Myoclonus is an involuntary muscle movement that appears as sudden, quick, or unexpected spasms or contractions. These movements can occur either in isolation or repeatedly and most often affect the arms or legs.
The causes of myoclonus may include spasms related to anxiety or physical exertion, involuntary movements during sleep, or, in some cases, neurological conditions such as epilepsy, brain injury, or spinal cord injury.
Treatment for myoclonus should be prescribed by a neurologist based on the underlying cause. It may involve anticonvulsants, tranquilizers, or surgery, especially in cases where spasms are frequent and interfere with quality of life.
Main symptoms
The main symptoms of myoclonus include:
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Sudden and rapid muscle contractions
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Isolated or repetitive spasms
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Spasms during sleep, mainly in the legs
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Involuntary movements of the facial muscles
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Difficulty eating, writing, walking, or speaking
Symptoms of myoclonus can vary in intensity and frequency, and in some cases, are associated with other neurological conditions, such as Parkinson’s disease.
Confirming a diagnosis
Diagnosis of myoclonus is made by a neurologist through an evaluation of the person’s medical history, symptoms, and a physical neurological exam.
The doctor may also order blood and urine tests, or a lumbar puncture, to check for infections, metabolic changes, or toxic substances. Imaging tests, such as MRI scans, may be used to detect abnormalities in the brain or spinal cord. Genetic testing is recommended when hereditary myoclonus is suspected.
To confirm the diagnosis, neurophysiological tests such as electroencephalogram (EEG) and electromyography (EMG) can be performed to identify the source of the spasms within the nervous system.
Possible causes
Myoclonus can be classified according to its cause into the following categories:
1. Sleep myoclonus
Sleep myoclonus occurs when involuntary muscle spasms happen while falling asleep. These spasms are often accompanied by a sensation of falling or imbalance, causing the arms or legs to move suddenly.
It is believed that sleep myoclonus is caused by a conflict between the brain systems responsible for wakefulness and sleep. Factors such as stress, anxiety, caffeine, nicotine, extreme fatigue, and sleep deprivation can increase its occurrence.
2. Physiologic myoclonus
Physiologic myoclonus occurs in healthy individuals and usually does not require treatment, as it is linked to normal bodily responses.
Common examples include hiccups, spasms triggered by anxiety or physical effort, and nocturnal myoclonus, such as the involuntary movements that occur in babies while sleeping.
3. Idiopathic myoclonus
Idiopathic myoclonus appears without an identifiable cause and is not associated with any other neurological disorders. However, it can interfere with daily activities such as eating, writing, walking, or speaking, particularly when spasms are frequent or intense.
Although the exact cause is unknown, it is thought that genetic or hereditary factors may play a role.
4. Epileptic myoclonus
Epileptic myoclonus is characterized by seizures that cause rapid and involuntary muscle movements, especially in the arms and legs. Possible causes include conditions such as Juvenile Myoclonic Epilepsy and Lennox-Gastaut Syndrome, as well as genetic mutations or brain lesions that increase neuronal activity, resulting in these involuntary movements during seizures.
5. Secondary myoclonus
Secondary myoclonus generally occurs as a result of other diseases, such as brain or spinal cord injuries, kidney or liver failure, Gaucher’s disease, poisoning, prolonged hypoxia, or reactions to medications.
It may also be linked to autoimmune disorders, such as Opsoclonus-Myoclonus Syndrome. Also called symptomatic myoclonus, other causes include stroke, brain tumors, Huntington’s disease, Creutzfeldt-Jakob disease, Alzheimer’s disease, Parkinson’s disease, corticobasal degeneration, and frontotemporal dementia.
Treatment options
The main treatments recommended by a neurologist for myoclonus include:
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Tranquilizers, such as clonazepam, are often the first line of treatment for myoclonus. However, they may cause drowsiness and, over time, may lose some of their effectiveness.
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Anticonvulsants, such as valproic acid, primidone, or levetiracetam, help control seizures and reduce spasms. They may cause side effects such as nausea, fatigue, dizziness, or sedation.
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Botox injections (botulinum toxin type A) are recommended for localized cases, such as facial spasms or palatal myoclonus. The toxin works by blocking the chemical responsible for muscle contraction.
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Immunotherapy is indicated when myoclonus is related to autoimmune diseases, such as Opsoclonus-Myoclonus Syndrome.
In cases where myoclonus is related to a tumor or lesion in the brain or spinal cord, surgery may be necessary to remove or relieve pressure on these structures. However, treatment may not be required when myoclonus symptoms are mild, do not interfere with daily activities, and are associated with physiologic myoclonus.