Myoclonic seizures are a type of generalized seizure that usually appear like sudden jerking movements. Generalized seizures are seizures that occur due to abnormal activity in both hemispheres (halves) of the brain. Partial seizures on the other hand occur when seizure activity happens in only a particular region of the brain.
The jerking (or twitching) movements in myoclonic seizures does not last long, usually one or two seconds. They’re so brief they can go unnoticed by nearby observers. Still, although myoclonic seizures are usually brief, multiple episodes of them can happen in a very short time. This might make the myoclonus – the rapid contracting and relaxing of muscles, causing the jerking movement – appear to be spreading. Myoclonus can start in one part of the body – like the arm – and move to other parts like the legs.
Sometimes myoclonic seizures happen without a known reason, sometimes they happen due to certain stresses (like poor sleep or lack of oxygen), and sometimes they occur as part of a medical or genetic condition.
The symptoms of myoclonic seizures can include the following:
There are several causes of myoclonic seizures, and they are categorized by what triggers them. Some myoclonus is due to hypersensitivity to normal events, like having a myoclonic seizure after seeing a bright light or hearing a loud noise. This is called stimulus-sensitive myoclonus. Other causes are due to sleep transitions (when waking up or going to sleep), called sleep myoclonus. Some are due to physical movements, called action myoclonus, when myoclonic seizures are triggered by trying to move in a particular way. Juvenile Myoclonic Epilepsy, also known as Janz syndrome, is a type of myoclonic seizures that occurs in young people aged 12 – 20, and can be due to sleep deprivation, alcohol use, or flickering lights.
More generally, myoclonic seizures can happen after a person experiences things like head trauma, a severe infection, very high fevers, or lack of oxygen to the brain.
The risk factors of having myoclonic seizures include:
Your doctor will usually start diagnosing myoclonic seizures by listening to the history of your symptoms and performing a physical exam. Then, some tests will be requested. One of the most important is the EEG, or electroencephalogram, a test that reads your brain waves and can record its electrical activity. A specially trained doctor uses these results to determine your brain activity and determine a diagnosis. Another test might be the EMG (electromyography) which can track muscular activity and jerking. You will require both urine and blood tests as well, to rule out some chemical causes of myoclonic seizures.
If the cause of myoclonic seizures is an organic or chemical problem (like low blood sugar, or drug use) then the treatment is to reverse the cause. Otherwise, myoclonic seizures are treated with anti-epileptics, a group of medicines that can treat many types of seizures and epilepsy. One of the most common drugs for myoclonic seizures is valproic acid.
If myoclonic seizures are caused by triggers, avoiding those triggers is a very important part of your treatment too.