Doppler sonography of vertebral-subclavian system.

The ultrasonographic study of vertebrobasilar system can be correctly carried out if based on the knowledge of the peculiar anatomical features of vertebrosubclavian system, of its variants and collateral vessels, of the close anatomofunctional relationship with carotid vessels. In the pathogenesis of vertebrobasilar insufficiency intrinsic and extrinsic steno-obstructive causes are separated. Particular attention is paid to the subclavian steal syndrome. Five types of steal are identified in relation to the involved arteries and to the site of steno-obstructive lesions. Specific aspects of color Doppler US with reference to normal or pathologic vertebral and subclavian arteries are examined with respect to the diagnosis of the cause of vertebrobasilar insufficiency and to monitoring after surgical or percutaneous treatment.