Prominent Dystonia Research Articles

An identical-by-descent novel splice-donor variant in PRUNE1 causes a neurodevelopmental syndrome with prominent dystonia in two consanguineous Sudanese families.

PRUNE1 is linked to a wide range of neurodevelopmental and neurodegenerative phenotypes. Multiple pathogenic missense and stop-gain PRUNE1 variants were identified in its DHH and DHHA2 phosphodiesterase domains. Conversely, a single splice alteration was previously reported. We investigated five patients from two unrelated consanguineous Sudanese families with an inherited severe neurodevelopmental disorder using whole-exome sequencing coupled with homozygosity mapping, segregation, and haplotype analysis. We identified a founder haplotype transmitting a homozygous canonical splice-donor variant (NM_021222.3:c.132+2T>C) in intron 2 of PRUNE1 segregated with the phenotype in all the patients. This splice variant possibly results in an in-frame deletion in the DHH domain or premature truncation of the protein. The phenotypes of the affected individuals showed phenotypic similarities characterized by remarkable pyramidal dysfunction and prominent extrapyramidal features (severe dystonia and bradykinesia). In conclusion, we identified a novel founder variant in PRUNE1 and corroborated abnormal splicing events as a disease mechanism in PRUNE1-related disorders. Given the phenotypes' consistency coupled with the founder effect, canonical and cryptic PRUNE1 splice-site variants should be carefully evaluated in patients presenting with prominent dystonia and pyramidal dysfunction.

Hyperbilirubinemia and Asphyxia in Children With Dyskinetic Cerebral Palsy

BackgroundWe aimed to study the clinical, etiologic, and radiological characteristics in children with dyskinetic cerebral palsy (DCP) and to compare the etiologic subtypes of hyperbilirubinemia and perinatal asphyxia. MethodsThis is a cross-sectional, observational study that enrolled consecutive children with DCP, aged one to 14 years. ResultsSixty-five children with DCP were evaluated. Most children were boys (77%, n = 50), and term gestation (80%, n = 52). Presenting concerns were global developmental delay (97%, n = 63) and involuntary movements (60%, n = 39). Hyperbilirubinemia (66%, n = 43) and perinatal asphyxia (29%, n = 19) were the most important causes. The majority (83%, n = 54) of children were severely disabled (level V and IV). The hyperbilirubinemia group had significant motor delay (63% vs 37%, P = 0.03) and upward gaze palsy (69.7% vs 31.5%, P = 0.005) when compared with the perinatal asphyxia group. Hyperbilirubinemia significantly involved pallidi (86% vs 10% P = 0.0001) and subthalamic nucleus (26% vs none, P = 0.01), whereas asphyxia significantly involved the putamen (58% vs none, P = 0.0001), thalamus (63% vs none, P = 0.0001), and periventricular white matter (79% vs 19%, P = 0.0001). ConclusionsDCP is the dominant type of cerebral palsy seen in term-born babies with severe dystonia, developmental delay, and motor impairment. Hyperbilirubinemia is the major cause of DCP in the study. Hyperbilirubinemia is associated with motor delay, upward gaze palsy, prominent dystonia, and involvement of globus pallidi and subthalamic nuclei.

Genetic Dystonias: Update on Classification and New Genetic Discoveries.

Since the advent of next-generation sequencing, the number of genes associated with dystonia has been growing exponentially. We provide here a comprehensive review of the latest genetic discoveries in the field of dystonia and discuss how the growing knowledge of biology underlying monogenic dystonias may influence and challenge current classification systems. Pathogenic variants in genes without previously confirmed roles in human disease have been identified in subjects affected by isolated or combined dystonia (KMT2B, VPS16, HPCA, KCTD17, DNAJC12, SLC18A2) and complex dystonia (SQSTM1, IRF2BPL, YY1, VPS41). Importantly, the classical distinction between isolated and combined dystonias has become harder to sustain since many genes have been shown to determine multiple dystonic presentations (e.g., ANO3, GNAL, ADCY5, and ATP1A3). In addition, a growing number of genes initially linked to other neurological phenotypes, such as developmental delay, epilepsy, or ataxia, are now recognized to cause prominent dystonia, occasionally in an isolated fashion (e.g., GNAO1, GNB1, SCN8A, RHOBTB2, and COQ8A). Finally, emerging analyses suggest biological convergence of genes linked to different dystonic phenotypes. While our knowledge on the genetic basis of monogenic dystonias has tremendously grown, their clinical boundaries are becoming increasingly blurry. The current phenotype-based classification may not reflect the molecular structure of the disease, urging the need for new systems based on shared biological pathways among dystonia-linked genes.

Kufor-Rakeb Syndrome with Prominent Dystonia and New Mutations in ATP13A2 Gene in Two Siblings (P4.8-022)

Kufor-Rakeb Syndrome with Prominent Dystonia and New Mutations in ATP13A2 Gene in Two Siblings (P4.8-022)

Mutations in the mitochondrial complex I assembly factor NDUFAF6 cause isolated bilateral striatal necrosis and progressive dystonia in childhood

AimTo perform a deep phenotype characterisation in a pedigree of 3 siblings with Leigh syndrome and compound heterozygous NDUFAF6 mutations. MethodA multi-gene panel of childhood-onset basal ganglia neurodegeneration inherited conditions was analysed followed by functional studies in fibroblasts. ResultsThree siblings developed gait dystonia in infancy followed by rapid progression to generalised dystonia and psychomotor regression. Brain magnetic resonance showed symmetric and bilateral cytotoxic lesions in the putamen and proliferation of the lenticular-striate arteries, latter spreading to the caudate and progressing to cavitation and volume loss. We identified a frameshift novel change (c.554_558delTTCTT; p.Tyr187AsnfsTer65) and a pathogenic missense change (c.371T>C; p.Ile124Thr) in the NDUFAF6 gene, which segregated with an autosomal recessive inheritance within the family. Patient mutations were associated with the absence of the NDUFAF6 protein and reduced activity and assembly of mature complex I in fibroblasts. By functional complementation assay, the mutant phenotype was rescued by the canonical version of the NDUFAF6. A literature review of 14 NDUFAF6 patients showed a consistent phenotype of an early childhood insidious onset neurological regression with prominent dystonia associated with basal ganglia degeneration and long survival. InterpretationNDUFAF6-related Leigh syndrome is a relevant cause of childhood onset dystonia and isolated bilateral striatal necrosis. By genetic complementation, we could demonstrate the pathogenicity of novel genetic variants in NDUFAF6.

Beta-propeller protein-associated neurodegeneration (BPAN), a rare form of NBIA: Novel mutations and neuropsychiatric phenotype in three adult patients

Neurodegeneration with brain iron accumulation (NBIA) comprises a group of rare neuropsychiatric syndromes characterized by iron accumulation in the basal ganglia. The pantothenate kinase-associated neurodegeneration (PKAN) was the first NBIA form to be genetically identified almost 15 years ago. Nowadays, eight types can be genetically distinguished. More recently, a novel NBIA was delineated and termed Static Encephalopathy of childhood with Neurodegeneration in Adulthood (SENDA), characterized by early intellectual disability followed by delayed progressive motor and cognitive deterioration with an onset in the second to third decade. Very recently, mutations in the WD repeat-containing protein 45 (WDR45) gene located on Xp11.23 were shown to be the causal factor. The protein encoded by WDR45 propels protein interaction important for autophagy. This form was therefore retermed Beta-propeller Protein Associated Neurodegeneration (BPAN). Here, the first three Dutch patients with genetically proven BPAN are comprehensively described with respect to course and neurological as well as neuropsychiatric phenotypes. All three showed a characteristic delayed progression of neurological symptoms with parkinsonism and prominent dystonia. Treatment with levodopa/carbidopa had limited effects only. Neuropsychiatric symptoms within the autistic and affective spectrum were present in the early phase of the disease. The specific course and prognosis should implicate restrained psychopharmacological interventions.The clinical picture and imaging hallmarks are often highly suggestive and should lead to suspect this specific disorder. However, the identification of a WDR45 mutation is needed for a definite diagnosis of BPAN.

The pallidopyramidal syndromes

Purpose of reviewThe aims of this review is to suggest a new nomenclature and classification system for the diseases currently categorized as neurodegeneration with brain iron accumulation (NBIA) or dystonia-parkinsonism, and to discuss the mechanisms implicated in the pathogenesis of these diseases.Recent findingsNBIA is a disease category encompassing syndromes with iron accumulation and prominent dystonia–parkinsonism. However, as there are many diseases with similar clinical presentations but without iron accumulation and/or known genetic cause, the current classification system and nomenclature remain confusing. The pathogenetic mechanisms of these diseases and the causes of gross iron accumulation and significant burden of neuroaxonal spheroids are also elusive. Recent genetic and functional studies have identified surprising links between NBIA, Parkinson's disease and lysosomal storage disorders (LSD) with the common theme being a combined lysosomal–mitochondrial dysfunction. We hypothesize that mitochondria and lysosomes form a functional continuum with a predominance of mitochondrial and lysosomal pathways in NBIA and LSD, respectively, and with Parkinson's disease representing an intermediate form of disease.SummaryDuring the past 18 months, important advances have been made towards understanding the genetic and pathological underpinnings of the pallidopyramidal syndromes with important implications for clinical practice and future treatment developments.

Dystonia in Parkinson’s disease

Dystonia can occasionally be found in idiopathic Parkinson's disease. It is very uncommon in untreated patients and is more frequently seen as a complication of its treatment. In this review, the various types of dystonia occurring in PD, the differential diagnosis with other parkinsonian syndromes associated with dystonia and treatments available are revised. Dystonia unrelated to treatment can be typical (blepharospasm, torticollis), atypical (parkinsonian writer's cramp, camptocormia, anismus), or occurring in earlyonset Parkinson disease (the so-called kinesigenic foot dystonia, considered a hallmark of early-onset Parkinson's disease). Early and prominent dystonia in untreated patients with parkinsonism should raise the suspicion of other entities other than Parkinson's disease, such as progressive supranuclear palsy, multiple system atrophy or corticobasal degeneration. In patients on chronic dopaminergic treatment, peak-dose dystonia, diphasic dystonia and off-dystonia can be seen. The later constitutes the major dystonic feature of chronic levodopa therapy, and a wide variety of strategies are available to manage this complication. Among them, deep brain stimulation of the subthalamic nucleus has proved to be the most effective one. Dystonic reactions (mainly involving oculomotor cranial nerves and limbs) in operated patients (especially carriers of deep brain stimulation (DBS) devices) are increasingly being reported, constituting a new type of dystonia in patients with Parkinson's disease: dystonia linked to surgical treatment.

Dystonia-predominant adult-onset Huntington disease: association between motor phenotype and age of onset in adults.

In juvenile Huntington disease (HD), dystonia as well as parkinsonism and eye movement abnormalities may be the predominant motor signs rather than chorea. Several patients have come to our attention with adult-onset HD in whom there is prominent dystonia and minimal chorea (ie, an adult-onset form of HD that resembles juvenile HD). To estimate the prevalence of these cases of dystonia-predominant HD in a clinic and to study the relationship between the motor phenotype and age of onset in HD. The Unified Huntington's Disease Rating Scale (UHDRS) was administered to 127 subjects during their initial visit to the Huntington's Disease Center at the New York State Psychiatric Institute, where dystonia, chorea, bradykinesia, rigidity, and eye movements were rated. The dystonia score was the mean UHDRS rating of dystonia in 5 body regions; the chorea score, the mean rating of chorea in 7 regions; the bradykinesia score, the mean rating of axial and limb bradykinesia; the rigidity score, the mean rating of rigidity in both arms; and the eye movement score, the mean rating of ocular pursuit, saccade initiation, and velocity. Dystonia-predominant HD was defined by the severity of dystonia relative to the severity of chorea. Fifteen (11.8%) of 127 subjects had dystonia-predominant HD. Age of onset correlated negatively (r= -0. 22, P=.02) with the dystonia score divided by the chorea score and negatively (r= -0.28, P=.002) with the severity of dystonia, bradykinesia, and eye movement abnormalities relative to chorea (ie, [(dystonia score + bradykinesia score + eye movement score)/3] - chorea score), suggesting that subjects with younger ages of onset had more severe dystonia, bradykinesia, and eye movement abnormalities relative to chorea. Cases of adult-onset HD with prominent dystonia and a paucity of chorea may represent 1 in 8 cases in specialty clinics. Age of onset was clearly associated with the motor phenotype. A younger age of onset was associated with more severe dystonia, bradykinesia, and eye movement abnormalities relative to chorea, supporting the notion that in adult-onset HD, the motor phenotype forms a continuum with respect to age of onset.

Actions of the D1 agonists A-77636 and A-86929 on locomotion and dyskinesia in MPTP-treated L-dopa-primed common marmosets.

Common marmosets show parkinsonian motor deficits following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration and develop dyskinesias during chronic L-dopa exposure. The D1 agonists A-77636 [(1R, 3S) 3-(1'-adamantyl)-1-aminomethyl-3, 4-dihydro-5, 6-dihydroxy-1H-2-benzopyran HCl] and A-86929 [(-)-trans 9, 10-hydroxy-2-propyl-4, 5, 5a, 6, 7, 11b-hexahydro-3-thia-5-azacyclopent-1-ena[c]phenanthrene hydrochloride] possess potent antiparkinsonian activity in the MPTP-treated marmoset and we now assess their influence on L-dopa-induced dyskinesias. MPTP-treated marmosets with stable motor deficits were treated with L-dopa plus carbidopa for 28 days to induce dyskinesias. Subsequently, they received A-86929 for 10 days, initially at 0.5 micromol/kg and then at 1.0 micromol/kg for a further 5 days. Several months later, L-dopa 12.5 mg/kg plus carbidopa 12.5 mg/kg was given orally twice daily for 7 days, followed by A-77636 1 micromol/kg for 10 days, and then both A-77636 and L-dopa plus carbidopa were given concurrently for 3 further days. In these L-dopa-primed animals, A-86929 effectively reversed akinesia and produced dose-dependent dyskinesias which were significantly less intense than those produced by L-dopa administration. A degree of behavioral tolerance was encountered, but antiparkinsonian activity was preserved and elicited behaviour was free of hyperkinesis and stereotypy and more naturalistic than that seen with L-dopa. After a week of twice-daily L-dopa dosing, administration of the long-acting D1 agonist A-77636 initially dramatically enhanced locomotion and reproduced dyskinesia with prominent dystonia, but after repeated administration of A-77636, dyskinesia and in particular chorea, gradually disappeared. Tolerance to locomotor stimulation greater than with A-86929 occurred, although activity remained significantly above baseline levels. There was a marked reduction in L-dopa-induced climbing, stereotypy and hyperkinesis and behaviour more closely resembled that of normal unlesioned marmosets. Upon reintroduction of L-dopa concurrently with continued A-77636 administration, dystonic, but virtually no choreic dyskinesias appeared and behaviour was once again free of stereotypy and hyperkinesis, contrasting dramatically with the presence of these behaviours along with abundant chorea when L-dopa is given alone. These results show a lesser liability of A-86929 and A-77636 to reproduce dyskinesia in L-dopa-primed MPTP-lesioned subjects while maintaining effective antiparkinsonian activity and producing a more naturalistic motor response. The differential effects of A-77636 on chorea and dystonia, with suppression of chorea and stereotypy on co-administration with L-dopa, may reflect an altered balance of activity in the direct and indirect striatofugal pathways. These results suggest a possible role for D1 agonists in the treatment of Parkinson's disease.

Fluorodopa and raclopride PET analysis of patients with Machado-Joseph disease.

We performed [18F]6-fluoro-L-dopa (6-FD) and [11C]raclopride (RAC) PET studies in six patients with Machado-Joseph disease (MJD) (age, 17 to 61 years; duration of illness, 3 to 10 years), normal controls (n = 10 in 6-FD-PET, n = 8 in RAC-PET), and patients with idiopathic parkinsonism (n = 15 in 6-FD-PET). The youngest patient with MJD had prominent dystonia and pyramidal features (type 1 MJD), whereas the remainder were prominently ataxic (types 2 and 3 MJD). Striatal RAC binding was normal in patients with MJD. Striatal 6-FD influx constants (Ki) were low in the range of idiopathic parkinsonism in two patients with MJD (youngest and oldest patients), whereas striatal Ki were normal in the remaining patients with MJD. The impairment of the nigrostriatal dopaminergic pathway did not correlate with the phenotype, CAG repeat length, disease duration, or age of onset of patients with MJD. Our results suggest that striatal D2 receptors are normal and the nigral damage is diverse in MJD.

Positron emission tomographic studies of dopa-responsive dystonia and early-onset idiopathic parkinsonism.

There are two major syndromes presenting in the early decades of life with dystonia and parkinsonism: dopa-responsive dystonia (DRD) and early-onset idiopathic parkinsonism (EOIP). DRD presents predominantly in childhood with prominent dystonia and lesser degrees of parkinsonism. EOIP presents before age 40 with parkinsonism (often with associated dystonia). Both disorders are exquisitely sensitive to levodopa, although the long-term prognosis in each appears to be different. Some have suggested, however, that DRD is a form of EOIP. We performed positron emission tomography with 6-fluoro-dopa in 10 patients with DRD and 18 patients with EOIP to study the integrity of their nigrostriatal dopaminergic systems. In DRD, we found normal striatal FD uptake. In contrast, patients with EOIP had reduced striatal FD uptake. We conclude that the patho-physiologies of DRD and EOIP are distinct. Although both disorders presumably represent a deficiency of striatal dopamine, the results suggest that in DRD dopa uptake, decarboxylation, and storage mechanisms are intact. This may explain the sustained response of DRD to low doses of levodopa. 6-Fluoro-dopa positron emission tomography distinguishes DRD from EOIP.