eMedicine Specialties > Neurology > Electromyography and Nerve Conduction Studies
Myokymia: Treatment & Medication
Updated: Oct 6, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Medical Care
Treatment of myokymia is focused largely on the underlying etiology. Most patients with facial or focal limb myokymia are not particularly disturbed by the myokymia itself. The accompanying symptoms of the particular neurological or medical conditions are the major concern to patients and their caretakers.
- For conditions secondary to thyrotoxicosis, poisoning, and alcoholic cramp syndrome, the myokymia disappears with resolution or improvement of the medical conditions.
- Patients with radiation plexopathy require no intervention.
- Myokymia seen in acute or chronic polyradiculoneuropathy usually improves with immunomodulatory therapy.
- Transient myokymia that develops after strenuous exercise resolves spontaneously over weeks to months.
Activity
No particular activity restriction is imposed on a patient with myokymia. For patients with stiffness and painful cramps, conditioning of muscles by range of motion and isometric exercise is helpful.
Medication
Phenytoin and carbamazepine have been proven to be effective in treating patients with generalized myokymia, specifically patients with continuous muscle fiber activity described by Isaacs syndrome. High therapeutic drug levels usually are required to reach satisfactory control of symptoms. EMG can objectively document the disappearance of myokymic discharges. Other medications, such as benzodiazepines, have been tried with no consistent benefit. Monitoring of potential adverse effects of phenytoin and carbamazepine and precautions for these drugs are no different from when they are used to treat epilepsy.
Antiepileptic agents
These agents prevent seizure recurrence and terminate clinical and electrical seizure activity.
Phenytoin (Dilantin)
Has promising results in patients with Isaacs syndrome. Relieves cramps and pain of involved muscles. EMG can document objective resolution of myokymic discharges. Mechanism of action possibly related to its effect on sodium channel.
Dosage adjusted according to blood level. Target level should be at high therapeutic range.
Adult
100-200 mg PO tid
Pediatric
10-15 mg/kg/d PO in divided doses
Amiodarone, benzodiazepines, chloramphenicol, cimetidine, fluconazole, isoniazid, metronidazole, miconazole, phenylbutazone, succinimides, sulfonamides, omeprazole, phenacemide, disulfiram, ethanol (acute ingestion), trimethoprim, and valproic acid may increase toxicity
Barbiturates, diazoxide, ethanol (chronic ingestion), rifampin, antacids, charcoal, carbamazepine, theophylline, and sucralfate may decrease effects
May decrease effects of acetaminophen, corticosteroids, dicumarol, disopyramide, doxycycline, estrogens, haloperidol, amiodarone, carbamazepine, cardiac glycosides, quinidine, theophylline, methadone, metyrapone, mexiletine, oral contraceptives, valproic acid
Documented hypersensitivity; sinoatrial block; second- and third-degree AV block; sinus bradycardia; Adams-Stokes syndrome
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Rapid IV infusion may result in death from cardiac arrest, marked by QRS widening
Perform blood counts and urinalyses when therapy is begun and at monthly intervals for several months thereafter to monitor for blood dyscrasias; discontinue use if skin rash appears and do not resume use if rash is exfoliative, bullous, or purpuric; caution in acute intermittent porphyria and diabetes (may elevate blood glucose); discontinue use if hepatic dysfunction occurs
Carbamazepine (Tegretol)
Has promising results in patients with Isaacs syndrome. Relieves cramps and pain of involved muscles. EMG can document objective resolution of myokymic discharges. Mechanism of action possibly related to its effect on sodium channel.
Dosage adjusted according to blood level. Target level should be at high therapeutic range.
Adult
200-400 mg PO tid
Pediatric
10-15 mg/kg/d PO in divided doses
Danazol may increase serum levels significantly within 30 days of coadministration (avoid whenever possible); do not coadminister with MAOIs; cimetidine may increase toxicity, especially if taken in first 4 wk of therapy; may decrease primidone and phenobarbital levels (their coadministration may increase carbamazepine levels)
Documented hypersensitivity; history of bone marrow depression; MAOIs within last 14 d
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Do not use to relieve minor aches or pains; caution with increased intraocular pressure; obtain CBCs and serum iron at baseline prior to treatment, during first 2 months, and yearly or every other year thereafter; can cause drowsiness, dizziness, and blurred vision; caution while driving or performing other tasks requiring alertness
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| Overview: Myokymia |
| Differential Diagnoses & Workup: Myokymia |
 Treatment & Medication: Myokymia |
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References
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Further Reading
Keywords
myokymia, myoclonus fibrillaris multiplex, myokymic discharges, neuromyotonia, Isaacs syndrome, involuntary muscular movement, facial myokymia, focal myokymia, segmental myokymia, generalized myokymia
