**1. Introduction**

The concept of epileptic encephalopathy (EE) is based on the clinical descriptions of some epileptic syndromes during the last century, such as West syndrome (WS) and Lennox-Gastaut syndrome (LGS). Delay in development in one, and intellectual disability in the other, was considered partly due to interictal epileptic discharges [1]. The idea that not only seizures but also apparently subclinical epileptic activity could affect cognitive functions was gaining strength in the scientific community related to epilepsy. According to this, the control of this epileptic activity could improve these deficits [1]. This notion was better profiled in the description of neuropsychological deficits related to continuous or sub-continuous paroxysmal activity during sleep, with the first description of the Landau-Kleffner syndrome (LKS) [2].

The definition of EE was better defined by Dulac in the 1990s and was incorporated into the proposed classification of the International League Against Epilepsy (ILAE) in 2001 [3]. In this proposal, the term EE was used for disorders in which "the epileptiform anomalies themselves are believed to contribute to the progressive disturbance of

brain function." In 2006, Engel defined EE as disorders in which the evidence suggests the idea that neurological impairment depends on epilepsy and not on an underlying metabolic, degenerative, or encephalitic process, so that it excludes these progressive etiologies from the possible etiologies of EE [4]. Engel also emphasizes the importance of distinguishing between the deficits that are due to the cause of epilepsy, those that are due to pharmacotherapy, and those that are due to epilepsy itself.

The ILAE Working Group of 2010 pointed out the recognition achieved by the scientific community in relation to the EE [5]. The notion that epileptic activity itself may contribute to cognitive and behavioral deficiencies that exceed beyond what might be expected from causal pathology alone underlies the concept of EE. Deficits caused by epileptic discharges can be global or focal and can occur in a broad spectrum of severity.

In 2012, Capovilla proposed the term epileptogenic encephalopathy. They refer to progressive disorders of various etiologies that can cause deterioration and epilepsy, such as brain tumors, neurodegenerative or metabolic diseases, and presumed inflammatory or autoimmune conditions [1]. In epileptogenic encephalopathies, deterioration is independent of epilepsy, even if epilepsy could worsen the clinical picture; in some cases, the same etiology can produce encephalopathy without epilepsy. This distinction is important for the treatment; in the EE the treatment must be aggressive. On the other hand, if the deterioration is due to the etiology, there is a risk of unjustified excessive treatment. It is known that drugs, especially in polytherapy, can aggravate the neuropsychological deficits in these patients.
