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Any condition that produces major brain abnormalities is a potential cause of Lennox-Gastaut syndrome, which has three defining characteristics: multiple seizure types, a distinctive brain-wave pattern and mental deficiency that can range from slight to profound cognitive impairment. The peak age of onset is between ages 3 and 5, with a slightly greater prevalence in males than females.
Lennox-Gastaut syndrome is rare, occurring in about 0.3 in 1,000 live births. Estimates of 20 percent to 60 percent of children with this syndrome have a prior history of infantile spasms. Diagnosis and treatment are difficult and seizure remission is rare.
The onset of Lennox-Gastaut does not typically begin with a specific type of seizure, although the first sign in about 1/3 of children with this syndrome is a prolonged or non-stop episode (status epilepticus). Tonic (muscle stiffening), atonic (loss of muscle tone / drop attacks) and absence (staring) seizures are common. Tonic-clonic (grand mal), myoclonic (sudden muscle jerks) and other seizure types can also occur. The seizures are usually repeated multiple times throughout the day.
Tonic seizures are most common, especially during sleep when they may occur throughout the night. These seizures range in duration from a few seconds to one minute, with an average of about 10 seconds. They disturb sleep but do not awaken the child. The episodes often go undetected because of their brevity.
Among signs parents might observe are a stiffening of muscles that throw the child off balance causing the child to fall, a slow forward motion of the head accompanied by drooling, sudden fall of the head only or sudden collapse of the body as a whole. Because the falls pose a serious risk of injury, the child might want to wear protective headgear.
The child's condition may not be identified as Lennox-Gastaut syndrome until the falls and behavioral changes—also typical of this syndrome—are observed.
Because many of its features occur with other seizure conditions, Lennox-Gastaut may not be diagnosed very quickly. The initial evaluation will include a medical history in which the doctor will look for signs of prior seizures— especially infantile spasms— and conditions— such as mental retardation, hearing and visual impairment, and tuberous sclerosis— that are sometimes present in children with this syndrome.
A key sign of Lennox-Gastaut is a specific brain-wave tracing that experts call a slow spike- and-wave pattern. The evaluation will likely include awake and sleep or nap EEG s that may be repeated on subsequent clinical visits. The procedure may also include video monitoring, which provides the doctor with split-screen images of the child's seizure and the concurrent brain wave tracing. Flashing light and hyperventilation (rapid breathing) tests may also be conducted as part of the brain-wave analysis.
Since brain abnormalities are common with this syndrome, brain imaging will be part of the evaluation, as well as testing of blood and urine .
Treatment for Lennox-Gastaut may include medications, the ketogenic diet, vagus nerve stimulation therapy, or a combination thereof. Occasionally, corpus callosotomy surgery is used. However, complete seizure control is rarely achieved in children with this syndrome.
Some of these children are prone to non-convulsive status epilepticus, a continuous seizure state that is associated with a change in the child's level of awareness. One goal of treatment is to avoid these episodes. When this is not successful, medical intervention is needed to bring the episodes to an end.
Seizures may also come in a series. Physicians may recommend that children especially prone to these attacks be treated with rectal diazepam or oral medication to stop the series.
The ketogenic diet produces a dramatic improvement in some children with this syndrome. About 1/3 to 1/2 experience an amazing benefit and another 1/3 have partial benefit from the diet. The regime is medically administered and, like all therapies, can have significant side effects.
Most children who have Lennox-Gastaut are treated with multiple drugs, a therapy that requires a careful balance between the best possible seizure control and potential toxic side effects such as fatigue, nausea and unsteadiness of movement.
Managing the condition from the medical perspective is somewhat of a rollercoaster with a succession of active and relatively inactive seizure periods.
Some children are developmentally normal when Lennox-Gastaut begins, but then lose skills, sometimes dramatically, in association with uncontrolled seizures. By age 6, most children with this syndrome have some degree of mental retardation.
As children with this syndrome grow older, the types of seizures change. In most cases, the drop attacks abate. They are replaced by partial, complex partial and secondarily generalized convulsions.
Behavioral problems are common, ranging from hyperactivity to autistic behaviors.
The outcome is likely to be best for children with an unknown cause compared to those whose seizures are symptomatic. Among risk factors for a poor prognosis are:
Prior history of infantile spasms
Onset before the age of 3
High frequency of seizures
Worsening periods of long durationRepeated episodes of status epilepticus