causes parkinsonism by pallidal lesion may be over-simplified; Mn exposure and parkinsonism may be more complex than previously thought. Further studies are required to elucidate the relationship between Mn and various forms of parkinsonism.

Personality traits in treated Wilson's disease determined by means of the Karolinska Scales of Personality (KSP)

OBJECTIVE

The aim was to elucidate the personality traits of patients with treated Wilsons disease (WD) in comparison to healthy volunteers.

METHOD

Twenty-five WD patients, ten females and 15 males, with a mean age of 35.2 +/- 8.3 years completed the Karolinska Scales of Personality (KSP), a self-report inventory comprising 15 separate scales. The results were compared to a control series comprising 200 men and 200 women drawn from the general population.

RESULTS

The patients with treated WD scored significantly lower than the healthy controls on aggressivity-hostility-related scales and the scale measuring Psychic Anxiety. Patients with predominantly hepatic symptoms had the lowest aggressivity-related scores and patients with predominantly neurological symptoms had the lowest Irritability, Guilt and Detachment scores and the highest Impulsiveness and Muscular Tension scores. Both groups scored low on the Somatic Anxiety scale.

CONCLUSION

The present results illustrate that patients with treated WD have significant deviations in personality traits, especially in aggressivity-hostility-related scales and Psychic Anxiety, compared to healthy controls when investigated by means of a self-report inventory, the KSP. The deviations were not related to age, age at onset or duration of the disease.

Comparison of MRI, EEG, EPs and ECD-SPECT in Wilson's disease

OBJECTIVES

The purpose of this study is to evaluate the efficiency of a few methodologies in detecting anatomo-functional brain abnormalities in patients with Wilson's disease.

MATERIALS AND METHODS

Twenty-three patients with Wilson's disease underwent almost simultaneously brain magnetic resonance imaging (MRI), computerized electroencephalography (EEG), multimodal evoked potentials (EPs) and ECD single photon computerized tomography (SPECT) evaluation. The clinical picture was of the neurologic type in 8 patients and of the hepatic type in 15.

RESULTS

MRI was abnormal in 7 patients with neurological manifestations. The EPs proved pathologic in 7 neurologically symptomatic patients and in 4 cases with hepatic form. These results agree with those reported in other case studies. The EEG records were abnormal only in 3 cases. Nevertheless, the most interesting finding of this study is the particular frequency (86%) of diffuse or focal decrease of ECD uptake shown by brain SPECT.

CONCLUSION

We highlight the use of this interesting procedure in the therapeutic monitoring of this disease.

Is Parkinson's disease the heterozygote form of Wilson's disease: PD = 1/2 WD?

Wilson's disease (WD) patients often present with Parkinson's disease (PD). Furthermore, most patients with PD have reduced ceruloplasmin, a characteristic of Wilson's disease. WD is an autosomal recessive disease (requires two faulty copies of a gene to produce a homozygote individual) that afflicts 1 in 1000 people. However, the number of people with one faulty copy (heterozygotes) is much larger, probably about 2% of the population. I hypothesize that the large number of heterozygotes for WD are at greatly increased risk for idiopathic PD, because these people accumulate free copper in the basal ganglia at a slower rate than homozygotes, which accounts for the fact that PD usually develops after 40 years of age. In WD, a ceruloplasmin deficiency results in accumulation of free Cu in the liver, brain, kidneys, etc. The excess Cu results in impaired Zn absorption, which would account for the low levels of Zn in the brains of PD patients. Moreover, the high levels of Fe found in the substantia nigra of PD patients may perhaps be explained by free Cu binding to iron binding protein-1 (IBP-1), causing it to malfunction and preventing it from detaching itself from the transferrin receptor (TfR) inhibition gene, resulting in expression of TfR even when the cell has plenty of Fe. The gradual accumulation of Fe and Cu would explain the damage inflicted on the substantia nigra by free radicals catalyzed by these two metals and which is exacerbated by the low levels of CuZnSOD, due to the Zn deficiency mentioned above. Moreover, if this hypothesis is correct, then PD could be used to help discover the gene (or genes) responsible for WD and vice versa. Furthermore, idiopathic PD could be prevented by identifying the heterozygote individuals and providing them with Zn supplementation, Cu chelation therapy and phlebotomy to eliminate Fe.