Pediatric myoclonus

What is pediatric myoclonus?

A child with this condition experiences quick, jerking muscle movements. These movements vary in how often they happen and how severe they are. Children may have small twitches once in a while, or big movements that happen often.

Myoclonus can affect many parts of the body, or just one part, like an arm or leg. Some forms occur on their own, like hiccups or repetitive jerks as a child is falling asleep. Other forms of myoclonus are caused by a nervous system (neurological) disorder, including epilepsy.

What are the different types of pediatric myoclonus?

There are many types of myoclonus, including:

• Action myoclonus - These twitches can affect the arms, face, legs or voice. Voluntary movements, such as writing or walking, either bring on the twitches or intensify them.

• Cortical reflex myoclonus - This form of myoclonus takes place in the part of the brain that processes movement. It can be a type of seizure, but it also has non-seizure causes. It can affect a few muscles on their own or many muscles in different parts of the body. It may be triggered by a loud noise, a change in lighting or other sudden changes.

• Essential myoclonus - A child with this form of myoclonus experiences jerks and twitches, but may not have other symptoms or an underlying illness. Sometimes this form is inherited. It also can occur with a type of muscle stiffness called dystonia.

• Palatal myoclonus - This rare type can affect the roof of the mouth (soft palate) or the face, tongue, throat or diaphragm. The twitches can occur very rapidly, and the contracting muscles in the soft palate may make a clicking noise.

• Benign neonatal sleep myoclonus - This is a relatively common form of myoclonus that usually starts in the first six weeks of life. This myoclonus starts as the infant falls asleep and stops when the child wakes up. This form of myoclonus usually goes away on its own without treatment. It is common to investigate with tests like an EEG (electroencephalogram), and perhaps an MRI (magnetic resonance imaging), if there is any uncertainty about this diagnosis.

• Progressive myoclonus epilepsy (PME) - This rare form begins in childhood and gets worse with time. A child with progressive myoclonus epilepsy will have an increasing number and different types of seizures as they age. This form of myoclonus is associated with progressive loss of developmental skills and disability.

• Reticular reflex myoclonus - This type begins in the part of the brainstem that controls breathing and heartbeat. While the muscle spasms may affect a child’s entire body, they also may affect just one body part at a time, such as the legs. Voluntary movements, like walking, loud noises or other triggers can cause the twitches.

• Stimulus-sensitive myoclonus - A child with this form may have muscle spasms that are triggered by loud noises, a surprise or other outside triggers.

What are the signs and symptoms of pediatric myoclonus?

The movements or muscle spasms in a child with myoclonus typically are quick, jerky and involuntary. Each type of myoclonus can affect different body parts and have different severity.

Some types of myoclonus come along with other neurological symptoms, like seizures or developmental delay.

How is pediatric myoclonus diagnosed?

Doctors usually diagnose this condition through a physical exam and careful observation. It can be important to diagnose and treat myoclonus in children early to find the cause and, in some cases, prevent it from getting worse.

To identify the underlying causes, your care team may also do tests such as an MRI (which creates a picture of the brain), an EEG (which looks at electrical activity in the brain), and an EMG (electromyogram, which evaluates the activity of muscles and the nerves that connect to them).

What causes pediatric myoclonus?

Children of any age can develop myoclonus. It has many different causes, including:

• Chemical or drug poisoning

• Epilepsy

• Genetic (inherited) condition

• Head trauma

• Lack of oxygen to the brain (hypoxia)

• Kidney failure

• Metabolic disorders

• Liver failure

• Multiple sclerosis

• Spinal cord injury

• Stroke

How is pediatric myoclonus treated?

In children, myoclonus can be treated by medications or by a type of surgery called deep brain stimulation (DBS). The treatment typically depends on what is causing the myoclonus.