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ELECTRO ENCEPHALO GRAPHY

  • 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


  • Awake
  • Drowsiness
  • Transitions
  • Sleep
  • Arousal
  • Activation

  • 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


  • Age-specific.
  • Significant maturational changes : Growth and development.
  • High amplitude, low frequency.
  • Unique waves POSTs.
  • Lambda wave.
  • Hypnagogic hypersynchrony.
  • Hypsarrythmia.
  • 3Hz SWC.
  • Rolandic Spikes.

  • Electroencephalogram (EEG)


  • 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.
  • b) Requirements

  • EEG machine (24/32 channels).
  • Silver cup electrodes/metallic bridge electrodes.
  • Electrode jelly.
  • Rubber cap.
  • 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 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 for several times in each montage).

  • EEG Electrodes


  • Each electrode site is labeled with a letter and a number.
  • The letter refers to the area of 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 ear lobe.

  • EEG Waves


  • 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


    a) Epilepsy


  • Generalized seizures.
  • Absence seizures.

  • b) To prognosticate


    c) Localize brain tumors.


    d) Sleep disorders (Polysomnography)


  • Narcolepsy
  • 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.
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