Background & Objectives: Many researches have been conducted on autoregulation of cerebral blood flow (CBF), but its possible variations coincidence with postvagal tachycardia have not yet been studied. The present study searched for the effect of this phenomenon on CBF in young and middle-aged persons.

 Methods: 52 healthy volunteers including 13 young males (mean age 23.9±0.8), 13 young females (mean age 24.2±0.7), 13 middle-aged males (mean age 58±0.9) and 13 middle-aged females (mean age 56.4±0.7) went under the study. Flow velocity in middle cerebral artery (MCA) was assessed using transcranial Doppler (TCD) ultrasonography apparatus. Eckberg’s neck suction device was utilized to stimulate carotid baroreceptors. The data were analyzed using Minitab and SPSS software (rel. 10).

 Results: Concomitant to the carotid baroreceptors stimulation there was a significant reduction in heart rate in all groups (p<0.05), but mean cerebral blood flow did not change significantly. After ending the carotid baroreceptors stimulation and concomitant to PVT, mean cerebral blood flow increased in all groups except middle-aged males. This increase in CBF became significant in middle-aged females (p<0.05).

 Conclusion: The results of the present study indicate that cerebral blood flow autoregulation act effectively concomitant to acute stimulation of carotid baroreceptors and this efficacy is maintained until the middle-age, but when faced with PVT, cerebral blood flow autoregulation dose not act effectively.

  Background & Objectives: Cerebrovascular diseases are the most common disabiling neurologic disorders and the third cause of death in the population over 45 years of age. Most of the strokes in adults are ischemic and almost one-fifth of them are due to intra- or extracranial internal carotid artery stenosis. Ultrasonography is a noninvasive, cost-effective and safe technique for evaluation of intra or extracranial vessels that is available in two methods: TCD and carotid Duplex. The present research is an attempt to investigate the appropriatens and comprehensiveness of TCD in diagnosing symptomatic significant carotid stenosis.

  Methods : This descriptive-analytical study was conducted on fifty patients admitted to the neurology ward of Imam Hospital who underwent both carotid duplex and TCD examination. Variables of blood flow velocities, collateral flow evidences and degree of carotid stenosis were assessed with both methods. The data were analyzed by SPSS (ver.11.5) using T.test, Chi-square and Fisher test.

  Results : 34 patieuts were. Male mean age of the patients was 66.70% of the subjects were above 65 and 68% of them had a history of hypertension. No statistically significant difference was seen between systolic and diatolic blood flow velocity in internal carotid artery and pulsatile index obtnined from reported by TCD and carotid Duplex. There was no statistically significant difference between the percentage of stenosis TCD finding of the patients with carotid stenosis showed collateral flow in 78.57% of the cases.

  Conclusion: Acceptable correlation of the flow velocity parameters and the percentage of carotid stenosis between TCD and Carotid Duplex results showed that the primary performance of TCD to diagnose significant carotid stenosis (that causes hemodynamic disorder) and screen ischemic cerebrovascular accident is a reliable and effective method, but for precise determination of stenosis, plaque typing and for diagnosing stenisis below 50% the performance of carotid duplex study is also necessary and to complemantory TCD.