Myoclonus: Causes, Symptoms, Investigations, Treatment
Myoclonus is a medical condition where a person experiences rapid, involuntary muscle jerks. Some of the types of myoclonus include hiccups and the sudden jerks or "sleep starts," which a person experiences before falling asleep. These all are those forms of myoclonus which occur in healthy individuals and do not present a problem.
Most of the times, a neurological disorder causes myoclonus, such as epilepsy. Myoclonus can also occur as a result of a reaction to a medication or some metabolic condition.
Treating the underlying cause, helps control the symptoms of myoclonus. If the underlying cause is not found out, or if it is not treatable, then treatment focuses on decreasing the symptoms of myoclonus and its effects on a person’s quality of life.
Causes & Types of Myoclonus
Different underlying problems can cause myoclonus. Myoclonus is differentiated into different types depending on the cause, and treatment plan is outlined accordingly.
The following are the different types of myoclonus based on its cause:
Essential myoclonus commonly occurs without any other symptoms and occurs on its own and is not related to any underlying illness. Essential myoclonus is commonly idiopathic, i.e. the cause is not known or is unexplained and in some cases it is hereditary.
This is a type of myoclonus, which occurs in normal and healthy individuals and most often does not require treatment. Some of the examples of Physiological Myoclonus are:
- Sleep starts.
- Muscle twitching in infants after a feeding or during sleep.
- Spasms or shakes after or during exercise.
- Spasms or shakes due to anxiety.
As the name itself indicates, this type of myoclonus is experienced as a part of an epileptic disorder. Muscle jerks could be the only sign of epileptic myoclonus or it could be accompanied by other symptoms too.
Symptomatic (Secondary) Myoclonus
This is one of the common forms of myoclonus. There are different underlying medical conditions which could be causing these muscle jerks such as:
- Injury to the head or spinal cord.
- Kidney failure.
- Liver failure.
- Poisoning from chemicals or drugs.
- Lipid storage disease.
- Reaction to medicine.
- Prolonged deprivation of oxygen.
- Metabolic disorders.
- Autoimmune inflammatory conditions.
Some of the Nervous Disorders which can Cause Secondary Myoclonus are:
- Brain tumor.
- Huntington's disease.
- Alzheimer's disease.
- Creutzfeldt-Jakob disease.
- Parkinson's disease and Lewy body dementia.
- Fronto-temporal dementia.
- Cortico-basal degeneration.
- Multiple system atrophy.
Signs & Symptoms of Myoclonus
- Individuals with myoclonus commonly describe their signs and symptoms as spasms, jerks or shakes, which are:
- Sudden, brief and involuntary.
- Shock-like in nature.
- Variable in frequency and intensity.
- Can be localized to a part of body or occurs in the entire body.
- Can be severe enough to interfere with a person’s daily habits, such as speaking, eating and walking.
Investigations for Myoclonus
To find out the cause of myoclonus along with excluding other underlying potential causes of it, the doctor will conduct the following tests:
- Medical history and physical examination.
- Electroencephalography (EEG) which measures the electrical activity of the brain and helps in finding out in which area of the brain the myoclonus is originating. Small electrodes are attached to the scalp and the patient is asked to take deep breaths for several minutes and also told to listen to sounds and look at bright lights.
- Electromyography (EMG) measures the electrical discharges, which are produced in the muscles and helps in determining the pattern of myoclonus. In this procedure, surface electrodes are placed on multiple muscles, especially those which are involved in spasms and jerking. The electrical activity from the muscles at rest and during contraction is recorded by an instrument. These signals help in establishing the pattern and origin of the myoclonus.
- Magnetic resonance imaging (MRI) is a scan, which is used to look for structural problems or tumors in the brain or spinal cord, which is causing the symptoms of the myoclonus.
- Blood and urine tests are done to check for other problems, such as autoimmune disease, drugs or toxins, metabolic disorders, diabetes, kidney or liver disease.
Treatment for Myoclonus
Treatment of myoclonus aims at treating the underlying cause. In many of the cases, the underlying cause cannot be cured. In such cases, treatment focuses on relieving the myoclonus symptoms, especially when they are affecting a person’s quality of life. The following steps are undertaken to relieve the symptoms of myoclonus.
Medications for Myoclonus
- Tranquilizers are the most commonly prescribed medicine for alleviating myoclonus symptoms. One of the examples of tranquilizers is clonazepam. Side effects include drowsiness and dizziness.
- Anticonvulsants medicines are used to control the epileptic seizures, which help in alleviating myoclonus symptoms. Some of the common anticonvulsants used for treating myoclonus are levetiracetam, valproic acid and primidone. Side effects of valproic acid include nausea. Side effects of levetiracetam include fatigue and dizziness.
- Botox (OnabotulinumtoxinA) injections are also helpful in treating different types of myoclonus. They are especially beneficial if only a single area is affected. Botulinum toxin acts by blocking the release of a chemical messenger which initiates the muscle contractions.
Surgery for Myoclonus
If a lesion or tumor in the brain or spinal cord is causing the symptoms of myoclonus, then surgery can be done for it. Surgery is also beneficial for those people whose myoclonus is affecting his/her ear or some parts of the face. Deep brain stimulation (DBS) is a procedure which can also be done in some patients having myoclonus or other movement disorders.