The main aims of this study are to gather information about how many children, teenagers and adults in Spain have been diagnosed with Dravet syndrome and Lennox-Gastaut syndrome as well as to learn about the number of new Dravet syndrome and Lennox-Gastaut syndrome cases in persons in Spain.

Participants' data will be taken from their medical records (charts), which were already collected as a part of their routine care in public hospitals in Spain between 01 January 2021 and 31 December 2022.

This is a non-interventional, retrospective study of participants from Spain with DS and LGS at public hospitals. The participants will be identified from their medical charts or hospital records and those who meet the eligibility criteria will be included.

This multi-center trial will be conducted in Spain. Data will be retrospectively collected for the observation period between 01 January 2021 to 31 December 2022. The total duration of the study is approximately 24 months.

Inclusion Criteria:

A. 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 tonicclonic, 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.

B. 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 seiures, atypical absence seizures, atonic seizures, myoclonic seizures, focal impaired awareness, epileptic spams, or non-convulsive status epilepticus v. Slow (<2.5 hertz [Hz]) spike-and-wave EEG pattern. vi. Paroxysmal fast activity (10 Hz or greater) in sleep.

Lennox-Gastaut syndrome - wider criteria:

• At least one the following criteria must be met:

  i. Tonic seizures. ii. Multiple types of seizures, including generalised tonic-clonic seizures, atypical absence seizures, atonic seizures, myoclonic seizures, myoclonic-atonic seizures, focal seizures, epileptic spams, or nonconvulsive status epilepticus.

• And at least one the following criteria must be met:

  i. Slow (<2.5 Hz) spike-and-wave EEG pattern. ii. Paroxysmal fast activity (10 Hz or greater) in sleep.

• And at least two of 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. Development/cognition impairment starts prior to seizures onset. iv. History of Infantile epileptic spasms syndrome (IESS), West or Ohtahara syndromes.

Exclusion Criteria

1. Participants with epileptic condition other than DS or LGS.
2. Participants with DS or LGS not residents in the reference area of the hospital.

Participants diagnosed with DS or LGS at public hospitals in Spain will be enrolled in the study.

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.