**3. Preparing pediatric patients for EEG study**

Performing electroencephalography (EEG) in children can be quite challenging as most of these children are not cooperative during this study due to the great fear and restlessness during the EEG procedure. It is vitally important to prepare a Pediatric patient for EEG study in order to have better interpretation of the EEG results. The application of psychological technique prior to the study and the availability of the parents during the procedure can be helpful to conduct the study smoothly and minimize the need for premedication drugs. However, the behavioral and psychological techniques are not always successful in a small proportion of children. Different premedication protocols have been proposed in order to alleviate the great distress and anxiety during the study. The ideal pharmacological agents for such procedure should have a minor impact on the EEG tracing with fast onset and few side effects. Benzodiazepine is the most common premedication agent used with Midazolam being the most popular drug to induce sedation for EEG study in children [15].

Chloralhydrate is another medication which has been used to induce sedation in the Pediatric population during different neurological studies including EEG. Chloralhydrate is a safe, cheap hypnotic non-opiate drug with no major side effects with the exception of vomiting in few cases. Chloralhydrate has been also shown to be effective and more time saving during EEG procedure [16].

### **4. Technical aspects of electroencephalography**

Electroencephalography EEG, since it's first introduction early in the 20th century, has been an essential and the most common neurophysiological device to monitor and study the electrical and functional activity of the brain [17]. EEG is a commonly used non-invasive tool to track and record the electrical field potentials captured by electrodes placed on the patient scalp. These electric field potentials

*Electroencephalography - From Basic Research to Clinical Applications*

during impaired consciousness level (**Figure 2**) [8–10].

*Hans Berger, German neurologist and psychiatrist (1873–1941) [11].*

In 1875, Richard Caton an English physician reported a spontaneous electrical variation from exposed cortical brain hemispheres of rabbits and monkeys [8]. Early in the twentieth century, specifically in 1912, Vladimir Vladimirovich Pravdich-Neminsky a Russian Physiologist reported the first electrical brain impulse and evoked response in animals (dog) [8]. However, in 1924 German Neurologist and Psychiatrist Hans Berger recorded the first human EEG in a graph paper which later named an electroencephalogram (EEG) device. Berger subsequently characterized different rhythmic nature and wave patterns of the brain activity based on the different physiological state of the subjects (**Figure 1**) [8]. The initial description of clinical encephalography was first reported by an American neurologist Frederic Andrews Gibbs in 1935 who initially documented the classical interictal spikes associated with epilepsy and first to demonstrate the typical 3 per second spike and wave discharges associated with absence epilepsy. He also described EEG pattern

**1.1 History**

**136**

**Figure 2.**

**Figure 1.**

*The classical 3 per second spike and wave discharges was first described by Frederic Gibbs [10].*

created by dipoles as a result of excitation of the epical dendritic postsynaptic potential at the cortical pyramidal cells [18, 19]. The measurement and assessment of the electric field potentials can be made by attaching conductive electrodes to the human scalp. At the present time the wet electrodes are the gold standard used for EEG study [19]. A conductive paste or gel need to be used during the application of wet electrodes to minimize electrode-skin impedance in order to achieve good conductivity of the electrical impulse. The typical value of skin impedance should be kept between 5 and 20 KΩ. This skin impedance should be continuously monitored during the EEG study to ensure proper and high-quality conductivity between the skin and the EEG electrode. Performing an EEG study is a time consuming process which require an expert EEG technician or neurophysiologist in order to obtain good quality EEG results for proper interpretation and reporting as the reading and analyzing EEG data is a hard task and must be interpreted by expert neurophysiologists. The location site and description of the scalp electrodes is well recognized by the international 10–20 system (**Figure 3**) [19, 20].

During the first EEG only 20–50% of patients with seizure disorder show interictal epileptiform discharges (IED) so the yield of the EEG study can be enhanced by many activation methods in order to capture the interictal epileptiform discharges which help confirming the diagnosis of epilepsy and seizure disorder [22]. The common activation procedure used in EEG laboratories includes Hyperventilation, intermittent photic stimulation (IPS), sleep and sleep deprived techniques. Hyperventilation (HV) is considered to be the first and oldest activation method used to trigger the interictal epileptiform discharges (IED) especially the one associated with absence epilepsy. HV is more effective in Pediatric population than in adult. A proper effective HV should be carried out for full 3 minutes with continuous recording and monitoring for one-minute post hyperventilation. HV is more efficient in diagnosing generalized seizures than focal epilepsy. The mechanism of HV to trigger interictal epileptiform discharges can be explained by hypocapnia induction which also manifest as background slowing or focal slowing in the EEG [22]. HV is a major provocation technique used to trigger the typical 3-Hz spike-and-wave discharge (SWD) which is characteristic for absence epilepsy as more than 90% of patients who have absence epilepsy show SWD during HV. The non-specific thalamic projection system (NSTPS) which is a part of the thalamocortical networks triggered by respiratory alkalosis and considered to be the major induction of SWD associated with absence epilepsy during the process of HV [23]. HV is an efficient and safe activation method for epilepsy and seizure disorder provocation however there are certain contraindication to perform HV during EEG study which includes patients with cardiopulmonary disease, sickle

**139**

*Basic Electroencephalogram and Its Common Clinical Applications in Children*

cell anemia, Moy-Moya disease, subarachnoid and intracerebral bleeding and

A standard activation procedure used during the routine EEG study is the intermittent photic stimulation. This procedure done in a dimmed light room and application of different light frequencies between 1 and 30 Hz for 5 to 10 seconds during eye closure. The flashing light device should be kept 30 cm form the patient eyes. The response to intermittent photic stimulation (IPS) can be seen as an evoked potentials at frequencies less than 5 Hz seen posteriorly or drive response at the occipital regions or in the form of photoparoxysmal response (PPR) which was previously named photoconvulsive response. The most common types seizure disorder seen with IPS are absence epilepsy, myoclonic and tonic–clonic seizures [22].

Among the activation techniques used during routine EEG study is the sleep and sleep deprived approach which produce the maximum yield of interictal epileptiform discharges (IED) as compared to the hyperventilation and intermittent photic stimulation procedure. The young age patients tend to have better yield of IED with

A Brain Computer Interface (BCI) which also named as Brain –machine Interface

The American Clinical Neurophysiology Society suggest at least 20 minutes' time duration for routine outpatient study. However, the International League against Epilepsy suggests a minimum 30 minute for routine EEG recording. Currently most routine EEG studies are done with an average time between 20 and 30 minutes. The abnormal epileptiform discharges found in 29–55% in patients with epilepsy on their first routine EEG study. Ambulatory prolonged EEG study is considered to be helpful diagnostic technique to capture interictal epileptiform discharges (IEDs) in epilepsy patients whom their first routine EEG studies reported normal. Prolonged ambulatory EEG study is considered to be superior to routine EEG in identifying IEDs specially during the natural sleep state. This procedure is also helpful to differentiate epileptic from non-epileptic psychogenic events. The duration of the ambulatory EEG study usually between 24 to 96 hours [27, 28].

Epilepsy Monitoring Unit (EMU) is an important and crucial part of the neurophysiological work up for the diagnosis and classification of epilepsy and evaluation of psychogenic non-epileptic seizures (PNES). EMU is also essential for patients

(BMI) is a computer- build network system that allow direct communication between cerebral brain activity and external recordable machine without using human muscles or peripheral nervous system. BCI utilize and analyzes the brain signals to collect information and send them to output system. BCI network consists of five phases: Signal Acquisition, Signal Magnification, Feature Extraction, Categorization and Control Interface. BCI assesses and analyze brain activity through mainly electrophysiological and hemodynamic studies. The electrophysiological study consists mainly of EEG, electrocorticography and magnetoencephalography. The hemodynamic study measures glucose uptake by an active neurons and this can be evaluated by procedures like functional magnetic resonance and infrared spectroscopy. BCIs commonly used EEG to gain details from brain activity. The design of BCI is complex due to restricted resolution and data reliability detected by

*DOI: http://dx.doi.org/10.5772/intechopen.94247*

each activation technique than older patients [24].

**5. Brain computer interface**

the brain [25, 26].

**6. Different types of EEG study**

severe carotid stenosis [22].

**Figure 3.** *The international 10-20 system [21].*

*Basic Electroencephalogram and Its Common Clinical Applications in Children DOI: http://dx.doi.org/10.5772/intechopen.94247*

cell anemia, Moy-Moya disease, subarachnoid and intracerebral bleeding and severe carotid stenosis [22].

A standard activation procedure used during the routine EEG study is the intermittent photic stimulation. This procedure done in a dimmed light room and application of different light frequencies between 1 and 30 Hz for 5 to 10 seconds during eye closure. The flashing light device should be kept 30 cm form the patient eyes. The response to intermittent photic stimulation (IPS) can be seen as an evoked potentials at frequencies less than 5 Hz seen posteriorly or drive response at the occipital regions or in the form of photoparoxysmal response (PPR) which was previously named photoconvulsive response. The most common types seizure disorder seen with IPS are absence epilepsy, myoclonic and tonic–clonic seizures [22].

Among the activation techniques used during routine EEG study is the sleep and sleep deprived approach which produce the maximum yield of interictal epileptiform discharges (IED) as compared to the hyperventilation and intermittent photic stimulation procedure. The young age patients tend to have better yield of IED with each activation technique than older patients [24].
