Color Doppler of the extracranial and intracranial arteries in the acute phase of cerebral ischemia

Abstract

Vascular imaging greatly improves the possibility of locating the site of vascular occlusion in patients with acute cerebrovascular disease. Different occlusive patterns may underlie the same clinical presentation, with different prognosis and different treatment: for this reason, a diagnostic tool able to identify quickly the status of the extra- and intracranial vessels is needed. Color Doppler ultrasound of the extracranial arteries is a reliable and accurate method able to localize and quantify the carotid artery stenosis. The ultrasound quantification of the degree of stenosis is based on both morphological and velocimetric criteria: B-mode, color or power Doppler and spectral analysis are used for this purpose. Also the analysis of the plaque is an integral part of the ultrasound examination: the B mode plaque characterization (structure and surface) plays an important role in the evaluation of risk of stroke. So color Doppler ultrasound is able to select patients who may require medical therapy, carotid endarterectomy or angioplasty and stenting. Transcranial color Doppler is an inexpensive, reliable, fast, non-invasive, bedside tool: in the acute phase of stroke, it is able to evaluate quickly the intracranial arteries and monitor the possible recanalization of occluded vessel ensuring the follow-up of dynamic lesions, such as the intracranial stenosis and occlusions.

Keywords: Atherosclerosis; Carotid and vertebral arteries; Stroke; Ultrasound.

Figures

Fig. 1

Stable plaque: homogenous, non-hemodynamic plaque with echogenic cap

Fig. 2

Unstable plaque: heterogeneous plaque with surface irregularity, and high degree of luminal stenosis

Fig. 3

Unstable plaque: high degree of luminal stenosis with flow acceleration (peak systolic velocity = 219 cm/s) in the region of the stenosis

Fig. 4

Inveterate ICA occlusion: ICA of small caliber and thrombus with a large hyperechoic component

Fig. 5

Recent ICA occlusion: ICA with preserved caliber and thrombus with large hypoechoic component

Fig. 6

Type 1 (“direct” sign 1): intimal flap with proximal ICA division into two compartments

Fig. 7

Type 2 (“direct” sign 2): bulbar hematoma (low-reflective thrombus)

Fig. 8

Type 3 (indirect signs): absence of atherosclerotic plaques (patency of the bulb and the first part of the ICA) and high-resistance flow pattern to the presence of hematoma in the ICA distal segment

Fig. 9

Narrowing of the middle cerebral artery lumen

Fig. 10

Narrowing of the middle cerebral artery lumen with local flow acceleration, disturbed flow with spectral broadening in the region of the stenosis due to the increase in low frequency and retrograde flow components

Fig. 11

Absence of power flow signal in the middle cerebral artery occluded and presence of normal appearance of other intracranial arteries