Of all of the neuro-physiological tests which are performed at our center, the electroencephalogram (EEG) is certainly one of the most important.  It enables us in most cases to : 1) confirm the diagnosis of Epilepsy 2) classify the particular epileptic syndrome 3) design an individualized therapeutic plan. In addition, it is a safe method which is innocuous and presents no discomfort to the patient.

EEGs can be divided as follows:

Standard EEG

It is comprised of  about 10 minutes with eyes closed in a relaxed state and about 5 minutes of EEG Activation. EEG Activation as defined by the International Federation of Clinical Neurophysiology Societies includes any procedure designed to enhance or elicit normal or abnormal EEG activity, especially epileptiform abnormalities.  Activation stimuli include various sensory modalities, electrical and pharmacological stimulation, and changes in behavioural state and consciousness.  Activation procedures used routinely in the EEG laboratory are: hyperventilation, photic stimulation, and sleep.

The purpose of these activation procedures is to identify abnormalities that might not otherwise be revealed. EEG is used to study the electrical activity of the brain, through the use of electrodes which are attached to the patient’s scalp..

The patient is placed in a comfortable bed or chair in a silent room with soft lights, and his/her eyes will be closed. He/she will be in a relaxed neuro-sensorial state.  The exam lasts about 15-20 minutes and entails two activation procedures.

1. Photic Stimulation

A bright strobe light, similar to that of strobe in a disco is flashed in front of the individual at different speeds.  This is done with eyes both open and closed. Flashing lights produce a standard response in the brain in most people, however, they can produce abnormal responses, including seizures in others.  This procedure can help identify individuals with photosensitive epilepsy who could  experience an epileptic seizure while in front of a flickering television screen or near a strobe light.

1. Hyperventilation

the individual is asked to breath more deeply than usual, with regular deep breaths in and out for about three minutes (depending on age and pathology). Over-breathing in this manner produces changes in the brain’s electrical activity and may highlight abnormalities that could not otherwise be seen in the normal EEG activity.

EEG after sleep deprivation

During this exam, the patient’s brain activity will be measured after he/she has slept a maximum of 3-4 hours the night before.  Early, the following morning, the individual will be placed in a comfortable bed where he/she will be asked to close his/her eyes, stay as relaxed as possible and attempt to fall asleep.  The objective of this exam is to reveal abnormalities that were not present in the standard EEG. This exam lasts longer than the standard EEG. As with the each EEG exam, the patient will undergo hypoventilation and photic stimulation.

EEG with additional electrodes

This exam is also similar to the EEG awake, but additional electrodes are placed in different areas of the scalp and the body, for example, on specific muscles in order to study the movements of these muscles in correlation with electrical brain activity. Likewise, it is possible to attach electrodes to other areas of the body, such as to the thorax (to record elettrocardiographic or respiratory activities), or next to the eyes for recording of ocular movements.

Quantitative EEG

In the not too distant past, EEGs were printed on paper using instruments similar to those of today, but although the cerebral signals represented were accurate – they did not provide an easy way to store the data, and most importantly, they did not offer a complete analysis of brain activity.

Quantitative  EEG in a term for analysis of the EEG signals with mathematical formulas or statistical comparisons. This has enabled further elaboration of the data by means of numerical results, statistical tables or datagraphs.

Ambulatory EEG Monitoring

This EEG provides long-term EEG recording that can be obtained in a non-clinical setting (e.g. home or office) without the need for continous supervision by technical personnel.

This EEG  monitors cerebral activity in the span of a about a 24-hour period (solar) while the patient is at home or performing normal daily activities.  Within these 24 hours, different movements are recorded in a diary which has been given to the patient.  This enables the identification of possible abnormalities or crisis that do not show up in the standard EEG and which usually last much less time.

Ten electrodes are positioned on the patient’s scalp and fixed by a collodion technique which enables the electrodes to stay in place for 24 hours without being dislodged, and the data is recorded on a portable computer attached to the patient. Upon completing the exam period, the patient returns to our center to have the electrodes removed.  It is a painless procedure which causes no discomfort. The information gathered in the personal diary is then studied by the appropriate medical staff.