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a method of examining the brain by recording the reflection of ultrasonic waves off brain structures differing in density. The main diagnostic criterion, of echoencephalography, suggested in 1955–56 by the Swedish physician L. Leksell, is deviation of the medial echo (M echo), that is, a reflection of ultrasound from the midline structures of the brain (epiphysis, third ventricle, pellucid septum, and intercerebral fissure). The M echo, recorded as a peak on the ultrasonic encephalogram, normally coincides with the midline of the head. In the presence of an intracranial tumor, hemorrhage, abscess, or other pathological mass, the M echo shifts toward the healthy hemisphere.
Other diagnostic criteria have been proposed: an increase in the distance between the echo signals off the lateral walls of the third ventricle in hydrocephalus and the comparatively rapid normalization of a displaced M echo in acute carotid artery obstruction. With echoencephalography, special ultrasonic encephalo-graphs transform reflected ultrasonic signals into electric impulses. These pulses are shown graphically on the screen of the apparatus and photographed.
Echoencephalography is an effective means of diagnosing and localizing massive intracranial pathological processes (for example, tumors) and foreign bodies.
REFERENCESKlinicheskaia ekhoentsefalografiia. Moscow, 1973.
Leksell, L. “Echo-encephalography: Detection of Intracranial Complications Following Head Injury.” Acta chirurgica scandinavica, 1956, vol. 110, pp. 301–15.
V. E. GRECHKO