Lennox-Gastaut Syndrome

Severe form of intractable epilepsy resulting in severe learning disabilities and impaired organization of movements. Poor prognosis: 5% of patients die within 10 years; 50% of affected adults are completely dependent and less than 20% are independent.

Childhood Epileptic Encephalopathy.

First described in 1770 by Tissot, who reported an 11-year-old boy with frequent drop attacks, myoclonus, and progressive functional impairment.

From 3 to 10% of children with epilepsy. Male predominance. No racial predominance.

Commonly, there is a history of epilepsy in the family of children with Lennox-Gastaut syndrome, but no familial case of this syndrome has been reported.

Unknown even though many favoring factors have been suggested, such as brain injury at birth, brain infections, genetic brain diseases (e.g., tuberous sclerosis and inherited metabolic brain diseases), brain malformations, and West syndrome. Excessive permeability in the excitatory interhemispheric pathways in the frontal areas might play a role. Immunogenetic mechanisms may be involved in triggering or maintaining some cases of Lennox-Gastaut syndrome. One study found a strong association between Lennox-Gastaut syndrome and the human lymphocyte antigen class I antigen B7, but a second study did not.

Clinical presentation and characteristic electroencephalographic (EEG) pattern. The EEG shows spikes and slow frequency waves of 1.5 to 2.5 Hz. The background rhythm is slow with multifocal spikes. The maximal voltage area is usually anterior.

Peak age for onset is between 3 and 5 years (extremes: 1-10 years). The syndrome consists of the triad of intractable seizures (tonic seizures, drop attacks, atypical absences), mental retardation, and characteristic EEG. Affected patients have a large variety of seizures that occur at any time (day and night). Consciousness may be only partially affected, and patients may remain rather active but “distant,” with loss of tone of muscles of the face and neck resulting in impaired balance or abnormal posture. Severe cases of status epilepticus may develop. Lennox-Gastaut syndrome may be preceded by infantile spasms (West syndrome), which worsens the prognosis. Antiepileptic agents are not effective against this baffling disorder. Felbamate currently seems to be the only agent with some efficacy.

Proper evaluation of the degree of epilepsy and the medications used in this situation. No known specific precautions other than the evaluation of the potential complications associated with this form of intractable seizure disease. Most patients are resistant to medications. In patients with frequent seizures, a ketogenic diet may be considered, and less conventional therapies such as intravenous immunoglobulin therapy may be worth considering.

No specific anesthetic considerations except for the importance and the frequency of seizure activities, which may affect the anesthetic management. Patients may be anxious and uncooperative. Induction of anesthesia should be performed in conditions adapted to the behavior of the patient. Use of preoperative sedative medication should be considered if there are no contraindications from the cardiopulmonary and intracranial clinical condition.

It is essential to avoid anesthetic medications that could trigger seizure activities (e.g., methohexital, enflurane, high and sustained concentration of sevoflurane during induction of anesthesia). The only treatment for this medical condition is felbamate, which is associated with a significant risk of hepatotoxicity. Therefore, anesthesia drugs with considerable hepatic metabolism probably should be avoided or used with great caution (e.g., halothane).

Other forms of infantile epilepsy include the following:

West Syndrome: Rare form of infantile spasm that manifests during the first months of life and is characterized by hypsarrhythmia (abnormal brain waves) and mental retardation. There are two forms: cryptogenic, which has no known cause, and symptomatic, which results from an underlying condition or factor. The cryptogenic form usually follows a normal pregnancy, birth, and development and is associated with a more favorable outcome. Patients affected with the symptomatic form often develop mental retardation. Clinical features include involuntary muscle spasms occurring during seizures, typically beginning suddenly and lasting a few seconds. They may occur during sleep or upon awakening, are characterized by sudden, involuntary contractions of the head, neck, and trunk, with uncontrolled extension of the legs and arms. The syndrome often develops into the Lennox-Gastaut form of epilepsy with seizures that are difficult to control, making early diagnosis very important.

Doose Syndrome (Photogenic Seizures): Characterized by myoclonic-astatic epilepsy occurring during childhood that is triggered by light and often called “cerebral light sensitivity” syndrome. It is inherited as an autosomal dominant pattern.

Aicardi Syndrome: Rare disorder characterized by partial or complete agenesis of the corpus callosum, infantile spasms (spasm-like epilepsy), mental retardation, and an ocular abnormality called lacunae of the retina. Often associated with other features such as microcephaly and porencephalic cysts. Onset is generally between the age of 3 and 5 months. The disorder affects only females.