Continuous Rheoencephalographic Monitoring of Cerebral Blood Flow

Abstract

Changes in cerebral function can occur in either the cerebral neurologic or circulatory systems. This study was conducted to correlate rheoencephalographic (REG) and electroencephalographic (EEG) measures of cerebral activity during mental effort and to demonstrate how REG may be used in the clinical environment. REG and topographical EEG were used to monitor responses of nine human subjects at two levels of a visual motor mathematical or a verbal processing cognitive task. In the first of two experimental series, a single-channel bipolar REG was used during five minutes of mathematical processing with the REG electrodes placed on the left and right sides of the head between the T3 - T5 and T4 - T6 EEG sites (International 10 - 20 Convention), respectively. REG hemodynamic measures were significantly (P<0.05) altered during mathematical processing. The total REG and EEG Fast Fourier Transform (FFT) powers were highly correlated during both the low (r = 0.88) and high (r = 0.95) mathematical processing tasks. In the second series, a four-channel tetraplar REG was used to measure the hemodynamic responses in four quadrants of the head during an extended (3.5 hour) verbal cognitive task. A strong positive relation was found between the EEG Band 3 (8–13 Hz) powers and REG blood flow values (ml/min) in the right (r = 0.93, P<0.008) and left (r = 0.89, P<0.02) anterior quadrants. A weak negative relation was found between these variables for the posterior quadrants of the head. These results show that a strong relationship exists between the cerebral circulatory and neurologic systems during cognitive processing. They also indicate that multichannel REG can be used to monitor intracranial blood flow on a continuous basis in the clinical environment