The significance of pathological spontaneous activity in various myopathies

doi:10.1016/j.clinph.2013.11.021

Clinical Neurophysiology

Volume 125, Issue 7, July 2014, Pages 1485-1490

https://doi.org/10.1016/j.clinph.2013.11.021 Get rights and content

Highlights

•
High frequency discharges (i.e., myotonic discharges and complex repetitive discharges) occur frequently in non-myotonic dystrophies as Pompe disease, sporadic inclusion body myositis, matrin 3 myopathy, and centronuclear myopathy.
•
High frequency discharges occur rarely in muscular dystrophies, e.g., facioscapulohumeral dystrophies and the limb girdle muscular dystrophies.
•
In non-myotonic myopathies, high frequency discharges are mainly composed of single elementary potentials, which discharge in a waning only or unchanging pattern, and are found frequently in the paravertebral muscles.

Abstract

Objective

Pathological spontaneous activity (PSA) in electromyography (EMG) has not yet been systematically analysed in various types of myopathies.

Methods

136 Patients with well-defined myopathies were retrospectively analysed for the presence of PSA in distal, proximal, and paravertebral muscles. PSA comprised fibrillations (fib)/positive sharp waves (PSW) and high frequency discharges (HFD; i.e., myotonic and complex repetitive discharges).

Results

fib/PSW occurred more frequently than HFD. HFD were rarely myotonic in nature. 50% and more patients presented with HFD in PROMM (80%), Pompe’s disease (70%), matrin-3 myopathy (60%), sIBM (50%), CNM (50%), while far less than 50% of the patients showed RD in LGMD2I (21%), LGMD2A (17%), LGMD2B (17%), LGMD2L (14%), FSHD (4%), BMD (0%). Four different HFD patterns were proposed.

Conclusion

The segregation of myopathies relative to the occurrence of PSA and especially HFD in a high prevalence group and in a low prevalence group may be diagnostically valuable.

Significance

The screening for HFD by means of EMG is also valuable in the diagnosis of non-myotonic myopathies.

Introduction

Pathological spontaneous activity (including the repetitive discharges) as detected by needle electromyography (EMG) is a nonspecific feature of various neuromuscular disorders including different types of myopathies (Liguori et al., 1997). For example, fibrillation potentials (fib) and positive sharp waves (PSW) are a typical finding in inflammatory myopathies and in Pompe’s disease (Müller-Felber et al., 2007, Felice and North, 2001, Blijham et al., 2006). Furthermore, EMG features of myotonia are classically associated with the dystrophic and non-dystrophic myotonias, but are not pathognomonic for these disorders (Day et al., 2003, Machuca-Tzili et al., 2005).

For non-myotonic entities, so far only Pompe’s disease, sporadic inclusion body myositis (sIBM), the dystrophinopathies, and myofibrillar myopathies have been systematically analysed for the occurrence of repetitive discharges, i.e., high frequency discharges (HFD) Hobson-Webb et al., 2011, Hanisch et al., 2013, Emeryk-Szajewska and Kopeć, 2008a, Lotz et al., 1989). The EMG findings of markedly increased muscle membrane irritability, typical and atypical myotonic discharges and complex repetitive discharges (CRDs) have been recently included in the diagnostic criteria for late-onset Pompe’s disease (American Association of Neuromuscular and Electrodiagnostic Medicine 2009). In some other non-myotonic muscular disorders as centronuclear myopathies and idiopathic inflammatory myopathies including sIBM, HFD have been reported to occur frequently (Lotz et al., 1989, Fischer et al., 2006, Felice and North, 2001, Blijham et al., 2006, Dabby et al., 2001). Other myopathies, especially limb girdle muscular dystrophies (LGMDs) have not yet been systematically analysed for HFD.

In the present study, EMG data of 136 patients with 10 different types of genetically confirmed myopathies and sIBM has been retrospectively analysed for the occurrence and characteristics of pathological spontaneous activity (PSA) including HFD. We also propose a new classification of HFD.

Section snippets

Patients

The records of the EMG studies of patients with the following genetically confirmed diagnoses were retrospectively analysed (for details see Table 1): LGMD2A (calpainopathy) (n = 17), LGMD2B/Myioshi myopathy type 1 (dysferlinopathy) (n = 6), LGMD2I (alpha-dystroglycan deficiency) (n = 14), LGMD2L/Miyoshi myopathy type 3 (anoctamin 5 deficiency) (n = 7), distal myopathy due to mutations in MATR3 (matrin 3 myopathy) (n = 10), centronuclear myopathy (CNM) due to mutations in DNM2 (n = 4), facioscapulohumeral

Results

EMG recordings were retrieved from 136 myopathy patients. The analysis comprised 291 proximal muscles and 119 distal muscles including 151 muscles from the upper limbs (37%), 155 muscles from the lower limbs (38%), and 104 lumbar paraspinal muscles (25%) (Table 1). The distribution of the examined muscles according to the diagnosis is shown in Fig. 1. Per patient, the number of examined muscles ranged from 1 to 6. The average number of analysed muscles per patient ranged from 2.7 to 3.7 in the

Discussion

In the present study, a systematic retrospective analysis of PSA and HFD in a wide range of genetically confirmed myopathies and sIBM is presented. It is noteworthy that paravertebral muscles have been routinely examined by means of EMG in myopathies for more than 12 years in our electrophysiology unit. The results might be biased, though, due to the retrospective nature of the study, the different panels of examined muscles, and the recording bias, which depended on the experience and the

Summary

In conclusion, the segregation of myopathies relative to the occurrence of PSA and especially HFD in a high prevalence group and in a low prevalence group may be diagnostically valuable. Thus HFD seem to occur frequently in muscle disorders associated structurally with protein accumulations, vacuoles and nuclear protein defects, e.g., Pompe’s disease, sIBM, MATR3 myopathy, CNM. In all non-myotonic myopathies, classic myotonic discharges (type 1 pattern) were rare. If HFD occured in these

Financial disclosure

F.H. received lecturer honoraria and travel fees from Astellas, Genzyme, and Biomarin Inc.

Acknowledgment

We thank Dr. Kathryn Birch for copy-editing the manuscript.

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These results differ significantly from previously published reports, in which fib., PSW or CRD were considered typical for sIBM. In large series of sIBM patients, abnormal SA was seen in all (Hatanaka and Oh, 2007; Joy et al., 1990; Lotz et al., 1989) or nearly all of them (Brannagan et al., 1997, Hanisch et al., 2014) and in 73–97% of the muscles examined (Hanisch et al., 2014; Luciano and Dalakas, 1997). In the newest report by Kazamel et al. (2016) fib.
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¹: Both authors contributed equally.

View full text

The significance of pathological spontaneous activity in various myopathies

Highlights

Abstract

Objective

Methods

Results

Conclusion

Significance

Introduction

Section snippets

Patients

Results

Discussion

Summary

Financial disclosure

Acknowledgment

Am J Hum Genet

Neuromuscul Disord

Am J Hum Genet

Neurophysiol Clin

Clin Neurophysiol

Neurophysiol Clin

Neuromuscul Disord

Neuromuscul Disord

Clin Neurol Neurosurg

Neuromuscul Disord

Neuromuscul Disord

Neuromuscul Disord

Diagnostic criteria for late-onset (childhood and adult) Pompe disease

Muscle Nerve

Needle electromyographic findings in 98 patients with myositis

Eur Neurol

Clinical and mutational spectrum of limb-girdle muscular dystrophy type 2I in 11 French patients

J Neurol Neurosurg Psychiatry

Facioscapulohumeral muscular dystrophy. Phenotype-genotype correlation in patients with borderline D4Z4 repeat numbers

J Neurol

Inclusion body myositis mimicking motor neuron disease

Arch Neurol

Myotonic dystrophy type 2: molecular, diagnostic and clinical spectrum

Neurology

Muscular dystrophy due to mutations in anoctamin 5: clinical and molecular genetic findings

Nervenarzt

Electromyographic pattern in Duchenne and Becker muscular dystrophy. Part I: Electromyographic pattern in subsequent stages of muscle lesion in Duchenne muscular dystrophy

Electromyogr Clin Neurophysiol

Electromyographic pattern in Duchenne and Becker muscular dystrophy. Part II. Electromyographic pattern in Becker muscular dystrophy in comparison with Duchenne muscular dystrophy

Electromyogr Clin Neurophysiol

Unusual clinical presentations in patients harboring the facioscapulohumeral dystrophy 4q35 deletion

Muscle Nerve