**2. Materials and methods**

### **2.1 Epileptic children**

Forty-three patients with ages of 3–9 years and with different forms of epilepsy were recruited. Three EEGs' registration took place: before treatment, second (3 months), and third (6 months) after treatment with valproic acid-depakin (Dep), 30–50 mg/kg treatment. They appealed at the Center of Experimental Biomedicene.

The diagnosis was done based on the International Classification of Epilepsy and Syndromes [4], clinical history, and neurological and MRI investigations. Classification of patients by seizure types and epileptic syndromes accurately identified the patients at risk for Dep-exacerbated epilepsy [22, 23]. Study involved both EEG and clinical analyses. Patients were characterized for the Dep dose, type and frequency of seizures, and EEG and Dep plasma levels [24, 25], both before and during the treatment. Out of 45 patients who received treatment, three of them developed undesirable effects. Although the physician adjusted the Dep dose, it did not improve the clinical outcome in two patients. Thus, these patients were excluded from the study. In summary, the present study included only 43 children of 3–9 years of age (**Table 1**).

The EEG investigation followed international performance standards [26] as part of the prescribed therapy plan. This plan was also approved by the parents and institutional ethics committee.

#### **2.2 The EEG recording and methods of analysis**

All patients underwent EEG recording three times: once—before administration of Dep (first visit) and twice—during Dep treatment, (i) 3–4 months later (the second visit) and (ii) 6–8 months later (the third visit).

The EEG registration was done with closed and open eyes. Functional test was performed with rhythmic photostimulation; hyperventilation and registration were ended with closed eyes. The duration of registration was 35–55 min.

The EEG signals were digitally recorded using a set of 19 scalp electrodes according to the International 10–20 system [26] and ENCEPHALAN 131–03, professional version "MEDICOM."

For an individual patient, a 10 s, artifact-free EEG pattern was analyzed.

A qualitative assessment of the EEG characteristics was performed in accordance of the age standards [27].

A quantitative EEG pattern of signal processing and the power spectrum was obtained for each lead. The spectral analysis was used to calculate the absolute value [28] of power (AVP, μV^2s) within six frequency bands: delta (0.5–4.0 Hz), theta-1 (4.0–6.0 Hz), theta-2 (6.0–8.0 Hz), alpha (8–13 Hz), beta-1 (13–24 Hz), and beta-2 (24–50.8 Hz) (**Figure 1**).


*The Dynamic of EEG Characteristics in Epileptic Children during the Treatment with Valproic… DOI: http://dx.doi.org/10.5772/intechopen.93574*

*GS: generalize seizure; ABS: absence; SPS: simple partial seizure; CPS: complex partial Seizure; and PSG: partial, sometimes with secondarily generalization.*

#### **Table 1.**

*Characteristic of patients.*

Alpha, beta, delta, and theta frequency bands were characterized by the wave amplitude, stability, and domination area.

Brain topography was conducted for the quantitative study.

#### **Figure 1.**

*Dynamics of absolute values of power spectra (AVP) at different stages of treatment. Summarizes results obtained from the quantitative analysis of the EEG dynamics, total of AVP (TAVP), and below the AVP of different frequency bands. X-line: F-frontal, C-central, T-temporal, O-occipital, and P-parietal regions of the brain cortex. Black columns—before treatment, shaded columns—3 months, and white columns—6 months after the initiation of Dep treatment. Y-line: power value—μV^2s.*

### **2.3 Statistical analysis**

Statistical significance for each endpoint measures was assessed using Mann– Whitney U-test (BIOSTAT). The data obtained before treatment served as a baseline for assessing the dynamics of EEG characteristics during treatment. Thus, each subject served as its own control in the evaluation of EEG during treatment.

*The Dynamic of EEG Characteristics in Epileptic Children during the Treatment with Valproic… DOI: http://dx.doi.org/10.5772/intechopen.93574*

The changes in the EEG characteristics were assessed using Wilcoxon signed-ranks test [29]. The significance was set at p < 0.05.
