Lennox-Gastaut Syndrome (LGS) represents a serious seizure syndrome that accounts for almost 4% of all epilepsy that occurs in children. This syndrome is often nonresponsive to different antiepileptic drugs. There are typically three characteristics that all patients must have in order to be appropriately diagnosed with this syndrome.
The individual must have multiple seizure types such as tonic, atonic, atypical absence with high seizure frequency, and often with status epilepticus.
They must show impaired intellectual function or behavioral problems.
They have a characteristic EEG that is called slow spike and wave while awake. Typically this means that there are epileptiform discharges that occur at a slow frequency. However, when the person has a seizure one may see a different seizure activity that is actually characterized by fast activity. These are important nuances but essential in making the diagnosis of the syndrome.
The clinical presentation of this condition depends on the ultimate cause that led to this. In some cases Lennox-Gastaut has evolved from conditions such as infantile spasms as a younger child. There does appear to be some window at which Lennox-Gastaut may occur, particularly in that first year of life. Changes in thinking and abilities to do schoolwork can occur before seizures actually occur.
The evolution of Lennox-Gastaut usually involves progressive deterioration of cognitive function. There is an increased frequency of seizures, and often episodes of status epilepticus. Seizures persist in a majority of cases with less than 10% ever having complete seizure freedom. Children who have had an earlier onset of their seizures tend to have a higher frequency of tonic seizures and repeated episodes of nonconvulsive status epilepticus.
One of the essential characteristics of this syndrome is the presence of numerous seizure types. The most characteristic seizure types that occur in this condition are tonic, atonic, and atypical absence. However, all seizure types may occur with this condition. Tonic seizures are the most typical seizure group in Lennox-Gastaut and are one of the ways that one can make the diagnosis. They have a characteristic EEG change. These seizures are associated with loss of bladder control, problems breathing, heart rate increases, and changes in eye function. This is one of the more concerning seizure types given how frequently that it occurs.
Atonic seizures, otherwise known as drop attack, are readily common in this condition. These seizures are associated with the sudden loss of tone that occurs without warning and results in falling. They can be subtle and simply present as a simple head nod or it can be very dramatic and result in a fall. Although atonic seizures may results in falls, most falls are secondary to tonic seizures. The EEG in this condition is typically characterized by bursts of generalized spike or poly spike and wave discharges at a slow frequency.
Atypical absence seizure is another common seizure type that can be seen in almost three-quarters of all Lennox-Gastaut patients. Atypical absences are characterized by transitory loss of consciousness and they can be delayed up to one second after the onset is noted on the EEG. Individuals may show activity which looks purposeful and it may be difficult to recognize the seizure to those who are unaware of how these seizures present. Unlike typical absence these events are not precipitated by hyperventilation or by photic stimulation. There is another characteristic finding associated with these seizures, typically a slow spike wave discharge, repeating at every 1.5 to 2.5 seconds in a cycle.
One of the more concerning aspects of Lennox-Gastaut is that status epilepticus is very frequent. Status epilepticus is an emergency in which seizures fail to respond to treatment and they occur one after another without recovery back to baseline. There is some concern that many of these events are precipitated by overtreatment with hypnotic sedative antiepileptic drugs, particularly drugs in the benzodiazepine family. Tonic status epilepticus and atypical absence status epilepticus are the most common, although any seizure type can result in status epilepticus. The EEG during the status may not appear to be distinctly different from the EEG when they are not seizing due to how frequently the EEG is abnormal.
As previously mentioned, one of the essential criteria for Lennox-Gastaut Syndrome is the presence of thinking problems or cognitive disorders. Mental retardation is a component of how Lennox-Gastaut may present. Mental retardation is not inevitable and up to 10% of patients can have a normal IQ, although most still demonstrate a slowed mental processing. There is a 72% risk of having severe mental retardation with Lennox-Gastaut Syndrome in those who have symptomatic causes for the condition. The medications used to treat seizures, the prolonged episodes of status epilepticus often are also contributors to the mental functioning of these patients, and is an important consideration when judging true cognitive abilities in these individuals.
One of the biggest concerns about Lennox-Gastaut Syndrome is the high risk of injury and death. A high incidence of injuries is associated with drop seizures, predominantly the tonic and atonic seizures. As noted tonic seizures are the most common cause of falls of children with Lennox-Gastaut and a major cause of morbidity with repeated injury often encountered. Beyond the frequent injuries from breakthrough seizures, behavior and cognitive problems often lead to overtreatment with medications that can compromise balance and gait and lead to other problems. Death may occur and is associated with accidental injury and estimated to be 10% over a 10-year followup period.
The treatment of patients with Lennox-Gastaut Syndrome includes efforts at managing the underlying cause of the cognitive or behavioral problems while attempting to control seizures and providing support for family or caretakers involved with their care.
Antiepileptic drugs are the cornerstone of therapy for patients with Lennox-Gastaut. Given that there are multiple seizure types the use of broad spectrum agents is often the top choice for situations involving Lennox-Gastaut. This means the use of valproic acid, lamotrigine, and topiramate are the most widely used agents and are useful. A recent report suggested that the combination of valproic acid and lamotrigine may actually be beneficial than using either drug by itself. Because these are broad spectrum agents it helps to cover numerous different seizure types.
There have been recent approvals in the United States for new agents. Recently rufinamide, a novel antiepileptic drug, was approved as adjunctive treatment for patients with Lennox-Gastaut for its utilization in atonic seizures. Clobazam has also been recently approved for use in the United States specifically for various seizure types in the Lennox-Gastaut Syndrome. However, it is important to know that although antiepileptic drugs can decrease the number of seizures, oversedation can actually worsen the seizures. Therefore, adjusting the dose of medications and getting it right is an essential component on how to manage these individuals. These patients often require numerous visits to improve and titrate their drug regimen, which is essential in order to give these folks the best quality of life that is possible. Dopamet, which is also a broad spectrum drug, has often been reserved as a third line antiepileptic drug for situations in which other antiepileptic drugs have not demonstrated ability to stop seizures. Felbamate does have a Lennox-Gastaut Syndrome indication by the FDA. There have been reports of improved alertness, increased verbal output. However, there is still a risk of aplastic anemia or hepatic failure in these cases.
Other drugs have been studied in small observational publications, which have included levetiracetam, zonisamide, acetazolamide, and others. Although they all have suggested some benefit, it is unclear how useful these agents are for the overall treatment of the condition.
The ketogenic diet, a specialized high fat, low carbohydrate diet can be very useful for Lennox-Gastaut Syndrome, and it may be particularly helpful in decreasing the number of atonic seizures, particularly when medical therapy has proven to be ineffective. In one perspective, multicenter study of children, 10% were seizure-free after one year on a ketogenic diet and another 30% had more than 90% improvement of seizure control.
Surgical options are usually palliative ( i.e. helps but does not cure) with corpus callosotomy and vagus nerve stimulation the most frequently utilized. Corpus callosotomy is a surgical procedure that disconnects the anterior two-thirds to three-fourths of the cerebral hemispheres to prevent seizure propagation to eliminate the risk of falls and injury by reducing spread of generalized seizures. Partial callosotomy is effective in 50-75% of cases, while complete callosotomy may reach 80-90% reduction of drop attacks associated with generalized tonic and atonic seizures that require transcallosal propagation to affect both hemispheres to result in falls.
Another surgical procedure that is often mentioned is one known as multiple subpial transection (MST). MST is designed to interrupt horizontal intracortical fibers to contain neocortical synchronously interacting regions of the brain to minimize seizure spread that leads to clinical seizures. As the benefit of the procedure has by some reports been found to be positive, however, it is unclear whether it is useful in all cases.
Some centers continue to use vagus nerve stimulation prior to corpus callosotomy. Vagus nerve stimulation can be helpful in Lennox-Gastaut Syndrome but it does not have the same type of benefit in partial seizures as it does for the atonic or drop seizures. A recent study demonstrated greater benefit of callosotomy compared to vagus nerve stimulation for the generalized tonic-clonic seizures, although there was obviously the risk of greater complications in the patients treated with callosotomy. Therefore, choosing the risk benefit that is most appropriate for the patient will be the most helpful.
The prognosis of Lennox-Gastaut Syndrome overall is poor. Very few patients lead independent lives as an adult as a result of the daily seizures, behavioral problems, and cognitive issues. Drug resistant seizures are the rule and the prognosis for normal intellectual function is very rare. An onset before the age of three is more likely to be associated with a mental retardation with the majority of these individuals requiring special classes or sheltered environments. Approximately half of symptomatic Lennox-Gastaut Syndrome and a third of those for which we have no clear cause for the syndrome lose the characteristics EEG that has been described above. Patients with an early age of onset, frequent seizures, repeated episodes of status epilepticus, and a preceding history of infantile spasms typically have a worse prognosis of all for normal cognitive development.
Lennox-Gastaut Syndrome is a challenging condition for which there are no easy answers. They require numerous office visits, they often land in the emergency room frequently, they take numerous medications, and they have a number of issues that need to be managed. As physicians it is important to remember the syndromic aspects of this condition. This is not your average daily epilepsy patient. These individuals and their families need guidance with regards to school and home environment. Safety considerations, appropriate counseling with regards to prognosis, expectations, listening to caregivers and helping caregivers find ways to deal with this becomes an important aspect of treating the entire family. There is no other situation where a holistic approach is needed more than in the treatment of Lennox-Gastaut Syndrome. Keeping aware of all developments in epilepsy and novel treatments is important in order to truly benefit the individual and the family surrounding them that has to deal with the Lennox-Gastaut Syndrome.
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