Discrepancies between the degrees of pathological change in intracranial main arteries and the carotid arteries are occasionally observed in patients with atherothrombotic brain infarction (AI). We studied the differences in severity between these vascular lesions and the risk factors in AI. A retrospective study was done on 46 hospitalized patients with AI between April, 2002 and October 2003. We evaluated the degrees of stenosis in intracranial lesions by MRA and in extracranial lesions by carotid ultrasonography. The severity of the vascular lesions was evaluated from the percentage diameter stenosis on MRA images for the intracranial lesions and plaque score on ultrasound images for the extracranial lesions. Age, sex, hypertension, diabetes mellitus, hyperlipidemia and smoking were selected as risk factors for AI. Stepwise multiple regression analysis revealed that age (p>0.01, β0.383) and smoking (p< 0.05, β 0.341) were independent risk factors for PS. We reviewed 43 patients with carotid artery lesions (PS ≥ 5.1) but without intracranial artery stenosis (≥ 50%) (Group1, n=13), with intracranial artery stenosis but without carotid artery lesions (Group2, n=13), and with both carotid artery lesions and intracranial artery stenosis (Group 3, n=17). The patients in Groups 1, 2 and 3 were aged 60.3±10.4 years, 71.0±10.2 years, and 72.1 ± 6.80 years, respectively (ANOVA, p < 0.05, p < 0.01). Patients in Group 1 were significantly younger than those in Group 2 and 3. Group 1 exhibited diabetes mellitus more frequently (p < 0.05) than Group 2 or 3. Group 1 exhibited hyperlipidemia more frequently (p < 0.05) than Group 2. In conclusion, there was some difference in the progression of atheromatous change between intracranial arteries and carotid arteries. Risk factors may contribute to this difference.

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In order to investigate whether combined measurement of the systemic vascular resistance index (SVRI) by Swan-Ganz catheter examination and transcranial Doppler (TCD) monitoring of cerebral blood flow velocity is more useful than TCD monitoring alone for detection of vasospasm after subarachnoid hemorrhage (SAH), we performed both examinations serially on 20 patients with SAH and compared the results with those of serial cerebral angiographic examinations for diagnosis of vasospasm. The TCD and SVRI criteria for vasospasm were > 120cm/s and > 1200, respectively. Cerebral angiography detected vasospasm in seven of the patients. TCD monitoring demonstrated an accuracy of 70% for diagnosis of vasospasm, while a combination of SVRI and TCD monitoring demonstrated an accuracy of 90%. Thus SVRI measurement in addition to TCD monitoring appears to allow accurate evaluation of vasospasm.

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Purpose: our aim was to evaluate the usefulness and limitations of ultrasound (US) examination following stenting for supraaortic artery stenosis. Methods: Twenty-four patients were examined; 9 had stenosis of the carotid artery bifurcation, 8 had stenosis of the proximal portion of the vertebral artery, and 7 had stenosis of the subclavian artery. US examinations were performed by B-mode and pulsed Doppler before and immediately after stenting, and every 3 months thereafter. Digital subtraction angiography (DSA) was performed immediately after and 6 months after stenting. Results: For carotid artery stenting, we were able to evaluate morphological patency by B-mode (84% of cases), and hemodynamics by pulsed Doppler in the stented portion. These data were confirmed by DSA.

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To investigate the influence of orthostatic stress on dynamic cerebral autoregulation (DCA), thirteen healthy subjects underwent graded head-upright til (HUT; 0,15,30,45,60, 90° (degrees)) stress. Dynamic cerebral autoregulation was evaluated by transfer function gain (TFG) and coherence function (CF) between blood pressure (BP) fluctuation (input) measured by photoplethysmography (Finapres) and cerebral blood flow (CBF) velocity fluctuation (output) in the middle cerebral artery measured by transcranial Doppler. In the very-low-frequency range (0.02∼0.07 Hz), many (33.3%) of the CF values were under 0.5 and the average CF value did not change significantly during the graded HUT stress. CF values in the low-frequency (LF: 0.07∼0.2 Hz) and high-frequency (HF: 0.2∼ 0.3Hz) ranges were always over 0.5. TFG in the LF and HF ranges decreased significantly at HUT 45° and 90° and during HUT 45∼90° simultaneously. These results suggest that HUT stress generally activates DCA, although the modes of activation differ according to the frequency range of BP and CBF fluctuations.

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In brain tumor surgery using the ultrasonic monitoring technique, surgical instruments such as microdissectors and suction tubes create imaging artifacts. In addition, recognition of the correct position of the suction tube tip under ultrasonic monitoring is difficult because conventional 2D ultrasound creates similar images regardless of the scanning position along the tube. The backscattering-like artifact from these surgical instruments is caused by ringing vibrations generated on the tube by the ultrasonic monitoring pulse. We have attempted to suppress this type of artifact in vivo using a suction tube covered with a high-attenuation heat-shrinkable coating devised on the basis of in vitro experiments, and confirmed that this was effective. To identify the position of the suction tip on the ultrasound image, 1.4-μm-radius microcapsules having a hard plastic shell were attached to the metal tube tip. The microcapsules vibrate in synchronization with the ultrasound monitoring pulse and regenerate harmonic signals, based on the same principle as contrast agents used in ultrasound imaging. By using the 2nd harmonic imaging method, the metal tube tip was found to be selectively emphasized on the ultrasound image. It is anticipated that these improvements will make intraoperative ultrasonic monitoring a more powerful tool for brain tumor surgery.

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