Myoclonus-dystonia Research Articles

Primary Myoclonus-Dystonia: A Diagnosis Often Missed in Children (IN10-1.004)

Objective: To review the manifestations of primary myolconus-dystonia in childhood and increase its awareness among clinicians to make an early diagnosis and institute a prompt effective treatment. Background Primary myoclonus-dystonia is a childhood-onset autosomal dominant movement disorder with myoclonus and dystonia due to epsilon sarcoglycan (SGCE) gene mutation or deletion. There are very few reports of this condition presenting in childhood. Its biological behavior in childhood is unclear. Design/Methods: A retrospective chart analysis of patients, ≤18 years at the Cleveland Clinic between 2008 and 2011 with myoclonus and dystonia. The cases with primary Myoclonus Dystonia (criteria by Gunewald, 2008) were reviewed in greater detail in respect to age of onset, age at final diagnosis, referral diagnosis, investigations, clinical features including video-observation, treatment, and prognosis. Results: We report 9 children (4 boys, 5 girls) with primary myoclonus dystonia from eight families. Mean age of onset of symptoms was 2.8 ± 3.86 years (8 months-13 years) but the diagnosis was made at 7.3 + 5.85 years. Myoclonus was the presenting symptom in 8 children. A known pathogenic mutation in SGCE gene was identified in 4 children and 2 children had mutations in the same gene not previously described. Good response to trihexyphenidyl and clonazepam was seen. One patient underwent bilateral globus pallidus pars interna deep brain stimulation surgery. In 7 children, the diagnosis of myoclonus-dystonia was not considered by the referring neurologists. The differentials included ataxia, developmental delay, tremor, gait problem. This initial misdiagnosis led to extensive investigations and a delay in final diagnosis. Conclusions: Finding 9 cases of primary myoclonus dystonia in children over a 3 year period in one center proves that this disorder is not so rare to manifest in children. We highlight the need for more awareness among the meurologists about myoclonus-dystonia presenting in childhood. Disclosure: Dr. Ghosh has received personal compensation for activities with Merz Pharma as a consultant. Dr. Indulkar has nothing to disclose.

Primary Myoclonus-Dystonia: A Diagnosis Often Missed in Children (P02.170)

Primary Myoclonus-Dystonia: A Diagnosis Often Missed in Children (P02.170)

Microdeletions detected using chromosome microarray in children with suspected genetic movement disorders: a single‐centre study

Chromosome microarray (CMA) can determine copy number variants such as microdeletions or microduplications. Microdeletions of movement disorder genes including epsilon-sarcoglycan (SGCE) and thyroid transcription factor-1 (TITF1) have been described in patients with myoclonus dystonia and benign hereditary chorea respectively. We examined whether CMA is a valuable tool in the investigation of children with suspected genetic movement disorders. A genetic movement disorder was suspected if there was a positive first-degree family history, or two or more of the following factors: normal or near-normal magnetic resonance imaging, negative history of brain injury, and negative investigations for metabolic disorders. Tic disorders were excluded. Twenty-five patients (18 males, seven females) with a mean age at movement disorder onset of 4 years 5 month (range 1 mo-14 y) were prospectively recruited with the following primary movement disorders: dystonia (n=10), paroxysmal kinesigenic dyskinesia (n=5), tremor (n=4), chorea (n=3), myoclonus (n=2), and paroxysmal non-kinesigenic dyskinesia (n=1). Comorbid associated features were common, particularly developmental delay or intellectual disability (19 out of 25) and attention-deficit-hyperactivity disorder (six out of 25). CMA was performed using Agilent aCGH 60K array. Seven out of twenty-five patients had a microdeletion determined by CMA. None of the microdeletions were considered benign variants. Four patients had a deletion of a known movement disorder gene including paroxysmal kinesigenic dyskinesia (PRRT2; n=2), SGCE (myoclonus dystonia, n=1), and TITF1 (benign hereditary chorea, n=1). Three patients had novel microdeletions of unknown but potential significance including 14q13.3 (chorea, n=1), 19p13.12 (tremor, n=1), and 19q13.12 (progressive dystonia). All seven patients had associated neurodevelopmental or behavioural problems. Assays that determine copy number variants may be a valuable first-tier investigation in patients with suspected genetic movement disorders, particularly when associated with intellectual disability or developmental disorders. Microdeletion syndromes may help the search for new movement disorder genes.

Alteration of Striatal Dopaminergic Neurotransmission in a Mouse Model of DYT11 Myoclonus-Dystonia

BackgroundDYT11 myoclonus-dystonia (M-D) syndrome is a neurological movement disorder characterized by myoclonic jerks and dystonic postures or movement that can be alleviated by alcohol. It is caused by mutations in SGCE encoding ε-sarcoglycan (ε-SG); the mouse homolog of this gene is Sgce. Paternally-inherited Sgce heterozygous knockout (Sgce KO) mice exhibit myoclonus, motor impairment and anxiety- and depression-like behaviors, modeling several clinical symptoms observed in DYT11 M-D patients. The behavioral deficits are accompanied by abnormally high levels of dopamine and its metabolites in the striatum of Sgce KO mice. Neuroimaging studies of DYT11 M-D patients show reduced dopamine D2 receptor (D2R) availability, although the possibility of increased endogenous dopamine, and consequently, competitive D2R occupancy cannot be ruled out.Methodology/Principal FindingsThe protein levels of striatal D2R, dopamine transporter (DAT), and dopamine D1 receptor (D1R) in Sgce KO mice were analyzed by Western blot. The striatal dopamine release after amphetamine injection in Sgce KO mice were analyzed by microdialysis in vivo. The striatal D2R was significantly decreased in Sgce KO mice without altering DAT and D1R. Sgce KO mice also exhibited a significant increase of dopamine release after amphetamine injection in comparison to wild-type (WT) littermates.Conclusion/SignificanceThe results suggest ε-SG may have a role in the regulation of D2R expression. The loss of ε-SG results in decreased striatal D2R, and subsequently leads to increased discharge of dopamine which could contribute to the behavioral impairment observed in DYT11 dystonia patients and in Sgce KO mice. The results suggest that reduction of striatal D2R and enhanced striatal dopamine release may contribute to the pathophysiology of DYT11 M-D patients.

1624 Myoclonus dystonia: a clinical and genetic description

BackgroundMyoclonus Dystonia Syndrome (MDS) is a childhood onset movement disorder involving trunk and upper limb myoclonus and dystonia of the neck and hands. Psychiatric co-morbidity has also been described and...

Deep Brain Stimulation of the Pallidum is Effective and Might Stabilize Striatal D2 Receptor Binding in Myoclonus–Dystonia

Purpose: To assess clinical efficacy of deep brain stimulation (DBS) of the pallidum in Myoclonus–Dystonia (M–D) patients, and to compare pre- and post-operative striatal dopamine D2 receptor availability. Methods: Clinical parameters were scored using validated rating scales for myoclonus and dystonia. Dopamine D2 receptor binding of three patients was studied before surgery and approximately 2 years post-operatively using 123-I-iodobenzamide Single Photon Emission Computed Tomography. Two patients who did not undergo surgery served as controls. Results: Clinically, the three M–D patients improved 83, 17, and 100%, respectively on the myoclonus rating scale and 78, 23, and 65% on the dystonia rating scale after DBS. Dopamine D2 receptor binding did not change after surgery. In the two control subjects, binding has lowered further. Conclusion: These findings confirm that DBS of the pallidum has beneficial effects on motor symptoms in M–D and suggest this procedure might stabilize dopamine D2 receptor binding.

A Novel Mutation in Exon 6 of the Epsilon-Sarcoglycan Gene in Myoclonus Dystonia Syndrome

Abstract Myoclonus-dystonia syndrome (MDS) is a rare hereditary movement disorder characterized by the early onset of myoclonus in the first or second decade of life. The first locus for MDS was mapped to chromosome 7q21 and identified as the epsilon-sarcoglycan (SGCE) gene, and numerous mutations were subsequently identified. We here present the first reported Turkish MDS patient identified with a novel mutation in exon 6 of the SGCE gene, which resulted in truncation of the protein before the transmembrane domain, presumably causing the loss of function either by mislocalization of the protein away from the plasma membrane or through nonsense-mediated decay.

Overview of primary monogenic dystonia

Primary monogenic forms of dystonia manifest solely or mainly with dystonia; they have been linked to a number of genes and loci and assigned "DYT" numbers. The pure dystonia syndrome early-onset primary dystonia (DYT1) manifests with dominantly-inherited generalized dystonia, often with focal onset in a limb. DYT1 is caused by a GAG deletion in the TOR1A gene. Mutations in the THAP1 gene cause DYT6, a form of pure dystonia that primarily involves cranio-cervical and upper limb muscles. Patients with the dystonia plus syndrome DYT5 display levodopa-responsive dystonia sometimes associated with tremor or parkinsonism (DYT5a, mutations in GCH1); a more severe phenotype with psychomotor involvement can be seen in recessive forms (DYT5b with TH mutations, SPR-deficiency syndrome). Other forms of dystonia plus syndromes include myoclonic dystonia (DYT11) and rapid-onset dystonia-parkinsonism (DYT12). Finally, paroxysmal exertion-induced dystonia (DYT18, GLUT1 deficiency) is caused by mutations in the SLC2A1 gene (DYT9 and DYT18). It is part of the paroxysmal dystonia group and manifests with paroxystic movements sometimes associated with seizures and psychomotor developmental delay.

A novel SGCE gene mutation causing myoclonus dystonia in a family with an unusual phenotype

Myoclonus dystonia is an autosomal dominant dystonia-plus syndrome, characterized by symptom variability within families. Most often is the myoclonus the most debilitating symptom, and many patients report myoclonus reduction after alcohol intake. In several families, mutations in the SGCE gene have been identified. We report of a three-generation family with myoclonus dystonia displaying a varied phenotype and maternal imprinting. Additionally, this family displays some unusual clinical presentations including alcohol-induced dystonia in an adult man, which will be discussed. A novel mutation c.386T>C [p.I129T] was found within exon 3 of the SGCE gene in all three affected family members. In addition, two additional mutations [c.305G>A and IVS3+15G>A], judged to be polymorphisms in the SGCE gene, were found in two affected and one healthy family member. This report presents a novel mutation in the SGCE gene causing myoclonus dystonia and extends the phenotype of myoclonus dystonia to also include alcohol-induced dystonia.

Abnormal nuclear envelopes in the striatum and motor deficits in DYT11 myoclonus-dystonia mouse models

DYT11 myoclonus-dystonia (M-D) is a movement disorder characterized by myoclonic jerks with dystonic symptoms and caused by mutations in paternally expressed SGCE, which codes for ε-sarcoglycan. Paternally inherited Sgce heterozygous knock-out (KO) mice exhibit motor deficits and spontaneous myoclonus. Abnormal nuclear envelopes have been reported in cellular and mouse models of early-onset DYT1 generalized torsion dystonia; however, the relationship between the abnormal nuclear envelopes and motor symptoms are not clear. Furthermore, it is not known whether abnormal nuclear envelope exists in non-DYT1 dystonia. In the present study, abnormal nuclear envelopes in the striatal medium spiny neurons (MSNs) were found in Sgce KO mice. To analyze whether the loss of ε-sarcoglycan in the striatum alone causes abnormal nuclear envelopes, motor deficits or myoclonus, we produced paternally inherited striatum-specific Sgce conditional KO (Sgce sKO) mice and analyzed their phenotypes. Sgce sKO mice exhibited motor deficits in both beam-walking and accelerated rotarod tests, while they did not exhibit abnormal nuclear envelopes, alteration in locomotion, or myoclonus. The results suggest that the loss of ε-sarcoglycan in the striatum contributes to motor deficits, while it alone does not produce abnormal nuclear envelopes or myoclonus. Development of therapies targeting the striatum to compensate for the loss of ε-sarcoglycan function may rescue the motor deficits in DYT11 M-D patients.

Abnormal nuclear envelope in the cerebellar Purkinje cells and impaired motor learning in DYT11 myoclonus-dystonia mouse models

Myoclonus-dystonia (M-D) is a movement disorder characterized by myoclonic jerks with dystonia. DYT11 M-D is caused by mutations in SGCE which codes for ɛ-sarcoglycan. SGCE is maternally imprinted and paternally expressed. Abnormal nuclear envelope has been reported in mouse models of DYT1 generalized torsion dystonia. However, it is not known whether similar alterations occur in DYT11 M-D. We developed a mouse model of DYT11 M-D using paternally inherited Sgce heterozygous knockout ( Sgce KO) mice and reported that they had myoclonus and motor coordination and learning deficits in the beam-walking test. However, the specific brain regions that contribute to these phenotypes have not been identified. Since ɛ-sarcoglycan is highly expressed in the cerebellar Purkinje cells, here we examined the nuclear envelope in these cells using a transmission electron microscope and found that they are abnormal in Sgce KO mice. Our results put DYT11 M-D in a growing family of nuclear envelopathies. To analyze the effect of loss of ɛ-sarcoglycan function in the cerebellar Purkinje cells, we produced paternally inherited cerebellar Purkinje cell-specific Sgce conditional knockout ( Sgce pKO) mice. Sgce pKO mice showed motor learning deficits, while they did not show abnormal nuclear envelope in the cerebellar Purkinje cells, robust motor deficits, or myoclonus. The results suggest that ɛ-sarcoglycan in the cerebellar Purkinje cells contributes to the motor learning, while loss of ɛ-sarcoglycan in other brain regions may contribute to nuclear envelope abnormality, myoclonus and motor coordination deficits.

Psychiatric disorders, myoclonus dystonia, and the epsilon‐sarcoglycan gene: A systematic review

Mutations in the maternally imprinted epsilon-sarcoglycan gene occur in 30%-50% of myoclonus-dystonia cases. Psychiatric symptoms, particularly obsessive-compulsive disorder, have been described in some patients. We systematically reviewed 22 reports of psychiatric symptoms in myoclonus-dystonia, dividing individuals according to clinical and mutation status. Clinically manifesting mutation carriers demonstrated an excess of psychiatric disorders compared with nonmutation carriers (P < .001). No differences were seen between non-motor-manifesting carriers and nonmutation carriers with the exception of alcohol excess/dependence, higher in non-motor-manifesting carriers. The results confirm the association of epsilon-sarcoglycan gene mutations with psychiatric disease and suggest a possible separation of the motor and psychiatric effects.

Atypical symptomatology of myoclonus dystonia (DYT‐11) with positive response to bilateral pallidal deep brain stimulation

Atypical symptomatology of myoclonus dystonia (DYT‐11) with positive response to bilateral pallidal deep brain stimulation

A role of diffusion tensor imaging fiber tracking in deep brain stimulation surgery: DBS of the dentato-rubro-thalamic tract (drt) for the treatment of therapy-refractory tremor

Deep brain stimulation (DBS) can alleviate tremor of various origins. A number of regions are targeted. In recent work our group was able to show the involvement of the dentato-rubro-thalamic tract (drt) in tremor control with fiber tracking techniques. Here we report for the first time the successful use of magnetic resonance tractography in combination with traditional landmark-based targeting techniques to perform the implantation of a bilateral DBS system in a patient with dystonic head tremor. We report on a 37-year-old female with long-standing pure head tremor from myoclonus dystonia. She was identified as a candidate for thalamic DBS. The use of head fixation in a stereotactic frame would blur target symptoms (head tremor) during surgery and was therefore avoided. Her dentate-rubro-thalamic tracts were visualized with preoperative diffusion tensor imaging (DTI) and tractography, and then directly targeted stereotactically with DBS electrodes. Three months after implantation, tremor control was excellent (>90%). A close evaluation of the active electrode contact positions revealed clear involvement of the drt. This is the first time that direct visualization of fiber tracts has been employed for direct targeting and successful movement disorder tremor surgery. In the reported case, additional knowledge about the position of the drt, which previously has been shown to be a structure for modulation to achieve tremor control, led to a successful implantation of a DBS system, although there was a lack of intra-operatively testable tremor symptoms. In concordance with studies in optogenetic neuromodulation, fiber tracts are the emerging target structures for DBS. The routine integration of DTI tractography into surgical planning might be a leading path into the future of DBS surgery and will add to our understanding of the pathophysiology of movement disorders. Larger study populations will have to prove these concepts in future research.

Familial 7q21.3 microdeletion involving epsilon-sarcoglycan causing myoclonus dystonia, cognitive impairment, and psychosis

Familial 7q21.3 microdeletion involving epsilon-sarcoglycan causing myoclonus dystonia, cognitive impairment, and psychosis

Impaired saccadic adaptation in DYT11 dystonia

BackgroundRecent neuroimaging studies point to a possible pathophysiological role of cerebellar dysfunction in dystonia. The authors investigated the association between sensorimotor adaptation, cerebellar dysfunction and the myoclonus–dystonia phenotype.MethodsThe authors prospectively...

A new familial syndrome with dystonia and lower limb action myoclonus

Myoclonus-dystonia (M-D) is genetic and clinically heterogeneous. Identification and description of rare M-D syndromes may contribute to gene identification. Here, we describe a new, autosomal dominant M-D syndrome in a 3-generation pedigree showing anticipation. Patients have progressive action-induced multifocal dystonia and generalized myoclonus. A remarkable feature of the syndrome is action myoclonus in the lower extremities triggered by upright posture, causing instability. Electrophysiological characterization shows a 12-Hz peak in the EMG autospectrum and corticomuscular and intermuscular coherences. A new familial M-D syndrome with progressive action myoclonus and dystonia is described.

Severity of dystonia is correlated with putaminal gray matter changes in Myoclonus-Dystonia

Myoclonus-dystonia (M-D) is an autosomal dominantly inherited movement disorder characterized by myoclonic jerks and dystonic postures or movements. Morphometric studies have been performed in other, mainly heterogenous, types of dystonia producing conflicting results. However, all these studies agree on abnormalities in sensorimotor structures, mainly in the basal ganglia. We aimed to study gray matter (GM) volumes in sensorimotor brain structures with magnetic resonance imaging (MRI) in a genetically homogeneous form of dystonia, M-D. Twenty-five clinically affected DYT11 mutation carriers (MC) and 25 matched control subjects were studied using T1-weighted 3D anatomical images of the entire brain, obtained with a 3.0 Tesla MRI. MC were clinically scored using the Burke Fahn Marsden dsytonia rating scale (BFMDRS) and the unified myoclonus rating scale (UMRS). GM volumes in sensorimotor cortices and basal ganglia of patients and controls were compared, and multiple regression analyses were used to correlate the GM volumes of patients with the clinical rating scales BFMDRS and UMRS. No significant differences were found between groups, but dystonia severity in MC was strongly correlated with increased GM volume in bilateral putamina. This study provides further evidence for the involvement of putamina as important motor structures in the pathophysiology of (myoclonus-) dystonia. Changes in these structures are associated with the severity of dystonia.

SGCE isoform characterization and expression in human brain: implications for myoclonus–dystonia pathogenesis?

Myoclonus-dystonia (M-D) is a neurological movement disorder with involuntary jerky and dystonic movements as major symptoms. About 50% of M-D patients have a mutation in ɛ-sarcoglycan (SGCE), a maternally imprinted gene that is widely expressed. As little is known about SGCE function, one can only speculate about the pathomechanisms of the exclusively neurological phenotype in M-D. We characterized different SGCE isoforms in the human brain using ultra-deep sequencing. We show that a major brain-specific isoform is differentially expressed in the human brain with a notably high expression in the cerebellum, namely in the Purkinje cells and neurons of the dentate nucleus. Its expression was low in the globus pallidus and moderate to low in caudate nucleus, putamen and substantia nigra. Our data are compatible with a model in which dysfunction of the cerebellum is involved in the pathogenesis of M-D.

POMD10 Do psychiatric disorders form part of the myoclonus-dystonia syndrome phenotype? A systematic review of published literature

Myoclonus–dystonia syndrome (MDS) is a rare movement disorder characterised by myoclonus mainly of the trunk and upper limbs in conjunction with dystonic posturing, usually of neck and hands. Mutations of...