Neuroimaging abnormalities in individuals exhibiting Parkinson's disease risk markers.

BACKGROUND: The concept of prodromal Parkinson's disease (PD) involves variable combinations of nonmotor features and subtle motor abnormalities as a result of ongoing neurodegeneration in the brain stem including substantia nigra (SN) and abnormal findings upon transcranial sonography and nuclear imaging. Except for nuclear imaging, the predictive value of risk markers for the conversion to overt PD is low. OBJECTIVE: The objective of this study was to determine whether PD risk markers are associated with changes in brain structure and to what extent cognitive changes are risk markers for PD. METHODS: Diffusion-weighted imaging, voxel-based morphometry, and cortical thickness analysis was performed in 29 individuals with hyposmia and/or an increased SN hyperechogenicity (SN+) upon transcranial sonography and 28 controls without these 2 risk markers. Classical parkinsonian signs were an exclusion criterion. All of the participants underwent a neuropsychological test battery addressing executive functions, learning ability, and verbal fluency. RESULTS: In the PD risk group, diffusion-weighted imaging mean diffusivity was increased in 4 left hemisphere clusters (posterior thalamus, inferior longitudinal fasciculus, fornix, corticospinal tract). A negative relationship of mean diffusivity and smell function was present for the posterior thalamus and the corticospinal tract. There was a significant correlation of mean diffusivity values and SN+ in all clusters. Neither voxel-based morphometry nor cortical thickness analysis revealed any group differences. No relevant group differences were observed for cognitive tests included. CONCLUSION: PD-free individuals with PD risk markers show microstructural changes of the white matter, including areas relevant for motor and limbic processes. In addition, our study provides for the first time a neuroanatomical correlate for SN hyperechogenicity. © 2018 International Parkinson and Movement Disorder Society.

Personality profiles are different in musician's dystonia and other isolated focal dystonias.

Psychological abnormalities have been reported in patients with musician's dystonia. To further differentiate these abnormalities, we evaluated personality traits in musician's dystonia and compared them to those in other isolated focal dystonias. Therefore patients with musician's dystonia (n = 101) and other isolated focal dystonias (n = 85) underwent the Neuroticism Extraversion Openness Five-Factor Inventory (NEO-FFI). Women with musician's dystonia had higher NEO-FFI neuroticism scores, and men significantly higher openness scores compared to women and men with other isolated focal dystonias, respectively. There were negative correlations in men with musician's dystonia between duration of dystonia and the NEO-FFI openness and extraversion scores and between age and extraversion scores. Women with other isolated focal dystonias showed correlations between age and agreeableness and conscientiousness scores. Patients with musician's dystonia are characterized by a specific personality profile with increased neuroticism and openness compared to other isolated focal dystonias. Whether this profile can be traced back to specific underlying disease mechanisms should be further investigated.

Associations of specific psychiatric disorders with isolated focal dystonia, and monogenic and idiopathic Parkinson's disease.

Comorbidity of psychiatric disorders in patients with movement disorders is common. Often, psychiatric symptoms manifest before the onset of the movement disorder, thus not representing a mere reaction to its burden. How the disease mechanisms of psychiatric and movement disorders are related is still poorly understood. The aim of the present study was to compare prevalence rates of specific psychiatric disorders between different movement disorders including isolated focal dystonia (IFD, N = 91), monogenic Parkinson's disease (PD, N = 41), idiopathic PD (N = 45), and a sample from a Northern Germany general population (TACOS Study; N = 4075). Our results indicate an odds ratio (OR) of 2.6 [confidence interval (CI) 1.7-4.0] for general axis I disorders in IFD, an OR of 2.5 (CI 1.4-4.7) in monogenic PD, and an OR of 1.4 (CI 0.8-2.6) in idiopathic PD. More specifically, the monogenic PD group showed the highest ORs for affective disorders including depression (OR = 4.9), bipolar disorder (OR = 17.4), and hypomanic episodes (OR = 17.0), whereas IFD expressed the highest rates of anxiety disorders (OR = 3.3). Psychotic symptoms were only observed in the PD groups but not in IFD. Our findings underline the notion that psychiatric disorders are part of the phenotypic spectrum of movement disorders. Moreover, they suggest that IFD, monogenic PD, and idiopathic PD are associated with specific psychiatric disorders indicating disturbances in a different neural circuitry for sensorimotor control.

A Brief Nonmotor Screen Combined with Transcranial Ultrasound may Improve Diagnostic Accuracy of Parkinson's Disease.

BACKGROUND: The addition of a simple nonmotor symptom (NMS) screen and transcranial sonography (TCS) to standard clinical assessment may improve the diagnostic accuracy of Parkinson's disease (PD). METHODS: Sixty-nine subjects (23 established PD group, 23 healthy controls, and 23 possible PD) were enrolled. All completed 3 "yes-no" NMS questions (score, 0-3) and had a transcranial ultrasound assessing nigral hyperechogenicity (score, 0-1). A combined PD risk score of 0 to 4 was obtained for each subject. A PD risk score of ≥2 was used as the diagnostic cutoff for PD. RESULTS: In the established PD group, there was an average of 2 NMSs per person or a group total of 46 of 69 possible NMSs, but only 4 of 69 NMSs in the healthy control group. Of the technically satisfactory TCS, 16 of 20 (80%) of the established PD group and 2 of 16 (12.5%) of the healthy control group were TCS positive. Using ≥2 NMSs alone as the cutoff identified 17 of 23 (74%) of the established PD and 100% of the healthy controls. The PD risk score of ≥2 identified 21 of 23 (91%) of the established PD as PD and 22 of 23 (96%) of the healthy control group as non-PD. In the possible PD group, the PD risk score identified 9 of 18 (50%) of those with a final clinical diagnosis of PD and 4 of 5 (80%) of non-PD. CONCLUSIONS: The combination of a brief NMS screen and TCS discriminated well between normal healthy controls and established PD. A positive TCS and one NMS, or a negative TCS with two NMSs, indicated a likely diagnosis of PD.

Intertemporal choice in Parkinson's disease and restless legs syndrome.

BACKGROUND: Impulse control disorders in Parkinson's disease are a potential consequence of dopaminergic therapy. Impulse control problems might be revealed by intertemporal choice tasks which entail to forgo an immediately available reward in favor of a larger but later reward. The steepness of the discounting curve can be quantified by the parameter k. METHODS: Participants (37 Parkinson patients [13 de novo, 24 medicated], 24 patients with restless legs syndrome, and 22 controls) were offered 54 choices between immediate smaller rewards and delayed larger and the k value was estimated from the participants' responses. Participants had the chance of winning one of their decisions. None of the participants had impulse control disorders. RESULTS: Unmedicated Parkinson patients had a higher discounting rate than controls and medicated patients with restless legs syndrome. The k values of medicated Parkinson patients and patients with restless legs syndrome did not differ from those of controls. No correlation was found between the k value and the dopamine agonist dose. CONCLUSION: Impulsive decision making in patients with Parkinson's disease may occur as part of the disease rather than as a consequence of dopamine agonist therapy.

Ultrasound-based motion analysis demonstrates bilateral arm hypokinesia during gait in heterozygous PINK1 mutation carriers.

Carriers of a single heterozygous PINK1 (PTEN-induced putative kinase 1) gene mutation provide an ideal opportunity to study the development of parkinsonian motor signs from the very beginning. Measuring tools that reliably represent mild motor symptoms could also facilitate the assessment of future neuroprotective therapies and early diagnosis of Parkinson's disease (PD). We investigated nine family members carrying a heterozygous PINK1 mutation in comparison with 25 age-matched healthy controls. Arm kinematics were quantified during treadmill walking at four different speeds using ultrasound-based motion analysis. Heterozygous PINK1 mutation carriers showed a bilateral reduction of arm swing amplitudes (P = 0.003) and arm anteversion (P = 0.001), which was more pronounced on the predominantly affected body side but also was present, albeit to a lesser degree, contralaterally (amplitude P = 0.01, anteversion P = 0.002, repeated measures analysis of covariance [rmANCOVA]). Single post-hoc comparisons revealed similar results for all speeds on both body sides (P < 0.05) except for 2.0 km/h on the less affected side. A single heterozygous mutation in the PINK1 gene is associated with a bilateral dopaminergic dysfunction in this family. Ultrasound-based three-dimensional motion analysis of arm swing during gait is a suitable tool to quantify even subtle hypokinesia in mildly affected PINK1 mutation carriers, which tends to be easily overlooked on the less affected body side during clinical examination. Therefore, this technique is a promising application in early stage PD and in at-risk populations for the disease.

A population-based study on combined markers for early Parkinson's disease.

The prerequisite for an earlier diagnosis of Parkinson's disease (PD) are markers that are both sensitive and specific for clinically definite PD and its prediagnosic phases. Promising candidates include enlarged hyperechogenicity of the substantia nigra (SN+) on transcranial sonography (TCS) and hyposmia. However, despite good sensitivity and specificity, both markers have yet failed to yield reliable predictions. We pursue the possibility of combined use in an ongoing population-based cohort. Subjects were recruited from 10,000 inhabitants of Luebeck/Germany aged 50 to 79 years and additional PD patients from our outpatient clinic. After neurological examination, 715 subjects were grouped into clinically definite PD (n = 106), possible prediagnostic PD (ppPD; n = 73), and a control group subdivided into healthy individuals (n = 283) and controls with diseases other than PD (n = 253). Subjects underwent TCS and smell testing. Sensitivity and specificity of SN+ and hyposmia were good for PD; however, positive predictive values (PPV) of both SN+ (5.2%) and olfaction (2.5%) were low. At least one positive/both positive markers were present in 33%/1% of healthy controls, 33%/2% of diseased controls, 62%/7% of ppPD, and 94%/51% of PD. When combining SN+ and hyposmia, PPV increased to 17.6%, with a sensitivity of 51% and a specificity of 98%. Both SN+ and hyposmia offer good enrichment towards PD and ppPD, are stable against other diseases, and the combination of markers highly increases specificity. However, if the combination of SN+ and hyposmia were used as criterion for PD diagnosis, almost half of clinically definite PD and more than 90% of ppPD would have been missed.

Mutations in GNAL: a novel cause of craniocervical dystonia.

IMPORTANCE: Mutations in the GNAL gene have recently been shown to cause primary torsion dystonia. The GNAL-encoded protein (Gαolf) is important for dopamine D1 receptor function and odorant signal transduction. We sequenced all 12 exons of GNAL in 461 patients from Germany, Serbia, and Japan, including 318 patients with dystonia (190 with cervical dystonia), 51 with hyposmia and Parkinson disease, and 92 with tardive dyskinesia or acute dystonic reactions. OBSERVATIONS: We identified the following two novel heterozygous putative mutations in GNAL: p.Gly213Ser in a German patient and p.Ala353Thr in a Japanese patient. These variants were predicted to be pathogenic in silico, were absent in ethnically matched control individuals, and impaired Gαolf coupling to D1 receptors in a bioluminescence energy transfer (BRET) assay. Two additional variants appeared to be benign because they behaved like wild-type samples in the BRET assay (p.Ala311Thr) or were detected in ethnically matched controls (p.Thr92Ala). Both patients with likely pathogenic mutations had craniocervical dystonia with onset in the fifth decade of life. No pathogenic mutations were detected in the patients with hyposmia and Parkinson disease, tardive dyskinesias, or acute dystonic reactions. CONCLUSIONS AND RELEVANCE: Mutations in GNAL can cause craniocervical dystonia in different ethnicities. The BRET assay may be a useful tool to support the pathogenicity of identified variants in the GNAL gene.

Non-motor phenotype of dopa-responsive dystonia and quality of life assessment.

BACKGROUND: Dopa-responsive dystonia (DRD) is a young-onset neurometabolic disorder often presenting with a combination of parkinsonism and dystonia. The pathophysiology includes an impairment of dopaminergic and serotonergic neurotransmission. Uncontrolled reports suggest an increased frequency of neuropsychiatric abnormalities and sleep impairment. METHODS: In 23 GCH1 mutation-positive DRD patients and 26 healthy controls, non-motor features and their effect on the quality of life (QoL) were assessed. Six patients underwent polysomnography (PSG). RESULTS: Depressive and anxiety symptoms were not more common among DRD patients. Average sleep quality was similar across groups. This was also true for self-reported mean sleep onset (27.5 vs. 27.1 min) and total sleep time (6.5 vs. 6.6 h). Upon PSG, the number of spontaneous arousals was increased in four patients. QoL was impaired with respect to physical health. Sleep impairment and depressive but not anxiety symptoms were associated with lower QoL. CONCLUSION: The present results do not confirm the clinical impression and biologically plausible assumption of an increased frequency of non-motor symptoms in DRD. The impairment of QoL is associated with a decline of the physical condition only but not with other factors.

Genome-wide association study in musician's dystonia: a risk variant at the arylsulfatase G locus?

Musician's dystonia (MD) affects 1% to 2% of professional musicians and frequently terminates performance careers. It is characterized by loss of voluntary motor control when playing the instrument. Little is known about genetic risk factors, although MD or writer's dystonia (WD) occurs in relatives of 20% of MD patients. We conducted a 2-stage genome-wide association study in whites. Genotypes at 557,620 single-nucleotide polymorphisms (SNPs) passed stringent quality control for 127 patients and 984 controls. Ten SNPs revealed P < 10(-5) and entered the replication phase including 116 MD patients and 125 healthy musicians. A genome-wide significant SNP (P < 5 × 10(-8) ) was also genotyped in 208 German or Dutch WD patients, 1,969 Caucasian, Spanish, and Japanese patients with other forms of focal or segmental dystonia as well as in 2,233 ethnically matched controls. Genome-wide significance with MD was observed for an intronic variant in the arylsulfatase G (ARSG) gene (rs11655081; P = 3.95 × 10(-9) ; odds ratio [OR], 4.33; 95% confidence interval [CI], 2.66-7.05). rs11655081 was also associated with WD (P = 2.78 × 10(-2) ) but not with any other focal or segmental dystonia. The allele frequency of rs11655081 varies substantially between different populations. The population stratification in our sample was modest (λ = 1.07), but the effect size may be overestimated. Using a small but homogenous patient sample, we provide data for a possible association of ARSG with MD. The variant may also contribute to the risk of WD, a form of dystonia that is often found in relatives of MD patients.

Altered resting state brain networks in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder affecting dopaminergic neurons in the substantia nigra leading to dysfunctional cortico-striato-thalamic-cortical loops. In addition to the characteristic motor symptoms, PD patients often show cognitive impairments, affective changes and other non-motor symptoms, suggesting system-wide effects on brain function. Here, we used functional magnetic resonance imaging and graph-theory based analysis methods to investigate altered whole-brain intrinsic functional connectivity in PD patients (n = 37) compared to healthy controls (n = 20). Global network properties indicated less efficient processing in PD. Analysis of brain network modules pointed to increased connectivity within the sensorimotor network, but decreased interaction of the visual network with other brain modules. We found lower connectivity mainly between the cuneus and the ventral caudate, medial orbitofrontal cortex and the temporal lobe. To identify regions of altered connectivity, we mapped the degree of intrinsic functional connectivity both on ROI- and on voxel-level across the brain. Compared to healthy controls, PD patients showed lower connectedness in the medial and middle orbitofrontal cortex. The degree of connectivity was also decreased in the occipital lobe (cuneus and calcarine), but increased in the superior parietal cortex, posterior cingulate gyrus, supramarginal gyrus and supplementary motor area. Our results on global network and module properties indicated that PD manifests as a disconnection syndrome. This was most apparent in the visual network module. The higher connectedness within the sensorimotor module in PD patients may be related to compensation mechanism in order to overcome the functional deficit of the striato-cortical motor loops or to loss of mutual inhibition between brain networks. Abnormal connectivity in the visual network may be related to adaptation and compensation processes as a consequence of altered motor function. Our analysis approach proved sensitive for detecting disease-related localized effects as well as changes in network functions on intermediate and global scale.

Mortalin mutations are not a frequent cause of early-onset Parkinson disease.

Dysfunctional mitochondria and the mitochondrial chaperone mortalin (HSPA9, GRP75) have been implicated in the pathogenesis of Parkinson disease (PD). We screened 139 early-onset PD (EOPD) patients for mutations in mortalin revealing one missense change (p.L358P) that was absent in 279 control individuals. We also found one additional missense variant among the controls (p.T333K). Although both missense changes were predicted to be disease causing, we detected no differences in subcellular localization, mitochondrial morphology, or respiratory function between wild-type and mutant mortalin. These findings suggest that variants in mortalin (1) are not a major cause of EOPD; (2) occur in patients and controls; and (3) do not lead to functional impairment of mitochondria.

Whispering dysphonia (DYT4 dystonia) is caused by a mutation in the TUBB4 gene.

OBJECTIVE: A study was undertaken to identify the gene underlying DYT4 dystonia, a dominantly inherited form of spasmodic dysphonia combined with other focal or generalized dystonia and a characteristic facies and body habitus, in an Australian family. METHODS: Genome-wide linkage analysis was carried out in 14 family members followed by genome sequencing in 2 individuals. The index patient underwent a detailed neurological follow-up examination, including electrophysiological studies and magnetic resonance imaging scanning. Biopsies of the skin and olfactory mucosa were obtained, and expression levels of TUBB4 mRNA were determined by quantitative real-time polymerase chain reaction in 3 different cell types. All exons of TUBB4 were screened for mutations in 394 unrelated dystonia patients. RESULTS: The disease-causing gene was mapped to a 23cM region on chromosome 19p13.3-p13.2 with a maximum multipoint LOD score of 5.338 at markers D9S427 and D9S1034. Genome sequencing revealed a missense variant in the TUBB4 (tubulin beta-4; Arg2Gly) gene as the likely cause of disease. Sequencing of TUBB4 in 394 unrelated dystonia patients revealed another missense variant (Ala271Thr) in a familial case of segmental dystonia with spasmodic dysphonia. mRNA expression studies demonstrated significantly reduced levels of mutant TUBB4 mRNA in different cell types from a heterozygous Arg2Gly mutation carrier compared to controls. INTERPRETATION: A mutation in TUBB4 causes DYT4 dystonia in this Australian family with so-called whispering dysphonia, and other mutations in TUBB4 may contribute to spasmodic dysphonia. Given that TUBB4 is a neuronally expressed tubulin, our results imply abnormal microtubule function as a novel mechanism in the pathophysiology of dystonia.

The Val158Met COMT polymorphism is a modifier of the age at onset in Parkinson's disease with a sexual dimorphism.

The catechol-O-methyltranferase (COMT) is one of the main enzymes that metabolise dopamine in the brain. The Val158Met polymorphism in the COMT gene (rs4680) causes a trimodal distribution of high (Val/Val), intermediate (Val/Met) and low (Met/Met) enzyme activity. We tested whether the Val158Met polymorphism is a modifier of the age at onset (AAO) in Parkinson's disease (PD). The rs4680 was genotyped in a total of 16 609 subjects from five independent cohorts of European and North American origin (5886 patients with PD and 10 723 healthy controls). The multivariate analysis for comparing PD and control groups was based on a stepwise logistic regression, with gender, age and cohort origin included in the initial model. The multivariate analysis of the AAO was a mixed linear model, with COMT genotype and gender considered as fixed effects and cohort and cohort-gender interaction as random effects. COMT genotype was coded as a quantitative variable, assuming a codominant genetic effect. The distribution of the COMT polymorphism was not significantly different in patients and controls (p=0.22). The Val allele had a significant effect on the AAO with a younger AAO in patients with the Val/Val (57.1±13.9, p=0.03) than the Val/Met (57.4±13.9) and the Met/Met genotypes (58.3±13.5). The difference was greater in men (1.9 years between Val/Val and Met/Met, p=0.007) than in women (0.2 years, p=0.81). Thus, the Val158Met COMT polymorphism is not associated with PD in the Caucasian population but acts as a modifier of the AAO in PD with a sexual dimorphism: the Val allele is associated with a younger AAO in men with idiopathic PD.