De Motu Cerebri: The History of the Study of Brain Pulsations

Abstract

Pulsations of the brain were observed and noted since antiquity. Galenic concepts that the brain pulsations pro- pel psychic pneuma to the nerves were challenged during the Renaissance and replaced by other theories. During the age of the Enlightenment, scientists began to study by observation and experiment whether these pulsations were generated by the dura mater, the respiratory movements or the beating of the heart through the arteries and the veins. The research ef- forts then moved to find out whether the pulsations were an innate physiological phenomenon or whether they appeared only when the skull was opened. The devices developed during the first half of the nineteenth century, enabled observing the brain while preserving the conditions of an unopened skull. They are the prototypes of nowadays instruments in clini- cal use. The invention of the kymograph transformed the naked eye impressions into records that were open to objective analysis, and established the close relation between the arterial pulse and its components to the waveform of the cerebral move- ments. By the end of the nineteenth century, the study of the brain movements was coupled with the extensive research of the cerebral circulation, emotional conditions and the physiology of intracranial pressure; however, this endeavor was abandoned for many decades. As continuous monitoring of intracranial pressure in the late 1970s became a routine clinical practice, the three-centuries- old research of brain pulsations was resumed with the not yet fulfilled aspiration to employ wave-form analysis of the pulsations as a means for non-invasive assessment of intracranial pressure.