If an SCA survivor is experiening involuntary movement (jump, jerk or twitch) of a muscle or muscle group they could be experiencing myoclonus.

Myoclonic seizures (twitches or jerks) are usually caused by sudden muscle contractions, called positive myoclonus, or by muscle relaxation, called negative myoclonus. Myoclonic seizures may occur alone or in sequence, in a pattern or without a pattern. They may occur infrequently or many times each minute. Myoclonus sometimes occurs in response to an external event or when a person attempts to make a movement. The twitching cannot be controlled by the person experiencing it.  Myoclonus can be mistaken for tics, tremors or clumsiness.


There are a number of types and causes of myoclonus, but in an SCA survivor, the cause is likely to be hypoxia – prolonged oxygen deprivation to the brain.

Some of the types of myoclonus an SCA survivor may experience include the following…

  • Action myoclonus is characterized by muscular jerking triggered or intensified by voluntary movement or even the intention to move. It may be made worse by attempts at precise, coordinated movements. This is the most disabling form of myoclonus and can affect the arms, legs, face, and even the voice.
  • Stimulus-sensitive myoclonus is triggered by a variety of external events, including noise, movement, and light. Surprise may increase the sensitivity of the individual.
  • Sleep myoclonus occurs during the initial phases of sleep, especially at the moment of dropping off to sleep. Some forms appear to be stimulus-sensitive.

Other types include Cortical Reflex, Essential, Palatal, Progressive and Reticular.


Myoclonus can range from being a minor inconvenience to severly debilitating.

Example of myoclonus

Myoclonus is common in people with Epilepsy and the following video is related to this but explains what myoclonic seizures (Jerks) are quite well.

And one from the Epilepsy Society (UK)

Note: Just because a survivor has myoclonic seizures does not mean that they have epilepsy


If you have myoclonus and it is severe enough to disrupt your daily life you should see a doctor for further diagnosis.  There are a number of medications which can help to reduce the symptoms and in severe cases surgery may be appropriate.

Further information on myoclonus can be found at the following…


Epilepsy Society

National Institute of Neurological Disorders and Stroke (US)