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Seizures (or convulsions) are temporary abnormal electrophysiologic 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 and various other symptoms. They are due to 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. 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 body, a brief loss of memory, sparkling of flashes, sensing an unpleasant odor, a strange epigastric sensation or a sensation of fear. Therefore seizures are typically classified as motor, sensory, autonomy, emotional or cognitive.
Symptoms experienced by a person during a seizure depend on where in the brain the disturbance in electrical activity occurs. A person having a tonic-clonic seizure (also known as a grand mal 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 (petit mal) seizure is rapid blinking or a few seconds of staring into space.
Types
There are more than 21 different types of seizures. Some seizure types are:
- Petit mal seizures (an absence seizure, or very brief loss of consciousness) typically have a sudden onset, present with motor arrest, sometimes eye blinking, and last a few seconds. In susceptible persons, these seizures can be induced by hyperventilation. Additionally, some learning difficulties may be symptomatic of this form of seizure.
- Simple partial seizures are usually motor or sensory seizures that are restricted to one part of the body, without alteration of consciousness.
- Complex partial seizures are characterized by alteration or loss of consciousness, behavioral or emotional symptoms, loss of memory, and/or automatisms; temporal lobe and frontal lobe seizures are often in this category.
- Generalized tonic-clonic seizures, also known as a grand mal seizures, rarely involve auras and can be preceded by a sense of general malaise. The tonic phase involves vocalization, severe hyperextension (opisthotonos, arcing of the back), possible respiratory arrest, cyanosis, and reflexive emptying of the bladder. The clonic phase involves rhythmic generalised jerking, followed by prolonged unconsciousness. After a seizure, aches, pains, headache, lethargy, and a bitten tongue are common.
- Atonic seizures, also known as "drop attacks," begins with a brief loss of muscle tone that usually results in an abrupt fall, if standing.
- Myoclonic seizures are characterized by abnormal, lightning-fast muscle contractions.
- A "secondarily generalized attack" is any type of partial seizure which immediately precedes a tonic-clonic seizure.
It is still disputable whether febrile seizures have to be regarded as an epileptic disorder or not; the dispute hinges on whether fever is considered a provocant. Contributing to this dispute is the knowledge that most children with simple febrile seizures outgrow them with no lasting ill effect. By definition, a patient with two or more episodes of unprovoked seizures is said to have epilepsy (a condition also known as a seizure disorder). Many people with epilepsy perceive "auras": telltale sensations such as strange lights, unpleasant smells or odd feelings before their seizures.
A person who is having seizures of any kind continuously, with little or no time separating one from the next, is said to be in "status epilepticus." This is a dangerous situation. It requires immediate emergency intervention, usually through the injection of appropriate anti-seizure drugs. When the person "in status" is pregnant, loss of the pregnancy is possible, raising the stakes even higher.
Diagnosis
An isolated abnormal electrical activity recorded by an electroencephalography examination without a clinical presentation is not called a seizure. Nevertheless, 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 epileptics 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 occasionally panic attacks and cataplexy. For more information, see non-epileptic seizures.
Management
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 does not hurt him or herself. 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, the seizure is shorter than 5 minutes and is typical for them, it is not immediately followed by another seizure, and the person is uninjured. Otherwise, or if in any doubt, medical assistance should be sought.
A seizure longer than 5 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.
Safety
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.
Unusual behaviour or violent jerks can sometimes 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 defenceless and may become the 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 anaesthetics
- infection, such as encephalitis or meningitis
- fever leading to febrile convulsions (but see above)
- metabolic disturbances, such as hypoglycaemia or hypoxia
- withdrawal symptoms (from 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.
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.
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