Seizures are temporary abnormal electro-physiologic phenomena of the brain, resulting in abnormal synchronization of electrical neuronal activity. They can manifest as an alteration in mental state, tonic or clonic movements, convulsions, and various other psychic symptoms (such as déjà vu or jamais vu).
They are caused by a temporary abnormal electrical activity of a group of brain cells.
The medical syndrome of recurrent, unprovoked seizures is termed epilepsy, but some seizures may occur in people who do not have epilepsy. The treatment of epilepsy is a subspecialty of neurology; the study of seizures is part of neuroscience.
Signs and symptoms
Seizures can cause involuntary changes in body movement or function, sensation, awareness, or behavior. A seizure can last from a few seconds to status epilepticus, a continuous seizure that will not stop without intervention.
A seizure is often associated with a sudden and involuntary contraction of a group of muscles. However, a seizure can also be as subtle as marching numbness of a part of the body, a brief loss of memory, sparkling or flashes, sensing an unpleasant odor, a strange epigastric sensation or a sensation of fear.
Therefore seizures are typically classified as motor, sensory, autonomic, emotional or cognitive. In some cases, the full onset of a seizure event is preceded by some of the sensations described above.
These sensations can serve as a warning to the sufferer that a full tonic-clonic seizure is about to occur. These “warning sensations” are cumulatively called an aura.
Symptoms experienced by a person during a seizure depend on where in the brain the disturbance in electrical activity occurs. Recent studies show that seizures happen in sleep more often than was thought.
A person having a tonic-clonic seizure may cry out, lose consciousness and fall to the ground, and convulse, often violently. A person having a complex partial seizure may appear confused or dazed and will not be able to respond to questions or direction.
Some people have seizures that are not noticeable to others. Sometimes, the only clue that a person is having an absence seizure is rapid blinking or a few seconds of staring into space.
It is commonly thought among healthcare providers that many seizures, especially in children, are preceded by tachycardia that frequently persists throughout the seizure. This early increase in heart rate may supplement an aura as a physiological warning sign of an imminent seizure.
Seizure types are organized according to whether the source of the seizure within the brain is localized (partial or focal onset seizures) or distributed (generalized seizures). Partial seizures are further divided on the extent to which consciousness is affected (simple partial seizures and complex partial seizures).
If it is unaffected, then it is a simple partial seizure; otherwise, it is a complex partial seizure. A partial seizure may spread within the brain – a process known as secondary generalization. Generalized seizures are divided according to the effect on the body but all involve loss of consciousness.
These include absence, myoclonic, clonic, tonic, tonic-clonic, and atonic seizures. Following standardization proposal published in 1970, out-dated terms such as “petit mal”, “grand mal”, “Jacksonian”, “psychomotor”, and “temporal-lobe seizure” have fallen into disuse.
An isolated abnormal electrical activity recorded by an electroencephalography examination without a clinical presentation is called a subclinical seizure. They may identify background epileptogenic activity, as well as help, identify particular causes of seizures.
Additional diagnostic methods include CT Scanning and MRI imaging or angiography. These may show structural lesions within the brain, but the majority of those with epilepsy show nothing unusual.
As seizures have a differential diagnosis, it is common for patients to be simultaneously investigated for cardiac and endocrine causes. Checking glucose levels, for example, is a mandatory action in the management of seizures as hypoglycemia may cause seizures, and failure to administer glucose would be harmful to the patient.
Other causes typically considered are syncope and cardiac arrhythmias, and occasional panic attacks and cataplexy. For more information, see non-epileptic seizures.
The first aid for a seizure depends on the type of seizure occurring. Generalized seizures will cause the person to fall, which may result in injury. A tonic-clonic seizure results in violent movements that cannot and should not be suppressed. The person should never be restrained, nor should there be any attempt to put something in the mouth.
Potentially sharp or dangerous objects should also be moved from the vicinity so that the individual is not hurt. After the seizure, if the person is not fully conscious and alert, they should be placed in the recovery position.
It is not necessary to call an ambulance if the person is known to have epilepsy if the seizure is shorter than five minutes and is typical for them, if it is not immediately followed by another seizure, and if the person is uninjured.
Otherwise, or if in any doubt, medical assistance should be sought. A seizure longer than five minutes is a medical emergency. Relatives and other caregivers of those known to have epilepsy often carry medicine such as rectal diazepam or buccal midazolam in order to rapidly end the seizure.
A sudden fall can lead to broken bones and other injuries. Children who are affected by frequent drop seizures may wear helmets to protect the head during a fall. The unusual, aggressive behavior sometimes resultant from the chaotic brain activity of a seizure can be misinterpreted as an aggressive act.
This may invoke a hostile response or police involvement, where there was no intention to cause harm or trouble. During a prolonged seizure, the person is defenseless and may become a victim of theft.
A seizure response dog can be trained to summon help or ensure personal safety when a seizure occurs. These are not suitable for everybody. Rarely, a dog may develop the ability to sense a seizure before it occurs.
Seizures without epilepsy
Unprovoked seizures are often associated with epilepsy and related seizure disorders.
Causes of provoked seizures include:
- head injury
- intoxication with drugs, drug toxicity, for example, aminophylline or local anesthetics normal doses of certain drugs that lower the seizure threshold, such as tricyclic antidepressants
- infection, such as encephalitis or meningitis
- fever leading to febrile convulsions
- metabolic disturbances, such as hypoglycemia, hyponatremia or hypoxia withdrawal from drugs (anticonvulsants and sedatives such as alcohol, barbiturates, and benzodiazepines)
- space-occupying lesions in the brain (abscesses, tumors)
- seizures during (or shortly after) pregnancy can be a sign of eclampsia.
- certain television and video games can trigger photosensitive epilepsy, such as the infamous episode of Pokémon, Dennō Senshi Porygon.
Some medications produce an increased risk of seizures and electroconvulsive therapy (ECT) deliberately sets out to induce a seizure for the treatment of major depression. Many seizures have unknown causes.
Seizures which are provoked are not associated with epilepsy, and people who experience such seizures are normally not diagnosed with epilepsy. However, the seizures described above resemble those of epilepsy both outwardly, and on EEG testing.