What are DEEs?

Here’s what you need to know about Developmental and Epileptic Encephalopathies (DEEs)

Watch Our Introductory Webinar

We launched this project with this overview of DEEs with Tracy Dixon-Salazar, PhD - Director of Research and Strategy, LGS Foundation

A predominant feature is that the epileptic activity itself may be contributing to severe cognitive and behavioral impairments distinct from what might be expected from the underlying etiologies. The science is of course very important – but we find this new concept also lays the groundwork for a new community of families, across genetic or other causes, sharing common experiences in optimizing the care of their similarly challenged children.

“The new concept of developmental and epileptic encephalopathy is based on the understanding that many genetic epilepsies are associated with developmental impairment as a direct consequence of the genetic mutation, in addition to the effect of the frequent epileptic activity on brain development. As an example, in infants with KCNQ2 or STXBP1 encephalopathy, seizures may be controlled early after onset or cease spontaneously after a few years, but the developmental consequences tend to remain profound. The term “developmental and epileptic encephalopathy” expresses the concept that the genetic defect may be responsible for both the epilepsy and adverse development which is crucial to understanding the disease process for both families and clinicians.”

— Neonatal Developmental and Epileptic Encephalopathies


“Epileptic encephalopathies represent a group of devastating epileptic disorders that appear early in life. They are characterized by pharmacoresistant generalized or focal seizures, persistent severe EEG abnormalities, and cognitive dysfunction or decline. The ictal and interictal epileptic discharges are age-specific and either are the main cause or contribute to cognitive deterioration in the idiopathic or symptomatic group, respectively. Despite choosing the most appropriate antiepileptic drugs for the seizure type and syndrome, the results are often disappointing, and polytherapy and/or alternative therapy becomes unavoidable; in those cases, consideration should be given to the quality of life of the child and carers.”

— Epileptic Encephalopathies in Infants and Children


“Epileptic encephalopathy refers to a group of epileptic disorders that epileptic activities per se cause adverse impacts to the patient’s development (1). Developmental and epileptic encephalopathy (DEE) is a recently introduced concept with the advances in genetic diagnosis, as genetic etiologies can cause developmental delay irrespective of epileptic activities (2). The causes of DEE can be various including structural and metabolic etiologies. Moreover, owing to advances in genetic testing technologies, such as next-generation sequencing (NGS), research has revealed that diverse genetic mutations, especially de novo monogenic mutations, constitute a significant portion of the etiologies of DEE (3). The discovery of causative genes for DEE has amplified the efforts to improve our understanding of the pathophysiology of each genetic mutation, with the ultimate objective of precision medicine.”

— Frontiers in Neurology


“The term epileptic encephalopathy describes a heterogeneous group of epilepsy syndromes associated with severe cognitive and behavioral disturbances. These disorders vary in their age of onset, developmental outcome, etiologies, neuropsychological deficits, electroencephalographic (EEG) patterns, seizure types, and prognosis, but all may have a significant impact on neurological development.

In 2001, the International League Against Epilepsy (ILAE) Task Force on Classification and Terminology proposed a modified diagnostic scheme for epileptic seizures and epilepsy that, for the first time, recognized epileptic encephalopathies as a distinct category.

The ILAE defined an epileptic encephalopathy as a condition in which “the epileptiform EEG abnormalities themselves are believed to contribute to a progressive disturbance in cerebral function.”
Later in 2010, researchers defined epileptic encephalopathy as a condition where the epileptic activity itself may contribute to severe cognitive and behavioral impairments above and beyond what might be expected from the underlying pathology alone (e.g., cortical malformation), and that these can worsen over time.

… A common feature is that these disorders are usually refractory to standard antiepileptic drugs (AEDs).”

— Epileptic and Epileptiform Encephalopathies