Differential diagnosis

Lennox-Gastaut syndrome (LGS) first appeared in the medical literature in 1969, even though important clinical and EEG features in this subgroup of epileptic patients had been noted as early as 1939. This syndrome comprises a clinical triad consisting of (1) diffusely slow spike-wave discharges (occurring at a frequency of 1 . 5-2 . 5 Hz), (2) psychomotor retardation, and (3) multiple electroclinical seizure types refractory to medical therapy (including generalized tonic, atonic, atypical absence, myoclonic, and tonic-clonic seizures) The hallmark seizure type is the generalized tonic seizure that most often occurs while falling asleep In most cases, LGS manifests between 2-8 years of age, represents 3-10% of all pediatric epilepsies and, in this condition, affects males more frequently than females There are two general subtypes: (1) cryptogenic (i . e . , there is no identifiable cause) in approximately a third of patients, and (2) symptomatic (i . e . , associated with a remote brain injury, usually acquired during the perinatal period or early infancy) . It is not uncommon for LGS to be preceded by a history of infantile spasms .

The major differential diagnostic consideration is myoclonic-astatic epilepsy (aka Doose syndrome), which appears between 2-5 years of age, often with generalized tonic-clonic seizures The affected child, however, is developmentally normal prior to onset of seizures, but developmental decline can occur if they are not controlled adequately. Within several months of onset, the characteristic drop attacks occur, along with atypical absence seizures There is also the syndrome of continuous spike-wave discharges in slow-wave sleep (aka electrical status epilepticus in slow-wave sleep, or ESES), which can result in speech/language regression, slow spike-wave discharges, as well as atonic and atypical absence seizures However, generalized tonic seizures do not occur with ESES Finally, epileptic spasms (i e , spasms that persist beyond infancy) can also produce drop attacks

Careful video-EEG monitoring of episodes can help distinguish between LGS and these other rare entities If the clinician obtains a generic history of drop attacks without other ancillary data (most importantly, the EEG), then other diagnostic considerations would include syncope (neurogenic or cardiogenic), cataplexy (seen in narcoleptic patients), and hyperekplexia (or "startle disease") It is important to note, however, that there are several epileptic syndromes and epileptic encephalopathies that share some but not all clinical and/or EEG features of LGS, and many LGS patients may lack all of the characteristic features, especially during the early stages of disease evolution

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