Echoencephalography (Echo-EG) is an ultrasound examination of brain tissues. The technique makes it possible to assess intracranial pressure, identify volumetric processes that cause displacement of brain structures, but does not make it possible to differentiate the detected pathological formations. It is usually used at the stage of primary diagnosis, preceded by other, more accurate methods of examination (CT, MRI). Echo-EG includes scanning itself and performing calculations to determine the internal size of the skull, the presence of displacement of brain structures and signs of intracranial hypertension. The cost is affected by the scanning mode, the level of diagnostics (normal, expert).
The technique is prescribed by a neurologist at the stage of primary diagnosis for neurological complaints: headaches, a feeling of pressure on the eyes, dizziness, nausea without connection with eating, attacks of “disconnection” or loss of consciousness, noise in the head, attacks of lack of air, deterioration of memory and attention, decreased efficiency, etc. Echo-EG is indicated if an increase in intracranial pressure is suspected or for its control measurement. Recently, in clinical neurology, Echo-EG is increasingly used as a method of preliminary examination, preceding an MRI or CT scan of the brain. Echoencephalography can be used to detect hydrocephalus, brain edema, volumetric formations in the cranial cavity (hematomas, tumors, foreign bodies, abscesses, cysts) when more modern diagnostic techniques (MRI, MSCT and CT) are unavailable. Ultrasound diagnostics is considered harmless, so Echo-EG has no contraindications.
Methodology of conducting
No preparation is required. Before starting the procedure, it is necessary to remove foreign objects from the head that can interfere with the Echo-EG (hairpins, hoops, etc.). The manipulation is performed by installing an ultrasonic sensor on the scalp in certain places. These areas are pre-lubricated with contact gel or vaseline oil to eliminate interference. As a rule, the following sensor positions are used on each side: above the external auditory canal, on the temple – at the outer edge of the eyebrow, behind the ear – 4-5 cm behind it. Ultrasonic signals sent by the sensor are reflected differently from the skin, skull bones and brain tissues. The reflected signals are picked up by the sensor and transmitted to the device, which displays them on the screen in the form of echo complexes resembling the teeth of an electrocardiogram.
During the Echo-EG, the doctor measures the distances between the initial, middle and final echo complexes. The length of the segment between the initial and final complexes gives information about the internal size of the skull. Comparing the segments from the initial and final complex to the middle one allows us to judge the displacement of brain structures in one direction or another. The difference in the length of these segments is called the displacement of the median M-echo and normally does not exceed 2 mm. In the presence of large volumetric processes, brain tissues shift, the symmetry of the recorded signals disappears, a change in this indicator is recorded on the Echo-EG. Additional echo complexes may be registered. Measurements are performed by alternately installing the sensor in each of the three positions on the right and left.
In the process of echoencephalography, the pulsation of the median echo signal is examined, determining its amplitude as a percentage. This is necessary to assess intracranial pressure. It is believed that the normal intracranial pressure corresponds to the pulsation amplitude of the median Echo-EG signal of 25%. If it ranges from 25-50%, this is a sign of mild intracranial hypertension, 50-75% indicate moderate, more than 75% – a marked increase in intracranial pressure. In severe cases, there is no pulsation. The echo-EG usually lasts no more than 10-15 minutes.
A separate type of echoencephalography is a two-dimensional Echo-EG, in which the doctor gradually moves the sensor, sliding it over the surface of the head. This allows you to get an image of a horizontal “slice” along the line of movement of the sensor and visualize formations located at this level. When performing two-dimensional echoencephalography, artifacts are often recorded on the image, which complicate the diagnosis and reduce its reliability.