Epilepsy is brain condition which leads to recurrent seizures. A seizure is caused by a sudden burst of excess electrical activity in the brain, which in turn causes a temporary disruption in the normal messages passing between brain cells. This disruption results in the brain’s messages becoming halted or mixed up.
What happens when a patient experiences a seizure will depend largely on where in the brain an epileptic activity begins and how widely and rapidly it spreads. For this reason, there are many different types of seizure and each person will experience epilepsy in a different way.
Types of seizures
Seizures are divided into two main types - generalised and partial.
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.
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 cause 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 collapse, often with only a brief loss of consciousness.
In these type of seizures the burst of electrical activity starts in, and stays in, one part of the brain. Therefore, you tend to have localised or 'focal' symptoms. Different parts of the brain control different functions and so symptoms depend on which part of the brain is affected.
Simple partial 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 partial seizures are another type. These commonly arise from a temporal lobe (a part of the brain) 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 partial seizures in that your consciousness is affected. You may not remember having a seizure.
What causes epilepsy?
Sometimes the reason epilepsy develops is clear. It could be because of brain damage caused by a difficult birth; a severe blow to the head; a stroke which starves the brain of oxygen; or an infection of the brain such as meningitis. Very occasionally the cause is a brain tumour. Epilepsy with a known cause is called ‘symptomatic’ epilepsy. For most people - six out of ten, there is no known cause and this is called ‘idiopathic’ epilepsy.
How is epilepsy diagnosed?
There is no conclusive test for epilepsy, although tests such as the electroencephalogram (EEG) – which record brainwave patterns - can give very useful information.
Epilepsy should be diagnosed by an epilepsy specialist who will use their own expert knowledge, along with many of the test featured below to make a diagnosis:
A brain scan (usually an MRI or CT scan) can show the structure of different parts of the brain. A brain scan is not always necessary.
EEG (ElectroEncephaloGram). 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'.
Medical treatment for epilepsy
At the moment there is no cure for epilepsy. However, with the right type and dosage of anti-epileptic medication, about 70 per cent of people with epilepsy have their seizures controlled.
Certain medicines can prevent seizures, they work by stabilising the electrical activity of the brain. You need to take medication every day to prevent seizures. Seizures are well controlled by medication in about 4 out of 5 cases. Deciding on which medicine to prescribe depends on such things as: the type of epilepsy, age, other medicines that you may take for other conditions, possible side-effects, pregnancy, etc.
One medicine can prevent seizures in most cases. A low dose is usually started at first. The dose may be increased if this fails to prevent seizures. In some cases two medicines are needed to prevent seizures.
Surgical treatment for epilepsy
Surgery to remove a cause of seizures in the brain is an option in a small number of cases. It may be considered when medication fails to prevent seizures. It is only possible for certain causes in certain areas of the brain. The type of surgery that a patient undergoes will depend greatly on what the surgeon hopes to achieve. The following is a list of some operations:
Selective amygdalo hippocampectomy - the removal of two structures in the temporal lobe which are commonly the site of seizure activity. Sometimes just the hippocampus part of the structure is removed.
Temporal lobectomy - a larger part of the temporal lobe is removed. This tends to be mainly the right side as the left side of the temporal lobe controls speech.
Sub-pial resection - fine cuts are made in the motor areas of the brain that do not affect the motor function but do prevent the spread of seizures.
Hemispherectomy - sometimes used to treat very severe epilepsy in children with damage to one whole side of the brain. The damaged side of the brain is removed.
Corpus callosotomy - again sometimes used to treat children with very severe epilepsy, this operation involves cutting the fibres that connect the two halves of the brain.
Removal of a lesion - such as a tumour or a cyst.
Vagal nerve stimulation - Vagus nerve stimulation (VNS) is a treatment for epilepsy where a small generator is implanted under the skin below the left collar bone. This is connected to a lead with three coils at one end. These coils are wrapped around the vagus nerve in the left side of the neck in a small operation. The VNS stimulates the vagus nerve at intervals to reduce the frequency and intensity of seizures.