Dystrophische und nicht-dystrophische Myotonien

Zusammenfassung

Myotone Syndrome sind seltene Erkrankungen der Skelettmuskulatur die mit einer klinischen und elektrischen Myotonie einhergehen. Die genetischen Defekte betreffen primär oder sekundär muskuläre Ionenkanäle und führen zu einer Übererregbarkeit der muskulären Membran. Zu den dystrophischen Myotonien gehören die myotone Dystrophie Typ 1 (DM1) und die myotone Dystrophie Typ 2 (DM2). Es handelt sich bei beiden um multisystemische Erkrankungen, bei denen neben der Myotonie und dystrophischen Veränderungen der Muskulatur (z. B. Muskelatrophie, Muskelschwäche) auch eine Beteiligung verschiedener anderer Organe (Katarakt, Diabetes, Herzerkrankungen, endokrine Störungen) vorhanden ist. Zu den nicht-dystrophischen Myotonien gehören u. a. die Chlorid- und Natriumkanal-Myotonie. Bei diesen steht das Symptom Myotonie im Vordergrund und gelegentlich werden andere muskuläre Auffälligkeiten (Muskelhypertrophie, transiente Muskelschwäche) beobachtet. Die Differentialdiagnose ist oft eine Herausforderung und die zeitliche Verzögerung bis zur endgültigen Diagnosestellung weiterhin sehr lang. In dieser Übersicht werden Hauptaspekte der klinischen Symptome, der Diagnosestellung und der symptomatischen Therapie der dystrophischen und nicht-dystrophischen Myotonien dargestellt.

Abstract

Myotonic syndromes are rare neuromuscular diseases characterized by the clinical or neurophysiological detection of myotonia. The genetic defects involve primarily or secondarily the muscular isoforms of the ion channels. The channel dysfunction consecutively leads to a hyper-excitability of the muscle membrane and the clinical symptom myotonia. Two forms of dystrophic myotonic diseases are currently known: the myotonic dystrophy type 1 (DM1) and the myotonic dystrophy type 2 (DM2). They are multisystemic diseases clinically characterized by a combination of myotonia and other muscular symptoms (muscle weakness, wasting and myalgia) together with the involvement of other organs and systems (cataract, diabetes, heart diseases, hormone dysfunctions). The non-dystrophic myotonic diseases are caused by mutations affecting either the chloride ion channels or the sodium ion channels. The clinical picture is dominated by the presence of myotonia and other minor muscular complaints as mild episodic weakness and muscle hypertrophy. The differential diagnosis among the myotonic syndromes is extremely challenging leading to a significant diagnostic delay. This review will update on the main clinical, diagnostic and therapeutic aspects of myotonic syndromes to guide general neurologists through an earlier diagnosis and better management.

Schlüsselwörter

DM1 - DM2 - PROMM - Myotone Dystrophien - Kongenitale Myotonien

Key words

myotonic dystrophy - DM1 - DM2 - PROMM - Myotonia

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