Neuromuscular Disorders
It is crucial to emphasize that neuromuscular diseases are a group of diseases of the muscles of the body and nerves located in the limbs, during which the primary pathological process is noted directly in the muscle or nerve. In this case, the central nervous system is not damaged. In addition, neuromuscular diseases are characterized by impairment of the voluntary muscles’ function and the loss or reduction of motor control (Van de Velde et al., 2022). These diseases occupy an important place in clinical neurology, also recognized as diseases of the peripheral nervous system. Thus, it is essential to provide information about neuromuscular diseases.
Muscular Dystrophy
It is significant to mention that the most common forms are Duchenne and Becker muscular dystrophies, which are caused by an absence or considerable decrease in the dystrophin protein in the muscle. In such a case, the pathological process involves the muscle fiber, while the nerve motor cells in the spinal cord, nerves extending from the spinal cord, and nerve endings are intact. The disease occurs in males, is genetically transmitted, and begins before age 5 (Pfaff et al., 2017). In addition, the first sign is difficulty climbing stairs and getting up from the floor. At the same time, an enlargement of the shin muscles is characteristic, and contractures develop in the glenoid vessels. Treatment with corticosteroids prolongs the ability to move independently for 3-4 years. A large number of patients have mental problems and cardiomyopathy. Furthermore, Becker muscular dystrophy begins at a later age, after 8-10 years (Pfaff et al., 2017). The clinical signs are the same as in Duchenne dystrophy. During this form, the patient retains the ability to move independently for longer.
The disease can be diagnosed by determining the blood enzyme creatine kinase, which is significantly increased in both forms. For this purpose, the electroneurogram examination is also performed, which makes it possible to establish myopathic records. The treatment is mainly focused on maintaining functional independence and quality of life(Hong et al., 2022). Additionally, physical therapy is directed against the development of contractures and scoliosis. The use of orthoses and timely tendon surgery improves walking (Hong et al., 2022). Furthermore, electrocardiographic and echocardiographic monitoring is performed if necessary. In addition, supplementary aortic ventilation is needed if required.
It is essential to remark that concomitant myopathies occur in infancy or early childhood by general muscle laxity. Histochemical and ultrastructural changes in the muscles and slow progression are characteristic (Hong et al., 2022). Such clinical signs as drooping eyelids, and cardiomyopathy, are essential. Furthermore, there is a classification of associated myopathies based on genetic and morphological changes, according to which the following myopathies are distinguished. These are protein accumulation, myopathies with an axis, myopathies with a central nucleus, and changes in fiber size (Hong et al., 2022). In addition, the diagnosis is made by biopsy of the muscle. Meanwhile, treatment focuses mainly on rehabilitation, the main goal of preserving functional independence and quality of life.
Spinal Muscular Atrophy
Spinal muscular atrophy is a hereditary progressive disease of the motor cells (motor neurons) located in the spinal cord (Ji et al., 2017). It also occurs with muscle weakness and is caused by the slow degeneration of these cells. Moreover, there are three main types of this disease. The first is Werdnig-Hoffmann disease, which is detected mainly in the first months of life. The child has difficulty holding his head, weak cries and coughs, and weakness of the respiratory muscles is also pronounced (Ji et al., 2017). Secondly, it is an intermediate form of childhood; weakness develops relatively late. There may be independent sitting, vascular contractures develop, and tardiness of food is noted. The third is Kugelber-Wielander disease, which is characterized by a late onset. Patients can walk independently, but scoliosis, difficulty swallowing, and coughing are observed (Ji et al., 2017). Instead, symmetrical weakness of the proximal muscles is characteristic, and the course of the disease is progressive, the rate decreasing with age.
Diagnosis is based on electroneuromyogram examination, that is, neurogenic recordings. It is also possible to determine creatine kinase in the blood and genetic examination, namely the deletion test. It is important to note that the care and treatment of patients with Werdnig-Hoffman disease include a tracheostomy, assisted ventilation, and feeding through a tube (Jones et al., 2021). For the other forms, treatment is symptomatic and aimed at preventing spine and lower extremities deformities. However, timely identification and proper management of the above diseases are essential.
Peripheral Neuropathies
It is essential to note that in peripheral neuropathy, pathological changes can damage the motor and sensory nerve fibers in the extremities. Depending on how many nerves and which anatomical domain of the nerve is injured, peripheral neuropathies are separated into the following types: polyneuropathy, mononeuropathy, multiple mononeuritis, radiculopathy, polyradiculopathy, and plexopathy (Pero et al., 2021). The most common degenerative disease of the peripheral nervous system is also peripheral motor and sensory polyneuropathy, known as Charcot-Marie-Tooth disease. Degenerative changes develop in the nerves in the extremities, causing difficulty walking, frequent falls, muscle atrophy, and later deformity of the foot, which is selectively characteristic of this disease.
Diagnosis is based on electroneuromyogram examination; a drop in electron pulse velocity is typical. In uncertain cases, molecular genetic analysis is resorted to. Meanwhile, treatment is based on the team observation of different specialists: the physical therapist, occupational therapist, orthopedist, and neurologist (Pero et al., 2021). Rehabilitation, and prevention of contractures, are also crucial for treatment. In conditions of fixed contractures, surgical treatment can be resorted to.
Myasthenia Gravis
Myasthenia gravis is the most typical disease of the neuromuscular synapse in childhood and is autoimmune. It is caused by a decrease in the receptors that receive the impulse in the synapse, which is the site of impulse transmission from the nerve to the muscle. The reduction of receptors is caused by antibodies produced in the body, the etiology of which is unknown. Symptoms also occur over the age of one year (Chia et al., 2022). Patients experience weakness, rapid fatigue, especially in the afternoon, difficulty chewing and swallowing drooping eyelids, and blurred vision. In the case of generalized forms of myasthenia gravis, weakness also extends to the muscles of the extremities (Laquerriere et al., 2022). In addition, myasthenia gravis is associated with other autoimmune processes, such as thyroid pathology and thymus gland disease.
Moreover, the severity of the disease is detected at a relatively early stage. It is important to note that diagnosis is based on detecting antibodies in the blood against acetylcholine receptors and electroneuromyogram examination. Additionally, treatment mainly uses medications that contain acetylcholinesterase, neostigmine, and pyridostigmine (Chia et al., 2022). Plasmapheresis and intravenous immunoglobulin, and immunosuppressants are also used. In some cases, removal of the thymus gland is resorted to.
Conclusion
Therefore, neuromuscular diseases are a huge layer of diseases of the peripheral nervous system and muscles. They include different types of myopathies, spinal amyotrophies, myasthenia gravis, myotonia, and more common mono-, poly- and plexopathies. Moreover, they are accompanied by a decrease in strength and limitation of motor activity. Furthermore, muscle weakness, development of muscle atrophy, decreased tendon reflexes and muscle tone are manifested.
References
Chia, R., Saez-Atienzar, S., Murphy, N., Chiò, A., Blauwendraat, C., International Myasthenia Gravis Genomics Consortium, & Traynor, B. J. (2022). Identification of genetic risk loci and prioritization of genes and pathways for myasthenia gravis: A genome-wide association study. Proceedings of the National Academy of Sciences, 119(5), e2108672119.
Hong, D., Wang, H., Zhu, M., Peng, Y., Huang, P., Zheng, Y., & Yuan, Y. (2022). Subclinical peripheral neuropathy is common in neuronal intranuclear inclusion disease with dominant encephalopathy. European Journal of Neurology, 1-10.
Ji, A. L., Zhang, X., Chen, W. W., & Huang, W. J. (2017). Genetics insight into the amyotrophic lateral sclerosis/frontotemporal dementia spectrum. Journal of Medical Genetics, 54(3), 145-154.
Jones, K., Hawke, F., Newman, J., Miller, J. A., Burns, J., Jakovljevic, D. G., & Ramdharry, G. (2021). Interventions for promoting physical activity in people with neuromuscular disease. Cochrane Database of Systematic Reviews, 5.
Laquerriere, A., Jaber, D., Abiusi, E., Maluenda, J., Mejlachowicz, D., Vivanti, A., & Melki, J. (2022). Phenotypic spectrum and genomics of undiagnosed arthrogryposis multiplex congenita. Journal of Medical Genetics, 59(6), 559-567.
Pfaff, J., Rivera Monroy, J., Jamieson, C., Rajanala, K., Vilardi, F., Schwappach, B., & Kehlenbach, R. H. (2017). Emery–Dreifuss muscular dystrophy mutations impair TRC40-mediated targeting of emerin to the inner nuclear membrane. Journal of Cell Science, 129(3), 502-516.
Pero, M. E., Meregalli, C., Qu, X., Shin, G. J. E., Kumar, A., Shorey, M., & Bartolini, F. (2021). Pathogenic role of delta 2 tubulin in bortezomib-induced peripheral neuropathy. Proceedings of the National Academy of Sciences, 118(4), e2012685118.
Van de Velde, N. M., Gegenava, T., Koeks, Z., Butcher, S. C., Roest, A. A., Bax, J. J., & Niks, E. H. (2022). Value of global longitudinal strain for identification and monitoring of left ventricular dysfunction in Becker muscular dystrophy. The American Journal of Cardiology, 162, 170-176.