Science Stories

Understanding Rare Forms of Epilepsy

Epilepsy is a neurological disorder characterized by the occurrence of at least two unprovoked seizures occurring more than 24 hours apart or by one unprovoked seizure with a high probability of further seizures.1 Epilepsy is one of the most common neurological diseases globally, with approximately 50 million people worldwide impacted by epilepsy.2

Neurological disorders, like epilepsy, can have significant, life-altering implications for patients, their families and caregivers. Specifically, within the epilepsy field, there is a large unmet patient need as approximately 1 million people living with epilepsy are resistant to current treatments, with an estimated 160,000 of those patients being pediatric patients.3

At Jazz, we have focused our efforts on epilepsy syndromes, which are rare and severe forms of epilepsy. An epilepsy syndrome is defined by a group of features that occur together, typically including specific seizure types, EEG patterns, comorbid conditions such as intellectual impairment and sometimes, genetic mutations.4 At Jazz, we are pursuing research approaches that address three types of epilepsy syndromes, including Dravet syndrome, Lennox-Gastaut syndrome (LGS) and tuberous sclerosis complex (TSC).

Dravet Syndrome

Dravet syndrome is a rare, severe, lifelong form of epilepsy that typically begins in the first year of life, and results in frequent and/or prolonged seizures. Previously known as severe myoclonic epilepsy in infancy (SMEI), it affects between 1 in 20,000 to 1 in 40,000 people in the U.S.5,6 Children with Dravet syndrome are also at risk of sudden unexpected death in epilepsy (SUDEP), prolonged seizures or seizure-related accidents such as infections.7

Most children with Dravet syndrome develop some level of developmental disability and have other conditions that are associated with the syndrome, including movement and balance issues, orthopedic conditions, delayed language and speech issues, growth and nutrition issues, sleeping difficulties, sensory integration disorders and disruptions of the autonomic nervous system.8 Some children may experience a prolonged seizure event, known as status epilepticus, that often requires medical intervention to bring the seizure to an end – these long seizures are very dangerous and increase the chance of mortality.8,9 The constant supervision required for many of these patients can be emotionally draining, highly stressful and financially overwhelming for families.10

Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is a form of childhood-onset epilepsy that can be one of the most difficult seizure disorders to treat due to its complex symptoms.11 Disease onset typically appears between two and eight years of age, and typically includes the presence of generalized seizures, drop seizures and delayed intellectual development.12 LGS accounts for approximately one to four percent of all cases of childhood epilepsy and affects an estimated 48,000 children and adults in the United States.13

Most children with LGS experience a multitude of health issues, ranging from physical impairments to emotional and intellectual disabilities, including behavioral and personality disturbances, such as poor social skills, inability to solve problems, mood instability and attention-seeking behavior.11 Similar to Dravet syndrome, children with LGS may experience status epilepticus, which can be very dangerous and increase mortality.9,11 Although there may be changes to seizure type, impaired mental function and behavioral issues remain, resulting in the need for lifelong care.11 The constant supervision required for many of these patients can be emotionally draining, highly stressful and financially overwhelming for families.

Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a highly variable, rare genetic disorder that causes tumors to form in the brain and other vital organs such as the kidneys, heart, eyes, lungs and skin.14 Nearly one million people worldwide are estimated to have TSC, and there are approximately 50,000 cases of TSC in the United States.15 Approximately 85% of individuals with TSC will have seizures at some point during their life.16

Individual signs of TSC vary from each patient, as well as the system and organs affected. TSC usually affects the central nervous system and results in a combination of symptoms — ranging from very mild to quite severe — including primarily focal seizures, cognitive impairment and behavior problems. While many people living with TSC show evidence of the disorder in the first year of life, numerous cases may remain undiagnosed for years or even decades due to the relative obscurity of the disease and the mild form that symptoms may first take in some people.15 Additionally, seizure burden, although is more variable in this population, can be emotionally draining and highly stressful for families.

Importance of Early Diagnosis & Commitment to Patients

Unfortunately, some people who are impacted with these rare and severe forms of epilepsy may experience a long road to diagnosis; many may experience uncontrolled seizures, with others even reaching adulthood before receiving an accurate and specific diagnosis.17 Although epilepsy syndromes such as Dravet syndrome, LGS and TSC can be difficult to diagnose, it is important to be diagnosed early as it can open the door to appropriate treatment options. Therefore, knowing the signs and symptoms can make all the difference. To learn more and for additional information on these rare and severe seizure disorders, please visit

It is crucial to manage the challenges of these rare and severe forms of epilepsy for all those impacted, from patients to loved ones to caregivers. Here at Jazz, we are committed to leveraging our experience in neuroscience to develop meaningful, differentiated options that address the needs of those living with epilepsy. We’re listening to patients, their care teams, and leading industry experts, while deepening our relationships with neurologists, so we can more comprehensively support those who need it. We do this knowing that, with every decision we make, we can improve a person’s physical, emotional and mental well-being—and even change the trajectory of their life.


  1. Fisher RS, Acevedo C, Arzimanoglou A, et al. ILAE official report: a practical clinical definition of epilepsy. Epilepsia. 2014;55(4):475-482.
  2. World Health Organisation. Epilepsy. June 2019. Available at: Accessed: Nov 2020.
  3. Epilepsy Foundation. Drug-Resistant Epilepsy. Available at: Accessed November 23, 2021.
  4. Epilepsy Foundation. Types of Epilepsy Syndromes. Available at:
  5. Dravet C. The core Dravet syndrome phenotype. Epilepsia. 2011;52(Suppl. 2):3-9.
  6. Dravet C, Bureau M, Oguni H, Cokar O, Guerrini R. Dravet syndrome (severe myoclonic epilepsy in infancy). In: Bureau M, Genton P, Dravet C, et al., eds. Epileptic Syndromes in Infancy, Childhood and Adolescence. Montrouge, France: John Libbey Eurotext Ltd.; 2012:112-156.
  7. Cooper MS, Mcintosh A, Crompton DE, et al. Mortality in Dravet syndrome. Epilepsy Res. 2016;128:43-47.
  8. Dravet Syndrome Foundation. What is Dravet Syndrome? Available at Accessed May 15, 2018.
  9. Epilepsy Foundation. What is Status Epilepticus? Available at Accessed May 15, 2018.
  10. Wirrell EC, Laux L, Donner E, et al. Optimizing the diagnosis and management of Dravet syndrome: recommendations from a North American consensus panel. Pediatr Neurol. 2017;68:18-34 e13.
  11. LGS Foundation. About Lennox-Gastaut Syndrome. Available at Accessed May 15, 2018.
  12. van Rijckevorsel, K. Treatment of Lennox-Gastaut syndrome: overview and recent findings. Neuropsychiatric disease and treatment 4, 1001–1019 (2008).
  13. LGS Foundation. Lennox-Gastaut Syndrome Fact Sheet. Available at Accessed November 23, 2021.
  14. Goh S, Kwiatkowski DJ, Dorer DJ, et al. Infantile spasms and intellectual outcomes in children with tuberous sclerosis complex. Neurology. 2005;65:235-238.
  15. TS Alliance, What is TSC? Accessed April 15, 2019.
  16. Kingswood JC, d’Augeres GB, Belousova E, et al. TuberOus Sclerosis registry to increase disease Awareness (TOSCA) — baseline data on 2093 patients. Orphanet J Rare Dis. 2017;12(1):2.
  17. Seizures are Signs. Seizure Disorders. Available at Accessed November 3, 2021.