Lennox-Gastaut syndrome (LGS) is a clinical condition which refers to a triad of signs and symptoms. These include (1) multiple seizure types, often medically refractory, with (2) a typical EEG pattern and (3) frequent moderate to severe cognitive disabilities. The most common seizure patterns are tonic, atypical absence, and “drop attacks” or atonic seizures, but generalized tonic-clonic and focal seizures can occur as well. The EEG abnormalities may vary, but usually there is high voltage, generalized slow spike and wave activity (usually less than 2.5 Hertz) in addition to bursts of generalized paroxysmal fast activity (GPFA) during sleep; waking background is often slow and disorganized. The degree of cognitive delay and behavioral dysfunction vary, but are extremely common and often severe. These challenges represent an epileptic encephalopathy which weakens learning, social interaction and quality of life in general. Seizure types may change over time, slow spike wave and GPFA may not be appear on every EEG (especially routine waking studies), but cognitive and behavioral disabilities are permanent. There are children who fulfill the diagnosis for LGS whose seizures are well controlled and have minimal learning, social and behavioral challenges. However, many LGS patients wear protective headgear to prevent serious injuries from unprotected falls, and suffer from the long term effects of regular seizures and multiple drugs usage.
LGS is a diagnosis based on the triad of seizure types plus EEG pattern as well as cognitive-behavioral dysfunction. None of these problems are specific to LGS, nor is there is single cause that leads to the syndrome, but it is important to make the diagnosis since it has great impact on treatment and prognosis. In sleep, the most typical seizure type in LGS is the generalized tonic seizure (often brief stiffening of all extremities). “Drop attacks” during wakefulness often occur dozens of times daily. They may include a brief tonic phase followed by loss of tone and falling. More subtle atonic seizures may present as head nods. Atypical absence seizures can be difficult to identify since they can have gradual onset and unclear termination; in other words, it is not always clear when they begin or end. Additionally, they are defined by brief episodes of loss of awareness, sometimes with head and eye deviation or subtle automatisms, such as eye flutter or muscle twitching. Not uncommon for children with LGS is to have periods of non-convulsive status epilepticus which can last for many minutes or days. This episode is characterized by altered awareness with almost continuous atypical absence seizures which may be interrupted by intermittent tonic or other seizure types. The presence of focal seizures may confuse the diagnosis, especially if the EEG does not show typical features of slow-spike wave or the decremental pattern called GPFA (generalized paroxysmal fast activity).
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