Spontaneous Myoclonus Research Articles

Characteristics and clinical course of myoclonus in Cavalier King Charles Spaniels.

Myoclonus has been described in aging Cavalier King Charles Spaniels (CKCS), but the natural course of the disease and response to treatment have not been described. Report the clinical features and course of myoclonus in CKCS. Twenty-seven caregivers provided questionnaire responses at a median of 24 months after the onset of myoclonus in their CKCS. Fifteen caregivers completed a second follow-up questionnaire at a median of 17 months after submission of the first questionnaire. The caregivers of affected CKCS were invited to provide video footage for review. Owners of CKCS with videos demonstrating myoclonus then completed the online questionnaire for further evaluation. A second shortened questionnaire was sent to participants at least 6 months after completion of the first. Most CKCS displayed spontaneous myoclonus affecting predominantly the head (25/27). Overall, the majority had episodes that increased in frequency (20/27) and severity (17/27). Eighteen dogs had developed changes in behavior since the onset of myoclonus. These dogs were typically older and had experienced myoclonic episodes for longer than dogs without behavioral changes. Generalized epileptic seizures were reported in 4/27 dogs. Ten dogs received medical treatment. Eight were prescribed levetiracetam; all had an initial decrease in episode frequency, but a subsequent increase in both frequency and severity of episodes was common. Myoclonus in CKCS tends to progress in frequency and severity regardless of treatment. Progressive behavioral changes suggestive of cognitive decline are common. These findings support the possibility of an underlying neurodegenerative process.

Adult-onset idiopathic opsoclonus-myoclonus syndrome.

Opsoclonus-myoclonus syndrome is extremely uncommon in adults with an autoimmune pathophysiology. Because of the rarity of the syndrome, international recognition of opsoclonus-myoclonus-ataxia syndrome needs to be improved urgently. Therefore, the goal of this study was to raise the awareness of the opsoclonus-myoclonus-ataxia syndrome and help doctors in better diagnosing and using immunotherapy. We present a case study of an adult-onset case of idiopathic opsoclonus-myoclonus syndrome characterized by spontaneous arrhythmic multidirectional conjugate eye movements, myoclonus, ataxia, sleep disorders, and intense fear. Additionally, we conduct a literature search and summarize the pathophysiology, clinical presentation, diagnosis, and treatment of opsoclonus-myoclonus-ataxia syndrome. Immunotherapies successfully treated the patient's opsoclonus, myoclonus, and ataxia. Further, the article also includes an update summary of the opsoclonus-myoclonus-ataxia syndrome. The prevalence of residual sequela in adults with opsoclonus-myoclonus-ataxia syndrome is low. Early diagnosis and treatment may result in a better prognosis. Furthermore, combined immunotherapy is expected to reduce the incidence of refractory and reoccurring opsoclonus-myoclonus-ataxia syndrome.

Canine Lafora Disease: An Unstable Repeat Expansion Disorder.

Canine Lafora disease is a recessively inherited, rapidly progressing neurodegenerative disease caused by the accumulation of abnormally constructed insoluble glycogen Lafora bodies in the brain and other tissues due to the loss of NHL repeat containing E3 ubiquitin protein ligase 1 (NHLRC1). Dogs have a dodecamer repeat sequence within the NHLRC1 gene, which is prone to unstable (dynamic) expansion and loss of function. Progressive signs of Lafora disease include hypnic jerks, reflex and spontaneous myoclonus, seizures, vision loss, ataxia and decreased cognitive function. We studied five dogs (one Chihuahua, two French Bulldogs, one Griffon Bruxellois, one mixed breed) with clinical signs associated with canine Lafora disease. Identification of polyglucosan bodies (Lafora bodies) in myocytes supported diagnosis in the French Bulldogs; muscle areas close to the myotendinous junction and the myofascial union segment had the highest yield of inclusions. Postmortem examination of one of the French Bulldogs revealed brain Lafora bodies. Genetic testing for the known canine NHLRC1 mutation confirmed the presence of a homozygous mutation associated with canine Lafora disease. Our results show that Lafora disease extends beyond previous known breeds to the French Bulldog, Griffon Bruxellois and even mixed-breed dogs, emphasizing the likely species-wide nature of this genetic problem. It also establishes these breeds as animal models for the devastating human disease. Genetic testing should be used when designing breeding strategies to determine the frequency of the NHLRC1 mutation in affected breeds. Lafora diseases should be suspected in any older dog presenting with myoclonus, hypnic jerks or photoconvulsions.

SY2.2. Evaluation of myoclonus

Myoclonus is a shock-like jerky movement observed in the extremities or the trunk without consciousness loss. This involuntary movement is generated by abnormal neuronal discharges in the central nerve system caused by many kinds of etiologies. Based on the physiological generator mechanism, myoclonus is classified mainly into the three groups; cortical myoclonus, subcortical myoclonus and spinal myoclonus. Cortical myoclonus includes spontaneous cortical myoclonus and cortical reflex myoclonus. In cortical myoclonus, an EEG spike precedes a muscle jerk. Backward EEG averaging time-locked to the onset of myoclonus (jerk-locked back averaging: JLA) often detects cortical spike preceding the myoclonus, which is unable to be shown by EEG-EMG polygraph recordings. The duration of EMG jerks is usually shorter than 50-100ms. Somatosensory evoked potentials are often enlarged (giant SEP) in cortical reflex myoclonus. Enhanced long loop reflex is also often seen in the polygraph in the cortical reflex myoclonus (so called “C” reflex). The disinhibition of the sensory cortex can be revealed by SEP recovery curve studied by paired pulse stimulation. The hyperexcitability of the motor cortex is shown by the paired pulse transcranial magnetic stimulation (TMS) technique. The short interval intra-cortical inhibition (SICI) was abnormally reduced. These physiological features indicate the cortical hyper- excitability. Subcortical myoclonus is supposed to be generated at the basal ganglia or brainstem. The duration of muscle jerk is longer than 50-100ms. In some subcortical myoclonus (reticular myoclonus), the latency of long loop reflexes is shorter than those of enhanced C-reflexes. JLA reveals no cortical spikes, and no giant SEPs are seen. Spinal myoclonus includes “segmental spinal myoclonus” which is generated by activation of certain spinal segments, and “propriospinal myoclonus” which originates from a certain spinal segment and spreads upward/downward slowly though the propriospinal tract. Simultaneous EMG recordings of many muscles are useful to estimate the spinal conduction between different spinal cord levels. Electrophysiological studies are useful to evaluate myoclonus and to suggest the generator mechanisms for myoclonus. Here, I will introduce some neurophysiological methods for analyses of myoclonus.

NCMP-04. OPSOCLONUS-MYOCLONUS SYNDROME ASSOCIATED WITH CONTACTIN-ASSOCIATED PROTEIN-LIKE 2 AUTOANTIBODY IN THE SETTING OF NON-SMALL CELL LUNG CARCINOMA

Abstract INTRODUCTION Opsoclonus–myoclonus syndrome (OMS) is a rare neurological disorder characterized by spontaneous multidirectional saccadic eye movements, myoclonus, and ataxia. It is suspected to be an autoimmune mediated process precipitated by a paraneoplastic or infectious trigger. Among the pediatric population, OMS is often associated with neuroblastoma and anti-Hu antibody. Paraneoplastic syndromes in adults manifesting as OMS are most commonly described in breast, gynecological and small cell lung cancer with associated anti-neuronal antibodies (ANNA-2; anti-Ri). We describe the first case of OMS associated with lung adenocarcinoma and Contactin-associated protein-like 2 (Caspr2) antibody. CASE REPORT: A 46-year-old-woman with history of limited small cell lung cancer (SCLC) status-post chemotherapy with cisplatin and etoposide and prophylactic whole brain radiation, presented with new onset gait instability, nausea, vomiting, vertigo, and opsoclonus. Two months prior to her presentation, a chest computed topography (CT) revealed no evidence of recurrent disease. Brain MRI revealed T2 hyperintensities in the white matter and central pons presumably related to chronic small vessel ischemic changes, unchanged from prior imaging. CSF studies revealed normal cell count, glucose, and protein. Gram stain, culture and meningoencephalitis panel were negative. Her paraneoplastic panel revealed a positive Caspr2 antibody. A repeat CT chest for cancer surveillance revealed a new lung mass. Immunotherapy treatment included plasmapheresis, corticosteroids, and intravenous immunoglobulin therapy. She underwent a biopsy of the new pulmonary lesion and the pathology was consistent with non-small cell lung carcinoma. Her symptoms slowly improved after treatment. Unfortunately, her disease progressed on repeat PET scan despite surgical resection of the lung mass. She ultimately elected for hospice. CONCLUSION We report a novel antibody, Caspr2, occurring in association with paraneoplastic OMS. While SCLC is the most common neoplasm associated with OMS among adults, non-small cell lung carcinoma should be considered. Prompt immunotherapy and neoplasm treatment may result in improvement.

Lafora disease in miniature Wirehaired Dachshunds

Lafora disease (LD) is an autosomal recessive late onset, progressive myoclonic epilepsy with a high prevalence in the miniature Wirehaired Dachshund. The disease is due to a mutation in the Epm2b gene which results in intracellular accumulation of abnormal glycogen (Lafora bodies). Recent breed-wide testing suggests that the carrier plus affected rate may be as high as 20%. A characteristic feature of the disease is spontaneous and reflex myoclonus; however clinical signs and disease progression are not well described. A survey was submitted to owners of MWHD which were homozygous for Epm2b mutation (breed club testing program) or had late onset reflex myoclonus and clinical diagnosis of LD. There were 27 dogs (11 male; 16 female) for analysis after young mutation-positive dogs that had yet to develop disease were excluded. Average age of onset of clinical signs was 6.94 years (3.5–12). The most common initial presenting sign was reflex and spontaneous myoclonus (77.8%). Other presenting signs included hypnic myoclonus (51.9%) and generalized seizures (40.7%). Less common presenting signs include focal seizures, “jaw smacking”, “fly catching”, “panic attacks”, impaired vision, aggression and urinary incontinence. All these clinical signs may appear, and then increase in frequency and intensity over time. The myoclonus in particular becomes more severe and more refractory to treatment. Signs that developed later in the disease include dementia (51.9%), blindness (48.1%), aggression to people (25.9%) and dogs (33.3%), deafness (29.6%) and fecal (29.6%) and urinary (37.0%) incontinence as a result of loss of house training (disinhibited type behavior). Further prospective study is needed to further characterize the canine disease and to allow more specific therapeutic strategies and to tailor therapy as the disease progresses.

Role of major and brain-specific Sgce isoforms in the pathogenesis of myoclonus-dystonia syndrome

Loss-of-function mutations in SGCE, which encodes ε-sarcoglycan (ε-SG), cause myoclonus-dystonia syndrome (OMIM159900, DYT11). A “major” ε-SG protein derived from CCDS5637.1 (NM_003919.2) and a “brain-specific” protein, that includes sequence derived from alternative exon 11b (CCDS47642.1, NM_001099400.1), are reportedly localized in post- and pre-synaptic membrane fractions, respectively. Moreover, deficiency of the “brain-specific” isoform and other isoforms derived from exon 11b may be central to the pathogenesis of DYT11. However, no animal model supports this hypothesis. Gene-trapped ES cells (CMHD-GT_148G1-3, intron 9 of NM_011360) were used to generate a novel Sgce mouse model (C57BL/6J background) with markedly reduced expression of isoforms derived from exons 3′ to exon 9 of NM_011360. Among those brain regions analyzed in adult (2month-old) wild-type (WT) mice, cerebellum showed the highest relative expression of isoforms incorporating exon 11b. Homozygotes (SgceGt(148G1)Cmhd/Gt(148G1)Cmhd or SgceGt/Gt) and paternal heterozygotes (Sgcem+/pGt, m-maternal, p-paternal) showed 60 to 70% reductions in expression of total Sgce. Although expression of the major (NM_011360) and brain-specific (NM_001130189) isoforms was markedly reduced, expression of short isoforms was preserved and relatively small amounts of chimeric ε-SG/β-galactosidase fusion protein was produced by the Sgce gene-trap locus. Immunoaffinity purification followed by mass spectrometry assessments of Sgcem+/pGt mouse brain using pan- or brain-specific ε-SG antibodies revealed significant reductions of ε-SG and other interacting sarcoglycans. Genome-wide gene-expression data using RNA derived from adult Sgcem+/pGt mouse cerebellum showed that the top up-regulated genes were involved in cell cycle, cellular development, cell death and survival, while the top down-regulated genes were associated with protein synthesis, cellular development, and cell death and survival. In comparison to WT littermates, Sgcem+/pGt mice exhibited “tiptoe” gait and stimulus-induced appendicular posturing between Postnatal Days 14 to 16. Abnormalities noted in older Sgcem+/pGt mice included reduced body weight, altered gait dynamics, and reduced open-field activity. Overt spontaneous or stimulus-sensitive myoclonus was not apparent on the C57BL/6J background or mixed C57BL/6J-BALB/c and C57BL/6J-129S2 backgrounds. Our data confirm that mouse Sgce is a maternally imprinted gene and suggests that short Sgce isoforms may compensate, in part, for deficiency of major and brain-specific Sgce isoforms.

Myoclonus

Myoclonus is defined as sudden, brief, jerky, shocklike, involuntary movements involving the extremities, face, and trunk, without loss of consciousness. Myoclonus is one of the most commonly encountered involuntary movements, and it can be seen in association with a variety of conditions. This review covers the epidemiology, classification, and diagnosis of myoclonus, as well as a thorough discussion of cortical myoclonus, myoclonus of brainstem origin, myoclonus of spinal cord origin, and myoclonus of undetermined origin. Figures show the principle of jerk-locked back-averaging, example data of jerk-lock averaging, schematic diagrams of cortical reflex myoclonus and spontaneous cortical myoclonus, a polygraphic electromyogram (EMG) recorded from a patient with postanoxic, reticular reflex myoclonus, surface negative slow electroencephalographic (EEG) potentials recorded before psychogenic jerks and voluntary movements mimicking the jerks in a patient with a diagnosis of psychogenic truncal movements, and an EEG-EMG polygraph in a patient with Creutzfeldt-Jakob disease. Tables list the classification of myoclonus based on the estimated site of origin, causes of cortical myoclonus, and causes of progressive myoclonus epilepsy and gene abnormalities. Key words: cortical myoclonus, EEG-EMG polygraph, epilepsy syndromes, involuntary movements, myoclonus This review contains 6 highly rendered figures, 3 tables, and 63 references.

Myoclonus

Myoclonus is defined as sudden, brief, jerky, shocklike, involuntary movements involving the extremities, face, and trunk, without loss of consciousness. Myoclonus is one of the most commonly encountered involuntary movements, and it can be seen in association with a variety of conditions. This review covers the epidemiology, classification, and diagnosis of myoclonus, as well as a thorough discussion of cortical myoclonus, myoclonus of brainstem origin, myoclonus of spinal cord origin, and myoclonus of undetermined origin. Figures show the principle of jerk-locked back-averaging, example data of jerk-lock averaging, schematic diagrams of cortical reflex myoclonus and spontaneous cortical myoclonus, a polygraphic electromyogram (EMG) recorded from a patient with postanoxic, reticular reflex myoclonus, surface negative slow electroencephalographic (EEG) potentials recorded before psychogenic jerks and voluntary movements mimicking the jerks in a patient with a diagnosis of psychogenic truncal movements, and an EEG-EMG polygraph in a patient with Creutzfeldt-Jakob disease. Tables list the classification of myoclonus based on the estimated site of origin, causes of cortical myoclonus, and causes of progressive myoclonus epilepsy and gene abnormalities. Key words: cortical myoclonus, EEG-EMG polygraph, epilepsy syndromes, involuntary movements, myoclonus This review contains 6 highly rendered figures, 3 tables, and 63 references.

Creutzfeldt-Jakob Disease in a Tertiary Care Hospital in Thailand: A Case Series and Review of the Literature

Creutzfeldt-Jakob Disease (CJD) is an incurable and inevitably fatal neurodegenerative disorder. Although CJD has a worldwide distribution, there are no official statistics on CJD in Thailand. A diagnosis of CJD is suspected when a patient develops rapidly progressive dementia with myoclonus. However, CJD may be mistaken for a variety of illnesses because its initial presentation frequently consists of non-specific symptoms. Here, we examined cases of sporadic CJD (sCJD) from Thammasat University Hospital (a tertiary care hospital in Thailand) between January 1, 2012 and December 31, 2014. Three cases of probable and possible sCJD were collected. All cases presented with rapidly progressive cognitive dysfunction accompanied by spontaneous myoclonus. Classical electroencehalography changes and typical abnormal MRI features were observed. All of the cases died within a period of 8 months. None of the patients underwent brain biopsy. Our findings raise questions about the prevalence of CJD in Thailand, which needs further study.

Suppression of myoclonus in corticobasal degeneration by levetiracetam.

Myoclonus in corticobasal degeneration (CBD) has often been associated with severe and difficult to treat disabilities. Levetiracetam is a new antiepileptic agent with antimyoclonic effects. Herein, we present a 72-year-old woman with clinically probable CBD and with spontaneous rhythmic myoclonus in the right foot, which was markedly ameliorated through treatment with levetiracetam. The effect of levetiracetam was associated with the decreased amplitude of enlarged cortical somatosensory evoked potentials. This result suggests that the antimyoclonic effect of levetiracetam might be mediated through the suppression of increased cortical excitability.

Neurophysiologic analysis of spontaneous nocturnal neck myoclonus in an 18-year-old patient

Introduction: While daytime myoclonus have been classified recently according to their topography in cortical, subcortical and propriospinal using EEG and poligraphic variables (Brown & Caviness, 2004, Cassim & Houdayer, 2006), little is known about spontaneous neck myoclonus related exclusively to sleep. In a recent study, nocturnal neck myoclonus (NNM) was systematically described and quantitative assessed during REM sleep in a sample of 190 patients (Frauscher et al, 2010). NNM was present in more than 50% of patients (Index 1.0+/-2.8/h). However, to date there are no descriptions in the literature assessing the neuropysiological features of NNM during both REM and non-REM sleep.

Exome sequencing reveals a novel MRE11 mutation in a patient with progressive myoclonic ataxia

Progressive myoclonic ataxia (PMA) is a clinical syndrome defined as progressive ataxia and myoclonus and infrequent seizures in the absence of progressive dementia. Due to the extremely heterogeneous nature of PMA, a large proportion of PMA cases remain molecularly undiagnosed. The aim of this study was to clarify the molecular etiology of PMA. The patient was a 52-year-old female from consanguineous parents. She developed a jerking neck movement at age 9, which gradually expanded to her entire body. On physical examination at age 47, she exhibited generalized, spontaneous myoclonus that occurred continuously. She also presented with mild limb and truncal ataxia. An electroencephalogram revealed no abnormalities. A brain MRI displayed no atrophy of the cerebellum. Electrophysiological studies suggested myoclonus of a subcortical origin. For further evaluation, we performed exome sequencing, and we identified a novel homozygous missense mutation in the MRE11 gene (NM_005590:c.140C>T:p.A47V). Subsequently, we analyzed the expression of MRE11 and related proteins (RAD50 and NBS1) via Western blot, and they were markedly decreased compared to a healthy control. Mutations in the MRE11 gene have been known to cause an ataxia–telangiectasia-like (ATLD) disorder. Accumulating evidence has indicated that its wide phenotypic variations in ATLD correspond to genotypic differences. Interestingly, our case exhibited a relatively mild decrease in NBS1 compared to previously reported cases of a homozygous missense mutation, which may account for the milder phenotype in this patient. Moreover, together with a recently reported case of an MRE11 mutation, it is suggested that MRE11 mutations can present as PMA.

Effects of Denosumab on 1/3 Radius Bone Mineral Density in Postmenopausal Women Across Randomized Controlled Clinical Trials

Loss-of-function mutations in SGCE, which encodes ε-sarcoglycan (ε-SG), cause myoclonus-dystonia syndrome (OMIM159900, DYT11). A “major” ε-SG protein derived from CCDS5637.1 (NM_003919.2) and a “brain-specific” protein, that includes sequence derived from alternative exon 11b (CCDS47642.1, NM_001099400.1), are reportedly localized in post- and pre-synaptic membrane fractions, respectively. Moreover, deficiency of the “brain-specific” isoform and other isoforms derived from exon 11b may be central to the pathogenesis of DYT11. However, no animal model supports this hypothesis. Gene-trapped ES cells (CMHD-GT_148G1-3, intron 9 of NM_011360) were used to generate a novel Sgce mouse model (C57BL/6J background) with markedly reduced expression of isoforms derived from exons 3′ to exon 9 of NM_011360. Among those brain regions analyzed in adult (2 month-old) wild-type (WT) mice, cerebellum showed the highest relative expression of isoforms incorporating exon 11b. Homozygotes (SgceGt(148G1)Cmhd/Gt(148G1)Cmhd or SgceGt/Gt) and paternal heterozygotes (Sgcem+/pGt, m-maternal, p-paternal) showed 60 to 70% reductions in expression of total Sgce. Although expression of the major (NM_011360) and brain-specific (NM_001130189) isoforms was markedly reduced, expression of short isoforms was preserved and relatively small amounts of chimeric ε-SG/β-galactosidase fusion protein was produced by the Sgce gene-trap locus. Immunoaffinity purification followed by mass spectrometry assessments of Sgcem+/pGt mouse brain using pan- or brain-specific ε-SG antibodies revealed significant reductions of ε-SG and other interacting sarcoglycans. Genome-wide gene-expression data using RNA derived from adult Sgcem+/pGt mouse cerebellum showed that the top up-regulated genes were involved in cell cycle, cellular development, cell death and survival, while the top down-regulated genes were associated with protein synthesis, cellular development, and cell death and survival. In comparison to WT littermates, Sgcem+/pGt mice exhibited “tiptoe” gait and stimulus-induced appendicular posturing between Postnatal Days 14 to 16. Abnormalities noted in older Sgcem+/pGt mice included reduced body weight, altered gait dynamics, and reduced open-field activity. Overt spontaneous or stimulus-sensitive myoclonus was not apparent on the C57BL/6J background or mixed C57BL/6J-BALB/c and C57BL/6J-129S2 backgrounds. Our data confirm that mouse Sgce is a maternally imprinted gene and suggests that short Sgce isoforms may compensate, in part, for deficiency of major and brain-specific Sgce isoforms.

Hashimoto encephalopathy presenting as progressive myoclonus epilepsy syndrome

We report an 11 year old girl with multi-focal spontaneous myoclonus, generalized seizures and behavioural changes. She was found to have sub-clinical hypothyroidism and elevated anti-thyroid peroxidase antibodies. A diagnosis of Hashimoto encephalopathy (or Steroid Responsive Encephalopathy with Autoimmune Thyroiditis) was made in view of consistent clinical and laboratory features. The patient showed and maintained significant improvement with valproate, clonazepam and long term prednisolone. Other findings included mild cerebral cortical grey matter atrophy on brain magnetic resonance imaging and intermittent slowing with generalized poly-spike-and-wave discharges on electroencephalography. Other causes of progressive myoclonus epilepsy (PME) syndrome including subacute sclerosing panencephalitis, Lafora body disease, Juvenile Neuronal Ceroid Lipofuscinosis, Late onset gangliosidosis, Sialidosis, mitochondrial disorders and coeliac disease were ruled out by appropriate investigations. No other auto-immune abnormality was detected. This case emphasizes that Hashimoto encephalopathy should be considered in the etiologies of PME syndrome in adolescents since it is a treatable entity.

Erratum to: Difficult differential diagnosis of Unverricht–Lundborg disease with spontaneous kinesogenic myoclonus and movement disorder

Erratum to: Difficult differential diagnosis of Unverricht–Lundborg disease with spontaneous kinesogenic myoclonus and movement disorder

Difficult differential diagnosis of Unverricht–Lundborg disease with spontaneous kinesogenic myoclonus and movement disorder

Difficult differential diagnosis of Unverricht–Lundborg disease with spontaneous kinesogenic myoclonus and movement disorder

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.

EFHC1: A gene for juvenile myoclonic epilepsy

We originally reported mutations of EFHC1 gene in patients with juvenile myoclonic epilepsy (JME). Subsequently, several other groups reported additional EFHC1 mutations in patients with JME and also in other types of idiopathic generalized epilepsy. We recently generated Efhc1-deficient mouse and found that the mouse showed spontaneous myoclonus and increased susceptibility to a convulsant, pentylenetetrazol. These results further support and confirm our proposal that EFHC1 is the gene for JME.

Electrophysiological studies of myoclonic jerks provoked by photic stimulation

A patient with a type of myoclonus produced by somatosensory and photic stimuli was studied electrophysiologically. Jerk-locked averaging showed cortical spikes in association with the spontaneous myoclonus. High amplitude somatosensory evoked potentials and high amplitude visual evoked potentials were observed. Somatosensory and photic stimuli produced 2 or 3 successive electromyographic (EMG) discharges. The time interval from the onset of the preceding EMG discharge to that of the following EMG discharge produced by photic stimulation corresponded to the latency of a long-loop reflex. It also corresponded to the time interval from the onset of the preceding EMG discharge to that of the following EMG discharge produced by somatosensory stimulation. Not only somatosensory but also photic stimuli might excite the loop of a long-loop reflex and cause myoclonic jerks.