There are many forms of epilepsy, each with its own characteristic symptoms. Whatever the form, the disease is caused by a problem in communication among the brain's nerve cells. Normally, such cells communicate with one another by sending tiny electrical signals back and forth. For someone with epilepsy, the electrical signals are at high risk of occurring with an abnormal rhythm, either in one particular region of the brain, multiple regions, or throughout the brain. A seizure that begins in one part of the brain may spread to other parts, depending on the severity of the epilepsy.
The underlying cause may be structural, including a brain injury such as a contusion, infection such as encephalitis, lack of oxygen to one part of the brain as occurs in a stroke, or a tumor. In some cases, there may be a brain malformation that developed before birth. In other cases, the cause may be a more generalized dysfunction of the brain that is not primarily structural, such as a genetic or metabolic disorder. In a large number of patients, the ultimate cause is not found at all, despite extensive testing.
Seizures are divided into two basic categories, generalized and partial. In generalized seizures, the abnormal electrical discharges occur throughout the brain, whereas partial seizures only affect a specific region of the brain. Within each of these major categories are two common seizure types. There are generalized tonic-clonic (“grand mal”) seizures, and absence (“petit mal”) seizures. There are complex partial seizures and simple partial seizures. Other types exist, but these are the major ones.
A generalized tonic-clonic (“grand mal”) seizure is the most dramatic. It begins with a tonic phase in which the individual falls to the ground unconscious, with stiffening of the entire body. This is followed by the clonic phase, in which the arms and legs jerk rhythmically and uncontrollably. This may last for several minutes and may be accompanied by tongue-biting and incontinence of bladder or bower function. The seizure is usually followed by a period of deep sleep or mental confusion, called a post-ictal period.
Absence (“petit mal”) epilepsy is typically a disease of childhood that does not usually persist past late adolescence. During such a seizure, the child suddenly stops in the middle of an activity and stares blankly around for a few seconds (sometimes up to half a minute), and is unaware of what is happening. There may be a slight jerking movement of the head or an arm, or sometimes lip smacking, but petit mal seizures do not generally involve falling to the ground and thus may be very subtle. Usually, there is no tongue-biting or incontinence. When the seizure ends, the child often does not realize that the brief blank spell has occurred and resumes the interrupted activity without a post-ictal phase (period of sleeping or drowsiness). A child may have dozens of these spells a day. Such children are often thought by teachers and parents to be "day-dreamers," and may be misdiagnosed with attention deficit hyperactivity disorder because of the difficulty concentrating.
A complex partial seizure causes a change of consciousness that may range from confusion to complete unresponsiveness. Some complex partial seizures, including temporal lobe seizures, may be preceded by an aura, which can occur just prior to the seizure or as much as several hours beforehand. The aura may consist of nothing but a sense of tension or some other ill-defined feeling, but some epileptics have quite specific auras such as an impression of smelling unpleasant odors or hearing peculiar sounds, distorted vision, or an odd bodily sensation, particularly in the stomach. Many epileptics learn to recognize their special aura, and this may give them time to prepare as much as possible for the seizure by sitting or lying down, or stopping a potentially dangerous activity. Because only part of the brain is affected, the seizure may be much more subtle than a generalized tonic-clonic seizure. There may be twitching of one part of the body on only one side, an unusual sensation in one location, lip smacking, chewing movements, blinking, or a combination of these, accompanied by a change in consciousness. Some complex partial seizures remain localized in the affected part of the brain, and the seizure may be so subtle that it may be confused with absence (“petit mal”) seizures. In other individuals, the seizure may start with focal symptoms but then spread throughout the brain, resulting in a generalized tonic-clonic seizure. This is an example of a mixed type of seizure. Complex partial seizures are typically followed by a post-ictal phase (period of sleeping of drowsiness).
Simple partial seizures are similar to complex partial seizures but are not accompanied by changes in consciousness. The individual will be able to talk and describe what he/she feels during the seizure. This is the only major type of seizure that the individual usually remembers, but is relatively rare outside of certain childhood seizure syndromes such as Rolandic epilepsy.
The basic symptom of epilepsy is a brief and abnormal phase of behavior, commonly known as a seizure, fit or convulsion. It is important to realize that a single such episode does not indicate that you have epilepsy. By definition, epileptic seizures recur.