Myoclonus

Myoclonus is a type of involuntary muscle movement that typically manifests as sudden jerking or twitching. The involuntary jerks or contractions can occur in different parts of the body and may be caused by a wide range of underlying health conditions, from benign to severe neurological disorders.

Classification and Types

Myoclonus can be classified according to its underlying cause, distribution, pattern, and origin within the central nervous system. There are several major types of myoclonus, including physiological myoclonus, essential myoclonus, epileptic myoclonus, and symptomatic (secondary) myoclonus. In terms of origin, myoclonus can be classified as cortical, subcortical, spinal, or peripheral.

Etiology and Pathophysiology

The causes of myoclonus are varied and may include genetic disorders, brain damage, encephalitis, Parkinson's disease, Alzheimer's disease, or Creutzfeldt-Jakob disease. Metabolic conditions such as kidney or liver failure can also induce myoclonus. Certain drugs, including levodopa, antidepressants, and opioids, are known to induce myoclonus as a side effect.

Clinical Presentation

The hallmark of myoclonus is the abrupt, rapid, and brief contraction of a muscle or group of muscles. Depending on the type and cause, these jerks may be isolated or occur in a series, may affect a specific area or the whole body, and may occur spontaneously or be triggered by external stimuli.

Diagnosis

Diagnosing myoclonus involves a careful clinical evaluation, which may include neurological examination, electroencephalography (EEG), electromyography (EMG), or imaging studies such as magnetic resonance imaging (MRI) to identify any underlying cause. Detailed patient history and familial history can also be significant in establishing the diagnosis.

Treatment and Management

The treatment approach for myoclonus typically involves addressing the underlying cause if it's identifiable and symptomatic treatment to manage the myoclonic jerks. Medications such as clonazepam, sodium valproate, levetiracetam, and primidone are often used. In severe cases, where symptoms are debilitating and refractory to medical treatment, surgical interventions such as deep brain stimulation might be considered.

Prognosis

The prognosis of myoclonus depends largely on the underlying cause. While some forms of myoclonus may be relatively benign and not impact life expectancy, others, associated with severe neurological disorders, may significantly affect a patient's quality of life and longevity.

References

• [1] Caviness, J.N. (2009). Treatment of Myoclonus. Neurotherapeutics, 6(2), 253–263.
• [2] Zutt, R., van Egmond, M.E., Elting, J.W., van Laar, P.J., Brouwer, O.F., Sival, D.A., Kremer, H.P., de Koning, T.J., Tijssen, M.A. (2015). A novel diagnostic approach to patients with myoclonus. Nature Reviews Neurology, 11(12), 687–697.

Myoclonus Resources
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