|Year : 2016 | Volume
| Issue : 3 | Page : 134-139
Evaluation of children with peripheral hypotonia by electroneuromyography
Kamel M Hewedi, Mohie El-Din Tharwat Mohamed, Mohamed S Yussef
Department of Neurology, Al-Azhar University, Cairo, Egypt
|Date of Submission||11-Nov-2016|
|Date of Acceptance||17-Nov-2016|
|Date of Web Publication||15-Feb-2017|
Mohie El-Din Tharwat Mohamed
Neurology Department, Faculty of Medicine, Al - Azhar University
Source of Support: None, Conflict of Interest: None
Hypotonia is the phenotype of several clinical conditions that do not always lead to a favourable outcome. Thus, it is important to make an immediate and prompt diagnosis with the help of neurophysiological examinations.
The objective of this study was to assess infants and children presenting with peripheral hypotonia by nerve conduction study and electromyography to identify the most common cause of peripheral hypotonia in a sample of Egyptian children.
Patients and methods
Thirty-nine patients who had clinical criteria of peripheral hypotonia were included in this study, which was supported by negative brain MRI findings. These cases underwent complete neurological history, examination, nerve conduction study and electromyography.
Peripheral neuropathy was observed in 18 (46.2%) cases, 11 (28.2%) had myopathic affection, seven (17.9%) had anterior horn cell (AHC) affection and three (7.7%) had the neuromuscular junction disorder.
Peripheral hypotonia in infants and children is an important disorder; therefore, it is essential to study these cases carefully. The most common neuromuscular disorder was peripheral neuropathy, whereas the least common cause was neuromuscular junction disorder.
Keywords: children, electromyography, neuromuscular disorder, peripheral hypotonia
|How to cite this article:|
Hewedi KM, Mohamed MDT, Yussef MS. Evaluation of children with peripheral hypotonia by electroneuromyography. Al-Azhar Assiut Med J 2016;14:134-9
|How to cite this URL:|
Hewedi KM, Mohamed MDT, Yussef MS. Evaluation of children with peripheral hypotonia by electroneuromyography. Al-Azhar Assiut Med J [serial online] 2016 [cited 2017 Oct 17];14:134-9. Available from: http://www.azmj.eg.net/text.asp?2016/14/3/134/200154
| Introduction|| |
Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Recognizing hypotonia is usually straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child’s development and later life depend primarily on the severity of the muscle weakness and the nature of the cause .
Criteria of peripheral hypotonia are absent or depressed tendon reflexes, failure of movements on postural reflexes, fasciculation and muscle atrophy .
Any of the components of the motor unit can be the site of involvement in conditions resulting in hypotonia. A sequential scheme of localization would begin with the AHC and progress to the peripheral nerve, neuromuscular junction (NMJ) and the muscle itself .
Electroneuromyography (ENMG) provides useful information on many neuromuscular diseases. We examine the children with peripheral hypotonia by nerve conduction study (NCS) and electromyography (EMG) to identify the most common peripheral disorder affecting these children.
| Patients and methods|| |
The present study included all children fulfilling the clinical criteria of peripheral hypotonia who attended the Paediatric Neurology Unit (outpatient and inpatient) of Al-Azhar University hospitals in the period between the beginning of November 2014 and the end of October 2015. All the patients below the age of 18 years were included in the study . A written consent was taken from parents of the patients or their caregivers before inclusion in the study. The study was approved by the ethics committee of faculty of medicine, Al - Azhar University, Cairo, Egypt.
Inclusion criteria were children presenting with peripheral hypotonia and who had normal brain MRI findings.
Clinical criteria suggestive of peripheral hypotonia  are as follows:
- Delay in motor milestones with relative normality of social and cognitive development.
- Family history of neuromuscular disorders/maternal myotonia.
- Reduced or absent spontaneous antigravity movements, reduced or absent deep tendon jerks and increased range of joint mobility.
- Frog-leg posture or ‘jug-handle’ posture of arms in association with marked paucity of spontaneous movement.
- Myopathic facies (open mouth with tented upper lip, poor lip seal when sucking, lack of facial expression, ptosis and restricted ocular movements).
- Muscle fasciculation (rarely seen but of diagnostic importance when recognized).
- Other supportive evidence including muscle atrophy and muscle hypertrophy.
Exclusion criteria were children who had central and mixed types of hypotonia.
All cases were subjected to the following procedures:
- Detailed medical and neurological history.
The history taking included the following:
- Personal history.
- Prenatal, natal and postnatal history to detect any environmental hazards, other medical conditions and other system affection.
- Family pedigree construction: to detect any hereditary disorders.
- Developmental history.
- Full general and neurological examination.
- EMG and NCS to localize the site of lower motor neuron affection.
ENMG included studies of motor conduction velocity on the median, ulnar, peroneal and posterior tibial nerves; sensory conduction velocity on the median and sural nerves; an EMG on gluteus maximus, tibialis anterior and biceps brachii for muscle contraction; and quadriceps for spontaneous activity at rest.
Axonal neuropathy was diagnosed by small or absent sensory response, normal or slightly prolonged distal motor latency, small compound motor action potential amplitude, normal or slightly reduced motor conduction velocity with the absence of conduction block and temporal dispersion . Demyelinating neuropathy was diagnosed by small or absent sensory response, prolonged distal motor latency, normal compound motor action potential amplitude, notably reduced motor conduction velocity with presence of conduction block and temporal dispersion .Combined axonal and demyelinating neuropathy was diagnosed when the two above-mentioned criteria were found in different nerves . Neurogenic alterations in EMG were identified by large polyphasic motor unit action potentials with incomplete interference pattern . A denervation pattern is very suggestive of AHC affection: large amplitude, long duration and polyphasic individual motor unit potentials; fasciculations; fibrillations; and positive sharp waves . A myopathic pattern was diagnosed by low amplitude, polyphasic and short duration motor unit potentials .
Repetitive nerve stimulation was performed in selected patients when clinical data suggested NMJ disorder. A decrementing response greater than 10% is characteristic .
All data were collected, presented and analysed by using an appropriate statistical package program (Statistical Package for Social Science (SPSS), version, 20). Qualitative data were presented by number and percentage.
| Results|| |
The study population included 39 children, 22 (56.4%) boys and 17 (43.6%) girls. At the time of the EMG assessment, the mean patient age was 9.11 years (range: 3 months–17 years). In the present study, 17 (43.6%) cases had a history of positive consanguinity, and family history of similar condition was found in nine (23.1%) cases.
In the current study, the clinical and neurophysiological assessment of patients demonstrated that seven (17.9%) cases had AHC disorder, 18 (46.2%) had peripheral neuropathy, three (7.7%) had NMJ disorder and finally 11 (28.2%) had myopathic affection [Table 1].
As regards patients with AHC disorder, these children were younger than those with other neuromuscular disorders, supporting the clinical diagnosis of spinal muscular atrophy (SMA); three cases out of seven had axonal changes (low amplitude) in NCS ([Table 2] and [Figure 1]).
|Table 2 Diagnostic data for the children ultimately diagnosed with anterior horn cell disorder|
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|Figure 1 Electromyography of a 10-year-old girl showing giant motor unit action potential diagnostic of anterior horn cell disorder.|
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In the present study, the most common neuromuscular disorder was peripheral neuropathy. As regards pathophysiological type of neuropathy, 11 cases had axonal neuropathy, four cases had demyelinating neuropathy and three cases had combined axonal and demyelinating neuropathy ([Table 3] and [Figure 2]).
|Table 3 Diagnostic data for the children ultimately diagnosed with peripheral neuropathy|
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|Figure 2 Nerve conduction study of an 11-year-old boy with combined axonal demyelinating neuropathy.|
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In the current study, three cases had symptoms suggesting NMJ disorder; repetitive supramaximal nerve stimulation was done for these children and it demonstrated decrementing response, supporting the clinical diagnosis of myasthenia ([Table 4] and [Figure 3]).
|Table 4 Diagnostic data for the children ultimately diagnosed with neuromuscular junction disorders|
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|Figure 3 Repetitive nerve stimulation of a 17-year-old girl showing decremented response diagnostic of neuromuscular junction disorder.|
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At the time of the EMG assessment, the ages of children with clinical features of myopathy ranged from 2 to 16 years, and all these cases showed myogenic alterations ([Table 5] and [Figure 4]).
|Table 5 Diagnostic data for the children ultimately diagnosed with myopathy|
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|Figure 4 Electromyography of a 9-year-old boy showing myogenic alterations.|
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| Discussion|| |
Children can present with a problem of hypotonia that is due to central or peripheral nervous abnormalities, NMJ lesions, as well as myopathies . The initial approach of hypotonia is to determine whether the problem is due to central or peripheral origin. This is of crucial importance when forming a plan for diagnostic investigations and management .
The present study was conducted on 39 children with peripheral hypotonia; their ages ranged from 3 months to 17 years, and the predominant age was from 6 to below 12 years (43.6%). Pisani and Carboni  reported that hypotonia occurs with a wide range in children but with increased percentage in children between 0 and 3 years of age. Kararizou et al.  and George et al. , reported that chronic inflammatory demyelinating polyneuropathy (CIDP) occurs with a percentage of 20% in teenage.
Regarding the sex of the studied children, 22 (56.4%) were boys and 17 (43.6%) were girls, showing predominance of boys with neuromuscular disorders, and this result disagrees with that of Cetin et al. , who reported that among 37 children with hypotonia of neuromuscular origin 19 were girls and 18 were boys.
As regards the final diagnosis in our patients, seven (17.9%) cases had AHC disorder, 18 (46.2%) had peripheral neuropathy, three (7.7%) had NMJ disorder and 11 (28.2%) had muscle disease. This is in agreement with the study by Erica et al. , who showed that peripheral neuropathy encompasses a wide range of disorders. The underlying causes of peripheral neuropathy may be diverse . Shora et al.  found that neuromuscular disorders accounted for 33 (6.16%) cases. Bell’s palsy was found in 10 (30.30%) cases. Myopathy was found in 10 (30.30%) cases. Myasthenia gravis was found in six (18.18%) cases. Guillain–Barre syndrome was found in four (12.12%) cases. SMA was found in two (6.06%) cases. Sciatic nerve injury was found in one (3.03%) case . Rabie et al. , showed that the muscle diseases had greater percentage than the neuronal diseases. Early recognition of peripheral neuropathies enables accurate genetic advice and detection of pathology. Compared with adults, children present with more autosomal recessive forms of disease related to point mutation. Children are also more likely to have undefined aetiologies than adults . Charcot–Marie–Tooth disease is the most common neuromuscular disorder based on adult prevalence studies or combined studies with paediatric figures integrated, with an estimated prevalence of 17–40 : 100 000 . Guillain–Barre syndrome is considered the common cause of acute weakness in childhood .
In the current study, seven (17.9%) cases had AHC disorder concomitant with the clinical diagnosis of SMA. In the diagnosis of SMA, when clinical characteristics are clearly identifiable (proximal hypotonia and weakness, absence of deep tendon reflexes), the first diagnostic test should be the SMN1 gene deletion test (research of homozygous deletion of the exon 7). In some cases, geneticians may ask for a neurophysiological diagnosis confirmation before the SMN1 gene study . SMA is a clinically heterogeneous disease. It is the most common recessive condition leading to death in children. This disorder is characterized by degeneration of motor neurons within anterior horn of spinal cord and brainstem leading to progressive symmetrical paralysis of the limbs and trunk associated with muscular atrophy . SMA is the second most common fatal autosomal recessive disorder after cystic fibrosis, with an estimated incidence of 1 in 6000 to 1 in 10 000 live births, with a carrier frequency of 1/40–1/60 .
In the current study, 11 (28.2%) cases had myopathy. At the time of the EMG assessment, the ages of children with clinical features of myopathy ranged from 2 to 16 years, and all these cases showed myogenic alterations. EMG in infants differs from use of the method in older children or adults. It is not possible to interpret motor unit recruitment and, thus, a potential disproportion between the motor unit number and the effort output, which may be the only alteration in many myopathies. Another difficulty is that in infants the normal characteristics of motor unit potentials may be very similar to those found in muscle diseases. Furthermore, many muscle diseases do not lead to alterations in the electrical signal; EMG can only authenticate myopathies that feature membrane dysfunction. Indeed, most congenital myopathies have a normal ENMG profile. Congenital muscular dystrophy could also be more prone to induce myopathic activity on needle EMG than nondystrophic lesions . Hellmann et al.  reported that the study of 498 cases with hypotonia showed that EMG can detect myopathy in 50% of children under 1 year of age, increasing to 64% by 1–5 years, and Rabie et al.  reported that it increases to 91% by 5–16 years.
In the current study, three cases had symptoms suggesting NMJ disorder; repetitive supramaximal nerve stimulation was done for these children and it showed decrementing response, supporting the clinical diagnosis of myasthenia. Finnis and Jayawant  reported that juvenile myasthenia gravis is a rare disorder of childhood, but up to 50% of all cases of myasthenia gravis present in childhood, with a peak age at presentation of 5–10 years, with prepubertal onset in less than 10% cases.
| Conclusion|| |
The NCS and EMG are the initial steps in evaluation of patients presenting with peripheral hypotonia. The electrodiagnostic test is useful in completing the examination, giving specific aetiologies and helping in the management. In neurogenic and NMJ disorders, the EMG has a very high detection rate in childhood and is accurate as a screening test in excluding motor unit pathology in hypotonic children. Peripheral neuropathy is the most common peripheral disorder in the present study, presenting in 46.2% of all studied children.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]