Myoclonic Disorders: Classification and Treatment
Fellow research review of: “Myoclonic disorders: a practical approach for diagnosis and treatment,” by Maja Kojovic, Kailash Bhatia, and Carla Cordivari
MYOCLONIC DISORDERS: CLASSIFICATION AND TREATMENT
HIGHLIGHTS:
Myoclonus is a disorder characterized by sudden involuntary muscle jerk or spasm. The symptoms exhibited may reflect the classification of myoclonus. Sudden muscle contraction may indicate positive myoclonus. Abrupt cessation of muscular activity, on the other hand, indicates negative myoclonus. However, there are several other classifications of myoclonus based on how it manifests. The causes of myoclonus are numerous; therefore, taking proper history is essential. This ensures you have the necessary details to properly characterize the condition so that you can stick to useful investigative procedures. When taking history in a patient with suspected myoclonus, it is necessary to get the age of onset, family history, characteristics, aggravating or alleviating factors.
Furthermore, examination of the characteristics of myoclonus is important. This helps determine if the myoclonus happens at rest, during a particular posture or movement, to identify the intensity and distribution of the stimuli. Electrophysiological tests can determine the etiology of myoclonus. Neurophysiology is another aspect that may be useful in diagnosing and treating myoclonus. Proper classification of myoclonus characteristics is important in treatment, which improves the prognosis of the condition. However, it does not get worse over time but remains stable. The treatment of myoclonus involves a combination of various drugs to achieve the desired result. Generally, clonazepam can be used in all forms of myoclonus. Antiepileptic drugs are an essential part of pharmacology therapy for cortical myoclonus. Botulinum Toxin injection may be the best option for segmental myoclonus.
myAir app focuses on improving the health of clients. myAir team often studies research like this one. This informs how we attend to the needs of clients with myoclonus. myAir app may ask questions to track the intensity and frequency of nuzzling spasms. In managing this disease process, adequate knowledge of the pathophysiology and treatment is important. The knowledge from this research serves as a foundation in creating the algorithm of myAir app. One crucial area of monitoring in myoclonic individuals is their drug therapy. They often need a combination of drugs to meet their needs. However, they can develop resistance or tolerance to the drugs. myAir app can help individuals track the changes to ascertain if the muscle jerk is reducing, unaffected, or increasing.
RESULT
According to this study, there are five broad classes of myoclonus. They include physiological, essential, epileptic, symptomatic, and psychogenic myoclonus. The treatment is specific for each classification. We shall explore the details on the classification and treatment of myoclonus in other sections of this article.
INTRODUCTION TO THE RESEARCH
The research aims to understand the various classification and treatment strategies of myoclonus. However, the first step in making these essential findings is examination. The individuals with myoclonus disorder need to be observed and asked specific questions to ensure we are right. In medicine, physical assessment is the first step before attempting diagnosis and treatment. Therefore, in this section, we shall discuss the process of assessing an individual with the myoclonic disorder.
The following questions are important when conducting a physical assessment:
At what age did it begin?
Did the muscle jerk start suddenly or gradually?
Are there situations that it is worse?
Is there a posture that makes it better?
Does any member of your family have this condition?
Do you feel like the symptoms are getting worse?
Do you experience impaired coordination like staggering?
In addition, cognitive assessment is also essential to determine if there is a decline in cognitive functions. Assessing the age of onset helps determine the category of myoclonus. Myoclonus in children or young adults with epilepsy, cognitive decline, and ataxia (impaired coordination) may indicate progressive myoclonic epilepsy. In the elderly, cognitive decline with myoclonus indicates dementia with Lewy bodies (DLB), corticobasal degeneration (CBD), and Alzheimer’s disease.
Spinal and peripheral myoclonus may be due to cord, root, or nerve injury. The presence of dementia or epilepsy eliminates the option of essential myoclonus. This leads to several investigations to identify the cause. In addition, it is necessary to observe the individual for neurological signs, especially dementia, abnormal eye movements, and other signs of systemic conditions.
When assessing an individual with myoclonus, observe if the spasm occurs at rest, certain posture(s), or with movement. Also, in this examination, it is best to note its frequency and distribution. An individual with myoclonus at rest shows the cause may be from the brainstem or spinal region. Action-induced myoclonus indicates a cortical origin. Generalized myoclonus is usually subcortical in origin. When the amplitude of the myoclonus is very large, it points to progressive myoclonic epilepsy. However, small amplitudes may indicate multiple system atrophy.
After ascertaining the origin of the myoclonus, we can now observe for stimulus sensitivity. You can trigger myoclonus by touching the outstretched fingers. Auditory stimuli (door sounds, tapping of a pen, loud speech, or clapping the hands) from the environment may trigger myoclonus in susceptible individuals.
We can easily identify precipitating factors in cases of intoxication, metabolic disturbances, and drug-induced myoclonic disorders. A factor that can alleviate myoclonic disorder is a high response to alcohol in myoclonus dystonia.
Acute onset of myoclonic disorder is usually seen in metabolic disorders like a renal and hepatic failure, electrolyte imbalances, thyrotoxicosis, misuse of drugs, and hypoxic brain injury.
CLASSIFICATION OF MYOCLONIC DISORDERS
There are two broad classifications of myoclonic disorders. The first classification is based on underlying physiology, while the second is based on etiology.
When we talk about classification based on underlying physiology, there are four sub-classes. Cortical myoclonus is the most common form of this disorder that affects the face and upper limbs. It may present as bilateral, generalized, multifocal, or focal. In addition, it is observed during voluntary movement. Cortisol myoclonus affects balance and speech. Individuals with myoclonic disorders may have positive or negative myoclonus existing together.
Negative myoclonus describes a sudden halt in muscle contraction. Lance Adam syndrome is a condition where the trunk or lower limbs are involved. The consequence of a sudden interruption is the person may fall. The negative myoclonus may originate from the cortical or subcortical region of the brain. Epileptic negative myoclonus is seen in idiopathic and symptomatic epilepsy.
The subcortical myoclonus originates from between the spinal cord and cortex. It can be further sub-divided into segmental and non-segmental types. The clinical manifestations of non-segmental myoclonus (brainstem myoclonus) are a generalized jerk and sensitivity to auditory stimuli. Specific subtypes of non-segmental myoclonus include startle (physiologic or pathologic) and reticular reflex. In a physiologic startle, the body’s reflex reaction to auditory stimuli is to assume a defensive position. It produces a startled-like movement consisting of grimace, neck, elbow, and knee flexion.
Segmental subcortical myoclonus describes a rhythmic contraction of the soft palate. It is usually due to essential palatal myoclonus(EPM) or symptomatic palatal myoclonus (SPM). EPM is absent during sleep, but SPM persists in sleep.
Spinal myoclonus is present during sleep, rest. However, Spinal segmental myoclonus may be irregular with a frequency between 1-200 per minute.
Propriospinal myoclonus is spontaneous, especially when the individual is in a recumbent position. Furthermore, tapping the abdomen may trigger it.
Finally, the peripheral myoclonus shows semi-rhythmic or rhythmic jerks. It originates from a disease of the root-lesion, plexus, nerve, or anterior horn cell.
The second broad group of classification is based on aetiology. Physiological myoclonus is often seen in healthy individuals. Examples include hiccups, startle response, and jerks while sleeping.
Myoclonus dystonia also called essential myoclonus is usually hereditary or sporadic. Hereditary myoclonus is usually inherited from the father. This condition begins in childhood and usually affects the head, neck, and arms.
Epileptic myoclonus describes a condition where myoclonus occurs with epilepsy. It may be primary generalized epilepsy or secondary generalized epilepsies.
Secondary myoclonus occurs due to an underlying neurologic or non-neurologic disorder. Other types include psychogenic myoclonus and progressive myoclonic epilepsy syndrome.
With the information from this study, myAir team has a comprehensive understanding of the classification of myoclonic disorders. This guides us in helping our clients enjoy a healthier life. myAir team understands the causes of the different types of myoclonus. This helps us make suitable recommendations that will benefit client wellness.
TREATMENT STRATEGIES FOR MYOCLONIC DISORDERS
As we have discussed earlier, myoclonic disorders have various origins and precipitating factors. Hence, the treatment strategy for each type of myoclonus is unique. Most times, combination pharmacology is the best alternative in managing myoclonic disorders. Different drugs have different effects on this condition depending on its origin. Before commencing treatment for myoclonus, it is critical to determine if it originates from the cortical, subcortical, or spinal region.
The treatment of cortical myoclonus involves the use of benzodiazepines (up to 15 mg daily). Piracetam (maximum dose is 20g daily) and Levetiracetam (max dose is 3000mg daily) are useful in treating it. Sodium valproate is another drug that may be useful to individuals with cortical myoclonus. The side effects of polypharmacy are ataxia and sedation.
Children with epileptic negative myoclonus may benefit from ethosuximide and Levetiracetam. Epileptic negative myoclonus gets worse when you treat it with carbamazepine, valproic acid, phenytoin, and lamotrigine.
According to the study, people with subcortical myoclonus do not benefit from the same therapy as those with cortical myoclonus. However, clonazepam may be an effective therapy. Myoclonic dystonia can be managed with deep brain stimulation.
The first choice of pharmacological intervention for spinal myoclonus is clonazepam. In a study carried out in 2002, Levetiracetam was also effective. However, the results are unsatisfactory. Segmental myoclonus may be treated with botulinum toxin injections.
Studies show that pharmacological therapy is not satisfactory in Peripheral myoclonus as seen in spinal myoclonus. However, carbamazepine or botulinum toxin injection may have some effect. In addition, Psychogenic myoclonus does not respond to drug therapy. The study shows that psychotherapy is the practical approach for this condition.
The result from this study is instrumental in providing a framework for myAir team to help clients with myoclonic disorders. myAir team understands that each subtype of this condition requires a unique management approach. myAir app can therefore make clinical therapeutic suggestions that may promote the life of clients.
CONCLUSION: MYOCLONIC DISORDERS: CLASSIFICATION AND TREATMENT
The causes of myoclonus are extensive. Thus the importance of proper history taking. History taking provides information that reduces the cost and amount of investigative procedures. When the origin of myoclonus is unidentified after good history taking, some tests may be routinely scheduled. They include glucose, thyroid function, EEG, electrolytes, renal, liver function, brain, and spinal imaging. Other investigative procedures may be due to clinical presentation.; they may include genetic testing, paraneoplastic antibody testing, enzyme activity assays, or spinal fluid examination.
Understanding the origin of myoclonic disorders is the first step in effectively treating them. Some causes of myoclonus are reversible, such as toxic metabolic states or drug intoxication. In most cases, the causes are not reversible. Hence, the symptoms are managed to improve the quality of life. Combination drug therapy in high doses is usually effective in managing the symptoms. Generally, clonazepam may be administered irrespective of the origin of the myoclonic disorder. However, antiepileptic drugs are only effective for individuals with cortical myoclonus.
The pathophysiology of myoclonus dystonia is not adequately understood. However, it begins in childhood and may coexist with anxiety, OCD, and depression. Certain metabolic disturbances like hormonal imbalance ( thyroid and calcium controlling hormones), ph imbalance, electrolyte imbalance, and hypoxia can cause symptomatic myoclonus.
Studies show a link between myoclonic disorders and neurodegenerative disorders. About 15% of individuals who have dementia with Lewy bodies or dementia with Parkinson’s disease have cortical myoclonus. Another study shows that about 50% of individuals with corticobasal degeneration have myoclonus. The myoclonus may be cortical or subcortical in origin.
Studies show that it is difficult to treat or reverse the causes of myoclonic disorders completely. Hence, managing symptoms is essential. myAir app focuses on helping clients improve wellness. Thus, myAir app is instrumental in helping these clients track changes in their health patterns.
Finally, the myoclonic disorder is also common among people with Alzheimer’s disease. Studies show that the symptoms present early in those with early-onset Alzheimer’s disease. Generally, symptoms appear in the middle or later stages of AD. Juvenile onset Huntington’s disease may also present with symptoms of myoclonic disorders.
References and Footnotes
Original publication: “Fellow research review of: “Myoclonic disorders: a practical approach for diagnosis and treatment”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036960/
By Maja Kojovic, Kailash Bhatia, and Carla Cordivari
Published in 2001 by PMC
Footnotes: No potential conflict of interest was recorded in this study
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