ELECTROENCEPHALOGRAM – Purpose, Mechanism, Wave Patterns, Preliminary Assessment, Preparation of the Patient and the Environment, Equipment, Procedure, Interpretation and Nursing Implications
Electroencephalogram (EEG) is a noninvasive procedure, in that electrodes are placed over the skull in many areas and the electric activity of the various segments of the brain is recorded
Electroencephalogram is painless and a safe technique for evaluating the brain pathology such as brain tumors, brain abscess and epilepsy
PURPOSE
- To detect any abnormality in the brain such as space occupying lesion (SQL)
- EEG serves best to identify seizure disorders by type and area of origin within the brain
- To measure the cerebral oxygen, glucose, and blood flow in the brain
MECHANISM
An EEG is an instrument of electrical activity of the superficial layers of the cerebral cortex. It demonstrates the electrical potentials from neuron activity, within the brain in the form of wave patterns. The intensity and pattern of electrical activity is influenced by the reticular activating system. The characteristics of the wave depend on the degree of cortical activity
Brain activity as recorded on an EEG correlates with the cerebral blood flow
A constant supply of oxygen, blood and glucose is needed to meet the metabolic demands of the brain. Decrease cerebral blood flow causes changes in mentation and decreased electrical activity on the EEG
WAVE PATTERNS
- Alpha: alpha waves are found during period of wake-fullness, prominent over the cortical and parietal areas
- Beta: beta waves are recorded with in turns activation of the CNS, prominent over frontal and parietal areas
- Theta: theta waves are recorded during periods of emotional stress or drowsiness, prominent over the temporal and parietal areas
- Delta: delta waves are recorded during periods of deep sleep
EEG Measures in Seizure
- Breathing deeply for several minutes to produce alkalosis
- Producing a sleep deprivation syndrome
- Producing a sleep either naturally or by drugs
- Photostimulation by flashing lights, etc
PRELIMINARY ASSESSMENT
Check
- Doctors order for any specific instructions
- General condition or diagnosis of the patient
- Mental status of the patient to follow instructions
PREPARATION OF THE PATIENT AND THE ENVIRONMENT
- Explain the procedure to the patient to gain cooperation. This procedure talks half an hour to two hours
- The purpose of the test an procedure should be explained to the client and the family
- The client and family may need to be reassured that electricity does not enter the brain
- Air shampoo is indicated on previous day, this helps the jelly to be fixed in the scalp
- This test can be done in sitting or lying position, so place according to the technician’s instructions
- The client will be asked to relax during the test, because anxiety can block alpha rhythms
- The nurse should be sure to send adequate supplies (i.e. intravenous fluids or oxygen to the laboratory)
- The EEG room should be kept – quite, minimum light, appropriate temperature and less distraction
- The client may keep awake the night preceding the test or sedation to induce sleep
EQUIPMENT
- EEG machine with electrodes
- Jelly
- Tissue paper
- Cotton balls
- Bed with adequate linen
PROCEDURE
- The patient is taken to an EEG room, where the technician does this test
- Electrodes are attached to the client’s scalp
- Electrodes are applied to the scalp and the ear loop with collodion
- Lead scan also be placed in nasopharynx to assist disorders in the temporal lobe
- The first portion of the test is performed with the clients as relaxed as possible to obtain a baseline recording
- Further readings are taken while the client is hyper-ventilating, sleeping or viewing flickering lights
- The wave forms are amplified and recorded on a moving paper strip, similar to an ECG
- EEGs are interpreted according to brain wave characteristics, frequency and amplitude
- If the client is comatose or unable to move, EEG can be performed at the bedside
INTERPRETATION
- Hyperventilation alters acid base balance (respiratory alkalosis) decreases cerebral blood flow
- Flickering lights may trigger seizures
- Sleep may evoke abnormal EEG patterns not present while the client is awake
- Absence of EEG waves (flat line) on EEG may be one of the criteria for defining brain death
NURSING IMPLICATIONS
- The preparation of the patient for EEG is extremely important because it can directly affect the accuracy of the test results. The patient should be explained about the procedure and reassured that EEG is no way painful and dangerous. He should be told tha tit is not a form of shock treatment or a way of hypnotizing the patient
- The explanation should be satisfactory to the patient to win his confidence and cooperation. ‘TO RECORD EEG, a relaxed and cooperative patient is necessary
- Withhold all medications, especially the nerve stimulants and depressants for 3 days prior to the test. This should include tranquilizers, anticonvulsions, analgesics, hypnotics, and sedatives
- The patient should not take coffee, tea, alcohol, alcoholic beverages, etc. on the day of the test, since these are stimulants to the central nervous system
- The patient should not be disturbed mentally before the test. Mental excitement and depression can alter the EEG tracings
- The patient should not sleep prior to the test this may induce sleep in the patient during the procedure. Sometimes, a sleep EEC is indicated to detect temporal lobe epilepsy. In such cases, sedation is administered 45 minutes prior the EEG and the procedure is performed when patient is sleeping
- The hair should be cleaned thoroughly with a shampoo. No oil or metal appliances should remain in the hair. No need to cut the hair
