A Case of Vasovagal Reflex Evaluated by Transcranial Doppler(Special Issue in Hornor of the Retirement of Professor Toshiko Takemiya at the Department of Neurology, Tokyo Women's Medical University)

We reported the cerebral hemodynamic changes of a 71 year-old man by means of transcranial Doppler (TCD) during sympathoinhibitory syncope (Bezold-Jarisch reflex) provoked by the cold pressor test. The time-averaged mean flow velocity of the middle cerebral artery decreased, and the pulsatility index (PI) increased. These effects were concomitant with decreased blood pressure and heart rate by sympathetic inhibition. The patient lost consciousness when his diastolic blood flow velocity decreased to zero. The increase in PI was considered to reflect the collapse of vessels induced by excessive vasodilatation but not by enhanced cerebrovascular resistance. TCD is useful for the diagnosis and evaluation of syncope, because TCD enables us to observe cerebral blood flow continuously and to know the instability of cerebral vasomotor reactivity or blood flow reduction which leads to syncope