Myoclonic epilepsy is a type of epilepsy that is characterized by myoclonic seizures or myoclonus. Myoclonus is a symptom and is the unintentional twitching or jerking of muscles. The word myoclonus is a compound word with ‘myo’ referring to muscle and ‘clonus’ to the rapid alternating between muscle relaxation and contraction.
Myoclonus not only occurs in people with epilepsy but also in people without epilepsy during hiccups or in instances when someone is suddenly awakened just as they are falling asleep. When the twitches or jerks are caused by muscle relaxation, this is referred to as negative myoclonus while those caused by muscle contraction are called positive myoclonus.
Myoclonic seizures last only a short time. Patients do not lose consciousness during these seizures. However, the seizures can be so sever as to interfere with a person’s ability to speak, walk, eat or move. Myoclonic epilepsy may also have other symptoms such as very fast blinking and uncontrollable sneezing.
There are 2 main types of myoclonic epilepsy; juvenile myoclonic epilepsy and progressive myoclonus epilepsy.
Juvenile myoclonic epilepsy (JME) is the most common form of epilepsy. It is also called the Janz syndrome. Typically, this form of epilepsy will present itself from puberty to late teenage years. This type of epilepsy is characterized by muscle jerks that occur in the morning upon waking up. They may also be experienced when waking up from a nap. The myoclonic jerks are usually felt in the arms and legs.
Some patients with juvenile myoclonic epilepsy may also experience absence seizures or generalized tonic clonic seizures. Quite commonly, seizures in JME are precipitated by fatigue or sleep deprivation.
This form of epilepsy responds well to anti-seizure medication. Treatment also includes lifestyle changes centering on avoiding seizure triggers such as alcohol consumption and sleep deprivation.
Progressive myoclonus epilepsy (PME) is a very rare form of epilepsy that is caused by genetic defects. Like in juvenile myoclonic epilepsy, patients experience tonic clonic seizures as well as myoclonic seizures, but the myoclonic seizures occur more than the tonic clonic seizures. The difference is that in progressive myoclonus epilepsy, there is progressive neurological damage.
The causes of progressive myoclonus epilepsy are disorders such as myoclonic epilepsy with ragged red fibers (MERRF), Unverricht Lundborg disease, sialidosis, neuronal ceroid lipofuscinoses and Gaucher disease (the noninfantile neuronopathic form).
Progressive myoclonus epilepsy is often confused with juvenile myoclonic epilepsy in the beginning. However, it becomes quite clear with the progression of the neurological dysfunction which includes dementia (decline in cognitive ability) and ataxia (problems with muscle coordination).
Treatment for progressive myoclonus epilepsy will usually include anti-epileptic or anti-convulsant medication but these do not work for very long as the syndrome worsens and the patient’s condition deteriorates.