Seizures Diagnosis

  • Diagnosis

    Seizures occur when abnormal events in the brain trigger changes in consciousness, muscle control, and sensations. Epilepsy is a term that describes a variety of syndromes characterized by the spontaneous recurrent seizures. Epilepsy and “seizure disorder” are synonymous. During a seizure, brain cells suddenly start firing rapidly in an abnormal fashion.

    A seizure may affect the entire brain (generalized seizure), or it may be confined to one neural region (partial seizure). The characteristics of a seizure depend on how much of the brain is affected, and which part of the brain is involved. Epilepsy syndromes (seizure disorders) are classified according to the type of recurrent seizure, when the seizures began (during childhood, adolescence, or adulthood), whether epilepsy runs in the family, or whether a brain abnormality is present on a diagnostic test.

    While seizures are a symptom of epilepsy, not all seizures are caused by epilepsy. Drug withdrawal, fever, and a sudden drop in blood sugar are among the things that can trigger a seizure in a person who has an otherwise normally functioning brain and no tendency to have seizures. Heavy alcohol use followed by a period of abstinence can cause a seizure.

    Any damage to the brain can cause seizures. Head trauma from a car accident or sports injury may lead to recurrent seizures (epilepsy). Brain tumors, strokes, and infections of the brain and surrounding tissues can also lead to epilepsy.In many people who suffer from seizures, no structural defects can be found, and the cause remains unknown. Some of these cases are the result of genetic abnormalities that affect brain signals.

    Symptoms vary according to how much of the brain is affected Table 01. Generalized seizures involve the entire brain, and are associated with loss of consciousness. Generalized seizures are classified as: tonic-clonic seizures (previously called grand mal seizures), absence seizures (previously called petit mal seizures), tonic seizures, clonic seizures, myoclonic seizures, and atonic seizures.

    A person having a grand mal seizure will fall down, become stiff, temporarily stop breathing, and start to jerk all over (convulse). This type of seizure starts with brief sustained muscular contraction during which the legs and arms extend or flex (the tonic phase). This activity progresses to rhythmic contractions of the limbs that gradually decrease in frequency (the clonic phase). Bladder and bowel control are sometimes lost. The entire event may last a few minutes, after which the patient will be disoriented and tired, and will have no recollection of the seizure. Some may experience the tonic phase or the clonic phase exclusively.

    A person having a myoclonic seizure will suffer a violent bodily jolt. This will sometimes manifest as suddenly dropping or involuntarily throwing objects.

    Absence seizures are characterized by a brief loss of consciousness. People with absence seizures (also called petit mal seizures) will typically stare blankly for a few seconds before regaining consciousness. If untreated, the syndrome can occur many times throughout the day.

    Atonic seizures (drop attacks) involve a loss of bodily control and a fall to the ground that may injure the head or body.

    Unlike grand mal seizures, however, atonic seizures are not associated with convulsions or arrested breathing.

    Partial (focal) seizures involve just one brain region, and are not associated with a loss of consciousness. Partial seizures can be either simple or complex. Depending on which part of the brain is affected, a simple partial seizure can manifest as jerking in a body part or sensing abnormal smells.

    In a complex partial seizure, consciousness is altered. The patient may stare blankly or exhibit random behavior (automatisms) such as chewing, lip-smacking, or hand-wringing. While the blank stare symptom is also characteristic of an absence seizure, complex partial seizures last longer, occur less frequently, and are usually associated with automatisms.

    Table 1.  Epilepsy Syndromes

    Seizure disorder Age of onset Type of seizure
    West syndrome 6-24 months Infantile spasms
    Lennox-Gastaut syndrome 2-5 years Tonic, atonic, atypical absence
    Benign childhood epilepsy 5-10 years Simple partial, complex partial
    Childhood absence epilepsy 4-10 years Absence, generalized tonic-clonic
    Juvenile absence epilepsy 10-17 years Absence, generalized tonic-clonic
    Juvenile myoclonic epilepsy 12-18 years Myoclonic, generalized tonic-clonic
    Temporal lobe epilepsy 10-30 years Complex partial
    Nocturnal frontal lobe epilepsy 5-20 years Frontal lobe complex partial

    Although seizure disorders afflict people of all ages, they are most common in younger age groups. Epilepsy affects about 3% of the U.S. population. Some types of epilepsy manifest only in childhood. For example, West syndrome, which is marked by infantile spasms (also called salaam attacks), usually appears before the first birthday.

    Although not considered epilepsy, fever-induced generalized tonic-clonic seizures (febrile seizures) occur in one out of every 100 children, usually between the ages of 3 months and 5 years. The seizure may occur when the child's temperature is rising or coming down.

    Some seizure disorders, such as juvenile absence epilepsy and juvenile myoclonic epilepsy, emerge during adolescence. Both appear to have a strong genetic link.

    Epilepsy is common in the elderly. The increased incidence of epilepsy in the elderly is due, in part, to the higher incidence of stroke in this age group. In addition, the elderly are more likely to experience events such as head trauma from falls, which can also lead to seizures. Temporal lobe epilepsy is the most commonly diagnosed seizure disorder in adults, but it typically begins during young adulthood and not in the elderly. Some people with this syndrome may have had fever-induced seizures in their youth, but the complex partial seizures don't show up until early adulthood.

    To determine what is causing your seizures, your doctor will start with a careful medical history. Because there are so many seizure disorders, medical history is essential for diagnosis. Clues such as the age at which seizures started and whether you have a family history of seizures will help your doctor pinpoint your syndrome. If someone you know has witnessed one of your seizures, it is a good idea to bring that person along so he or she can describe the seizure to your doctor.

    Your doctor may order an electroencephalogram (EEG) to record the electrical activity of your brain and help determine what kind of seizures you have Figure 01. During an electroencephalogram, or EEG, your doctor will attach electrodes to your head to measure the electrical activity of your brain. The procedure takes about 20 minutes, and is painless. He or she will expose you to different stimuli (such as a strobe light) in an attempt to provoke seizure-like brain wave abnormalities. A series of EEGs may be needed to offer a complete picture of your brain's electrical patterns. Your doctor may use simultaneous video/EEG monitoring to capture a seizure in progress.

    Brain imaging studies can isolate the area of your brain that is causing your seizures.

    Both computed tomography (CT) and magnetic resonance imaging (MRI) reveal structural information about the brain that can be useful in locating tumors, cancer, previous strokes, and brain lesions although MRI generally gives a more detailed picture. Other types of brain scans, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), may further aid your doctor in isolating the source of your seizures.

    Your doctor may order basic tests such as blood work, urinalysis, and an electrocardiogram to weed out any non-neurological problems that may be causing your seizures. In some cases, an overnight sleep study will reveal a sleep disorder to be the underlying cause. Likewise, a psychiatric evaluation can expose a psychological problem that may be contributing. A person with new-onset seizures and a fever may undergo a spinal tap to rule out an infectious cause of the seizures.

    Click to enlarge: Electroencephalogram (EEG) of Seizure Activity

    Figure 01. Electroencephalogram (EEG) of Seizure Activity

    Wearing a helmet while riding a bike or motorcycle, or while doing anything where you might fall and injure your head, can prevent a head injury that could lead to a seizure disorder. If you have a seizure disorder, taking your prescribed medication in the correct doses can help prevent seizures from coming on. Avoiding heavy alcohol use can prevent alcohol-withdrawal seizures.

  • Prevention and Screening

    Wearing a helmet while riding a bike or motorcycle, or while doing anything where you might fall and injure your head, can prevent a head injury that could lead to a seizure disorder. If you have a seizure disorder, taking your prescribed medication in the correct doses can help prevent seizures from coming on. Avoiding heavy alcohol use can prevent alcohol-withdrawal seizures.

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