Cortical sensorimotor alterations classify clinical phenotype and putative genotype of spasmodic dysphonia.

BACKGROUND AND PURPOSE: Spasmodic dysphonia (SD), or laryngeal dystonia, is a task-specific isolated focal dystonia of unknown causes and pathophysiology. Although functional and structural abnormalities have been described in this disorder, the influence of its different clinical phenotypes and genotypes remains scant, making it difficult to explain SD pathophysiology and to identify potential biomarkers. METHODS: We used a combination of independent component analysis and linear discriminant analysis of resting-state functional magnetic resonance imaging data to investigate brain organization in different SD phenotypes (abductor versus adductor type) and putative genotypes (familial versus sporadic cases) and to characterize neural markers for genotype/phenotype categorization. RESULTS: We found abnormal functional connectivity within sensorimotor and frontoparietal networks in patients with SD compared with healthy individuals as well as phenotype- and genotype-distinct alterations of these networks, involving primary somatosensory, premotor and parietal cortices. The linear discriminant analysis achieved 71% accuracy classifying SD and healthy individuals using connectivity measures in the left inferior parietal and sensorimotor cortices. When categorizing between different forms of SD, the combination of measures from the left inferior parietal, premotor and right sensorimotor cortices achieved 81% discriminatory power between familial and sporadic SD cases, whereas the combination of measures from the right superior parietal, primary somatosensory and premotor cortices led to 71% accuracy in the classification of adductor and abductor SD forms. CONCLUSIONS: Our findings present the first effort to identify and categorize isolated focal dystonia based on its brain functional connectivity profile, which may have a potential impact on the future development of biomarkers for this rare disorder.

Cognitive and Antipsychotic Medication Use in Monoallelic GBA-Related Parkinson Disease.

Mutations in glucosidase, beta, acid (GBA) are associated with cognitive impairment in Parkinson disease (PD) as well as dementia with Lewy bodies. For both of these diseases, dementia and hallucinations are typically treated with cholinesterase inhibitors and antipsychotics. However, in some lysosomal storage disorders certain antipsychotic medications are poorly tolerated. This study examined cholinesterase inhibitor and antipsychotic use in monoallelic GBA-related PD to explore potential pharmacogenetic relationships. Monoallelic GBA mutation carriers with PD (GBA-PD) with at least two clinic visits (n = 34) were matched for age-of-onset and gender to GBA and leucine-rich repeat kinase 2 (LRRK2) mutation negative idiopathic PD subjects (IPD) (n = 60). Information regarding cholinesterase inhibitor and antipsychotic use as well as impaired cognition (UPDRS Mentation >1) and hallucinations (UPDRS Thought Disorder >1) were obtained. GBA-PD more frequently reported hallucinations (HR = 5.0; p = 0.01) and they were more likely to have cognitive impairment but this was not statistically significant (HR 2.2, p = 0.07). Antipsychotic use was not significantly different between GBA-PD and IPD (HR = 1.9; p = 0.28), but GBA-PD were more likely to have sustained cholinesterase inhibitor use (HR = 3.1; p = 0.008), even after adjustment for cognition and hallucinations. Consistent with reports of worse cognition, GBA-PD patients are more likely to use cholinesterase inhibitors compared to IPD. While there was no difference in antipsychotic use between IPD and GBA-PD, persistent use of quetiapine in GBA-PD suggests that it is tolerated and that a significant interaction is unlikely. Further prospective study in larger samples with more extensive cognitive assessment is warranted to better understand pharmacogenetic relationships in GBA-PD.

Transcranial sonography and functional imaging in glucocerebrosidase mutation Parkinson disease.

BACKGROUND: Heterozygous glucocerebrosidase (GBA) mutations are the leading genetic risk factor for Parkinson disease, yet imaging correlates, particularly transcranial sonography, have not been extensively described. METHODS: To determine whether GBA mutation heterozygotes with Parkinson disease demonstrate hyperechogenicity of the substantia nigra, transcranial sonography was performed in Ashkenazi Jewish Parkinson disease subjects, tested for the eight most common Gaucher disease mutations and the LRRK2 G2019S mutation, and in controls. [(18)F]-fluorodeoxyglucose or [(18)F]-fluorodopa positron emission tomography is also reported from a subset of Parkinson disease subjects with heterozygous GBA mutations. RESULTS: Parkinson disease subjects with heterozygous GBA mutations (n = 23) had a greater median maximal area of substantia nigral echogenicity compared to controls (n = 34, aSNmax = 0.30 vs. 0.18, p = 0.007). There was no difference in median maximal area of nigral echogenicity between Parkinson disease groups defined by GBA and LRRK2 genotype: GBA heterozygotes; GBA homozygotes/compound heterozygotes (n = 4, aSNmax = 0.27); subjects without LRRK2 or GBA mutations (n = 32, aSNmax = 0.27); LRRK2 heterozygotes/homozygotes without GBA mutations (n = 27, aSNmax = 0.28); and GBA heterozygotes/LRRK2 heterozygotes (n = 4, aSNmax = 0.32, overall p = 0.63). In secondary analyses among Parkinson disease subjects with GBA mutations, maximal area of nigral echogenicity did not differ based on GBA mutation severity or mutation number. [(18)F]-fluorodeoxyglucose (n = 3) and [(18)F]-fluorodopa (n = 2) positron emission tomography in Parkinson disease subjects with heterozygous GBA mutations was consistent with findings in idiopathic Parkinson disease. CONCLUSIONS: Both transcranial sonography and positron emission tomography are abnormal in GBA mutation associated Parkinson disease, similar to other Parkinson disease subjects.

Variant ataxia-telangiectasia presenting as primary-appearing dystonia in Canadian Mennonites.

OBJECTIVE: To compare the phenotype of primary-appearing dystonia due to variant ataxia-telangiectasia (A-T) with that of other dystonia ascertained for genetics research. METHODS: Movement disorder specialists examined 20 Canadian Mennonite adult probands with primary-appearing dystonia, as well as relatives in 4 families with parent-child transmission of dystonia. We screened for the exon 43 c.6200 C>A (p. A2067D) ATM mutation and mutations in DYT1 and DYT6. Clinical features of the individuals with dystonia who were harboring ATM mutations were compared with those of individuals without mutations. RESULT: Genetic analysis revealed a homozygous founder mutation in ATM in 13 members from 3 of the families, and no one harbored DYT6 or DYT1 mutations. Dystonia in ATM families mimicked other forms of early-onset primary torsion dystonia, especially DYT6, with prominent cervical, cranial, and brachial involvement. Mean age at onset was markedly younger in the patients with variant A-T (n = 12) than in patients with other dystonia (n = 23), (12 years vs 40 years, p < 0.05). The patients with A-T were remarkable for the absence of notable cerebellar atrophy on MRI, lack of frank ataxia on examination, and absence of ocular telangiectasias at original presentation, as well as the presence of prominent myoclonus-dystonia in 2 patients. Many also developed malignancies. CONCLUSION: Ataxia and telangiectasias may not be prominent features of patients with variant A-T treated for dystonia in adulthood, and variant A-T may mimic primary torsion dystonia and myoclonus-dystonia.

Gender differences in the IL6 -174G>C and ESR2 1730G>A polymorphisms and the risk of Parkinson's disease.

The -174G>C (rs1800795) single nucleotide polymorphism (SNP) in the promoter of the interleukin-6 (IL6) gene and the 1730G>A (rs4986938) SNP in the estrogen receptor beta (ESR2) may influence the risk of Parkinson's disease (PD). We investigated these SNPs in 380 unrelated US Caucasian PD cases and 522 controls, including 452 individuals of Ashkenazi Jewish (AJ) origin (260 PD, 192 controls). The G allele of the -174G>C SNP was more common in AJ PD cases (p=0.033) as well as in Non-Jewish (NJ) men with PD (p=0.022). The GG genotype increased the risk of PD by over two fold in NJ men (OR=2.11, 95%CI: 1.14-3.89, p=0.017), and approached significance in the total AJ group with PD (OR=1.42, 95%CI: 0.97-2.06, p=0.067). The A allele of the ESR2 1730G>A SNP was associated with a decreased risk for PD in AJ women, and in this group, having the AA genotype decreased the risk of PD by half (OR=0.45, 95%CI: 0.22-0.92, p=0.029). Our data supports a role for the IL6 -174G>C G allele in AJ individuals overall. In NJ Caucasians, this role appears to be gender mediated. In both groups, the effect is independent from ESR2 1730G>A. A separate association for the ESR2 1730G>A SNP was found exclusively in women of AJ descent. Other polymorphisms in tight linkage disequilibrium with the SNP differentially influencing expression, ethnic differences in allele distribution, and gender differences in genetic load related to PD, may underlie our findings. Larger studies in diverse populations, including analysis of surrounding regions are recommended.

Olfactory dysfunction in LRRK2 G2019S mutation carriers.

BACKGROUND: Olfactory dysfunction is an established nonmotor feature of idiopathic Parkinson disease (PD), which may precede disease onset. Olfaction is likely disturbed in patients with PD with leucine-rich repeat kinase (LRRK2) G2019S mutations, although the degree of impairment is debated. It is also unclear whether mutation carriers who have not yet manifested with PD have olfactory disturbances. METHODS: Thirty-one subjects with LRRK2 G2019S mutation-related PD (PD-manifesting carriers [PD-MC]), 30 subjects with PD without mutations (PD noncarriers [PD-NC]), 28 mutation carrier family members (nonmanifesting carriers [NMC]), and 46 controls completed the University of Pennsylvania Smell Identification Test (UPSIT). Generalized estimating equations were applied to determine whether olfactory score was associated with PD and LRRK2 mutation status. RESULTS: As expected, having PD was associated with impaired olfaction regardless of LRRK2 mutation status. More importantly, however, impaired olfaction was increased overall in LRRK2 carriers both with and without PD, though the impairment was only present in a subset of NMCs. Compared to controls, the mean score was lower among NMC (difference = -3.518, p = 0.006), MC (difference = -7.677, p < 0.0001), and idiopathic PD (PD-NC) (difference = -13.810, p < 0.0001). Olfaction was better among MC (PD-MC) than non-LRRK2 PD (PD-NC) (difference = 6.13, p = 0.0012). Group differences from the continuous analysis were maintained in dichotomous analysis stratifying at 15th percentile for age and gender. CONCLUSION: Olfaction is impaired in LRRK2 G2019S-mutation related PD, although less overall than other PD. Further, olfaction is impaired in a subset of LRRK2 NMC, suggesting that olfaction may be a marker for development of PD in this group, and that longitudinal studies are warranted.

Gender differences in the risk of familial parkinsonism: beyond LRRK2?

G2019S mutations in the LRRK2 gene are responsible for up to 18% of PD in individuals of Jewish descent. While a male preponderance of Parkinson disease (PD) has been consistently reported, this gender difference is not noted in LRRK2 G2019S mutation carriers. In order to test whether there is an increased genetic component in women of Jewish background in general, we examined family history of parkinsonism in 175 Jewish PD patients (82 female and 93 male) and assessed whether parkinsonism was more frequent in family members of women with PD in comparison with family members of men with PD, adjusting for LRRK2 G2019S mutations in the proband. Using Cox proportional hazard models to evaluate the risk of parkinsonism among family members of PD subjects, having a daughter with PD compared with a son was associated with increased risk of parkinsonism in the parent (HR 2.59, p=0.014) as was having a child with a LRRK2 G2019S mutation (HR 3.19, p=0.003). The increased risk among parents of women with PD persisted when adjusting for LRRK2 status (HR 2.19, p=0.023). Among individuals of Jewish descent, there is a relatively greater genetic load in women with PD, and this is not fully accounted for by the G2019S mutation. Further study that evaluates family information bias and assesses the role of glucocerebrosidase mutations is indicated.

Expression profiling in peripheral blood reveals signature for penetrance in DYT1 dystonia.

DYT1 dystonia is an autosomal-dominantly inherited movement disorder, which is usually caused by a GAG deletion in the TOR1A gene. Due to the reduced penetrance of approximately 30-40%, the determination of the mutation in a subject is of limited use with regard to actual manifestation of symptoms. In the present study, we used Affymetrix oligonucleotide microarrays to analyze global gene expression in blood samples of 15 manifesting and 15 non-manifesting mutation carriers in order to identify a susceptibility profile beyond the GAG deletion which is associated with the manifestation of symptoms in DYT1 dystonia. We identified a genetic signature which distinguished between asymptomatic mutation carriers and symptomatic DYT1 patients with 86.7% sensitivity and 100% specificity. This genetic signature could correctly predict the disease state in an independent test set with a sensitivity of 87.5% and a specificity of 85.7%. Conclusively, this genetic signature might provide a possibility to distinguish DYT1 patients from asymptomatic mutation carriers.

Differential effects of COMT on gait and executive control in aging.

Walking speed is associated with attention and executive control processes subserved by the prefrontal cortex. Because polymorphisms in catechol-O-methyltransferase (COMT) influence these cognitive processes we hypothesized that the same polymorphisms may influence gait velocity. We examined the associations between the Val(158)Met polymorphism in COMT and gait velocity as well as attention and executive function. Participants were 278 non-demented older adults. The results revealed that methionine (Met)/valine (Val) was associated with faster gait velocity. This association can be explained by the putative role of the Val allele in regulating tonic dopamine release in the striatum. In contrast, Met/Met was associated with better attention and executive function. Stratification by gender revealed that the association between COMT genotype and gait was significant only in men. Conversely, the association between COMT genotype and attention and executive function was significant only in women. These findings suggest a differential effect in relating the Val(158)Met polymorphism to gait and to cognitive function while supporting the previously described sexual dimorphism in the phenotypic expressions of COMT.

Is the early-onset torsion dystonia (EOTD) linked to TOR1A gene as frequent as expected in France?

Early onset torsion dystonia are rare movement disorders. Molecular defect is known for only a subgroup, consisting of a unique and recurrent mutation in the TOR1A gene. We undertook a nationwide census of French TOR1A-mutation carriers and the assessment of clinical associated signs. Overall, 53 index cases and 104 relatives were studied and haplotypes linked to the mutation constructed. The previously reported Ashkenazi-Jewish haplotype was found in 11 families with the remainder carrying distinct haplotypes suggesting independent mutation events. This study demonstrates the scarcity of this disease in France with estimated disease frequency of 0.13:100,000 and mutation frequency of 0.17:100,000.

Myoclonus-dystonia: significance of large SGCE deletions.

Myoclonus-dystonia (M-D) is an autosomal-dominant movement disorder caused by mutations in SGCE. We investigated the frequency and type of SGCE mutations with emphasis on gene dosage alterations and explored the associated phenotypes. We tested 35 M-D index patients by multiplex ligation-dependent probe amplification (MLPA) and genomic sequencing. Mutations were found in 26% (9/35) of the cases, all but three with definite M-D. Two heterozygous deletions of the entire SGCE gene and flanking DNA and a heterozygous deletion of exon 2 only were detected, accounting for 33% (3/9) of the mutations found. Both large deletions contained COL1A2 and were additionally associated with joint problems. Further, we discovered one novel small deletion (c.771_772delAT, p.C258X) and four recurrent point mutations (c.289C>T, p.R97X; c.304C>T, p.R102X; c.709C>T, p.R237X; c.1114C>T, p.R372X). A Medline search identified 22 articles on SGCE mutational screening. Sixty-four unrelated M-D patients were described with 41 different mutations. No genotype-phenotype association was found, except in patients with deletions encompassing additional genes. In conclusion, a rigorous clinical preselection of patients and careful accounting for non-motor signs should precede mutational tests. Gene dosage studies should be included in routine SGCE genetic testing.

Myoclonus-dystonia, obsessive-compulsive disorder, and alcohol dependence in SGCE mutation carriers.

Although myoclonus and dystonia are the hallmarks of myoclonus-dystonia (M-D), psychiatric features, particularly obsessive-compulsive disorder and alcohol dependence, have been reported in three families linked to chromosome 7q21. As the epsilon sarcoglycan (SGCE) gene for M-D was subsequently identified, we evaluated the relationship between psychiatric features and SGCE mutations in these original and two additional families and confirm that OCD and alcohol dependence are associated with manifesting mutated SGCE.

Phenotype-genotype correlation in Dutch patients with myoclonus-dystonia.

The epsilon-sarcoglycan (SGCE) gene is an important cause of myoclonus-dystonia (M-D), although the majority of cases with an M-D phenotype test negative. Seven of 31 patients with the M-D phenotype carried a mutation in the SGCE gene. Positive family history and truncal myoclonus were independent prognostic factors. Early disease onset, onset with both myoclonus and dystonia, and axial dystonia were detected significantly more often in the mutation carriers.

The North American Multiple System Atrophy Study Group.

The North American Multiple System Atrophy Study Group involves investigators in 12 US medical centers funded by a grant from the National Institutes of Health. The objectives are to examine the environmental and genetic risk factors for MSA; elucidate pathogenic mechanisms underlying the disorder; and refine evaluations used for assessment. During its first year, the group enrolled 87 patients, implemented four cores, and initiated four scientific projects. Most patients among the 87 had parkinsonian features, which frequently began asymmetrically and remained asymmetrical; one-third responded to levodopa and many developed levodopa complications; almost two-thirds of the patients had cerebellar dysfunction, of these 90% had ataxia; urinary incontinence occurred commonly, and sleep disorders affected most. The investigators studied the effects of oxidative and nitrative stress upon the formation of alpha-synuclein inclusions; generated transgenic models of alpha-synuclein accumulation that recapitulate several behavioral and neuropathological features of MSA; and compared the severity of the autonomic features of MSA, Parkinson's disease and dementia with Lewy bodies.

Genetic heterogeneity in rapid onset dystonia-parkinsonism: description of a new family.

Rapid onset dystonia-parkinsonism (RDP) is a rare movement disorder with autosomal dominant inheritance, characterised by sudden onset of dystonic spasms and slowness of movement. To date, three families have been described that share linkage to the same location on chromosome 19q13, designated DYT12. Very recently, mutations in the ATP1A3 gene at the DYT12 locus have been demonstrated in seven unrelated patients, including the three previously linked families. A large RDP family is reported here, with eight definitely and one possibly affected members, that is not linked to the DYT12 region and has no mutation in the ATP1A3 gene. Predominant cranial-cervical involvement of dystonia occurred in this family, which has also been described in patients with idiopathic torsion dystonia linked to the DYT6 region on chromosome 8 and is a rare finding in DYT1 dystonia. Molecular genetic analysis also excluded linkage to the DYT6 locus and the GAG deletion in DYT1, suggesting at least one additional RDP gene.

High mutation rate in dopa-responsive dystonia: detection with comprehensive GCHI screening.

Mutations in GTP cyclohydrolase I (GCHI) are found in 50 to 60% of cases with dopa-responsive dystonia (DRD). Heterozygous GCHI exon deletions, undetectable by sequencing, have recently been described in three DRD families. We tested 23 individuals with DRD for the different mutation types by conventional and quantitative PCR analyses and found mutations, including two large exon deletions, in 87%. The authors attribute this high mutation rate to rigorous inclusion criteria and comprehensive mutational analysis.

Phenylalanine loading as a diagnostic test for DRD: interpreting the utility of the test.

Phenylalanine loading has been proposed as a diagnostic test for autosomal dominant DRD (dopa-responsive dystonia), and recently, a phenylalanine/tyrosine (phe/tyr) ratio of 7.5 after 4 h was reported as diagnostic of DRD. To test the utility of this test in another sample with DRD, we administered an oral challenge of phenylalanine (100 mg/kg) to 11 individuals with DRD and one non-manifesting gene carrier. Only 6/12 had a 4 h phe/tyr ratio of greater than 7.5, suggesting that additional parameters must be set to avoid missing the diagnosis of DRD, including the need for the plasma phenylalanine to reach a minimum level 600 in order for the test to be valid. We propose that in cases where this minimum plasma phenylalanine level is not reached, plasma tetrahydrobiopterin should be measured or alternatively other symptomatic family members should be screened.

Increased risk for recurrent major depression in DYT1 dystonia mutation carriers.

BACKGROUND: Prior studies suggest that dystonia is comorbid with affective disorders. This comorbidity could be a reaction to a chronic debilitating disorder or expression of a predisposing gene. The authors took advantage of the identification of a gene for dystonia, DYT1, to test these alternative explanations. METHODS: The authors administered a standardized psychiatric interview to members of families with an identified DYT1 mutation. The authors classified family members into three groups: mutation carriers with dystonia (manifesting carriers; n = 96), mutation carriers without dystonia (non-manifesting carriers; n = 60), and noncarriers (n = 65). RESULTS: The risk for recurrent major depressive disorder was increased in both non-manifesting carriers (RR = 4.95, CI = 1.72 to 14.29) and manifesting carriers (RR = 3.62, CI = 1.00 to 10.53) compared with noncarriers. Mutation carriers also had earlier age at onset of recurrent major depressive disorder than noncarriers. The severity of motor signs was not associated with the likelihood of recurrent depression. Mutation carriers did not have an increased risk for other affective disorders, such as single major depression or bipolar disorder. CONCLUSIONS: Early-onset recurrent major depression is associated with the DYT1 GAG mutation and this association is independent of motor manifestations of dystonia. These findings suggest that early-onset recurrent depression is a clinical expression of the DYT1 gene mutation.

Genetic heterogeneity in ten families with myoclonus-dystonia.

BACKGROUND: Myoclonus-dystonia (M-D) is a movement disorder with autosomal dominant inheritance and reduced penetrance but may also occur sporadically. Recently, mutations in the epsilon-sarcoglycan gene (SGCE) were shown to cause M-D. Furthermore, single variants in the dopamine D2 receptor (DRD2) and DYT1 genes were found in combination with SGCE mutations in two M-D families, and another M-D locus was recently mapped to chromosome 18p11 in one family. METHODS: The authors clinically and genetically characterised ten consecutive cases with myoclonus-dystonia; seven familial and three sporadic. Twenty nine M-D patients and 40 unaffected family members underwent a standardised clinical examination by a movement disorder specialist. Index cases were screened for mutations in the SGCE, DYT1, and DRD2 genes and for deletions of the SGCE gene. Suitable mutation negative families were tested for linkage to the SGCE region and to chromosome 18p11. RESULTS: Two SGCE mutations were detected among the seven familial but no mutation in the sporadic cases. Haplotype analysis at the new M-D locus was compatible with linkage in two families and excluded in another family, suggesting at least one additional M-D gene. There were no obvious clinical differences between M-D families with and without detected mutations. CONCLUSION: M-D is genetically heterogeneous with SGCE mutations accounting for the disease in only part of the clinically typical cases.