Definition & Epidemiology
Lennox-Gastaut syndrome (LGS) is a severe form of childhood epilepsy syndrome. It is characterised by the triad of multiple drug-resistant seizure types (commonly tonic, atonic and atypical absence seizure), a specific interictal electroencephalographic (EEG) pattern showing bursts of slow spike-wave (SSW) complexes or generalized paroxysmal fast activity (GPFA) and intellectual and cognitive impairment.
Lennox-Gastaut syndrome develops in the first decade of life, commonly between 3 to 5 years of age and mostly before the age of 8 years old. Prevalence of Lennox-Gastaut syndrome is estimated to be between 1 to 2% of all patients with epilepsy and make up between 1 to 10% of all childhood epilepsies. This condition is found to be more common in males than in females but the reason for this male predominance is still unclear.
Signs and symptoms
Manifestation of various types of classical seizures and varying degree of cognitive impairment are the usual signs and symptoms of Lennox-Gastaut syndrome. The common type of seizures associated with Lennox-Gastaut syndrome are:
- Tonic seizures (most common) – This seizure is characterized by sustained muscle contractions, leading to stiffness. Such stiffness may be mild but it may even lead to brief interruption in breathing or more significant problems such as muscle spasm of the face. Tonic seizures are usually brief (lasting between a few seconds to a minute) and are especially prevalent at night during sleep, but can also occur during the day.
- Atonic seizures – Atonic seizures cause a sudden loss of muscle tone and limpness, leading to ‘drop attacks’ where the patient would fall unexpectedly, often landing to the ground with full impact to the head and face. Atonic seizures may only partially affect consciousness and usually last only a few seconds.
- Atypical absence seizures – Characterised by brief periods of ‘zoning out’ or blank-staring. During this period, patient is unconscious and therefore, after the seizure ends, patient usually resumes activity with no memory of the episode. Eye blinking, chewing movements, lip smacking, or slight jerking movements of the lips may occur. Absence seizures do not cause convulsions and may be so mild that they go unnoticed.
Along with cognitive problems, many patients with Lennox-Gastaut syndrome have behavioral and psychiatric problems such as:
- Attention problems
- Autistic behaviors
Affected children may also experience delays in reaching developmental milestones such as sitting, crawling or walking. Children with Lennox-Gastaut syndrome may develop normally before the onset of seizures, and then lose previously acquired skills (psychomotor regression). Due to the fact that seizures associated with Lennox-Gastaut syndrome are usually resistant to treatment, intellectual impairment and learning problems may worsen over time.
The causes of Lennox-Gastaut syndrome can be divided into two groups, namely identifiable and unknown (cryptogenic).
Identifiable causes are due to underlying genetic, structural or metabolic problems and it can be due to any of those factors or a combination of two or more factors. Between 65% to 75% of patients with Lennox-Gastaut syndrome were found to have identifiable causes and they include:
- Brain damage (e.g., birth asphyxia or head injuries)
- Infections of the central nervous system
- Structural defect of the brain
- Neurocutaneous syndromes
- Hereditary metabolic disorders
Risk factors associated with these causes include:
- Perinatal complications (including hypoxic-ischemic insults, sepsis, low birth weight, and hyperbilirubinemia),
- Meningitis, encephalitis and other infections of the central nervous system
- History of significant head trauma and injuries
- West syndrome (Infantile spasm)
As mentioned earlier, the diagnosis of Lennox-Gastaut syndrome is made based on its triad. Therefore, the test of choice to help make the diagnosis is Electroencephalography (EEG). Two patterns of interest to look for in EEG are bursts of slow spike-wave (SSW) complexes and generalized paroxysmal fast activity (GPFA). Either of these two patterns help to form the diagnosis of LGS with the former being the most commonly seen pattern and the later being observed during sleep.
The goal of treatment is to control the seizures in Lennox-Gastaut syndrome which will then, control the severity and frequency of seizure attack and mitigate associated complications (e.g., hypoxia and drop attacks)
Antiepileptic drugs (AED)
The ketogenic diet is found to be effective in childhood refractory seizures in specific genetic disorders (e.g., Glut-1 deficiency syndrome). It consists of a high fat, low carbohydrate ratio and up to 50% of patients achieve significant seizure reduction. However, the effectiveness may decline with time and it requires a supportive team and committed parents. The common side effects of the ketogenic diet are constipation, vomiting, abdominal pain, increase appetite, hypercholesterolemia, mineral deficiencies and growth retardation. The use of a low glycemic index diet and modified Atkins diet (containing nuts/seeds, fruits, or dairy products) are also effective in these patients.
The best surgical option for managing Lennox-Gastaut syndrome is corpus callosotomy which involves cutting through the corpus callosum, the part of the brain which is responsible for connecting the fibres between the two hemispheres of the brain. By reducing the connection between the two hemispheres, the propagation of seizure impulse will be limited. The surgery can be done either partially (cutting through 4/5 or 2/3 of the corpus callosum) or complete callosotomy. Although complete callosotomy resulted in better improvements, partial callosotomy is used to mitigate the side effect associated with complete callosotomy such as decreased speech output, hemiparesis, gait disturbance, and disconnection syndrome.
Aside from corpus callosotomy, vagal nerve stimulation and focal cortical resection are amongst other surgical procedures that are also being done to treat refractory seizures.
If you have any questions, please consult with your doctor to better understand the best solution for you.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: February 12, 2019 | Last Modified: February 12, 2019