Epilepsy

Description

Diagnosis

A diagnosis of epilepsy is often made during an emergency visit for a seizure. If a person seeks medical help for a previous or suspected seizure, the physician will take a complete medical history, including a history of seizure events, from either the patient or the parent.

One interesting study suggested that a physician might be able to identify the location in the brain where the seizure is originating by watching the patient wipe his or her nose. A runny nose is common after a temporal lobe seizure but not after seizures in other locations. Furthermore, the hand with which the patient wipes the nose coincides with the side of the brain in which the seizure occurs.

Ruling Out Serious Causes

Health- or life-threatening causes of seizures should first be ruled out. They include the following:

• Alcohol withdrawal.
• Infections (encephalitis or meningitis).
• Head injuries.
• Poisoning.
• Drug overdose.
• Hypoglycemia.
• Stroke. Major and minor stokes are important causes of seizures in older people. Small strokes, called transient ischemic attacks, are often difficult to distinguish from mild epileptic seizures, and, in fact, a first seizure in an adult might be a precursor to stroke.
• Cardiac arrest.

Ruling Out Conditions with Similar Symptoms

Syncope. Syncope, a brief lapse of consciousness in which blood flow is reduced to the brain, can mimic epilepsy and is misdiagnosed as epilepsy in many cases. A misdiagnosis of epilepsy in such patients can cause serious problems. Research continues to suggest that taking the patient's history and giving a physical exam rather than administering an assortment of cardiac tests is the most effective way to diagnose syncope.

Migraines. Migraine headaches, particularly migraine with auras, may sometimes be confused with epilepsy. With epileptic seizure, the preceding aura is often seen as multiple, brightly colored, circular spots, while migraine sufferers tend to see black, white, or colorless lined or zigzag flickering patterns. Typically the migraine pain expands gradually over minutes toward one side.

Panic Attacks. One study reported on patients with partial seizures that resembled panic disorder. Symptoms of panic disorder include palpitations, sweating, trembling, sensation of breathlessness, chest pain, feeling of choking, nausea, faintness, chills or flushes, and fear of losing control and fear of dying.

Narcolepsy. Narcolepsy, a sleep disorder that causes a sudden loss of muscle tone and excessive daytime sleepiness, can be confused with epilepsy.

Electroencephalogram

The most important diagnostic tool for epilepsy is an electroencephalogram (EEG), which measures brain waves. Ideally, it should be performed within 24 hours of a seizure. An EEG recording session may last for less than an hour, but in some cases the physician will want a day-long recording. Long-term monitoring may be necessary in some cases when patients do not respond to medications. Portable EEG units are available in some places, which can be used to monitor patients throughout normal activities. EEGs are not foolproof; in one study half of people who had experienced an epileptic seizure showed a normal EEG reading. Repeated EEGs are often needed to confirm a diagnosis, particularly for certain partial seizures that often produce an initially normal EEG reading.

Imaging Techniques

Computerized Tomography (CT) Scans. The doctor will usually order brain scans using computerized tomography (CT) for most adults and children with a first seizure. This imaging technique is sensitive enough for most purposes. In children, even if the scan is normal, the doctor will follow up to be sure other problems are not present.

A CT or CAT scan (computed tomography) is a much more sensitive imaging technique than X-ray, allowing high definition not only of the bony structures, but of the soft tissues. Clear images of organs such as the brain, muscles, joint structures, veins and arteries, as well as anomalies like tumors and hemorrhages may be obtained with or without the injection of contrasting dye.

Magnetic Resonance Imaging (MRI). Experts now strongly recommend MRIs for children with first seizures in certain cases, such as children under one years old, those with seizures that are associated with any unexplained significant mental or motor problems, and other conditions. These images may help to determine if the disorder is treatable by surgery and may be used as a guide for surgeons.

Other Advanced Imaging Techniques. More advanced scanning techniques, particularly magnetic resonance spectroscopy (MRS), magnetoencephalography (MEG), positron emission tomography (PET), and single-photon emission computer tomography (SPECT), are becoming important tools for epilepsy researchers. They are also useful for detecting abnormalities, such as changes in brain activity, damaged or scarred locations in the brain where partial seizures are triggered, or tumors and other abnormalities that may be causing seizures. Some, such as MEG, may also become important in evaluating patients with severe epilepsy who might be candidates for surgery.

Polysomnography

Some researchers recommend polysomnography for certain patients. This test is used to detect sleep disorders, such as obstructive sleep apnea, that is associated with epilepsy in some people.

Investigative Diagnostic Approaches

Low brain levels of the neurotransmitter gamma aminobutyric acid (GABA) are associated with an increased risk of seizure recurrence. Some researchers suggest that measuring GABA levels, along with EEG recordings, may help in assessing the risk of recurring seizures and in identifying those patients who could benefit from drugs that stimulate GABA function.