Myoclonus

Myoclonus: Excerpt from Signs & Symptoms: A 2-in-1 Reference for Nurses

Myoclonus — sudden, shocklike contractions of a single muscle or muscle group — occurs with various neurologic disorders and may herald onset of a seizure. These contractions may be isolated or repetitive, rhythmic or arrhythmic, symmetrical or asymmetrical, synchronous or asynchronous, and generalized or focal. They may be precipitated by bright flickering lights, a loud sound, or unexpected physical contact. Intention myoclonus, is evoked by intentional muscle movement.

Myoclonus occurs normally just before falling asleep and as a part of the natural startle reaction. It also occurs with some poisonings.

Emergency Actions

If you observe myoclonus, check for seizure activity. Take vital signs to rule out arrhythmias or a blocked airway. Have resuscitation equipment on hand. If the patient has a seizure, gently help him lie down. Place a pillow or a rolled-up towel under his head to prevent concussion. Loosen any constrictive clothing, especially around the neck, and turn his head (gently, if possible) to one side to prevent airway occlusion or aspiration of secretions.

History

If the patient is stable, evaluate level of consciousness (LOC) and mental status. Ask about the frequency, severity, location, and circumstances of myoclonus. Has he ever had a seizure? If so, did myoclonus precede it? Is the myoclonus ever precipitated by a sensory stimulus?

Physical assessment

Check for muscle rigidity and wasting, and test deep tendon reflexes. Then complete the neurologic and musculoskeletal assessments.

Medical causes

Alzheimer’s disease

Generalized myoclonus may occur in advanced stages of this slowly progressive dementia. Other late findings in Alzheimer’s disease include mild choreoathetoid movements, muscle rigidity, bowel and bladder incontinence, delusions, and hallucinations.

Creutzfeldt-Jakob disease

Diffuse myoclonic jerks appear early in Creutzfeldt-Jakob disease — a rapidly progressive dementia. Initially random, they gradually become more rhythmic and symmetrical, typically occurring in response to sensory stimuli. Associated effects include ataxia, aphasia, hearing loss, muscle rigidity and wasting, fasciculations, hemiplegia, and vision disturbances or, possibly, blindness.

Encephalitis (viral)

With viral encephalitis, myoclonus is usually intermittent and either localized or generalized. Associated findings vary but may include rapidly decreasing LOC, fever, headache, irritability, nuchal rigidity, vomiting, seizures, aphasia, ataxia, hemiparesis, facial muscle weakness, nystagmus, ocular palsies, and dysphagia.

Encephalopathy

Hepatic encephalopathy occasionally produces myoclonic jerks in association with asterixis and focal or generalized seizures.

Hypoxic encephalopathy may produce generalized myoclonus or seizures almost immediately after restoration of cardiopulmonary function. The patient may also have a residual intention myoclonus.

Uremic encephalopathy commonly produces myoclonic jerks and seizures. Other signs and symptoms include apathy, fatigue, irritability, headache, confusion, gradually decreasing LOC, nausea, vomiting, oliguria, edema, and papilledema. The patient may also exhibit elevated blood pressure, dyspnea, arrhythmias, and abnormal respirations.

Epilepsy

With idiopathic epilepsy, localized myoclonus is usually confined to an arm or leg and occurs singly or in short bursts, usually upon awakening. It’s usually more frequent and severe during the prodromal stage of a major generalized seizure, after which it diminishes in frequency and intensity.

Myoclonic jerks are usually the first signs of myoclonic epilepsy, the most common cause of progressive myoclonus. At first, myoclonus is infrequent and localized, but over a period of months, it becomes more frequent and involves the entire body, disrupting voluntary movement (intention myoclonus). As the disease progresses, myoclonus is accompanied by generalized seizures and dementia.

Other causes

Drug withdrawal

Myoclonus may be seen in patients with alcohol, opioid, or sedative withdrawal, or delirium tremens.

Poisoning

Acute intoxication with methyl bromide, bismuth, or strychnine may produce an acute onset of myoclonus and confusion.

Special considerations

If your patient’s myoclonus is progressive, take seizure precautions. Keep an oral airway and suction equipment at his bedside, and pad the side rails. Because myoclonus may cause falls, remove potentially harmful objects from the patient’s environment, and remain with him while he walks.

As needed, administer drugs that suppress myoclonus: ethosuximide, L-5-hydroxytryptophan, phenobarbital, clonazepam, or carbidopa. An EEG may be needed to evaluate myoclonus and related brain activity.

Pediatric pointers

Although myoclonus is relatively uncommon in infants and children, it can result from subacute sclerosing panencephalitis, severe meningitis, progressive poliodystrophy, childhood myoclonic epilepsy, and encephalopathies such as Reye’s syndrome.

Patient counseling

Instruct the patient and his family about the need for safety and seizure precautions. Discuss with the family safety measures to perform during a seizure. Provide support to the family and caregivers during end-stage Alzheimer’s disease and encephalopathy. Educate them about the disease involved, and refer them to social service and community resources as needed.

Pictures

Book Source Details

• Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
• Author(s): Springhouse
• Year of Publication: 2007
• Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Signs & Symptoms: A 2-in-1 Reference for Nurses Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-58255-318-1

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