Evaluation of intracranial hemodynamics by transcranial Doppler ultrasonography (TCD) has the problem of variation in skull thickness. Using an adult dog, we studied the effect of skull thickness on the cerebral blood flow measured with TCD through the exposed temporal bone of three different thicknesses. While mean flow velocity (MFV) and pulsatility index (PI) values were not influenced by skull thickness at a fixed sampling depth, the S/N ratio was greatly influenced by MFV and PI, while the sampling depth had a small effect on MFV and a large effect on PI. These results should be considered when assessing intracranial hemodynamics by TCD.
High-resolution B-mode ultrasonography was used for postoperative evaluation of 72 carotid arteries in 65 patients after carotid endarterectomy (CEA) . The intima-media complex (IMC) and the dilative parameter (d-CEA/d-CCA) were measured. The IMC of the VP-A group (operated on with a vein patch, within 4 years of follow-up, N=30) (mean±SD: 0.85±0.51 mm) was relatively thinner than that of the NON-VP-A group (operated on without a vein patch, within 4 years of follow-up, N=25) (1.13±0.73 mm) . The d-CEA/d-CCA of the VP-A group (1.65±0.42) was significantly higher than that of the NON-VP-A group (1.24±0.24) . In conclusion, CEA with a vein patch led to smooth dilatation of the treated carotid artery and seemed to be effective for reducing restenotic changes in endarterectomized arteries.
In three patients with vertebral artery dissection presenting subarachnoid hemorrhage, hemodynamic changes in the affected arteries were investigated by transcranial Doppler sonography (TCD) . On measurement of the vertebrobasilar system by TCD, a combined midline and lateral approach was used for accurate evaluation of the hemodynamic state of the system. Two-layered Doppler waveform was recorded in two patients, and decrease of the flow velocity in the affected artery compared with the contralateral vertebral artery was recorded in the other patient. This two-layered waveform may be a direct finding of arterial dissection.
Transcranial Doppler ultrasonography (TCD) is a useful tool for detecting cerebral vasospasm following subarachnoid hemorrhage. However, some problems are associated with this procedure, such as misdiagnosis due to a mismatch between flow velocity and vascular diameter. Therefore, the present study investigated the discrepancy between the angiographic findings and flow velocity measured by TCD in the detection of cerebral vasospasm. False positive cases showing increased velocity without angiographic vasospasm in 12.1% of the present subjects. Similarly, false negative cases that showed no increase in velocity despite angiographic findings suggestive of vasospasm accounted for 21.2% of the present subjects. False positive cases were most frequent in younger subjects, whereas false negative cases were seen more frequently in older subjects. Accurate examination of elderly patients can sometimes present difficulties due to thickening of the cranial window or elongation of the arteries. Therefore, in addition to the absolute flow velocity, the clinical changes, angiographic findings and cerebral blood flow must also be considered.