 | This article needs more reliable medical references for verification or relies too heavily on primary sources. (November 2020) |  |
| Myotonia | |
|---|---|
| Specialty | Neurology, neuromuscular medicine, medical genetics  |
Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation, and the muscle shows an abnormal EMG.[1][2]
Myotonia is the defining symptom of many channelopathies (diseases of ion channel transport) such as myotonia congenita, paramyotonia congenita and myotonic dystrophy.[3][4]
Brody disease (a disease of ion pump transport) has symptoms similar to myotonia congenita, however, the delayed muscle relaxation is pseudo-myotonia as the EMG is normal.[5] Other diseases that exhibit pseudo-myotonia are myositis, glycogen storage diseases, hyperkalemic periodic paralysis, root disease, anterior horn cell disorders, Isaacs syndrome, and Hoffmann syndrome.[2][6][7]
Generally, repeated contraction of the muscle can alleviate the myotonia and relax the muscles thus improving the condition, however, this is not the case in paramyotonia congenita. This phenomenon is known as the "warm-up" reflex[8] and is not to be confused with warming up before exercise, though they may appear similar. Individuals with the disorder may have trouble releasing their grip on objects or may have difficulty rising from a sitting position and a stiff, awkward gait.
Myotonia can affect all muscle groups; however, the pattern of affected muscles can vary depending on the specific disorder involved.
People with disorders involving myotonia can have life-threatening reactions to certain anaesthetics called anaesthesia-induced rhabdomyolysis.
- ^ Gutmann, Laurie; Phillips, Lawrence H., 2nd (September 1991). "Myotonia congenita". Seminars in Neurology. 11 (3): 244–8. doi:10.1055/s-2008-1041228. PMID 1947487. S2CID 20602810.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link) - ^ a b Killian, James M. (1 January 2010), Rolak, Loren A. (ed.), "CHAPTER 26 - Electromyography", Neurology Secrets (Fifth Edition), Philadelphia: Mosby, pp. 428–435, ISBN 978-0-323-05712-7, retrieved 28 May 2023
- ^ "Myotonia Information Page | National Institute of Neurological Disorders and Stroke". www.ninds.nih.gov. Retrieved 1 October 2019.
- ^ Kim, June-Bum (January 2014). "Channelopathies". Korean Journal of Pediatrics. 57 (1): 1–18. doi:10.3345/kjp.2014.57.1.1. ISSN 1738-1061. PMC 3935107. PMID 24578711.
- ^ Braz, Luís; Soares-Dos-Reis, Ricardo; Seabra, Mafalda; Silveira, Fernando; Guimarães, Joana (October 2019). "Brody disease: when myotonia is not myotonia". Practical Neurology. 19 (5): 417–419. doi:10.1136/practneurol-2019-002224. ISSN 1474-7766. PMID 30996034. S2CID 122401141.
- ^ "Isaacs Syndrome - Neurologic Disorders". Merck Manuals Professional Edition. Retrieved 28 May 2023.
- ^ Tyler, Frank H. (1966), Kuhn, Erich (ed.), "The Differentiation of Myotonia and Pseudomyotonia", Progressive Muskeldystrophie Myotonie · Myasthenie: Symposium vom 30. November bis 4. Dezember 1965 anläßlich der 125. Wiederkehr des Geburtstages von Wilhelm Erb (in German), Berlin, Heidelberg: Springer, pp. 289–294, doi:10.1007/978-3-642-92920-5_39, ISBN 978-3-642-92920-5, retrieved 28 May 2023
- ^ Birnberger, KL; Rüdel, R; Struppler, A (1 September 1975). "Clinical and electrophysiological observations in patients with myotonic muscle disease and the therapeutic effect of N-propyl-ajmaline". Journal of Neurology. 210 (2): 99–110. doi:10.1007/BF00316381. PMID 51920. S2CID 10804605.