Pediatric myoclonus is a sudden, involuntary, muscle jerk followed by relaxation.
Myoclonus twitches happen unexpectedly and will range from small disturbances (such as hiccups) to severe, jarring movements that affect a person’s quality of life (including problems eating, talking or walking). They are part of a larger movement disorder class called dyskinesia.
Myoclonus movements can’t be controlled and can occur at any point – often happening at night when the body begins to relax at the beginning of sleep. The actions can also move from one location of the body to another, and may vary in frequency from multiple twitches a minute to a few spasms per hour.
Myoclonus can occur at any age and be due to several possible triggers, which include:
- Brain tumor
- Chemical or drug poisoning
- Genetic/inherited condition
- Head trauma
- Hypoxia (lack of oxygen to the brain)
- Illness (multiple sclerosis or Parkinson’s disease)
- Kidney or liver failure
- Lipid storage disease
- Spinal cord injury
There are eight classifications of myoclonus:
- Action myoclonus – Twitches that are caused or intensified by coordinated movements. This type has the most dramatic impact on the quality of life, affecting the arms, face, legs or voice.
- Cortical reflex myoclonus – A type of epilepsy that takes place in the cerebral cortex (information processing) part of the brain. It can affect a few muscles in one part of the body or impact multiple muscles in numerous locations.
- Essential myoclonus – This type has no medical reason and can impact multiple family members or occur randomly.
- Palatal myoclonus – Causes contractions near one or both sides of the roof of the mouth (soft palate). It can also affect the face, tongue, throat or diaphragm. The twitches can make a clicking noise, occur rapidly (as often as 150 per minute) and can take place during sleep.
- Progressive myoclonus epilepsy (PME) – A rare disorder that begins in childhood and becomes worse over time. It includes seizures and problems walking or talking.
- Reticular reflex myoclonus – This is a type of epilepsy that begins in the brain stem, specifically the location that controls breathing and heartbeat. Typically, the muscle spasms affect the entire body, but for some people, it will only disturb one specific body part at a time, like the legs. The twitches can be caused by voluntary movements or an outside trigger
- Stimulus-sensitive myoclonus – These muscle spasms are caused by outside triggers like a surprise or loud noise.
- Sleep myoclonus – This type causes muscle jerks to occur when a person first begins to fall asleep.
Symptoms of myoclonus include sudden, involuntary muscle spasms. The type of myoclonus will indicate the level of frequency, intensity, time of occurrence and location of the twitches.