Ultrasound echoencephalography
Last reviewed: 23.04.2024
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Ultrasound echoencephalography (EchoEG) is based on the principle of echolocation.
The goal of Echoencephalography (EchoEG)
The goal of EchoEG is to identify gross morphological disorders in the structure of the brain ( subdural hematomas, cerebral edema, hydrocephalus, large tumors, displacement of median structures ), as well as intracranial hypertension.
How is echoencephalography performed?
The echoencephalograph sends short ultrasonic pulses to the brain, which are generated by a special piezoelectric radiator (a crystal that changes its linear dimensions under the applied high-frequency electric voltage). They are partially reflected from the boundaries of media and tissues with different acoustic resistance ( skull bones and brain envelopes, brain tissue and cerebrospinal fluid in the brain's ventricles).
To transfer ultrasonic pulses from the radiator to the scalp without reflection, the skin and surface of the probe (radiator-sensor) are covered with a layer of conducting liquid (vaseline oil or special gel).
The signals detached from brain structures are captured by a special sensor, and their intensity and time delay with respect to the moment of exit of the pulse is analyzed by electronic devices and displayed as an echoencephalogram on the monitor. The horizontal scanning of the monitor starts when the ultrasonic pulse is sent.
The position of the reflected signals on the screen allows us to judge the mutual arrangement of the structures of the brain.
Three basic signal complexes are distinguished on the echoencephalogram. The initial and final complexes are the reflection of ultrasonic pulses from the skin and bones of the skull on the side of the sensor location and on the opposite side of the head, respectively. In the same complexes it is possible to distinguish low-amplitude signals reflected from the boundaries between the gray and white matter of the brain. High-amplitude medial complex ("M-echo" signal) when the probe is placed on the temporal region corresponds to the reflection of ultrasonic pulses from the middle cerebral structures (third ventricle, epiphysis and transparent septum). Normally, the position of the "M-echo" signal should coincide with the so-called "middle head line", which is determined at the beginning of the study. Echoencephalogram in pathology
The displacement of the median brain structures of the patient (a displacement of 2 mm or more is considered to be diagnostic) is determined from the asymmetric shift of the M-echo signal relative to the midline, and the presence of intracranial hypertension is determined by the magnitude of its amplitude pulsation (more than 30-50%).
The presence of cerebral edema, subdural hematomas, large tumors, or ventricular expansion is determined by the appearance of additional signals and refined by shifting the position of the sensor.
Alternative methods
The method of EchoEG previously used very widely because of its simplicity of implementation and interpretation of the results, low cost of equipment, as well as practical absence of contraindications. At present, more and more informative neuroimaging methods of diagnostics are increasingly being replaced.
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