What is Epilepsy?

Epilepsy is a brain disorder in which clusters of nerve cells, or neurons, in the brain sometimes signal abnormally. In epilepsy, the normal pattern of neuronal activity becomes disturbed, causing strange sensations, emotions, and behavior or sometimes convulsions, muscle spasms, and loss of consciousness.

Epilepsy is a disorder with many possible causes. Anything that disturbs the normal pattern of neuron activity – from illness to brain damage to abnormal brain development – can lead to seizures. Epilepsy may develop because of an abnormality in brain wiring, an imbalance of nerve signaling chemicals called neurotransmitters, or some combination of these factors. Having a seizure does not necessarily mean that a person has epilepsy. Only when a person has had two or more seizures is he or she considered to have epilepsy. EEGs and brain scans are common diagnostic test for epilepsy.

About three quarters of those diagnosed with epilepsy can control their seizures with medicine or surgery. However, about 25 to 30 percent will continue to experience seizures even with the best available treatment. Doctors call this intractable (treatment-resistant) epilepsy. In some cases, people with epilepsy will develop a severe condition called status epilepticus, which is characterized by a seizure that continues for more than 5 minutes or seizures that recur without recovery of consciousness. Status epilepticus damages the brain and is life-threatening.

Seizures

Doctors classify seizures into two groups. Focal seizures begin in one area of the brain, and may, or may not, spread to other parts. Generalized seizures are the result of abnormal neuronal activity on both sides of the brain.

About 60 percent of people with epilepsy have focal seizures. Simple focal seizures cause unusual sensations, feelings, or movements, but do not cause loss of consciousness. Complex focal seizures cause a change in or loss of consciousness and may produce a dreamlike experience or strange, repetitive behavior. Focal seizures are often described by the area of the brain in which they originate. For example, temporal lobe epilepsy, or TLE, begins in the temporal lobes located on either side of the brain. TLE is the most common type of epilepsy to feature focal seizures. Unfortunately, it is also one of the most difficult to treat.

Generalized seizures may cause loss of consciousness, falls, or massive muscle spasms. There are several different types of generalized seizures. In absence seizures, which usually begin in childhood or adolescence, an individual may appear to be staring into space or may have jerking or twitching muscles. Tonic seizures cause stiffening of muscles. Clonic seizures cause repeated jerking movements of muscles on both sides of the body. Myoclonic seizures cause jerks or twitches of the upper body, arms, or legs. Atonic seizures cause a loss of normal muscle tone, which may lead to falls or sudden drops of the head. Tonic-clonic seizures cause a mixture of symptoms, including stiffening of the body and repeated jerks of the arms or legs as well as loss of consciousness.

Just as there are different kinds of seizures, there are different kinds of epilepsy. Doctors have identified many kinds of epilepsy syndromes, which are disorders characterized by a specific set of symptoms that include epilepsy. A minority of these syndromes appear to be hereditary. For most of the epilepsy syndromes, the cause is unknown.

Epilepsy in Infants and Children

Many epilepsy syndromes, such as infantile spasms, Lennox-Gastaut syndrome, and Rasmussen’s encephalitis, begin in childhood. Infantile spasms usually begin before the age of 6 months and may cause a baby to bend forward and stiffen. Children with Lennox-Gastaut syndrome have severe epilepsy with several different types of seizures, including atonic seizures, which cause sudden falls called drop attacks. Rasmussen’s encephalitis is a rare, chronic inflammatory disease that usually affects only one hemisphere of the brain.  It causes frequent and severe seizures, loss of motor skills, and can lead to severe disability.

Some childhood epilepsy syndromes, such as childhood absence epilepsy, tend to go into remission or stop entirely as a child matures. However, other syndromes such as juvenile myoclonic epilepsy and Lennox-Gastaut syndrome are usually present for life.

Benign and Progressive Epilepsy

Epilepsy syndromes that are easily treated, that do not seem to impair cognitive functions or development, and that stop spontaneously are often described as benign. Benign epilepsy syndromes include benign infantile seizures and benign neonatal seizures. Other syndromes, such as early myoclonic encephalopathy, include neurological and developmental problems. It is often not clear whether the neurological damage in these syndromes is caused by the seizures or by underlying neurodegenerative processes. Epilepsy syndromes in which the seizures or the individual’s cognitive abilities get worse over time are called progressive epilepsy.

Source: National Institute of Neurological Disorders and Stroke, 2010