*9.3.1 Background*

*Epilepsy - Advances in Diagnosis and Therapy*

During the wakefulness, it depends on the underlying etiology.

and 14 years and develops 1 or 2 years after the onset of seizures.

During the wakefulness, the EEG is characterized by focal or multifocal slow spikes, frequently intermixed with diffuse slow spikes and waves. In some children, the interictal EEG pattern may be similar to those observed in idiopathic focal epilepsies; in other cases, a background asymmetry, the presence of polyspikes or repetitive fast spikes, or other features may indicate underlying structural pathologies (e.g., disorders of neuronal migration). These interictal EEG abnormalities may increase when ESES starts; in addition, diffuse bursts of 2–3-Hz spike-and-wave

The typical EEG pattern consisted of continuous or sub-continuous slow spikeand-waves, at 1.5–2.5 Hz, persisting through all NREM sleep; it appears immediately after patients fall asleep. This EEG pattern is commonly observed between 4

The epileptic discharges can vary from mainly focal (frontal, centrotemporal,

etc.) or multifocal to unilateral, or diffuse (occasionally with shifting from a unilateral to a diffuse pattern in the same patient). In the original description, a spike-wave index (SWIs), ranging from 85 to 100% and measured during overnight sleep EEG recording, was considered an essential feature for the diagnosis [92]; however, SWIs under 85% have been used for the diagnosis of

The good outcome is the rule, independent of the etiology and is observed besides cortical malformations such as multilobar polymicrogyria. ESES syndrome has been associated with a few genes including neuroserpin/SRPX2 and ataxin 1/ ATX1 [23]; most recently, pathogenic de novo involves genes previously associated with autism (MDGA2 and SHANK3), seizures (GRIN2A), or language impairment (CDH13) [93]. Furthermore, SLC9A6 mutations have been found in patients with Christianson syndrome and CSWS [94]. The reason for manifestation of ESES in

The first description of the Landau and Kleffner syndrome (LKS) is due to William Landau and Frank Kleffner, who in 1957 reported six children with different types of seizures and acquired aphasia [2]. No other descriptions were made

LKS is a type of ESES syndrome which manifests with an acquired epileptic aphasia (auditory agnosia) that occurs in the child with already developed ageappropriate speech. Like ESES, LKS is characterized by epileptic EEG pattern particularly prominent during sleeping, with or without manifest clinical seizures. Although in the first descriptions LKS is not related to brain organic lesions, patients with LKS may have congenital or acquired brain lesions [11].

until the 1980s, when different authors described several new cases [95].

**8.3 Electroencephalography**

*8.3.2 Interictal abnormalities*

discharges may appear [11].

ESES syndrome as well [11].

most patients is not known [23].

**9. Landau-Kleffner syndrome (LKS)**

**8.4 Etiology**

**9.1 Overview**

*8.3.1 Background*

**96**

Normal.
