Hereditary essential myoclonus in a large Norwegian family

Are functional movement disorder phenotypes or age at onset correlated with perfectionism or history of abuse?

Objective

To assess if the phenotype or age at onset of Functional Movement Disorders (FMD) vary as a function of presence of a perfectionism or history of abuse. Detecting such a potential association might help guide future research into the pathophysiology of FMD.

Methods

Charts of all patients diagnosed with FMD by a movement disorder specialist using the commonly accepted clinical diagnostic criteria for FMD seen at a tertiary center over 8 years were reviewed. Data collected were sex, age at the onset of the first FMD, phenotype of the first predominant FMD, history of perfectionism and history of childhood abuse (physical, sexual, emotional, or neglect). Statistical analyses were performed as appropriate.

Results

68 patients with FMD were identified from which 12 were excluded for incomplete documentation. 56 patients were included in the analysis, 43 (76.8%) were women, with average age at onset 41.5y (range 13-74.4). The most frequent predominant initial FMD phenotypes were tremor (39%), dystonia (20.3%) and gait disorders (20.3%).Perfectionism was reported in 30 (53.6%) patients and history of abuse in 27 (48.2%).There was no significant correlation between each of the FMD phenotypes and perfectionism or history of childhood abuse. There was also no correlation between the age at symptoms onset and perfectionism or history of abuse.

Conclusion

We could not demonstrate a significant correlation between FMD phenotype or age at onset and perfectionist personality trait or history of abuse. Factors leading to the development of one specific FMD phenotype rather than another are still to be elucidated.

Medical management of myoclonus-dystonia and implications for underlying pathophysiology

Myoclonus-dystonia is an early onset genetic disorder characterised by subcortical myoclonus and less prominent dystonia. Its primary causative gene is the epsilon-sarcoglycan gene but the syndrome of "myoclonic dystonia" has been shown to be a heterogeneous group of genetic disorders. The underlying pathophysiology of myoclonus-dystonia is incompletely understood, although it may relate to dysfunction of striatal monoamine neurotransmission or disruption of cerebellothalamic networks (possibly via a GABAergic deficit of Purkinje cells). A broad range of oral medical therapies have been used in the treatment of myoclonus-dystonia with a varying response, and limited data relating to efficacy and tolerability, yet this condition responds dramatically to alcohol. Few well conducted randomized controlled trials have been undertaken leading to an empirical ad hoc approach for many patients. We review the current evidence for pharmacological therapies in myoclonus-dystonia, discuss implications for underlying pathogenesis of the condition and propose a treatment algorithm for these patients.

Sporadic and familial myoclonic dystonia: Report of three cases and review of literature

Myoclonic dystonia refers to a clinical syndrome characterized by rapid jerky movements along with dystonic posturing of the limbs. Clinically, it is characterized by sudden, brief, electric shock-like movements, mostly involving the upper extremities, shoulders, neck and trunk. Characteristically, the movements wane with consumption of small dose of alcohol in about 50% of cases. Additionally, dystonic contractions are observed in most of the patients in the affected body parts and some patients may exhibit cervical dystonia or graphospasm as well. It may manifest as an autosomal dominant condition or sometimes, as a sporadic entity, though there are doubts whether these represent cases with reduced penetrance. The condition is usually treated with a combination of an anticholinergic agent like, benztropine, pimozide and tetrabenazine. We report one sporadic case and one familial case where the father and the son are affected. The cases were collected from the Movement Disorders Clinic of Bangur Institute of Neurosciences, Kolkata, West Bengal in a period of ten months. Myoclonic dystonia is a rare condition and to the best of our knowledge, this series is the first one reported from our country. Videos of the patients are also provided with the article.

SGCE and myoclonus dystonia: motor characteristics, diagnostic criteria and clinical predictors of genotype

Myoclonus dystonia syndrome (MDS) is a young-onset movement disorder. A proportion of cases are due to mutations in the maternally imprinted SGCE gene. We assembled the largest cohort of MDS patients to date, and determined the frequency and type of SGCE mutations. The aim was to establish the motor phenotype in mutation carriers and utility of current diagnostic criteria. Eighty-nine probands with clinical features compatible with MDS were recruited from the UK and Ireland. Patients were phenotypically classified as "definite", "probable" or "possible" MDS according to previous guidelines. SGCE was analyzed using direct sequencing and copy number variant analysis. In those where no mutation was found, DYT1 (GAG deletion), GCH1, THAP1 and NKX2.1 genes were also sequenced. Nineteen (21.3%) probands had an SGCE mutation. Three patterns of motor symptoms emerged: (1) early childhood onset upper body myoclonus and dystonia, (2) early childhood onset lower limb dystonia, progressing later to more pronounced myoclonus and upper body involvement, and (3) later childhood onset upper body myoclonus and dystonia with evident cervical involvement. Five probands had large contiguous gene deletions ranging from 0.7 to 2.3 Mb in size with distinctive clinical features, including short stature, joint laxity and microcephaly. Our data confirms that SGCE mutations are most commonly identified in MDS patients with (1) age at onset ≤10 years and (2) predominant upper body involvement of a pure myoclonus-dystonia. Cases with whole SGCE gene deletions had additional clinical characteristics, which are not always predicted by deletion size or gene involvement.

Primary Myoclonus-Dystonia: A Diagnosis Often Missed in Children

Primary myoclonus-dystonia is a childhood-onset autosomal-dominant movement disorder with myoclonic jerks and dystonia. The authors report 9 children (4 boys, 5 girls) with myoclonus-dystonia from 8 families seen over a 4-year period at Cleveland Clinic. The mean age of onset of symptoms was 2.8 years, but the diagnosis was made at a mean of 7.3 years. Myoclonus was the presenting symptom in 8 children. A known pathogenic mutation in the ε-sarcoglycan gene (SGCE) was identified in 4 of the 9 children, and 2 other children had novel mutations in the same gene. Good response to trihexyphenidyl and clonazepam was seen. Two patients underwent deep brain stimulation surgery of the bilateral globus pallidus pars interna. In 7 children, the diagnosis of myoclonus-dystonia was not considered by the referring child neurologists, which led to extensive investigations and a delay in the final diagnosis. In this report, the authors highlight the need for increased awareness of this entity among child neurologists.

Familial psychogenic movement disorders

BACKGROUND

Psychogenic (or functional) movement disorders (PMDs) are considered sporadic. Despite the growing literature describing the clinical features and the natural history of sporadic cases with PMDs, their occurrence in familial clusters is not reported.

METHODS

We identified 10 patients from 5 families affected by PMDs. In this report, we describe the clinical characteristics along with videos and long-term follow-up of these patients.

RESULTS

Clinical clues from the history and signs suggesting a functional origin of the symptoms in these patients with familial PMD were similar to those identified in sporadic cases. The phenomenology of the PMD was similar in the affected members of the same family.

CONCLUSIONS

We wish to highlight that a positive family history does not necessarily imply an organic disorder. When a positive family history for a condition is reported by a patient with PMD, examination of these further affected members may be needed and may identify further family members suffering from PMDs. A positive family history of PMDs may be an additional risk factor for developing PMDs. © 2013 Movement Disorder Society.

Nonprimary dystonias

Dystonias can be classified as primary or secondary, as dystonia-plus syndromes, and as heredodegenerative dystonias. Their prevalence is difficult to determine. In our experience 80-90% of all dystonias are primary. About 20-30% of those have a genetic background; 10-20% are secondary, with tardive dystonia and dystonia in cerebral palsy being the most common forms. If dystonia in spastic conditions is accepted as secondary dystonia, this is the most common form of all dystonia. In primary dystonias, the dystonic movements are the only symptoms. In secondary dystonias, dystonic movements result from exogenous processes directly or indirectly affecting brain parenchyma. They may be caused by focal and diffuse brain damage, drugs, chemical agents, physical interactions with the central nervous system, and indirect central nervous system effects. Dystonia-plus syndromes describe brain parenchyma processes producing predominantly dystonia together with other movement disorders. They include dopa-responsive dystonia and myoclonus-dystonia. Heredodegenerative dystonias are dystonic movements occurring in the context of other heredodegenerative disorders. They may be caused by impaired energy metabolism, impaired systemic metabolism, storage of noxious substances, oligonucleotid repeats and other processes. Pseudodystonias mimic dystonia and include psychogenic dystonia and various orthopedic, ophthalmologic, vestibular, and traumatic conditions. Unusual manifestations, unusual age of onset, suspect family history, suspect medical history, and additional signs may indicate nonprimary dystonia. If they are suspected, etiological clarification becomes necessary. Unfortunately, potential etiologies are legion. Diagnostic algorithms can be helpful. Treatment of nonprimary dystonias, with few exceptions, does not differ from treatment of primary dystonias. The most effective treatment for focal and segmental dystonias is local botulinum toxin injections. Deep brain stimulation of the globus pallidus internus is effective for generalized dystonia. Antidystonic drugs, including anticholinergics, tetrabenazine, clozapine, and gamma-aminobutyric acid receptor agonists, are less effective and often produce adverse effects. Dopamine is extremely effective in dopa-responsive dystonia. The Bertrand procedure can be effective in cervical dystonia. Other peripheral surgery, including myotomy, myectomy, neurotomy, rhizotomy, ramizectomy, and accessory nerve neurolysis, has largely been abandoned. Central surgery other than deep brain stimulation is obsolete. Adjuvant therapies, including orthoses, physiotherapy, ergotherapy, behavioral therapy, social support, and support groups, may be helpful. Analgesics should also be considered where appropriate.

Myoclonus-dystonia: an update

Our knowledge of the clinical, neurophysiological, and genetic aspects of myoclonus-dystonia (M-D) has improved markedly in the recent years. Basic research has provided new insights into the complex dysfunctions involved in the pathogenesis of M-D. On the basis of a comprehensive literature search, this review summarizes current knowledge on M-D, with a focus on recent findings. We also propose modified diagnostic criteria and recommendations for clinical management.

Movement disorders and alcohol misuse

Many movement disorders, including tics, chorea, tremor, myoclonus and parkinsonism, may result from substance abuse. However, alcohol in particular is associated in a more complex manner with two specific movement disorders, essential tremor (ET) and myoclonus-dystonia (M-D). In this review we discuss the comorbidity of alcohol abuse in both ET and M-D, the ameliorative effects of alcohol in both diseases, and review the data evaluating alcohol abuse secondary to self-medication. We also discuss shared pathophysiologic mechanisms in the understanding of both of these disorders, as the elucidation of the mechanisms by which alcohol exerts its effects may lead to novel therapeutic approaches.

Inherited myoclonus-dystonia and epilepsy: Further evidence of an association?

Epilepsy and electroencephalogram (EEG) abnormalities have been considered exclusion criteria for the clinical diagnosis of myoclonus-dystonia (M-D). We report on the second M-D family in which several clinically affected epsilon-sarcoglycan gene (SGCE) mutation carriers have seizures in addition to myoclonus and dystonia, adding to the evidence that epilepsy and EEG abnormalities may form part of the phenotypic spectrum of the condition. A nonsense mutation in exon 3 (289C-->T) of SGCE resulting in the insertion of a premature stop codon (R97X) was detected in affected members of this family.

Mutations in the gene encoding epsilon-sarcoglycan cause myoclonus-dystonia syndrome

The dystonias are a common clinically and genetically heterogeneous group of movement disorders. More than ten loci for inherited forms of dystonia have been mapped, but only three mutated genes have been identified so far. These are DYT1, encoding torsin A and mutant in the early-onset generalized form, GCH1 (formerly known as DYT5), encoding GTP-cyclohydrolase I and mutant in dominant dopa-responsive dystonia, and TH, encoding tyrosine hydroxylase and mutant in the recessive form of the disease. Myoclonus-dystonia syndrome (MDS; DYT11) is an autosomal dominant disorder characterized by bilateral, alcohol-sensitive myoclonic jerks involving mainly the arms and axial muscles. Dystonia, usually torticollis and/or writer's cramp, occurs in most but not all affected patients and may occasionally be the only symptom of the disease. In addition, patients often show prominent psychiatric abnormalities, including panic attacks and obsessive-compulsive behavior. In most MDS families, the disease is linked to a locus on chromosome 7q21 (refs. 11-13). Using a positional cloning approach, we have identified five different heterozygous loss-of-function mutations in the gene for epsilon-sarcoglycan (SGCE), which we mapped to a refined critical region of about 3.2 Mb. SGCE is expressed in all brain regions examined. Pedigree analysis shows a marked difference in penetrance depending on the parental origin of the disease allele. This is indicative of a maternal imprinting mechanism, which has been demonstrated in the mouse epsilon-sarcoglycan gene.

Excessive blinking in childhood: a prospective evaluation of 99 children

OBJECTIVE

To determine the characteristics and causes of excess blinking in children and to determine outcomes after treatment.

DESIGN

Prospective, noncomparative, consecutive case series.

PARTICIPANTS

Ninety-nine consecutive children who presented for evaluation of excessive blinking over a 2 year period.

METHODS

Children less than 16 years of age who had excessive blinking as their sole or major chief complaint underwent detailed history and ophthalmologic examination. Treatment was recommended based on clinical examination findings. Follow-up evaluations were performed at least 2 months after initial examination.

MAIN OUTCOME MEASURES

Etiology of excess blinking and patient characteristics in each diagnostic group.

RESULTS

The majority (89%) of children presented with bilateral excessive blinking. Boys outnumbered girls at a ratio of almost 2:1. The most common etiologies were anterior segment and/or lid abnormalities (37%), habit tics (23%), uncorrected refractive errors (14%), intermittent exotropia (11%), and psycogenic blepharospasm (10%). A history of neurologic disease was present in 22% of the patients but was not causally related to the excessive blinking in most cases. Vision-threatening disease was noted in 6% and was easily detected on standard clinical examination. Life-threatening disease was the cause in 4% of the children, but the presence of life-threatening disease was already known in all such patients.

CONCLUSIONS

Excessive blinking in children can occur because of a large number of potential problems. Most cases are caused by benign and/or self-limiting conditions. The cause can usually be determined after careful history and clinical examination and routine neurologic evaluation and neuroimaging is unnecessary.

Myoclonus

The diagnosis and treatment of myoclonus pose a particular challenge to the neurologist. Few well-controlled double-blind studies of antimyoclonic agents have been performed, and clinical rating of the effectiveness of treatment has been primarily descriptive. As a result, therapy is often empiric. This article reviews the author's approach to treating patients with myoclonus. Three principles guide treatment. First, the cause and physiology of the myoclonic jerks must be ascertained before choosing the appropriate therapy. Second, multiple drugs often must be used in combination to achieve functional improvement. Third, given the paucity of adequately controlled trials, the treating physician must rely on well-documented case series of patients with myoclonic syndromes who obtained benefit from a drug.

Localization of a gene for myoclonus-dystonia to chromosome 7q21-q31

Essential myoclonus-dystonia is a neurological condition characterized by myoclonic and dystonic muscle contractions and the absence of other neurological signs or laboratory abnormalities; it is often responsive to alcohol. The disorder may be familial with apparent autosomal dominant inheritance. We report a large kindred with essential familial myoclonus-dystonia and map a locus for the disorder to a 28-cM region of chromosome 7q21-q31.

Association of a missense change in the D2 dopamine receptor with myoclonus dystonia

Hereditary autosomal dominant myoclonus dystonia (MD) is a movement disorder characterized by involuntary lightning jerks and dystonic movements and postures alleviated by alcohol. Although various large families with MD have been described, no positive linkage has been found to a chromosomal location. We report a family with eight members with MD. Linkage analysis identified a 23-centimorgan region on chromosome 11q23 that cosegregates with the disease state (maximum multipoint logarithm of odds score = 2.96 at D11S897). This region contains an excellent candidate gene for involvement in the etiology of MD, the D2 dopamine receptor (DRD2) gene. Neurotransmission mediated by DRD2 is known to have a key role in the control of movement and also has been implicated in reward and reinforcement mechanisms and psychiatric disorders. Sequencing of the coding region of DRD2 indicated that all affected and obligate carriers were heterozygous for a Val154Ile change in exon 3 of the protein, which is highly conserved across species. This change was found neither in other unaffected members of the pedigree nor in 250 control chromosomes. Our finding provides evidence for the involvement of DRD2 in a disorder of the central nervous system and should lead to further insight into the function of the dopaminergic system in dystonia and other movement and mood disorders.

Two cases of essential myoclonus, epilepsy, mental retardation and anxiety disorders

We examined an 18-year-old female and an 18-year-old male with mild mental retardation who suffered from the oscillatory form of sporadic essential myoclonus from an age of 3 years. Although the generalized oscillatory myoclonus resembled severe essential tremor, surface electromyography revealed small myoclonic jerks with frequencies of 6-8 Hz. As concomitant symptoms, the female case exhibited overanxious irritability from early childhood and generalized epileptic seizures occurred from the age of 4 years. In the male case, an obsessive-compulsive disorder and photosensitive convulsive seizures were persistently noted from early childhood. All their symptoms had been stable for at least the last 10 years. Thus, although non-progressive tremulous movements are rare in early childhood, sporadic essential myoclonus is causative. In contrast to hereditary essential myoclonus, sporadic essential myoclonus is considered to be more heterogeneous, especially in the various associated symptoms.

Linkage studies in alcohol-responsive myoclonic dystonia

A large German family with "myoclonic dystonia with lightning jerks responsive to alcohol" was identified. Eleven affected pedigree members and six obligate gene carriers from five generations were identified. A description of one branch of this pedigree was published in 1964. Our examination 30 years after the initial report confirms the clinical syndrome of a nonprogressive movement disorder characterized by myoclonic jerks affecting the proximal muscles and the muscles of the trunk, accompanied by mild dystonic features in some affected family members. Segregation analysis favors autosomal dominant inheritance with high, but incomplete, penetrance in males and much lower penetrance in females. Linkage analysis was performed using simple sequence repeat polymorphisms (CA repeats) closely associated with or spanning the chromosomal regions containing 15 candidate genes: the gene for early-onset generalized torsion dystonia, DYT1 (chromosome 9q34); the genes for subunits alpha 2, beta 1, and gamma 1 (chromosome 4p12-4q13); for alpha 1, alpha 6, beta 2, and gamma 2 (chromosome 5q31.1-5q31.3); for alpha 4, alpha 5, beta 3, and gamma 3 (chromosome 15q11-15q13); for rho 1 and rho 2 (chromosome 6q14-6q21) of the gamma-aminobutyric acid A receptor; and for the alpha subunit of the glycine receptor (chromosome 5q31). By a combination of pairwise and multipoint linkage analysis, it could be excluded that any of these candidate gene-bearing chromosomal regions contain the disease gene in this family. We also excluded major portions of three chromosomal regions syntenic with mouse chromosome 3, which carries the murine beta subunit of the glycine receptor.

Essential myoclonus and myoclonic dystonia

This review explores the history and use of the terms essential myoclonus and myoclonic dystonia. In addition, the review proposes that hereditary essential myoclonus and dominantly inherited myoclonic dystonia, with lightning jerks and dramatic response to alcohol, are the same disease, although proof of this hypothesis must come from ongoing genetic studies.