Epilepsy | Research & Encyclopedia Articles

Epilepsy

Epilepsy is a disease of abnormal brain activity that causes recurrent seizures. Seizures are sudden, brief episodes of altered states of consciousness, often accompanied by spasmodic or unusual motor activity. For centuries, their frightening and violent quality made objective analysis of their nature difficult.

In ancient Greece, the cause of epilepsy was usually thought to be supernatural--the Greeks felt it to be an affliction of the gods. Indeed, the name for the disease comes from the Greek epilepsis, which means "a taking hold" in the sense that a great power might take over someone's body. Because epilepsy was believed to be a "sacred disease," its interpretation was put into the hands of religious adepts who administered an assortment of ineffective remedies such as tortoise blood or camel hair. Their practices were attacked as fraudulent in the fifth century by the Hippocratic school of thought and Greek physicians who were convinced that epilepsy had a natural cause, although these physicians had no idea of what that cause might be. The idea that epilepsy was a supernatural phenomenon persisted into the Middle Ages and became linked with demonic possession cured only by exorcism. Even during the intellectual enlightenment of the Renaissance period that followed, epilepsy remained a mystery. A scientific understanding of epilepsy would not occur until the nineteenth century, when the disease came to the attention of physicians who studied the brain and nervous system. Their realization that epilepsy had a neurological cause opened the door for its improved treatment--both social and medical.

In the 1860s John Hughlings Jackson (1835-1911), an English neurologist, made one of the first important studies of epilepsy. He concluded from his careful experiments and observations that epileptic seizures began at specific locations somewhere on the cerebral cortexes of its victims. He also clarified the symptoms of epilepsy. In particular, he characterized a type of seizure that typically involves only one side of the body and does not involve a loss of consciousness. This type of epilepsy has come to be known as Jacksonian epilepsy.

With the invention of the electroencephalograph (EEG ) by Hans Berger (1873-1941) in the 1920s, it became possible to observe the electrical activity of the brain directly while a seizure occurred. Subsequent observations made it clear that a seizure resembled an "avalanche" of brain activity in which an electrical impulse beginning in a given spot on the cortex spreads uncontrollably throughout an entire hemisphere or even the entire cortex. In time, medications providing effective relief for the symptoms of epilepsy were developed, and as neurologists studied the life histories of their patients, the causes of their seizures (including serious childhood illness and brain damage resulting from injuries, or tumors) began to be better understood.

According to international surveys, approximately one adult in 200 adults suffers from recurrent epilepsy. When infants who have had seizures due to fevers, which is usually a temporary condition, and adults who have only had one seizure are factored in, the figure rises to approximately one in 80. One of the earliest successful treatments for epilepsy were bromides, compounds formed by combining bromine with another element or radical. Barbiturates and phenobarbitone have also been used to treat epilepsy, with phenobarbitone being the most widely prescribed epilepsy medication by the 1970s. New anti-epileptic drugs are constantly undergoing development and testing.

In the past dozen years, computerized axial tomography (CAT) and magnetic resonance imaging (MRI) have given physicians the ability to view detailed images of the brain and locate precisely where certain types of seizures begin, paving the way for surgery to offer epileptics a complete cure. Because of the risks involved, brain surgery to treat epilepsy is used primarily for patients who do not respond to medications. Surgery works best when the abnormal electrical discharge that is the source of epilepsy originates in one specific area of the brain. For instance, it appears that certain types of epilepsy are caused when an episode of high fever and convulsions during infancy leaves a small area of scar tissue in the brain, which then triggers periodic seizures. Using accurate scanning of the brain and delicate surgery, specialists can sometimes remove the offending speck of tissue, giving the patient a new life free from debilitating seizures. Another approach to controlling epilepsy, called vagus nerve stimulation, is undergoing testing. The approach uses a device similar to a heart pacemaker to deliver low-level, intermittent electrical pulses to the vagus nerve in the neck, which seems to control seizures by traveling to certain brain centers like the temporal lobe.

Research has shown that there is no known cause in nearly 60% of epilepsy cases. Known causes included head trauma, cerebrovascular disease, brain tumors, developmental disorders, infections, and poising. Epilepsy may also be inherited, although such cases are rare. In recent years, scientists have identified some of the genes responsible for inherited epilepsy. A gene on chromosome 21 is responsible for progressive myoclonus epilepsy, which causes nerve degeneration and progressive dementia. It is believed that the disease results from a mutation blocking the production of the enzyme cystatin B. A gene on the X chromosome has also been identified as causing a rare form of epilepsy and mental retardation only in women, even.though the gene is passed on by the father.