Periodical fluctuation of blood pressure (BP) is known to be the associated with autonomic nerve function. Using transcranial Doppler and the tonometry method, we developed a system for simultaneous measurement of BP and blood flow velocity (FV) in the middle cerebral artery (MCA) for each cardiac beat. We analyzed the relationship between the periodic fluctuations of mean BP (MBP) and mean FV (MFV) . The waves were subjected to spectral analysis using the maximum entropy method (MEM) . The subjects were 12 healthy volunteers, 3 patients with cerebrovascular disease (CVD), and 3 patients with dysautonomia.
Spectral analysis of MBP in healthy volunteers indicated two peaks in the power spectrum (LF: under 0.1 Hz and HF: 0.2-0.5Hz) . Similar results were obtained for MFV in healthy volunteers. In some patients with CVD, the fluctuation of MFV tended to be disassociated from that of MBP. LF of MFV was lower than that of MBP. In the patients with dysautonomia, analysis of MBP revealed a significantly lower LF. Analysis of MFV showed variation between normal and lower LF. From these results, we classified the manner of LF into 4 patterns.
LF (Mayer wave) is considered to reflect symptomatic nerve function. Disassociation of the fluctuation of MBP form that of MFV suggests, a specific feature of the autonomic nerve system in the brain. This method seems to be useful clinically in assessing autonomic nerve function and cerebral hemodynamics under various loads.

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Resistance index (RI) is used to evaluate cerebral blood flow. We previously reported that changes in systemic flow also influenced the RI. We recently observed two infants with congenital heart disease who evidenced not only an abnormal RI, but also changes in patterns of cerebral blood flow. Case 1 was a 5-month-old boy with Down's syndrome and endocardial cushion defect. He developed heart failure with impending shock, accmpanied by bacterial diarrhea. The Doppler frequency spectrum at the anterior cerebral artery three days after his condition worsened showed a diastolic peak, and on the next day, revealed two diastolic peaks. Abnormal flow was seen at the ascending aorta, the left common carotid artery and the descending aorta. The administration of catecholamines led to improvement, and the diastolic peak at the anterior cerebral artery and the abnormal flow at the other vessels disappeared. Case 2 was an 8-day-old boy with hypoplastic left ventricle syndrom. His systolic flow came through the ductus arteriosus, and ascended via the descending aorta, circulating to the head and extremities. The flow parrern at the basilar artery was irregular with the peak in the end-systolic to early-diastolic period.

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