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Muscular dystrophy and arthritis
Published in Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize, Developmental and Adapted Physical Education, 2019
Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize
Myotonic muscular dystrophy (Steinert’s disease) is the second most common adult form of muscular dystrophy. It is autosomal dominant and characterized by abnormalities in muscle contraction (Jones, 1985). Myotonia, the primary characteristic of this disease, is usually not clinically or electromyographically evident until 5 years of age, unless it is the congenital form that is diagnosed at birth and results in severe cognitive deficits (Sarnac, 1992). Myotonia is the delay or inability to relax muscles after repetitive discharge, or contraction, of a single muscle fiber after activation induced by the stretch reflex or electrical stimulation (Sarnac, 1992). Myotonia is commonly demonstrated in the hands and distal muscles. Speech is often affected because of involvement of the muscles of the face, tongue, and pharynx. Cardiac involvement is manifested by blocks in the Purkinje system, and arrhythmias instead of cardiomyopathy present in other dystrophic conditions (Sarnac, 1992). Facial features include masseter muscle atrophy and inability to close the lips. The eye muscles are weak, affecting the ability to close the eyes. Neck muscles atrophy and are weak mainly in flexion, causing some cervical lordosis. Weakness in the extremities is present in distal muscles, characterized by weak hand muscles and foot drop. As with other types of muscular dystrophy, learning difficulties may occur, and no specific medical treatment can counteract these symptoms.
Neuromuscular disorders
Published in Ashley W. Blom, David Warwick, Michael R. Whitehouse, Apley and Solomon’s System of Orthopaedics and Trauma, 2017
Myotonia, the inability to relax a muscle after the end of a voluntary contraction or effort, is a prominent feature in certain genetic disorders. The two least rare of these conditions are considered here: dystrophia myotonica, in which myotonia is part of a more widespread systemic disorder, and myotonia congenita, in which myotonia is usually the only abnormal clinical feature.
Psychosocial Issues and Case Management in Myotonic Muscular Dystrophy
Published in Leon I. Charash, Robert E. Lovelace, Claire F. Leach, Austin H. Kutscher, Rabbi Jacob Goldberg, David Price Roye, Jill C. Crabtree, Muscular Dystrophy and Other Neuromuscular Diseases: Psychosocial Issues, 2014
Myotonic muscular dystrophy (DM) is the most prevalent form of muscular dystrophy. Steinert (1909) described it as a slowly progressive disease that initially affects the distal musculature with weakness and atrophy. Facial muscles are also involved, causing the “myotonic facies,” a hatchet-like appearance, often in conjunction with alopecia. This disease can progress to involve the proximal muscles and may cause severe ambulation difficulties that require the patient to use a wheelchair for mobility. Clinically, myotonia is the difficulty of the muscle to relax. Myotonia is demonstrated as sustained deplorization (dive bomber effect) on electromyogram (EMG) (Davison 1961; Lipicky and Bryant 1973) and by percussion on clinical exam (Appel and Roses 1978; Harper 1979).
Ophthalmological Manifestations of Hereditary Myopathies
Published in Journal of Binocular Vision and Ocular Motility, 2022
Marta Saint-Gerons, Miguel Angel Rubio, Gemma Aznar, Ana Matheu
Myotonic syndromes are a group of very heterogeneous etiology disorders that are characterized by the presence of clinical or electrical myotonia. Myotonia is clinically defined as a difficulty of post-contraction muscle relaxation. In electromyography, the presence of high-frequency discharges, derived from excessive irritability of the muscular membrane is observed. Two groups can be differentiated: the first consisting of myotonic dystrophy and proximal myotonic myopathy, and the second, non-dystrophic myotonia. In contrast to myotonic dystrophy, in the non-dystrophic myotonia, there is no significant destruction of muscle tissue, most of them are caused by alterations of the genes that encode subunits of ion channels. This group includes periodic paralysis syndrome, paramyotonia congenita, and myotonia congenita in its dominant or recessive forms43 (Table 3).
Sodium Channel Myotonia and a Novel Gly701Asp Mutation in the SCN4A Gene: From an Ophthalmological Symptom to a Familial Disease
Published in Neuro-Ophthalmology, 2021
Filipa Sampaio, Sérgia Soares, Sara Pereira, José Alberto Lemos, Ágata Mota
The non-dystrophic myotonias are caused by dysfunction of key skeletal muscle ion channels. The worldwide prevalence of non-dystrophic myotonia has been estimated to be 1 in 100 000.1 The major clinical manifestation of the non-dystrophic myotonias is muscle stiffness and additional common symptoms include pain, weakness and fatigue.2,3 Myotonia can be demonstrated on examination as delayed muscle relaxation following muscle contraction. Non-dystrophic myotonias are classified as myotonia congenita, caused by mutations in the skeletal muscle chloride channel gene (CLCN1) and inherited in a dominant or in a recessive fashion; paramyotonia congenita and the sodium channel myotonias, characterised by allelic, autosomal dominant disorders caused by mutations in the skeletal muscle sodium channel gene (SCN4A); and hyperkalaemic periodic paralysis, also caused by mutations in SCN4A gene in which episodic paralysis is usually the dominant feature (Table 1).4
Improving genetic diagnostics of skeletal muscle channelopathies
Published in Expert Review of Molecular Diagnostics, 2020
Vinojini Vivekanandam, Roope Männikkö, Emma Matthews, Michael G. Hanna
Myotonia Congenita (MC) is the most common skeletal muscle channelopathy. It is caused by mutations in the CLCN1 gene, which encodes the voltage-gated chloride channel ClC-1. The functional channel protein is comprised of two gene products [5]. The symptoms of myotonia generally present in the first or second decade of life [6]. Symptoms of myotonia are prominent at the initiation of movement and often improve with repeated activity – a phenomenon known as ‘warm up.’ Patients with recessively inherited myotonia congenita tend to have more severe symptoms compared to patients with dominant mutations [5] and additionally, some patients with recessive MC have transient weakness at the initiation of movement. Hundreds of pathogenic mutations have been identified in CLCN1, the majority of CLCN1 mutations are missense, with Gly230Glu the most common [2,7].