A myoclonic seizure is a type of seizure characterized by sudden, brief, shock-like muscle jerks. These involuntary movements result from abnormal electrical activity in the brain. The term “myo” refers to muscle, and “clonus” describes rapid, alternating contraction and relaxation, or jerking, of a muscle. Myoclonic seizures are typically very short, lasting only a second or two.
Visual Manifestations
Myoclonic seizures appear as abrupt, uncontrollable muscle movements, often described as a jolt or twitch. These sudden movements can affect a single muscle or a group of muscles. Common areas involved include the arms, shoulders, neck, and sometimes the face, with movements also potentially occurring in the legs or trunk.
During a myoclonic seizure, an individual typically remains awake and aware of their surroundings. This preservation of consciousness distinguishes them from other seizure types. The involuntary muscle contraction can be strong enough to cause a person to drop an object they are holding, or lead to a fall. These jerks can occur as isolated events, or they may happen in a series or cluster.
Common Patterns and Triggers
Myoclonic seizures often happen shortly after waking up in the morning or after a nap, or during periods of drowsiness.
Triggers for myoclonic jerks include sleep deprivation, which is a common trigger. Other non-specific triggers include high levels of stress or anxiety, flashing lights (known as photosensitivity), and alcohol consumption. Fatigue and sudden movements or startling stimuli can also induce these jerks in some individuals.
Differentiating from Other Movements
It is important to distinguish myoclonic seizures from other involuntary movements that might appear similar. Benign physiological movements, such as hypnic jerks or “sleep starts,” are a common example. Hypnic jerks typically occur only as a person is falling asleep and are not associated with the abnormal brain activity seen in epileptic myoclonus.
Myoclonic seizures also differ from tics, which are typically suppressible by conscious effort, unlike the involuntary nature of a myoclonic jerk. Tremors are characterized by rhythmic oscillations, which contrasts with the sudden, shock-like nature of myoclonus. Other seizure types present differently; tonic-clonic seizures involve a loss of consciousness, followed by sustained muscle stiffness and then rhythmic jerking movements, lasting much longer than a myoclonic jerk. Atonic seizures involve a sudden loss of muscle tone, leading to a collapse, while clonic seizures are characterized by rhythmic jerking, as opposed to the single or few twitches of myoclonus.
When to Seek Medical Advice
If you or someone you know experiences what appears to be a myoclonic seizure, consulting a healthcare professional is advisable for proper diagnosis. While myoclonic seizures themselves are often brief and not inherently dangerous, they can be a symptom of an underlying medical condition. A doctor can evaluate the symptoms and determine if further investigation is needed.
Diagnosis often involves a thorough neurological evaluation, including a detailed medical history. An electroencephalogram (EEG), which measures electrical activity in the brain, is a common diagnostic tool to identify characteristic brainwave patterns. Seeking timely medical advice allows for accurate identification and appropriate management of the condition.