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For further information, see CMDT Part 24-14: Movement Disorders

Key Features

  • Myoclonic jerks are sudden, shock-like muscle contractions

  • Occasional myoclonic jerks may occur in anyone, especially when drifting into sleep

  • General or multifocal myoclonus: common in patients with idiopathic epilepsy and certain hereditary disorders

  • Generalized myoclonic jerking may

    • Accompany uremic and metabolic encephalopathies

    • Result from therapy with levodopa or cyclic antidepressants

    • Occur in alcohol or drug withdrawal states

    • Follow anoxic brain damage

  • It is common in subacute sclerosing panencephalitis and Creutzfeldt-Jakob disease

Clinical Findings

  • Myoclonus can be focal or generalized and can occur spontaneously or in response to certain stimuli (eg, noise)


  • Clinical diagnosis

  • Electroencephalography is often helpful in clarifying an epileptic basis, and CT or MRI scan may reveal the causal lesion


  • Myoclonus may respond to

    • Anticonvulsant drugs, especially valproic acid or levetiracetam

    • Benzodiazepines, particularly clonazepam (Table 24–2)

    • Piracetam (up to 16.8 g daily; not available in United States)

  • Myoclonus after anoxic brain damage may respond to

    • Clonazepam (sometimes)

    • Oxitriptan (often), given in gradually increasing doses up to 1.0–1.5 mg daily

  • In patients with segmental myoclonus, a localized lesion (spinal or cerebral) should be searched for and treated appropriately

Table 24–2.Medication treatment for seizures in adults (in alphabetical order within classes).

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