Cortical Myoclonus Research Articles

Photomyogenic response in Niemann–Pick type C: a case report

Photomyogenic response in Niemann–Pick type C: a case report

Myoclonus in Creutzfeldt‐Jakob disease: Polygraphic and video‐electroencephalography assessment of 109 patients

We used electroencephalography (EEG)-polygraphic recordings to classify myoclonus in 109 patients with Creutzfeldt-Jakob disease (CJD) on the basis of its electromyography (EMG) pattern, time course, distribution, and EEG correlates. We recorded myoclonic jerks in 55 patients (50.4%), and we classified them as periodic myoclonus in 28, rhythmic in 13, and irregular in 20 (6 patients showed two types of myoclonus). Myoclonus occurred as a prominently negative event (interrupting the EMG discharge) in 10. Periodic sharp-wave complexes (PSWCs) were present in all but one patient with myoclonic jerks but were time-locked with EMG-bursts only in case of periodic myoclonus. Jerk-locked back averaging revealed a variable EEG-EMG transfer-time commonly exceeding that characterizing cortical myoclonus. Myoclonus was frequently associated with Met/Met polymorphism at codon 129 of the prion protein gene, but it was also observed in association with Met/Val or Val/Val polymorphisms provided that the EEG showed the presence of the PSWC pattern. The presence of enlarged somatosensory evoked potentials significantly correlated with the myoclonic presentation, as did MR signal hyperintensity involving the cortical mantle. Our observations on the basis of standard polygraphic criteria suggest that CJD associates with a remarkable variety of myoclonic jerks, and therefore different brain structures are probably involved as generators. The significant association between the presence of all myoclonus types with PSWCs suggests that hyperexcitable corticosubcortical loops are always required to generate (or allow) both myoclonus and the EEG complexes, either they are time locked or not.

S5-4 High-frequency oscillations in cortical myoclonus

S5-4 High-frequency oscillations in cortical myoclonus

P14-7 Somatosensory evoked potentials recovery function in patients with cortical myoclonus

P14-7 Somatosensory evoked potentials recovery function in patients with cortical myoclonus

P22-14 Cortical and non-cortical myoclonus of Creutzfeldt-Jakob disease (CJD): Precious lesson learned from a patient

P22-14 Cortical and non-cortical myoclonus of Creutzfeldt-Jakob disease (CJD): Precious lesson learned from a patient

Post‐hypoxic cortical myoclonus mimicking spinal myoclonus – electrophysiological and functional MRI manifestations

European Journal of NeurologyVolume 18, Issue 1 p. e4-e5 Post-hypoxic cortical myoclonus mimicking spinal myoclonus – electrophysiological and functional MRI manifestations H.-C. Huang, H.-C. Huang Department of NeurologySearch for more papers by this authorJ.-C. Chen, J.-C. Chen Department of NeurologySearch for more papers by this authorM.-K. Lu, M.-K. Lu Department of NeurologySearch for more papers by this authorJ.-M. Chen, J.-M. Chen Department of RadiologySearch for more papers by this authorC.-H. Tsai, C.-H. Tsai Department of Neurology School of Medicine, College of Medicine Graduate Institute of Neural and Cognitive Sciences, China Medical University and Hospital, Taichung, TaiwanSearch for more papers by this author H.-C. Huang, H.-C. Huang Department of NeurologySearch for more papers by this authorJ.-C. Chen, J.-C. Chen Department of NeurologySearch for more papers by this authorM.-K. Lu, M.-K. Lu Department of NeurologySearch for more papers by this authorJ.-M. Chen, J.-M. Chen Department of RadiologySearch for more papers by this authorC.-H. Tsai, C.-H. Tsai Department of Neurology School of Medicine, College of Medicine Graduate Institute of Neural and Cognitive Sciences, China Medical University and Hospital, Taichung, TaiwanSearch for more papers by this author First published: 16 August 2010 https://doi.org/10.1111/j.1468-1331.2010.03186.xCitations: 5 Dr. C. H. Tsai or M. K. Lu, Department of Neurology, China Medical University Hospital, 2, Yuh-Der Road, 404 Taichung, Taiwan (tel.: +886 4 22062121 ext. 5035; fax: +886 4 22344055; e-mail: [email protected] or [email protected]). Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume18, Issue1January 2011Pages e4-e5 RelatedInformation

Familial cortical myoclonic tremor with epilepsy

Familial cortical myoclonic tremor with epilepsy (FCMTE) is defined by autosomal dominant adult-onset cortical myoclonus (CM) and seizures in 40% of patients. Two loci, 8q23.3-q24.11 (FAME1/FCMTE1) and 2p11.1-q12.2 (FAME2/FCMTE2), were previously reported without an identified gene. Unlinked families argue for a third mutated gene. A genome-wide scan was performed in a large FCMTE family using Linkage-12 microarrays (Illumina). Refinement of the locus on 5p was performed by genotyping 13 polymorphic microsatellite markers in the 45 available family members. This large French FCMTE family included 16 affected relatives. The first symptoms were CM in 5 patients (31.2%), seizures in 5 patients (31.2%), and both at the same time in 6 patients (37.5%). A total of 12.5% (2/16) had only CM without seizures. The genome-wide scan identified a single region on 5p15.31-p15, with a multipoint lod score of 3.66. Further genotyping of all family members confirmed that the region spans 9.31 Mb between D5S580 and D5S2096, 2-point lod scores reaching 6.3 at theta = 0 for D5S486. Sequencing of the SEMA5A and CTNND2 genes failed to detect mutations. We report the clinical and genetic characteristics of a large familial cortical myoclonic tremor with epilepsy family. The third gene maps to 5p15.31-p15. Identification of the mutated gene is ongoing.

Short and long interval cortical inhibition in patients with Unverricht-Lundborg and Lafora body disease

Myoclonus has different clinical and neurophysiological features in patients with Unverricht-Lundborg (ULD) and Lafora body disease (LBD), probably because of a different cortical hyperexcitability profile. To investigate the role of intracortical inhibition in such different presentations, we used paired-pulse transcranial magnetic stimulation (TMS) in ten ULD and five LBD patients, all with a positive molecular diagnosis. All of the patients were treated with antiepileptic drugs (AEDs). In comparison with healthy subjects, both patient groups had significantly defective short intracortical inhibition (SICI), however LBD patients, but not ULD and healthy subjects, had a clear inhibition at ISI 6 ms and ISI 10 ms. Moreover, defective long interval cortical inhibition (LICI) was found in LBD but not ULD patients. The substantial reduction in SICI suggests that both ULD and LBD patients have impaired inhibitory interneuron pools which are involved in the generation of cortical reflex myoclonus, whereas the inhibition found in LBD patients at ISI 6 and 10 ms, as well the reduced inhibition found at long intervals, suggest a more complex circuitry dysfunction possibly involving both excitatory and inhibitory systems. These findings are probably related to the high epileptogenic propensity characterizing LBD with respect to ULD and to the more severely distorted neuronal network resulting from the pathogenesis of LBD.

Physiology of epilepsia partialis continua and subcortical mechanisms of status epilepticus

Physiology of epilepsia partialis continua and subcortical mechanisms of status epilepticus

Introduction

Introduction

Familial benign nonprogressive myoclonic epilepsies

Work on the classification of epileptic syndromes is ongoing, and many syndromes are still under discussion. In particular, special difficulty still persists in correctly classifying epilepsies with myoclonic seizures. The existence of special familial epileptic syndromes primarily showing myoclonic features has been recently suggested on the basis of a clear pattern of inheritance or on the identification of new chromosomal genetic loci linked to the disease. These forms in development include familial infantile myoclonic epilepsy (FIME), benign adult familial myoclonic epilepsy (BAFME), or autosomal dominant cortical myoclonus and epilepsy (ADCME), and, maybe, adult-onset myoclonic epilepsy (AME). In the future, the identification of responsible genes and the protein products will contribute to our understanding of the molecular pathways of epileptogenesis and provide neurobiologic criteria for the classification of epilepsies, beyond the different phenotypic expression.

Levetiracetam accumulation in renal failure causing myoclonic encephalopathy with triphasic waves

Triphasic waves are seen in the electro-encephalogram of adult patients with toxic-metabolic encephalopathies of various origins. Levetiracetam is a broad spectrum anti-epileptic drug with renal elimination and no hepatic metabolism. We describe the case of encephalopathy with triphasic waves concomitant with levetiracetam accumulation in a patient with chronic renal failure. The condition was reversible after down-titration of levetiracetam with no change of the renal function. Other causes of metabolic encephalopathy were excluded. Moreover, this patient suffered from a probable cortical myoclonus that relapsed after cessation of the drug but was well controlled by a low dosage adapted to the renal failure. In cases of metabolic encephalopathy with triphasic waves in a patient with renal failure taking levetiracetam, it is important to exclude toxic accumulation of levetiracetam among other causes.

Methyl bromide myoclonus: an electrophysiological study

We report a case of myoclonus from overnight exposure to methyl bromide. Myoclonus was either spontaneous or induced by somatosensory stimulation or voluntary movements, multifocal and sometimes generalized. Median SEP showed normal size P14-N20, but giant parietal P25, N33 and frontal P22-N30 waves. Back-averaging showed a biphasic EEG spike of maximal amplitude at the central region contralateral to the corresponding myoclonic jerk recorded from abductor pollicis brevis and preceding it by a short interval consistent with conduction in corticospinal pathways. Long latency reflexes from cutaneous and mixed nerve stimulation were enhanced. The above electrophysiological findings suggest that myoclonus following methyl bromide poisoning belongs to the cortical reflex myoclonus category.

Cortical myoclonus masquerading as spinal myoclonus

Cortical myoclonus masquerading as spinal myoclonus

Predominant cortical dysfunction in Guadeloupean parkinsonism

Atypical parkinsonism is extremely frequent in Guadeloupe and may have an environmental cause. One-half of the patients with this tauopathy have dopa-resistant parkinsonism, tremor, subcortical dementia and abnormal eye movements suggestive of progressive supranuclear palsy (PSP). They also have hallucinations, dysautonomia, which are not characteristic of PSP. Furthermore, the oculomotor abnormalities and the tremor, which is jerky, differ from what is observed in classical PSP patients. We therefore undertook an electrophysiological study to characterize these features in greater detail. Nine representative Guadeloupean PSP-like (Gd-PSP) patients were selected for electro-oculographic recordings of horizontal eye movements [visually guided saccades (VGS), antisaccades (AS) and smooth pursuit], clinical evaluation of vertical saccade velocity and electrophysiological analysis of abnormal limb movements [electromyographic polygraphy, EEG jerk-locked-back-averaging (JLBA) and long-loop C-reflex]. Vertical saccade velocity was reduced in five patients. The velocity of horizontal VGS was normal, although the latencies were increased and horizontal smooth pursuit (HSP) was mostly saccadic. The AS error rate was above 70% in most patients. Myoclonus was detected in 89% of the Gd-PSP patients. It was mainly small amplitude rest and action myoclonus in the upper limbs, characterized by short arrhythmic 24-76 ms bursts and was of cortical origin, as confirmed by JLBA in five patients. In conclusion, Gd-PSP patients have cortical myoclonus and cortical oculomotor impairments, but only minor signs of brainstem oculomotor dysfunction, suggesting that cortical dysfunction predominates over brainstem impairments. This electrophysiological study, added to previous clinical, neuropsychological and neuroradiological studies, has enriched the characterization of Guadeloupean atypical parkinsonism, which thus appears to be a new clinical entity.

Stimulus-induced bilateral central periodic discharges, cortical myoclonus and arousal responses in mild reversible coma

Objective: To study the association between stimulus-induced periodic epileptiform discharges (PEDs), arousal EEG responses and limb jerking in a comatose patient with reversible viral encephalitis. Methods: We recorded video EEG in Intensive Care Unit (ICU) for strictly clinical purposes. Back averaging was performed off-line using Neuroscan 4.3. Results: We recorded spontaneous and stimulus-induced bilateral central PEDs (bi-central PEDs) that were followed by phasic vertex potentials, customarily considered as EEG arousal responses. Bi-central PEDs were associated with myoclonus when provoked by strong and protracted stimuli, but remained subclinical when elicited by auditory or mild tactile stimuli. Spontaneous and stimulus-induced bi-central PEDs disappeared after full neurological recovery. Conclusion: These findings link stimulus-induced PEDs to epileptic cortical myoclonus, and further suggest that in certain comatose patients they may represent reflex epileptic activity, even when clinically silent. The term “reflex seizures of the critically ill” may be appropriate in such patients. Our findings may also provide a model of the reciprocal relationship between arousals and epileptiform activity. Significance: Consideration of the possibility that stimulus-induced PEDs are reflexive epileptic phenomena in some comatose ICU patients may rationalise further their acute management, including antiepileptic treatment.

Electrophysiological features of myoclonus‐dystonia

Inherited myoclonus-dystonia (M-D) is an autosomal dominant disorder characterized by myoclonus and dystonia that often improves with alcohol. To examine the electrophysiologic characteristics of M-D, we studied 6 patients from 4 different families and 9 age-matched healthy subjects. Neurophysiological studies performed include electromyography (EMG)-electroencephalography (EEG) polygraphy, jerk-locked back-averaged EEG, somatosensory evoked potentials (SEP), long-latency reflex (LLR) to median and digital nerve stimulation, and transcranial magnetic stimulation studies with short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long-interval intracortical inhibition (LICI). All 6 patients showed myoclonus and dystonia on clinical examination and EMG testing. The EMG burst durations ranged from 30.4 to 750.6 milliseconds (mean, 101.5 milliseconds). Jerk-locked back-averaged EEG failed to reveal any preceding cortical correlates. Median nerve SEP revealed no giant potential. No patients had exaggerated LLR to median or digital nerve stimulation. There was no significant difference in SICI, ICF, and LICI between M-D patients and normal subjects. Myoclonus in inherited M-D is likely of subcortical origin. Normal intracortical inhibition and facilitation suggest that the GABAergic circuits in the motor cortex are largely intact and that the mechanisms of myoclonus and dystonia are different from those for cortical myoclonus and other dystonic disorders.

Primary progressive myoclonus of aging

Myoclonus in older individuals usually occurs in the context of associated neurologic features which allow the diagnosis of the underlying disorder. We encountered 7 patients with a newly recognized myoclonus syndrome; we use the term primary progressive myoclonus of aging (PPMA) for this syndrome. Our purpose was to characterize the clinical and electrophysiological properties of this syndrome. Our database was searched for the presence of "myoclonus" in the physical examination. Medical records and laboratory data were retrospectively reviewed, including electrophysiology data. We applied our criteria for PPMA: (1) asymmetric symptomatic action myoclonus, (2) >/=65 years of age, (3) cortical myoclonus physiology, (4) no dementia, (5) no associated features of defined neurodegenerative disorders, and (6) no secondary cause found. Seven patients fulfilled criteria. Age at presentation ranged from 70 to 87 years. Mean duration from myoclonus onset to last follow-up was 2.9 years. Electrophysiology showed positive-negative back-averaged transients, consistent with cortical myoclonus. No patient demonstrated dementia. Brain imaging in all cases was unremarkable. PPMA is a unique syndrome with characteristic findings that differentiate it from dementias and defined neurodegenerative syndromes. It is important to distinguish primary PPMA from other syndromes seen in older individuals to avoid diagnostic confusion. Some cases showed a response to levetiracetam.

Myoclonus

Myoclonus is a hyperkinetic movement disorder characterized by quick, involuntary jerks. It encompasses a vast range of etiologies and widespread anatomic locations. Treatment frequently requires multiple agents and is often only partially beneficial. These patients pose a considerable challenge for the clinician, further complicated by the fact that many of the treatment choices lack evidence-based support. In the past few years, publications regarding therapy have been largely observational case reports or series. Although the literature on treatment of cortical myoclonus appears to be growing, evidence regarding myoclonus of noncortical origin is less well established. Investigation of more satisfactory treatments is needed, as this condition can be disturbing, debilitating, and sometimes harmful for patients. Continuing investigations are using various animal models (mostly of posthypoxic myoclonus), electrophysiologic studies, new imaging techniques such as diffusion tensor imaging, and genetic studies. Meanwhile, the clinical approach to diagnosing and classifying myoclonus remains largely unchanged. This review updates readers on current investigations and suggests guidelines for diagnosing and treating myoclonus.

Difference in intracortical inhibition of the motor cortex between cortical myoclonus and focal hand dystonia

Objective The short interval intracortical inhibition (SICI) of the motor cortex (M1) is reduced in both cortical myoclonus and focal hand dystonia. This reduction has been attributed to the dysfunction of GABAergic system within the motor cortex. However, the precise mechanisms underlying the reduction may not be entirely identical in these two disorders, being due to primary pathological involvement in M1 or secondary to functional changes outside M1. The aim of this study was to elucidate possible differences in intracortical inhibition between these two disorders. Methods Subjects were 11 patients with benign myoclonus epilepsy, 7 with focal hand dystonia, and 11 normal volunteers. We studied SICI using anterior–posterior (AP) directed and posterior–anterior (PA) directed induced currents in the brain. Results In both disorders, SICI with PA-directed currents was reduced as reported previously. In contrast, SICI studied with AP currents was normal in patients with focal hand dystonia, but reduced in patients with cortical myoclonus. Conclusions The difference between the two disorders might reflect the underlying pathological difference. In cortical myoclonus, the inhibitory interneurons of the motor cortex are affected, whereas the same interneurons are intact in dystonia. The difference in SICI induced by AP and PA directed currents in dystonia may be explained by the following possibilities: the difference in composition of I-waves contributing to EMG generation and the difference in modulation of the interneuronal activity by voluntary contraction. These changes may be secondary to dysregulation of the motor cortex by the basal ganglia or related cortices in dystonia. Significance The SICI using AP directed currents together with the conventional SICI using PA directed currents was able to demonstrate some difference in the intrinsic circuits of M1 between myoclonus and focal hand dystonia. SICI using AP directed currents can provide additional information about the motor cortical excitability changes over those obtained by the previously reported methods.