Overall, this observational cohort study aims too:

1. Implement rapid trio WGS for all children presenting to our health systems with epilepsy onset under 12 months of age.
2. Utilize electronic healthcare records and research databases to unite phenotypic and genomic data and to create a "virtual" registry across all institutions that will promote ongoing discovery.
3. Assess the impact of early genetic diagnosis on epilepsy, developmental, and health economic outcomes through formal longitudinal assessments of all children enrolled.

In the past decade, the genomic revolution has led to the identification of underlying genetic aetiologies for childhood epilepsy, in the form of monogenic disorders affecting ion channels, neurotransmitter receptors, synaptic proteins, and other families of proteins. In a growing number of cases, the specific genetic diagnosis informs prognosis and genetic counselling, leads to the opportunity to participate in natural history studies, and even to changes in treatment that, to date anecdotally, may change outcomes in seizures and in neurodevelopment. However, a major challenge in clinical practice is that early intervention requires early diagnosis.

Currently the diagnostic odyssey in early-onset epilepsy is long and arduous for patients and their families. The timing and nature of genetic testing for such patients varies widely within and across countries and institutions. Our collective expertise includes epilepsy genetics research, genomic research, clinical epilepsy, clinical trials, and team science across four leading paediatric institutions in the IPCHiP Consortium: Boston Children's Hospital (US), Great Ormond Street Hospital and UCL Great Ormond Street Institute of Child Health (UK), Royal Children's Hospital Melbourne and Murdoch Children's Research Institute (Australia), and The Hospital for Sick Children ("Sick Kids", Canada). Each of our institutions has a proven track record of discovery and translation to patients, and our combined efforts in epilepsy will set a new standard for multi-institutional research, data sharing, and improvement. To investigate our hypothesis that rapid genetic diagnosis and tailored management could improve outcomes, we propose a novel approach to streamline and accelerate diagnostics in these severely affected children.

Overall, this observational cohort study aims too:

1. Implement rapid trio WGS for all children presenting to our health systems with epilepsy onset under 12 months of age.
2. Utilize electronic healthcare records and research databases to unite phenotypic and genomic data and to create a "virtual" registry across all institutions that will promote ongoing discovery.
3. Assess the impact of early genetic diagnosis on epilepsy, developmental, and health economic outcomes through formal longitudinal assessments of all children enrolled.

Inclusion Criteria:

• Children under 12 months of age presenting with epilepsy.

Exclusion Criteria:

• Simple febrile seizures.
• Acute or remote symptomatic seizures due to sepsis, haemorrhage, cerebral infarction, hypoxic ischaemic encephalopathy or non-accidental injury.
• Structural malformations of the brain where the likely genetic cause is known such as tuberous sclerosis or lissencephaly.

Children with epilepsy onset under 12 months of age presenting to an epilepsy service. This is an international multi-centre collaborative study with GOSH as the UK sponsor.