Seizure types

The brain controls the body’s actions, sensations and emotions through nerve cells also known as neurons. These neurones carry messages between the brain and the body and if it so happens that these messages are confused, a seizure, which is a sudden disruption in normal brain activity, resulting in unusual movements, odd feelings or changed behavior occurs.

Many people think that the word ‘seizure’ means a convulsion, where someone becomes unconscious and falls, with their limbs jerking. However, this is just one type of seizure called a tonic clonic seizure/grand mal/ fit.

Seizures can however also be referred to as convulsions, spells, attack, fit, or spasms. It is also important to note that there are different types of seizures.

Some people may have episodes where they 'go blank' for a few seconds or minutes while some people remain fully conscious during a seizure and can describe their experience. For others, consciousness is affected and they are confused by the time the seizure ends. A seizure may involve the whole brain (generalized seizure) or part of the brain (partial or focal seizure).

Partial seizures
Only one part of the brain is affected during a partial seizure. The signs and symptoms will depend on which part of the brain the seizure comes from, and which body functions are controlled by that part of the brain. Signs and symptoms can vary from person to person.

1. Simple partial: the person remains conscious, but they may have unusual sensations or movements. The seizure may be confined to either rhythmical twitching of one limb or part of a limb, or to unusual tastes or sensations such as pins and needles in a specific part of the body. Simple partial seizures sometimes develop into other sorts of seizures and so they may be referred to as a 'warning' or 'aura'. 
2. Complex partial seizure: this differs from simple partial seizures in that consciousness is affected and so the person may have limited or no memory of the seizure. The seizure may begin with an odd taste or smell, a rising feeling in the stomach, or a sense of déjà vu. This may be followed by a loss of awareness during which the person may make movements such as chewing or tapping, fiddling with clothes or objects, mumbling or wandering about and general confusion. The person may respond if spoken to. Complex partial seizures most often involve the temporal lobes of the brain, in which case the person may be said to have 'temporal lobe epilepsy', however they can also affect the frontal, partial and occipital lobes. The person is often confused after the seizure.
3. For some people either of these partial seizures may spread to involve the whole of the brain. This is called a secondarily generalized seizure and the person will lose consciousness. If this spread is rapid, the person may not be aware of the partial seizure onset.

Generalized seizures
In these seizures the whole of the brain is involved and consciousness is lost. They often occur with no warning and the person will have no memory of the event. The seizure may take one of the following forms:

1. Tonic clonic (convulsive) seizure: It is the most recognised type of seizure. It is sometimes referred to as a ‘grand mal’ seizure.  In the first part of the seizure the person becomes rigid and may fall. The muscles then relax and tighten rhythmically causing the person to convulse/ jerk. At the start of the seizure the person may bite their tongue or cry out. Breathing may become labored and they may be incontinent. After the seizure the person may feel tired, confused, have a headache and may need to rest to recover fully.
2. Absence seizure: occurs most commonly in children and is sometimes called 'petit mal'. The person experiences a brief interruption of consciousness and becomes unresponsive. They may appear 'blank' or 'staring' usually without any other features, except perhaps for a fluttering of the eyelids. Absence seizures often last for only a couple of seconds and as they are subtle they may go unnoticed.
3. Tonic seizure: there is general stiffening of the muscles without rhythmical jerking. The person may fall to the ground with consequent risk of injury but generally recovery is quick. 
4. Atonic seizure: also known as drop attacks. These involve a sudden loss of muscle tone, causing the person to fall. Again, there is consequent risk of injury but recovery is generally rapid. 
5. Myoclonic seizure: involves brief and abrupt jerking of one or more limbs. This often happens within a short time of waking up, either on their own or with other forms of generalized seizure.

Some seizure patterns may not fit into any of the above categories or may include elements of different seizures. These are called unclassifiable seizures.

Some people experience seizures only during sleep. As these will usually be at night they are called nocturnal seizures. These seizures could also occur during the day if the person were to fall asleep. This does not describe the form that the seizures take, only the time when they occur.