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Intraoperative measurement of cortical blood flow and its CO2 response in childhood moyamoya disease.

Cortical blood flow was monitored during craniotomy for bypass surgery to treat childhood moyamoya disease. The patients were hyperventilated, and changes in cortical surface blood flow were detected by a heat clearance method with plate type thermocouple probes. End-tidal CO2 was monitored during hyperventilation to avoid excessive reduction of CO2. There were three types of blood flow responses to hyperventilation: simple reduction, prolonged reduction, and increase. Simple reduction was noted in four cases and was related to constriction of basal and ethmoidal moyamoya vessels. Prolonged reduction was noted in three cases and was related to excessive constriction of basal moyamoya vessels. Increase was noted in four cases and was related to increase in blood flow from cranial vault moyamoya vessels. The results indicate that the basal moyamoya vessels are constricted by hyperventilation. This may be the cause of ischemic symptoms provoked by hyperventilation.