Electroencephalography (EEG ) - Causes, Symptoms and Treatment .MF .
Electroencephalography (EEG) - method for studying the functional state of the brain based on its registration of bioelectrical activity of the covering of the head through the intact tissue.The first record of the brain biocurrents was produced in 1928 by Hans Berger.The EEG is recorded electrical brain activity is generated in the cortex, synchronizes, and modulates the thalamus and reticular activating structures.Register bioelectric potentials of the brain and their graphic images photographically or by ink recording made by a special device - electroencephalograph .
How is electroencephalography (EEG)
on a person's head to wear a cap with antenna electrodes connected to the device itself.Signals from the cerebral cortex transferred to electroencephalograph which converts it into a graphical image (wave).This image recalls the rhythm of the heart on an electrocardiogram (ECG).
During registration biocurrents brain patient is in a chair in a comfortable position (reclining).At the same time he should not:
a) be under the influence of sedatives;
b) be hungry (in a state of hypoglycemia);
c) be able to psycho emotional excitation.
EEG Electroencephalography is used for all neurological, mental and speech disorders.According to the EEG, you can explore the cycle of "sleep and wakefulness", set aside the defeat, the location of the lesion, to evaluate the effectiveness of the treatment, to monitor the dynamics of the rehabilitation process.EEG has great importance in the study of patients with epilepsy, as only can be detected on the EEG brain seizure activity.
recorded curve, which reflects the nature of biocurrents brain is called the electroencephalogram (EEG).
electroencephalogram reflects the total activity of a large number of brain cells and is made up of many components.Analysis of EEG reveals her waves, different in form, the permanence, the oscillation period and amplitude (the voltage of).The electroencephalogram (EEG), a healthy person has traits from all regions of the cortex is given rhythmic activity with a frequency of about 10 Hz and amplitude of 50 - 100 mV - alpha rhythm.On the electroencephalogram (EEG) recorded as other rhythms: a lower - delta and theta (2 - 4, 5 - 7 Hz), and more vysokie- beta rhythms (13 - 30 sec) but their amplitude is normally low, and they overlap alpha vibrations.
In a healthy adult, is in a state of rest, usually on the EEG revealed:
a) alpha waves, which have a frequency of 8-13 Hz and an amplitude of 30-100 mV, are symmetrical, a sine form, it is better expressed in the patient's eyes closedprimarily defined in occipital-parietal region;These waves increase and decrease spontaneously and usually disappear quickly when the patient focuses or opens his eyes;
b) beta-waves with a frequency of oscillation greater than 13 Hz (usually 16-30) and the amplitude of 15 mV at normal electroencephalograms are symmetrical and are particularly common in the frontal region;
c) delta waves having a frequency of between 0.5-3 Hz, and the amplitude of 20-40 mV;g) a theta wave with a frequency of 4-7 Hz and with an amplitude in the same range.
electroencephalogram (EEG) changes with the functional state.For example, when the transition to sleep slow waves, become dominant, and the alpha rhythm disappears.With great excitement to the damage of the alpha rhythm revealed dramatic changes: they manifest themselves in enhancing slow oscillations, sometimes beta rhythm, regularity and frequency of the violation of the alpha rhythm.These and other changes are nonspecific.
When expressed alpha activity of delta and theta rhythms in healthy adult human are almost invisible because they overlap have a more pronounced amplitude of alpha rhythm.However, when inhibition of alpha-rhythm usually arises when excited by the patient as well as dormant and shallow sleep (first and second stage), delta and theta rhythm EEG occur and may increase their amplitude, respectively 150 and 300 mV.When deep sleep (third stage) in the EEG recorded a maximum slow activity.Slow waves often appear as diffuse, less local (in the pathological focus area in the brain), the rhythmic oscillations emerging in the "flash."wakefulness level affects the character of the EEG Normally, a sleeping adult rhythm bioelectrical activity is symmetric, while there are growing in amplitude slow waves and sleep spindles in the parietal areas.Any orientation reaction to external influences is reflected in the EEG of a healthy person in a temporary flattening of the curve.Emotional and mental stimulation is usually accompanied by the appearance of fast rhythms.
In the transition from infancy to adulthood character
normal EEG is changing.In early childhood her reflected mainly slow oscillations, which are gradually replaced by more frequent, and is formed by the alpha rhythm to 7 years.Fully completed the evolution of the EEG in 15-17 years, getting to this age features of the EEG of an adult.At the age of 50-60 years of normal EEG is different from that in younger persons decrease in the frequency of the delta-rhythm in violation of its regulation and the increasing number of theta waves.
are theta and delta activity, as well as epileptic activity
If the value of pathological activity in the EEG of the waking adult human.
particularly significant EEG examination is the detection of epileptic activity, indicating a predisposition to convulsive states and manifests itself by the following features:
1) sharp waves (peaks) - potential oscillation having steep rise and a steep decline, with the sharpness of the wave usually exceedsbackground oscillation amplitude with which they are combined;sharp waves can be single or group, identified in one or many leads;
2) peak-wave complexes, which represent potential oscillations consisting of acute waves (peak) and the accompanying slow wave;epilepsy, these complexes can be single or follow each other in a series;3) paroxysmal rhythms - rhythms are oscillations in the form of flashes of high amplitude of different frequencies, common paroxysmal rhythms theta and delta oscillations or slow waves of 0.5-1.0 Hz.
According to the EEG is possible to distinguish diffuse brain damage from a local pathological process, set aside and a certain degree of localization of the pathological focus, differentiate superficial pathological focus on deep, coma and recognize the degree of its severity;identify focal and generalized epileptic activity.
expansion of EEG features in determining the functional state of the brain and some of its pathological conditions, especially epileptic activity, promote specific provocative tests: npoba hyperventilation - deep breathing movement with a frequency of 20 per minute, leading to alkalosis and a narrowing of cerebral vessels, a sample with lightirritant - photostimulation with the aid of a powerful light source (strobe), a sample from the sound stimulus.Thus, the patient's response to photostimulation give confidence that the examinee perceives at least light.If there is no response to photostimulation in, one hemisphere, it can be seen that on its side has been a violation of the conduction of visual impulses from the subcortical centers to cortical areas of the visual analyzer.If photostimulation -provotsiruet appearance abnormal EEG waves, it is necessary to think about the presence of increased excitability of cortical structures.In this case a longer photic stimulation can trigger the appearance of EEG true convulsive discharges, and at a particularly high readiness to convulsive states sometimes develop distinct myoclonic jerking of muscles of the face, neck, shoulders, hands that may become generalized true muscle cramps (fotoparoksizmalnaya reaction).
Informative electroencephalogram increases if her entry is made in the patient being in a dream state.
Using EEG receive information about the functional state of the brain at different levels of consciousness of the patient.The advantage of this method is its harmless, painless, non-invasive.
Electroencephalography has been widely used in the neurological clinic.Especially significant EEG findings in the diagnosis of epilepsy, they can have a role in the recognition of an intracranial tumor localization, vascular, inflammatory, degenerative brain diseases
brain, coma.EEG with photic stimulation or stimulation of sound can help differentiate true and hysterical disturbances of vision and hearing, or simulation of such disorders.EEG can be used to monitor the observation of the patient.The lack of EEG signs of bioelectrical activity of the brain is one of the most important criteria for his death.
In neurosurgical institutions during surgery when indicated can be made biocurrents record with a naked brain - electric kortikografiya.Sometimes in a neurosurgical operating electroencephalogram recordings are being made by means of electrodes immersed in the brain.Using a computer or dedicated spectrum analyzers allows automatic processing of the EEG, which makes it possible to identify
quantitative characteristics of its frequency content.Possibility of compressed spectral analysis of the EEG-based computerized transformation of primary EEG power spectrum by Fast Fourier converter enables to evaluate EEG quantitatively, to present it in a more visible manner, so to as to the spectrograms reflected power or amplitude of EEG frequency components of the investigatedthe length of time (epoch), which makes it possible to determine the ratio of the power of different EEG rhythms and identify frequencies that are not detected by simply examining the EEG curve, and thus increase the information content of the survey results.
Toposelektivnoe mapping the electrical activity of the brain.In an analysis of 16-channel EEG it is possible to transform the survey results in numeric form in the form of the power spectrum electrogenesis the cerebral cortex of the brain.Then, the data presented in the form
power distribution maps of various types of brain electrical activity.The map features
electrical activity in different parts of the cerebral cortex are reproduced in the conventional color, and in black and white - as hatching;wherein each power value (coherence) corresponds to the color or hatching density.
Electroencephalography allows you to objectively assess the severity of EEG asymmetry, presence and the generalized and focal changes of brain electrical activity, manifesting itself during EEG studies.
Electroencephalography (EEG) has lost its role in the objectification of local brain lesions in TBI
With the development of CT and MRI diagnostics of electroencephalography (EEG).However, it remains essential to assess the functional state of the brain at different periods of severe TBI.
In the acute period of mild TBI observed blurred abnormalities mainly in the form of alpha-rhythm irregularities and increased frequent fluctuations with a rapid regression of pathological changes in the electroencephalogram (EEG).
At moderate injury and severe traumatic brain injury changes of the electroencephalogram (EEG) coarser, flow phase.Intensity of slow waves and alpha-rhythm disturbances depend on the degree of involvement in the pathological process of stem structures, the presence of contusion foci and intracranial hematomas.In the projection display of contusion foci of slow activity depends on the location and extent of injury zone.
most rough local changes in the background as a crude expression of brain changes detected with massive cortico-subcortical foci of contusion.Pathological changes in these cases have a tendency to grow during the first 5-7 days.
In the acute phase often absent pronounced cerebral changes during epidural hematomas;have the character delineated focal slow waves or local suppression of the alpha rhythm.
When subdural hematomas changes in the electroencephalogram (EEG) are diverse, characterized by significant brain changes: general inhibition activity, the presence of polymorphic delta waves during deceleration, and reducing the disruption of the alpha rhythm, a manifestation of outbreaks of slow waves "Stem" type.Focal changes are characterized by a broad, vague demarcated.Often detected only hemispheric asymmetry without a clear focus.
When intracerebral hematomas in the electroencephalogram (EEG) showed pronounced cerebral delta-theta waves.Focal changes in the projection area of bruising - in the shape of the prevalence of slow waves.Of particular importance for the assessment of the status and prognosis is electroencephalography (EEG) in severe traumatic brain injury, accompanied by long-term coma.In these observations, the changes of the electroencephalogram (EEG) are varied and depend on the severity of the injury, the presence and localization of foci of contusion and intracranial hematoma.
for patients after a serious injury with a reversible flow, phase change characterized by an electroencephalogram (EEG).At the initial stage - polyrhythm with a predominance of slow forms of activity, at least - a decrease of the oscillation amplitude.Typically the presence of sigma-rhythm (13-15 Hz) typical of normal sleep, bilateral theta waves or low-frequency alpha rhythm, sharp waves on the background of the delta oscillation.Manifested hemispheric asymmetry, to stimuli weakened reactivity.There have been "stem" outbreaks of slow waves.In the future, when you exit out of a coma after a phase of general decline in the activity of the gradual recovery of activity.
In severe head injury that ended lethally, against the backdrop of a deep disturbance of consciousness and vital functions in the electroencephalogram (EEG) is dominated by slow activity of slow waves to beta waves (alpha coma, beta-coma), characterized by monotony, areactivity to stimuli inincluding pain, smoothness regional differences.Focal slow waves in the area of contusion or hematoma did not occur.Typically, the predominance of theta rhythm of low frequency (5 Hz), indicating the total blockade of cortical activity and the dominance of the regulation on the part of the brain stem and subcortical systems.
In the late period CCT electroencephalography (EEG) to determine the seizure activity.Pathologic features of the electroencephalogram (EEG) are usually stored longer than clinical symptoms.Regeneration of the electroencephalogram (EEG) is dependent on the severity of the injury.The most persistent changes in the electroencephalogram (EEG) are in the area of contusion foci or former hematoma.In these areas of the brain are often formed by epileptic activity.
Changes electroencephalogram (EEG) in the late period of penetrating head injury may occur to a large extent over the years.They are both cerebral in nature, due to progress to that time violations of hemodynamics and liquorodynamics and manifested local changes (epileptic and slow activity) in the area of primary brain damage.