References for this Review were found through searches of Medline and EMBASE from 1966 until December, 2009, by use of the search terms “myoclonus”, “myoclon*”, “therapy”, “treatment”, “intervention”, “randomised controlled trial”, “double blind”, “single blind”, “clinical trial”, “placebo”, “epidemiologic research design”, “comparative study”, “cross-over”, and “hyperekplexia”. References of relevant publications were also searched. The abstracts of retrieved studies were assessed for
ReviewManagement of patients with myoclonus: available therapies and the need for an evidence-based approach
Introduction
Myoclonic jerks are sudden, brief, shock-like involuntary movements caused by muscular contractions (positive myoclonus) or interruptions of tonic muscle activity (negative myoclonus).1, 2 Pathological and persistent myoclonus has a lifetime prevalence of 8·6 cases per 100 000 population,3 and 0·5% of patients in nursing homes display myoclonus.4 Patients with transient (eg, drug-induced) myoclonus are not included in these estimates, but they represent 27·6% of all patients with myoclonus who visit an emergency room for a movement disorder.5
Myoclonus must be differentiated from other movement disorders such as tics, tremor, dystonia, chorea, simple partial seizures, fasciculations, and psychogenic jerks. The following are important clinical clues for differentiation of myoclonus: non-suppressible and simple movement, not preceded by an urge to move, generally arrhythmic, not influenced by a geste antagonistique, can be synchronous and stimulus sensitive, rarely incorporated in voluntary actions, and does not show entrainment.6, 7, 8, 9, 10 However, myoclonic jerks regularly occur in patients with other movement disorders,1 and electrophysiological studies might be needed for a correct diagnosis.7, 9 Correct identification and classification of myoclonus are crucial for adequate treatment and might help to inform prognosis.1, 11 Treatment should first focus on cure of the underlying disorder, such as removal of a medication or toxin, or reversal of an acquired abnormal metabolic state.12, 13 Unfortunately, this approach is often not possible and symptomatic treatment is necessary.
In this Review, we discuss treatment strategies for myoclonus based on the anatomical classification. Because seizures generally dominate in patients with myoclonic epilepsy, myoclonic seizures are not covered; we refer to available literature for recommended therapies for myoclonic seizures.14, 15, 16
Section snippets
Classifications of myoclonus
The three generally accepted classifications of myoclonus according to clinical signs, aetiology, and anatomic origin (panel) are outlined separately.1, 6, 17 However, these classification systems are interrelated, because clinical signs are important for establishing aetiology and anatomic origin, and information on anatomic origin is often mandatory for an aetiological diagnosis.18 Current treatment regimens are mainly based on the anatomic origin of myoclonus, making this the most important
Treatment according to anatomic classification
In this section we discuss treatment recommendations for myoclonus, guided by the anatomic classification and based on evidence from literature and clinical practice. Additionally, we give information about therapy for psychogenic myoclonus. Treatment of myoclonus is often difficult. Several drug trials might be necessary to find the best therapy, and drugs are usually only partly beneficial in treating myoclonus. Treatment is often limited by side-effects, and initial low dosages with a slow
Conclusions
Myoclonus is a somewhat common movement disorder. The choice of symptomatic therapy is based on the anatomical classification of myoclonus, and polytherapy is frequently required. Still, the effect of treatment is often disappointing. Present practice is mainly based on small observational studies and expert opinion, with very limited evidence on symptomatic treatment of myoclonus. A more evidence-based approach could vastly improve myoclonus treatment. Double-blind, randomised controlled
Search strategy
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