A Study on Dravet Syndrome (DS) and Lennox-Gastaut Syndrome (LGS) in Children, Teenagers and Adults in Portugal

The main aim of this study is to learn about the percentage of persons diagnosed with Dravet Syndrome (DS) and Lennox-Gastaut-Syndrome (LGS) in 2022 and of persons newly diagnosed in 2021 and 2022 compared to the overall population in Portugal. Other aims are to understand how many percent of the persons diagnosed with DS and LGS are children, teenagers or adults and gather additional information on diagnosis and persons diagnosed with DS and LGS in Portugal. Information will be taken from a participant's existing medical hospital records. It is planned to review data in approximately 3 public hospitals in Portugal. No personal information of the participants will be collected.

Inclusion Criteria: 1. Diagnosis criteria for DS: • All the following criteria must be met: i. Seizures onset within 1-20 months (usually within the first year of life). ii. Normal initial development prior to presentation (no cognitive or behavioural disability before the onset of seizures) followed by behaviour and cognitive impairment. iii. Recurrent focal clonic (hemiclonic) febrile and afebrile seizures (which often alternate sides from seizure to seizure), focal to bilateral tonic-clonic, and/or generalized clonic seizures. • And at least one of the following criteria must be met: i. Emergence of other seizure type, including atypical absence seizures, myoclonic seizures, atonic seizures, or non-tonic-clonic status epilepticus between 1-4 years. ii. Seizures triggered by fever due to illness or vaccinations, hot baths, sudden temperature changes, high level of activity, or by strong lighting or exposure to certain visual patterns. iii. Mutations or copy number variants in the SCN1A gene. 2. Diagnosis criteria for LGS: Given the uncertainties associated with the diagnosis of this condition, two different criteria will be used, a stricter criterion, intended to identify "pure" Lennox-Gastaut syndrome participants, and a wider criterion, intended to also include the so-called Lennox-Gastaut-like participants. Lennox-Gastaut syndrome - stricter criteria: • All the following criteria must be met: i. Seizures onset before 18 years of age, typically from 1 to 8 years. ii. Progressive development/cognition impairment after seizures onset. iii. Tonic seizures. iv. At least one additional seizure: generalised tonic-clonic seizures, atypical absence seizures, atonic seizures, myoclonic seizures, focal impaired awareness, epileptic spams, or non-convulsive status epilepticus v. Slow (less thank \[\