Epilepsy Syndromes

 

Features of Epileptic Syndromes

  • Specific seizure type(s)
  • Typical EEG pattern
  • Associated clinical features
  • Natural history
  • Precipitating factors
  • Response to antiepileptic drugs
  • Inheritance pattern

Classifying epilepsy by seizure type alone leaves out other important information about the patient and the episodes themselves. Classifying into syndromes takes a number of characteristics into account, including the type of seizure; typical EEG recordings; clinical features such as behavior during the seizure; the expected course of the disorder; precipitating features; expected response to treatment, and genetic factors.

Epileptic syndromes can be either idiopathic (of unknown cause) or symptomatic of underlying brain damage or disease. In general, idiopathic forms have a better prognosis in terms of both seizure control and eventual remission than do symptomatic forms. Epileptic syndromes include seizure syndromes in newborns; febrile convulsions; West syndrome (infantile spasms); Lennox-Gastaut syndrome; childhood absence epilepsy; juvenile myoclonic epilepsy; Rolandic epilepsy; Landau-Kleffner syndrome; Rasmussen’s encephalitis (syndrome); progressive myoclonic epilepsy; temporal lobe epilepsy, and frontal lobe epilepsy. Types of epilepsy that appear in infancy range from benign to severe, although persistent epilepsy that begins during the first year of life tends to remain severe, sometimes throughout life. Some authorities would not include febrile (fever-generated) seizures in this list. Many consider them to be non-epileptic seizures because they cease to be a problem as the child grows older.

Epileptic syndromes in newborns include benign neonatal convulsions; familial benign neonatal convulsions; early myoclonic encephalopathy; and severe idiopathic status epilepticus. Usually, seizures in newborn babies are caused by identifiable metabolic or infectious conditions, many of which are associated with complications around the time of birth. In general, outcome following neonatal seizures depends more on the cause of the seizure than on the specific type. Newborns whose seizures are due to transient metabolic causes, who have normal clinical and EEG examinations, and who develop normally usually do not have epilepsy and do not require prolonged antiepileptic therapy.

Newborns whose seizures are due to disorders that affect brain structure (encephalopathies) are at risk for later epilepsy. This is especially true for newborns with brain malformations or hypoxic-ischemic disease that causes permanent brain damage and produces cerebral palsy.

Seizure-like phenomena. A variety of medical conditions may produce sudden episodes which have some similarities to epileptic seizures. Migraine and transient ischemic attacks (TIA’s), for example, may produce visual disturbances; hyperventilation produces tingling, light-headedness and occasionally loss of consciousness, as does syncope (fainting).

In children, breath holding spells may lead to blueing of the lips and some jerking; tics likewise produce jerking; sleepwalking and other sleep disturbances may mimic seizure symptoms, while episodic dyscontrol syndrome produces rage attacks that may be erroneously identified as epileptic seizures.

Non-epileptic seizures. Non-epileptic seizures (also referred to as pseudoseizures, psychogenic or cryptogenic seizures) are episodic, paroxysmal events not related to abnormal electrical activity in the brain. Considered to be of psychological rather than physical origin, they offer a major challenge to diagnosis and treatment. In one study, fully 25 percent of patients referred to an epilepsy center to be evaluated for surgery had non-epileptic seizures.

The episodes resemble true epileptic seizures in many ways. Nevertheless, they have characteristics which differ from true seizures in important points, including repeatedly normal EEG readings between seizures; lack of any response to therapeutic levels of antiepileptic drugs; and violent thrashing of all four limbs, especially if not synchronous, during an episode.

Non-epileptic seizures may occur in people who also have true epileptic seizures. Successful treatment usually involves psychological counseling and may include treatment with psychiatric medication.

Common Epilepsy Syndromes

Infantile spasms (West Syndrome). Clusters of rapid myoclonic jerks causing a baby to double up and jerk forward with their arms either bent or extended. They have a distinctive EEG pattern called hypsarrhythmia. This epilepsy syndrome is time limited, starting in the first year of life. Many children with infantile spasms have associated developmental delay and may go on to develop other forms of epilepsy, such as Lennox-Gastaut syndrome. Treatment may include steroid hormones, ACTH and antiepileptic drugs.

Lennox-Gastaut syndrome. Difficult to treat epilepsy syndrome with mixed seizures -- including absence, tonic seizures causing stiffening, often during sleep; drop attacks, convulsive seizures on wakening, and a distinctive EEG pattern. Begins between the ages of 1 and 8. Children often have developmental delay and mental subnormality.

Childhood absence epilepsy (petit mal epilepsy). Accounts for 2-4 percent of epilepsy in children and begins between ages 3 and 10. Seizures are brief staring spells with associated distinctive spike and wave EEG pattern. Absence seizures tend to occur very frequently. Forty percent of children with this epilepsy syndrome will outgrow it or go into remission by their teenage years.

Juvenile myoclonic epilepsy. (Also called Janz's syndrome, impulsive petit mal, myoclonic epilepsy of adolescence, and jerk epilepsy). Typically begins at puberty in otherwise healthy children. The first symptom is usually a generalized convulsion. These children may also have myoclonic seizures (jerking of the muscles) on awakening. Convulsions may also occur. Can be controlled with medication, but not likely to be outgrown.

Benign Rolandic epilepsy (also called benign partial epilepsy of childhood). Accounts for more than one third of epilepsy beginning in middle childhood between ages 3 and 13. Involves simple partial seizures affecting the face, causing drooling and inability to speak, which may be followed by a convulsion. Seizures typically occur at night and these children otherwise are normal and healthy. The prognosis is favorable with 95% of children outgrowing their seizures by age 15.

Rasmussen's syndrome (also known as Rasmussen's encephalitis). Rare condition. Affects one half of the brain, producing seizures and affecting control of the opposite side of the body. Various treatments have been tried, including surgery to remove the affected half of the brain.

Landau-Kleffner syndrome. Also a rare disorder beginning between ages of 3 and 7. Produces seizures and affects speech. Children develop normal speech, and then slowly lose it. Simple partial and tonic clonic seizures. Treated with antiepileptic drugs to control seizures, and, possibly, steroids.

Temporal lobe epilepsy. Complex partial seizures and simple partial seizures. Generalized tonic clonic seizures may be part of this syndrome as well. Treated with medication, surgery, or, in some cases, with VNS therapy.

Frontal lobe epilepsy. May produce weakness or inability to use certain muscles, including those that govern speech. Frontal lobe seizures may involve thrashing movements during sleep, also stiffening with the head turned to one side and the arm rising into a brief frozen state. Some seizures may be dramatic and upsetting to others, with screaming, bicycling movements of the legs, running. Treatment is with medication, and, in some cases, surgery.

Reflex epilepsy. Seizures triggered by something in the environment. Photosensitivity (the tendency to have seizures in response to flashing lights, strobe lights, or alternating patterns of light and dark) most common type. Begins in childhood, is associated with absence epilepsy, and may disappear in adulthood.

Progressive myoclonic epilepsy. A rare, form of epilepsy with myoclonic (jerking) and tonic-clonic (grand mal) seizures. Children with this condition may have trouble with maintaining balance and experience rigid muscles. There is also a loss of mental ability. A gene for this disorder has recently been discovered.