Myoclonus associated with the use of gabapentin

PURPOSE: To report on the occurrence of myoclonus in patients receiving gabapentin (GBP) for the treatment of epilepsy. METHODS: Clinic charts of 104 consecutive patients started on GBP were reviewed. All patients were treated by the same physician, and most were specifically asked about the presence of myoclonus. RESULTS: We found 13 cases of myoclonus. All patients had refractory epilepsy and were taking other antiepileptic drugs (AEDs). Six patients had a severe chronic static encephalopathy; five patients had no medical diagnosis other than seizures. Ten patients developed multifocal myoclonus. Three patients developed focal myoclonus, contralateral to their epileptic focus. Two patients had an exacerbation of preexistent myoclonus. An EEG performed during myoclonus on three patients showed no correlate. The myoclonus tended to persist as long as GBP was maintained, whereas discontinuance of GBP resulted in rapid cessation of the myoclonus. In all cases the myoclonus was subtle and did not significantly interfere with daily activities. CONCLUSIONS: GBP-associated myoclonus appears to be relatively frequent. It is usually mild and can easily be overlooked. Discontinuation of therapy is not necessary in most cases.     

Treatment of myoclonic syndromes with paroxetine alone or combined with 5-HTP

Paroxetine is a specific presynaptic 5-hydroxytryptamine (5-HT) reuptake inhibitor which ameliorated posthypoxic intention myoclonus in 2 out of 3 patients, when given alone or in combination with L-5-hydroxytryptophan (5-HTP) with carbidopa. The concentration of 5-HT in the cerebrospinal fluid from 1 patient was only 3 nmol/l despite the presence of 600 nmol/l of 5-HTP during steady state treatment with the amino acid and paroxetine. No effect of the combined medication was found in 2 patients disordered by palatal myoclonus.     

Role of prostaglandins in the antimyoclonic action of clonazepam

Possible involvement of prostaglandins (PG) in the antimyoclonic action of clonazepam was examined in the p,p′-DDT-animal model of myoclonus. PG synthesis inhibitors and the PG antagonist polyphloretin phosphate (PPP) counteracted the antimyoclonic action of clonazepam in mice. PGE₂ reduced DDT-induced myoclonus; this effect was blocked by PPP. Another antimyoclonic drug combination, L-5-hydroxytryptophan plus chlorimipramine, was not blocked by PPP or indomethacin. The antimyoclonic action of clonazepam may be mediated by enhancement of PG synthesis.     

A novel conserved mutation in SGCE gene in 3 unrelated patients with classical phenotype myoclonus–dystonia syndrome

Abstract

Objective and importance: Myoclonus–dystonia syndrome (MDS, DYT11) is an inherited disorder characterized by clinical and genetic heterogeneity. MDS is inherited in autosomal dominant pattern and caused by heterozygous mutations in the gene encoding epsilon-sarcoglycan (SGCE) on chromosome 7q21. SGCE gene mutations are present in about 30–50% patients classified as definite-MDS. Earlier onset of motor symptoms is indicated in MDS patients who are SGCE mutations carriers. We present clinical phenotype of three unrelated MDS patients bearing novel, not described yet, mutation in SGCE gene.

Clinical presentation: Presence of a substantial mutation in exon 3, changing aspartic acid to asparagine in codon 96 (D96N) of SGCE protein has been revealed. Three unrelated individuals, bearing the same mutation have diversity of symptoms, with some common features. Age of onset of our patients differs: 2, 14 to 38 years of age.

Intervention/technique: Detection of mutations in SGCE gene was performed via direct sequencing of SGCE gene.

Conclusions: Our results confirm the role of the SGCE gene in the pathogenesis of MDS and call into question the impact of SGCE mutations on the age of onset. The existing list of known mutations and diversity of symptoms in patients bearing the same mutation indicates that there is a lack of genotype–phenotype correlation. Heterogeneity of disease indicates necessity for further research in order to find the molecular fingerprint which may be a landmark in diagnostic studies of MDS.     

Survival to akinetic mutism state in Japanese cases of MM1‐type sporadic Creutzfeldt–Jakob disease is similar to Caucasians

Background: It is not known whether the clinical course of Japanese sporadic Creutzfeldt–Jakob disease (sCJD) cases differs from that of Caucasian sCJD cases. Patients and methods: To investigate the clinical course of Japanese sCJD, clinical findings from 29 patients with Japanese MM1‐type sCJD were retrospectively evaluated and compared to Caucasian sCJD findings. Results: Survival of Japanese MM1‐type sCJD up to the time of akinetic mutism state is similar to that of Caucasian subjects. However, the total disease duration of Japanese patients was approximately three times longer. Conclusions: The present observations indicate that Japanese sCJD cases generally show a longer disease duration because of the longer survival period after reaching the akinetic mutism state.     

Homozygous SQSTM1 nonsense variant identified in a patient with brainstem involvement

In recent years, with advances in molecular genetics, many new mutations with various ataxic syndromes have been identified. Recently, homozygous sequestosome 1 (SQSTM1) gene variant with a progressive childhood-onset cerebellar ataxia, dystonia and gaze palsy was described. Here we describe a patient with progressive cerebellar ataxia and gaze palsy, as well as myoclonus, cognitive impairment and growth retardation with a homozygous SQSTM1 variant NM_003900.5:c.55G > T (p.Glu19*). Our case had brainstem lesions on brain magnetic resonance imaging that have not been previously reported. This novel finding expands the SQSTM1 gene-associated neuroradiologic spectrum. Homozygous SQSTM1 variant should be considered in the differential diagnosis in patients presenting with cerebellar findings, gaze palsy, and cognitive impairment to facilitate early diagnosis and genetic counseling.     

Orthostatic myoclonus: An underrecognized cause of unsteadiness?

Background and purposeRecently, orthostatic myoclonus (OM) has been suggested as a cause of gait impairment and unsteadiness in neurodegenerative diseases. The aim of this study was to investigate the frequency of orthostatic myoclonus, its clinical characteristics and the underlying associated neurological disorders.MethodsA retrospective analysis of clinical data and electromyogram surface recordings from subjects with unexplained unsteadiness/gait impairment was performed. Diagnosis of OM was made when a pattern of non-rhythmic bursts was observed (duration range 20–100 ms; bursts per second ≤16).ResultsAmong 93 subjects studied, OM was the most frequent disorder (n = 16; 17.2%), followed by orthostatic tremor (13.9%) and low frequency tremors during orthostatism (12.9%). All patients with OM complained about unsteadiness during orthostatism and/or during gait. Leg jerking was only observed by visual inspection during orthostatism in four subjects and two also presented falls. Eleven out of 16 patients (68.7%) with OM had an associated neurodegenerative disease, such as multiple system atrophy (n = 3) Parkinson's disease (n = 2), Alzheimer's disease (n = 2), mild cognitive impairment (n = 2) and normal pressure hydrocephalus (n = 2). Although four subjects showed improvement of orthostatic myoclonus with antimyoclonic treatment, the follow-up was not systematic enough to evaluate their therapeutic effect on OM.ConclusionsOrthostatic myoclonus is often underdiagnosed and can be considered a possible cause of unsteadiness in subjects with neurodegenerative diseases. Electromyography surface recording is thereby an aid for investigating unsteadiness of unknown origin.