Incidence

The most common ages of incidence are under the age of 18 and over the age of 65. It has been estimated that about 1% of the population meets the diagnostic criteria for epilepsy at any given time, but some theorize that the prevalence might in fact be much higher.

What provokes the seizure usually?

Some people with epilepsy have certain triggers that will undoubtedly produce a seizure.

If the trigger is considered to be part of the daily life and yet it causes a seizure, the seizures are considered as unprovoked. Examples of these normal provocants include:

• reading,
• hot water on the head,
• hyperventilation and
• flashing or flickering lights.

Types of seizures

Seizures may be described as

• partial (focal) - only involve a localized part of the brain
• generalized - involve the entire cortex.

The term secondary generalization is used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalized.

Partial seizures

These seizures may further be subdivided into:

1. Simple seizures - Simple seizures cause no interruption to consciousness, although they may cause sensory distortions or other sensations.
2. Complex seizures - These seizures interrupt consciousness to varying degrees, although this does not necessarily mean that the person experiencing this sort of seizure will fall unconscious.

The effects of partial seizures can be quite dependent on the area of the brain which they are affected. Some of the most common effects are:

• particular sensory experience,
• movement in particular groups of muscles,
• particular thoughts or internal visual images
• mystical or ecstatic experiences

When the effects of a partial seizure appear as a 'warning sign' before a more serious seizure, they are known as an aura.

Generalized seizures

Generalized seizures can be sub-classified into a number of categories

1. Absence seizures – This type of seizure involves an interruption to consciousness where the person that is experiencing the seizure seems to become vacant and unresponsive for a short period of time
2. Tonic-clonic seizures – This type of seizure involves an initial contraction of the muscles which may involve
   • tongue biting,
   • urinary incontinence and
   • the absence of breathing,
   • rhythmic muscle contractions.
3. Myoclonic seizures involve sporadic muscle contraction and can result in spontaneous and quick movements of muscles or muscle groups.
4. Atonic seizures involve the loss of muscle tone, causing the person to fall to the ground. These are sometimes called 'drop attacks' but should be distinguished from similar looking attacks that may occur in narcolepsy or cataplexy.