If you had a collapse or an episode of odd behaviour or some similar event, it is possible that you had an epileptic seizure. This leaflet gives some information about what your doctor may wish to know and what tests may be advised after such an event.
This leaflet is part of our series on epilepsy
What is a seizure?
A seizure is a short episode of symptoms caused by a burst of abnormal electrical activity in the brain. Typically, a seizure lasts from a few seconds to a few minutes.
The brain contains millions of nerve cells (neurons). Normally, the nerve cells are constantly sending tiny electrical messages down nerves to all parts of the body. Different parts of the brain control different parts and functions of the body. Therefore, the symptoms that occur during a seizure depend on where the burst of electrical activity occurs in the brain.
Different types of epilepsy and seizures
Seizures are divided into two main types - generalised and focal (used to be called partial). (There are also other uncommon types of seizure.) If you have epilepsy you usually have recurrences of the same type of seizure. However, some people have different types of seizure at different times.
These occur if the abnormal electrical activity affects all or most of the brain. The symptoms tend to be general and involve much of your body. There are various types of generalised seizure:
- A tonic-clonic seizure is the most common type of generalised seizure. With this type of seizure your whole body stiffens, you lose consciousness, and then your body shakes (convulses) due to uncontrollable muscle contractions.
- Absence seizure is another type of generalised seizure. With this type of seizure you have a brief loss of consciousness or awareness. There is no convulsion, you do not fall over, and it usually lasts only seconds. Absence seizures mainly occur in children.
- A myoclonic seizure is caused by a sudden contraction of the muscles, which causes a jerk. These can affect the whole body but often occur in just one or both arms.
- A tonic seizure causes a brief loss of consciousness, and you may become stiff and fall to the ground.
- An atonic seizure causes you to become limp and to collapse, often with only a brief loss of consciousness.
In focal seizures the burst of electrical activity starts in, and stays in, one part of the brain. Therefore, you tend to have localised (focal) symptoms. Different parts of the brain control different functions and so symptoms depend on which part of the brain is affected:
Simple focal seizures are one type. You may have muscular jerks or strange sensations in one arm or leg. You may develop an odd taste, or pins and needles in one part of your body. You do not lose consciousness or awareness.
Complex focal seizures are another type. These commonly arise from a part of the brain (called a temporal lobe) but may start in any part of the brain. Therefore, this type is sometimes called temporal lobe epilepsy. Depending on the part of the brain affected, you may behave strangely for a few seconds or minutes. For example, you may fiddle with an object, or mumble, or wander aimlessly. In addition, you may have odd emotions, fears, feelings, visions, or sensations. These differ from simple focal seizures in that your consciousness is affected. You may not remember having a seizure.
Sometimes a focal seizure develops into a generalised seizure. This is called a secondary generalised seizure.
What is epilepsy?
If you have epilepsy, it means that you have had repeated seizures. If you have a single seizure, it does not necessarily mean that you have epilepsy. About 1 in 20 people have a seizure at some time in their life. It may be the only one that occurs. The definition of epilepsy is more than one seizure.
Epileptic seizures arise from within the brain. A seizure can also be caused by external factors which may affect the brain. For example, a high temperature (fever) may cause a febrile convulsion. Other causes of seizures include lack of oxygen, a low blood sugar level, poisons and a lot of alcohol. Seizures caused by these external factors are not classed as epilepsy.
Getting the right diagnosis
The most important part of making a diagnosis is to have a clear description of what happened. This is both from the person affected and, if possible, from an eye-witness.
It can be difficult for a doctor to say definitely that you have had a seizure if the description is not typical. For example, a faint can sometimes cause brief stiffening of the body followed by a few jerks of the arms and legs. This may appear to an onlooker to be a short seizure; however, it is not a seizure. A doctor may ask questions to try to find the cause of what happened. If your doctor is unsure about the cause of the event, you may be referred to a specialist.
The specialist and tests
The specialist will want to go over the story of what happened. Below is a list of the sort of questions that you may be asked. Try to go over the answers before your appointment:
- What exactly happened before, during and after the event?
- Did you lose consciousness?
- Were you confused before or after the event?
- Did any parts of your body shake? If so, for how long, and in what way?
- Did you bite your tongue or pass urine?
- How long did it last?
- Did you have any unusual feelings, sensations or emotions before the event?
- Do you have any other symptoms at all, even apparently unrelated?
- Had you taken any alcohol, medicines or street drugs before the event?
- Has anything like this ever happened before?
- Does anyone in the family have epilepsy?
- Have you had any head injuries or illnesses affecting your brain in the past?
- Did you feel well before the event or did you feel poorly, light-headed, hot or distressed?
- Can you think of anything to explain what happened?
It is very helpful to the specialist if a person who saw what happened goes with you to the appointment. Sometimes the specialist can give a cause of the event from the description and examination alone. Sometimes further tests are advised. These may include the following:
- A brain scan - usually a magnetic resonance imaging (MRI) scan or computed tomography (CT) scan - can show abnormalities affecting the structure of different parts of the brain.
- Electroencephalograph (EEG). This test records the electrical activity of the brain. Special stickers are placed on various parts of the scalp. They are connected to the EEG machine. This amplifies the tiny electrical messages given off by the brain and records their pattern on paper or computer. The test is painless. Some types of seizure produce typical EEG patterns. However, a normal recording does not rule out epilepsy, and not all EEG abnormalities are related to epilepsy.
- Blood tests and other tests may be advised to check on your general well-being. They may also look for other possible causes of the event.
Although helpful, tests are not foolproof. It is possible to have epilepsy with normal test results. Also, if an abnormality is found on a brain scan, it does not prove that it causes seizures. However, tests may help to decide if the event was a seizure or caused by something else.
Sometimes no firm cause can be found to explain the event. A doctor may advise to wait and see if it happens again if there is doubt about the diagnosis.
What if it is a seizure?
Even if a seizure is diagnosed, it may be the only one you ever have. For this reason epilepsy is not usually diagnosed after a single seizure. The definition of epilepsy is recurrent seizures. See the other leaflets in this series for information about the different types of epilepsy.
Further help & information
Dr Tim Kenny
Dr Colin Tidy
Prof Cathy Jackson