Seizure disorder

Encyclopedia of Medicine, Apr 06, 2001 by Maureen Haggerty

The origin of 50-70% of all cases of epilepsy is unknown. Epilepsy is sometimes the result of trauma at the time of birth. Such causes include insufficient oxygen to the brain; head injury; heavy bleeding or incompatibility between a woman's blood and the blood of her newborn baby; and infection immediately before, after, or at the time of birth.

Other causes of epilepsy include:

• Head trauma resulting from a car accident, gunshot wound, or other injury.
• Alcoholism.
• Brain abscess or inflammation of membranes covering the brain or spinal cord.
• Phenylketonuria (PKU, a disease that is present at birth, is often characterized by seizures, and can result in mental retardation) and other inherited disorders.
• Infectious diseases like measles, mumps, and diphtheria.
• Degenerative disease.
• Lead poisoning, mercury poisoning, carbon monoxide poisoning, or ingestion of some other poisonous substance.
• Genetic factors.

Status epilepticus, a condition in which a person suffers from continuous seizures and may have trouble breathing, can be caused by:

• Suddenly discontinuing anti-seizure medication.
• Hypoxic or metabolic encephalopathy (brain disease resulting from lack of oxygen or malfunctioning of other physical or chemical processes).
• Acute head injury.
• Blood infection caused by inflammation of the brain or the membranes that cover it.

Personal and family medical history, description of seizure activity, and physical and neurological examinations help primary care physicians, neurologists, and epileptologists diagnose this disorder. Doctors rule out conditions that cause symptoms that resemble epilepsy, including small strokes (transient ischemic attacks, or TIAs), fainting (syncope), pseudoseizures, and sleep attacks (narcolepsy).

Neuropsychological testing uncovers learning or memory problems. Neuro-imaging provides views of brain areas involved in seizure activity.

The electroencephalogram (EEG) is the main test used to diagnose epilepsy. EEGs use electrodes placed on or within the skull to record the brain's electrical activity and pinpoint the exact location of abnormal discharges.

The patient may be asked to remain motionless during a short-term EEG or to go about his normal activities during extended monitoring. Some patients are deprived of sleep or exposed to seizure triggers, such as rapid, deep breathing (hyperventilation) or flashing lights (photic stimulation). In some cases, people may be hospitalized for EEG monitorings that can last as long as two weeks. Video EEGs also document what the patient was doing when the seizure occurred and how the seizure changed his behavior.

Other techniques used to diagnose epilepsy include:

• Magnetic resonance imaging (MRI), which provides clear, detailed images of the brain. Functional MRI (fMRI), performed while the patient does various tasks, can measure shifts in electrical intensity and blood flow and indicate which brain region each activity affects.
• Positron emission tomography (PET) and single photon emission tomography (SPECT) monitor blood flow and chemical activity in the brain area being tested. PET and SPECT are very effective in locating the brain region where metabolic changes take place between seizures.