Familiarize with the principles of techniques involved.
To know about frequencies and amplitudes of the record obtained.
Categories the records into.
appropriate rhythms – α, β, θ,and δ.
Identify and describe changes produced by - provocation tests.
e.g. eye opening & closing, intermittent photic stimulation (IPS) clapping sound, induce thinking & hyperventilation.
Appreciate clinical uses of EEG specially in Intensive care setup-NICU & PICU.
The Ideal EEG should Contain
Hyperventilation : when able to cooperate and if not medically contraindicated (HgbSS, Congenital heart disease, CF or active asthma).
Photic Stimulation: if greater than 6 months of age.
Characteristics of pediatric EEG
Significant maturational changes : Growth and development.
High amplitude, low frequency.
Unique waves POSTs.
The first recordings were made by Hans Berger in 1929.
Graphical depiction of cortical electrical activity, usually recorded from the scalp.
Advantage of high temporal resolution but poor spatial resolution of cortical disorders.
EEG is the most important neurophysiological study for the diagnosis, prognosis, and treatment of epilepsy.
Physiological Basis of the EEG
a) Site of EEG Generation
Extracellular dipole generated by excitatory post-synaptic potential at apical dendrite of pyramidal cell.
EEG machine (24/32 channels).
Silver cup electrodes/metallic bridge electrodes.
Quiet dark comfortable room.
Skin pencil & measuring tape.
Procedure of EEG Recording
A standard EEG makes use of 21 electrodes linked in various ways (Montage).
Ask the subject to lie down in bed.
Apply electrode according to 10 / 20% system.
Check the impedance of the electrodes.
Select a montage.
Press run switches on to run the paper.
Press the calibration knob to check voltages & time constant.
Always observe the subject for any abnormal muscle activity.
Ask the subject to open eyes for 10 sec.and ask him/her to close eyes. (do this procedure several times in each montage).
Each electrode site is labelled with a letter and a number.
The letter refers to the area of the brain underlying the electrode.
e.g. F - Frontal lobe and T - Temporal lobe.
Even numbers denote the right side of the head and.
Odd numbers the left side of the head.
Bipolar – both the electrodes are at active site Bipolar montage are parasagital montage.
Unipolar – one electrode is active and the other is indifferent kept at the ear lobe.
Alpha wave -- 8 – 13 Hz.
Beta wave -- >13 Hz. (14 – 30 Hz.)
Theta wave -- 4 – 7.5 Hz.
Delta waves – 1 – 3.5 Hz.
Use of EEG
b) To prognosticate
c) Localize brain tumours.
d) Sleep disorders (Polysomnography)
Sleep apnea syndrome
Insomnia and parasomnia
e) Helpful in knowing the cortical activity, toxicity, hypoxia and encephalopathy.
f) Determination of brain death.
Flat EEG(absence of electrical activity) on two records run 24 hrs apart.