Elisabeth M. J. Foncke

Local field potentials and oscillatory activity of the internal globus pallidus in myoclonus–dystonia

The pathophysiology of myoclonus–dystonia (M–D), an autosomal dominantly inherited movement disorder characterized by myoclonic jerks and dystonic contractions, is largely unknown. In the present study, local field potential (LFP) activities in the globus pallidus internus (GPi) from two genetically proven M–D patients are investigated. Coherence analysis between GPi LFP activity and electromyographic muscle activity (EMG) and synchronization of GPi neuronal activity using event‐related spectral perturbation (ERSP) in a go–no‐go paradigm were studied. Significant increased coherence in the 3 to 15 Hz frequency band was detected between GPi LFP activity and several muscles, with the LFP leading the muscles. The ERSP analysis revealed synchronization in the 3 to 15 Hz frequency band within the GPi before the imperative cue of the go–no‐go task and desynchronization in the same band after the cue. The LFP recordings of the GPi in M–D show that the low‐frequency band previously described in dystonia is also involved in the dystonia plus syndrome M–D. The 3 to 15 Hz synchronization in the go–no‐go paradigm has not been described previously and may point to the existence of (myoclonus–)dystonia specific oscillatory activity in the GPi.

Myoclonus–dystonia: clinical and genetic evaluation of a large cohort

Background: Myoclonus–dystonia (M-D) is an autosomal dominant inherited movement disorder. Various mutations within the epsilon-sarcoglycan (SGCE) gene have been associated with M-D, but mutations are detected in only about 30% of patients. The lack of stringent clinical inclusion criteria and limitations of mutation screens by direct sequencing might explain this observation. Methods: Eighty-six M-D index patients from the Dutch national referral centre for M-D underwent neurological examination and were classified according to previously published criteria into definite, probable and possible M-D. Sequence analysis of the SGCE gene and screening for copy number variations were performed. In addition, screening was carried out for the 3 bp deletion in exon 5 of the DYT1 gene. Results: Based on clinical examination, 24 definite, 23 probable and 39 possible M-D patients were detected. Thirteen of the 86 M-D index patients carried a SGCE mutation: seven nonsense mutations, two splice site mutations, three missense mutations (two within one patient) and one multiexonic deletion. In the definite M-D group, 50% carried an SGCE mutation and one single patient in the probable group (4%). One possible M-D patient showed a 4 bp deletion in the DYT1 gene (c.934_937delAGAG). Conclusions: Mutation carriers were mainly identified in the definite M-D group. However, in half of definite M-D cases, no mutation could be identified. Copy-number variations did not play a major role in the large cohort.

Late-onset Huntington disease with intermediate CAG repeats: true or false?

Huntington disease (HD) is a neurodegenerative disorder associated with an expanded CAG trinucleotide repeat length in the huntingtin gene. ‘Intermediate alleles’ with 27 to 35 CAG repeats generally do not cause HD but are unstable upon germ-line transmission. Insights in CAG repeat mosaicism and enhanced trinucleotide expansion in postmitotic neurons indicate that in the intermediate range, other factors than the CAG repeat length in diagnostic tests have to be considered. Here, we report two patients with mild, late onset HD and an intermediate repeat allele. The authors anticipate that intermediate repeats can cause late-onset HD due to disease modifiers and may be more common than previously stated.

Distal myoclonus and late onset in a large Dutch family with myoclonus–dystonia

We report a large myoclonus–dystonia (M-D) pedigree with a two-base pair deletion in Exon 5 of the epsilon-sarcoglycan gene. Three individuals had onset after age 40 years. Distal myoclonus of the arms was present in all 20 symptomatic mutation carriers. These findings expand the known phenotype of M-D and require revision of the current diagnostic criteria. Five of 14 asymptomatic mutation carriers who inherited the mutation from their mother showed minimal axial dystonia, arguing against a maternal imprinting mechanism.

Hereditary myoclonus–dystonia associated with epilepsy

A five-generation Dutch family with inherited myoclonus–dystonia (M-D) is described. Genetic analysis revealed a novel truncating mutation within the ε-sarcoglycan gene (SGCE). In three of five gene carriers, epilepsy and/or EEG abnormalities were associated with the symptoms of myoclonus and dystonia. The genetic and clinical heterogeneity of M-D is extended. EEG changes and epilepsy should not be considered exclusion criteria for the clinical diagnosis of M-D.

Is psychopathology part of the phenotypic spectrum of myoclonus-dystonia?: a study of a large Dutch M-D family

BackgroundMyoclonus-dystonia (M-D) is a movement disorder frequently caused by mutations in the epsilon-sarcoglycan gene (SGCE, DYT11). In several M-D families, psychiatric symptoms accompanying the motor symptoms have been reported, but a shared genetic etiology remains unclear. ObjectiveTo assess neuropsychologic functioning and psychopathology in DYT11 mutation carriers (MC) and their family members using standardized neuropsychologic and psychiatric measures. MethodsCognitive and behavioural characteristics of 27 DYT11 MC (14 symptomatic and 13 asymptomatic) and 42 control subjects from 1 large Dutch M-D family were studied. Neuropsychologic tests encompassed memory, language, mental speed, concentration, visuospatial function, and executive functions. Psychiatric assessment addressed qualitative (according to Diagnostic and Statistical Manual-IV criteria) as well as quantitative measures of depression, anxiety, panic attacks, and obsessive-compulsive disorder (OCD), using selfadministered and interview-based scales. ResultsNo differences were observed on tests of cognitive functioning between DYT11 MC and controls. The frequency of Diagnostic and Statistical Manual-IV diagnoses was higher in the symptomatic DYT11 MC than in controls. The symptomatic DYT11 MC showed more depressive and anxiety symptoms, including panic attacks but no increase of OCD compared with controls. No differences were found between asymptomatic DYT11 MC and controls on any of the psychopathologic tests. ConclusionsNeither cognitive dysfunction nor OCD seems to be associated with the DYT11 phenotype in this large Dutch pedigree. Depressive and anxiety symptoms are increased in symptomatic, but not in asymptomatic DYT11 MC. Future research has to be carried out to determine whether the psychiatric symptoms are part of or secondary to the DYT11 phenotype.

Disorganized Sensorimotor Integration in Mutation-Positive Myoclonus-Dystonia: A Functional Magnetic Resonance Imaging Study

BACKGROUND Myoclonus-dystonia is an autosomal dominantly inherited movement disorder clinically characterized by myoclonic jerks and dystonic postures or movements of the upper body. Functional imaging studies in other, mainly heterogeneous groups of dystonia do agree on dysfunction of the striato-pallido-thalamo-cortical circuit. OBJECTIVE To study cerebral activation patterns with functional magnetic resonance imaging in a genetically defined homogeneous group of patients with dystonia. DESIGN, SETTING, AND PATIENTS Thirteen clinically affected SGCE mutation carriers and 11 control subjects were studied in a case-control study. Intervention A finger-tapping motor task was performed in a block design using 3.0-T magnetic resonance imaging. MAIN OUTCOME MEASURES Blood oxygenation level-dependent signals were compared between groups. RESULTS In SGCE mutation carriers, we observed significant hyperresponsiveness in contralateral inferior parietal cortical areas, ipsilateral premotor and primary somatosensory cortex, and ipsilateral cerebellum during the motor task compared with healthy control subjects. CONCLUSIONS The cortical activation patterns in SGCE mutation carriers during this motor task point to a disorganized sensorimotor integration in this uniform group of patients with dystonia and are consistent with functional neuroimaging studies in other types of (hereditary) dystonia.

Normal cortical excitability in Myoclonus-Dystonia - A TMS study

OBJECTIVE The aim of the present study is to investigate cortical excitability in patients with DYT 11 positive Myoclonus-Dystonia (M-D), using transcranial magnetic stimulation (TMS). METHODS Silent period, motor evoked potential (MEP) recruitment curve, short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and short interval intracortical facilitation (SICF), with short interstimulus intervals (ISIs) ranging from 1.2 to 3.2 ms, were studied in 15 DYT 11-positive M-D patients and their matched controls. In four patients and matched controls peripheral double pulse electrical nerve stimulation was performed. RESULTS All TMS parameters of cortical excitability were normal compared to healthy controls. In the SICF protocol we observed more variable and polyphasic MEPs in M-D patients. Cross-covariance analysis of MEP area revealed a significant correlation difference at ISI 2.2 and 2.8 ms. This increased variability was not seen in other TMS protocols or with peripheral nerve stimulation. CONCLUSIONS In contrast with other types of dystonia, no changes in cortical excitability were found in DYT 11 patients. Our findings suggest that M-D is both clinically and pathophysiologically a separate entity from other dystonic disorders. Polyphasic MEPs during the SICF protocol in M-D patients could reflect central neuron membrane instability. Application of the SICF protocol in other patient groups has to prove its value in movement disorders.

Effect of Pallidal Deep Brain Stimulation on Psychiatric Symptoms in Myoclonus-Dystonia due to ε-Sarcoglycan Mutations

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Psychiatric disorders, myoclonus dystonia and SGCE: an international study

Myoclonus‐dystonia (M‐D) is a hyperkinetic movement disorder, typically alcohol‐responsive upper body myoclonus and dystonia. The majority of autosomal dominant familial cases are caused by epsilon‐sarcoglycan gene (SGCE) mutations. Previous publications have observed increased rates of psychiatric disorders amongst SGCE mutation‐positive populations. We analyzed the psychiatric data from four international centers, forming the largest cohort to date, to further determine the extent and type of psychiatric disorders in M‐D.