Hereditary neuromuscular diseases
Section snippets
Definition
Neuromuscular diseases are described as diseases of a series of functional entities called motor units. A motor unit consists of a motor neuron situated either in the anterior horn of the spinal cord or in a number of motor nuclei of the brain stem. Its axon travels through a peripheral nerve towards a particular muscle in which several muscle cells are contacted by means of neuromuscular junctions. According to the site of the lesion within the motor unit, neuromuscular diseases are given
Radiological findings in neuromuscular diseases
The diagnosis of a neuromuscular disease can be established through a comprehensive work-up involving a complete physical and neurological examination, routine hematological and biochemical investigations, muscle power testing, electromyography (EMG), clinical biochemistry, serum creatine kinase (CK) and pyruvate kinase levels, muscle biopsy, mode of inheritance and genetic analysis [5].
CT imaging of muscle provides information that is otherwise not obtainable by clinical examination, and it
Clinical presentation and pathogenesis of muscular dystrophies
All muscular dystrophies present with muscular weakness, insidious onset and progressive nature, but the age of onset of symptoms and the rate of progression vary from one type of muscular dystrophy to another [14].
Becker and Duchenne muscular dystrophy
Duchenne and Becker MD cause similar patterns of weakness and disability and are both inherited as X-linked recessive manner. The responsible gene is mapped on locus Xp21, encoding dystrophin protein [15]. Becker MD is a less severe form of Duchenne MD. The prevalence for Duchenne MD
Myotonic dystrophy (Steinert's disease, congenital myotonic dystrophy)
Myotonic dystrophy, dystrophia myotonica or Steinert's disease is an autosomal dominant hereditary condition [11], with a prevalence of 1/8000 [35]. The association with myotonia, relatively mild muscular weakness and other system involvement separate the disease from the other muscular dystrophies. The genetic defect has recently been shown to result from an unstable DNA sequence of the myotonin protein kinase gene, located on chromosome 19q13 [36]. The disease can be divided into three
Congenital myopathies
Most cases of myopathies start in infancy and very rarely the disease may be present at birth. Due to myopathic nature of the disease, there is usually no obvious muscle weakness and no remarkable radiologic abnormality. Later on, the child may show delayed motor development, and non- or slowly-progressive muscle weakness, affecting the facial muscles, and the proximal musculature. The specific diagnosis of myopathy is made by muscle biopsy.
Metabolic myopathies
Metabolic myopathies are a group of disorders in which metabolic abnormalities either intrinsic to muscle or secondary to other influences result in a variable spectrum of muscle weakness. In general, the weakness tends to be proximal. The radiologic findings in patients with metabolic myopathies are not remarkable, if existing not specific.
Inherited auto-immune and inflammatory myopathies or myositis
Inclusion body myositis (IBM) is a slowly progressive inflammatory myopathy characterized by slowly progressive limb-girdle muscle weakness, dysphagia, and mixed myopathic and neurogenic changes on EMG. The radiological features include both dystrophic and neurogenic type of involvement, namely atrophy and fatty infiltration, that are not specific for disease and highly variable. According to literature, quadriceps muscles are remarkable spared, but our experience does not share this finding.
Spinal muscular atrophy (SMA)
The disorder is characterized by degeneration of the anterior horn cells leading to symmetrical muscle weakness and wasting of voluntary muscles. Patients with spinal muscular atrophy have been classified into three types based on the age of onset and severity.
The responsible gene in all three types is mapped on chromosome 5q13 [46].
Hereditary motor and sensory neuropathies
The term hereditary motor and sensory neuropathy (HMSN) is used to describe a group of conditions marked by slowly progressive weakness and wasting of the muscles below the knees and often those of the hands. Radiologically, there is a typical distribution of lesions. While shoulder and upper limb muscles are normal, the lower limb muscles, especially those below the level of pelvic floor show remarkable neurogenic characteristics of involvement, namely atrophy. The involvement is symmetric (
Conclusion
The radiological features of neuromuscular diseases include changes of muscle volume and attenuation values. This includes atrophy, hypertrophy, pseudohypertrophy and fatty infiltration. CT of patients with hereditary neuromuscular disease discloses large differences in the type of abnormal density, the distribution of atrophic and hypertrophic muscle lesions between individual muscles. In the course of the disease, certain muscles are significantly more or less affected than others. Although
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Cited by (32)
Magnetic resonance of complete body for muscle study and quantification of fatty fraction in pediatric patients with congenital myophaties
2018, Revista Medica Clinica Las CondesVariability in magnetic resonance quantification of muscle fat fraction using Dixon's technique
2016, Revista Chilena de RadiologiaThe trefoil with single fruit sign in muscle magnetic resonance imaging is highly specific for dystrophinopathies
2015, European Journal of RadiologyCitation Excerpt :However, certain other diseases are too rare in China to have been represented in this study. These include, for example, LGMD2E/2F/2L and other LGMDs, which have different patterns of muscle involvement from dystrophinopathies according to the literature [15,20,21]. Taken together, our findings suggest that the trefoil with single fruit sign in muscle MRI represents a new auxiliary method for diagnosing dystrophinopathies.
Investigating glycogenosis type III patients with multi-parametric functional NMR imaging and spectroscopy
2010, Neuromuscular DisordersMouse model of skeletal muscle adiposity: A glycerol treatment approach
2010, Biochemical and Biophysical Research CommunicationsCitation Excerpt :Ectopic fat cell deposition in skeletal muscle is a characteristic of various disorders, such as obesity, sarcopenia and particularly muscular dystrophies. The latter refer to an heterogeneous group of genetically inherited disorders, characterized by a progressive fibro-adipose degeneration of skeletal muscles, and leading to a clinical phenotype consisting in muscular weakness and atrophy [1–3]. Fat cell accumulation has even been shown to be an accurate assessment of Duchenne muscular dystrophy (DMD) severity [4].
MRI for the demonstration of subclinical muscle involvement in muscular dystrophy
2007, Clinical RadiologyCitation Excerpt :Furthermore, severe muscle involvement on MRI was demonstrated in a significant proportion of cases in which MRC grading was normal, indicating that focally advanced disease is not infrequently undetectable clinically. A number of studies have shown that MRI is more likely than CT to demonstrate fatty replacement in muscles, and this is likely to account for the higher detection rate of muscle involvement in the present study.18–20 The signal intensity difference between muscle and fat is significant, and this results in the ready subjective detection of fatty involvement.