Lennox-Gastaut syndrome (LGS) is a severe form of childhood epilepsy defined by multiple seizure types, a distinctive brainwave pattern on EEG, and cognitive difficulties. It accounts for roughly 1% to 10% of all childhood epilepsies, with symptoms typically appearing between infancy and age nine, at an average onset of about three years old. LGS is notoriously difficult to treat, and seizures usually persist into adulthood.
What Defines LGS
Doctors identify LGS by three features that appear together. First, a child experiences more than one type of seizure. Second, an EEG recording shows a specific abnormal pattern: slow spike-and-wave discharges firing at less than 2.5 cycles per second, along with bursts of fast electrical activity during sleep at 10 cycles per second or higher. Both of these EEG findings are required for the diagnosis. Third, there is some degree of cognitive impairment, which may be present from the start or develop over time as seizures continue.
Types of Seizures in LGS
Children with LGS experience several seizure types, often in the same day. The most common include:
- Tonic seizures: The body suddenly stiffens, the eyes roll upward, pupils dilate, and breathing patterns change. These happen most often during sleep and are the hallmark seizure type in LGS.
- Atonic seizures: Muscle tone drops abruptly, causing the child to collapse or fall. These “drop attacks” carry a high risk of head and facial injuries.
- Atypical absence seizures: Prolonged staring spells where the child becomes unresponsive but may not fall. These can be subtle and easy to miss.
Many children also develop tonic-clonic (convulsive) seizures or myoclonic jerks. There are often periods of frequent, clustered seizures mixed with relatively seizure-free stretches, making the condition unpredictable from week to week.
What Causes LGS
About 60% of cases have an identifiable underlying cause, usually some form of diffuse brain injury or structural abnormality. Common causes include brain malformations that developed before birth, oxygen deprivation during delivery (birth trauma), central nervous system infections like meningitis or encephalitis, tuberous sclerosis complex, frontal lobe injuries, brain tumors, and metabolic disorders.
In many of these children, genetic mutations also play a role. Researchers have identified changes in several genes that affect how brain cells communicate, including genes involved in sodium channels and receptors for GABA, the brain’s primary calming chemical signal. Some children with no obvious brain injury turn out to have spontaneous (de novo) mutations in these genes.
For about 40% of children diagnosed with LGS, no cause is ever identified despite thorough testing. These cases are sometimes called cryptogenic, and they tend to have a somewhat better cognitive outlook than cases with clear structural brain damage.
Cognitive and Behavioral Effects
Intellectual disability is one of the defining features of LGS, and it tends to worsen over time. Some children develop normally before seizures begin, then gradually lose skills. Others show developmental delays from infancy. The ongoing seizure activity, the electrical disruption it causes during sleep (when the brain consolidates learning), and the effects of the underlying brain pathology all contribute to cognitive decline.
Behavioral challenges are common and can include hyperactivity, aggression, and autistic-like features. For many families, these behavioral issues become as significant a burden as the seizures themselves, affecting schooling, social relationships, and daily routines.
How LGS Is Treated
LGS is one of the most drug-resistant forms of epilepsy. Most children require combinations of anti-seizure medications, and even then, complete seizure control is rare. The realistic goal for many families is reducing seizure frequency and severity rather than eliminating seizures entirely. Several medications are specifically approved for seizures associated with LGS, including cannabidiol (a purified cannabis-derived compound) and fenfluramine, which is approved for patients two years and older.
Because medications alone are often insufficient, non-drug approaches play an important role. The ketogenic diet, a very high-fat, low-carbohydrate eating plan used under medical supervision, produces a greater than 50% seizure reduction in roughly half of LGS patients. Some achieve a 90% or greater reduction. Vagus nerve stimulation, a small device implanted under the skin that sends mild electrical pulses to the brain through a nerve in the neck, shows similar results: about half of patients experience a greater than 50% seizure reduction, and the benefit tends to improve over time.
In select cases where seizures originate from a specific brain region, surgery may be an option, though this is less common in LGS than in other forms of epilepsy because the electrical abnormality typically involves the whole brain.
Living With LGS Into Adulthood
LGS does not go away. The vast majority of people continue having seizures as adults, and the cumulative effect of years of uncontrolled seizure activity, medication side effects, and the underlying brain condition means most adults with LGS need lifelong support. Mortality rates are higher than in the general population, estimated at about 14 per 1,000 person-years. Risk factors for early death include respiratory and cardiovascular problems, sleep apnea, and reduced mobility.
The transition from pediatric to adult neurology is a well-recognized challenge. Pediatric epilepsy centers typically offer coordinated, multidisciplinary care. Adult neurology, by contrast, may have fewer specialists familiar with LGS, limited access to support services, and less experience managing the complex needs of this population. Both caregivers and physicians consistently identify the lack of effective long-term treatments, insufficient community services, and uncertainty about adult care planning as major unmet needs.
For caregivers, the emotional and physical demands of supporting someone with LGS are significant and lifelong. Planning for housing, supervision, therapies, and legal guardianship well before the child turns 18 can help ease what is often a difficult transition.