Transcranial Doppler ultrasonography may be used by clinicians as a noninvasive screening tool for the diagnosis of intracranial arterial stenosis. Data regarding the sensitivity and specificity of transcranial doppler (TCD) in the diagnosis of middle cerebral artery (MCA) stem (Ml) and intracranial vertebral artery and basilar artery stenoses have been published elsewhere. In our study we used velocity criteria to predict intracranial stenoses of MCA, Ml, intracranial vertebral and basilar artery segments. The TCD criteria for stenosis are: ( 1 ) stenosis of 50% or greater in diameter gives a peak systolic frequency shift of 2 KHz or greater, using a 2 MHz probe, (2) stenosis of 75% produces severe flow disturbances combined with direct and reverse low frequency, high energy signals or with damped velocity beyond the stenosis. We assume that asymmetry in arterial velocity (> 30%) is an important parameter. We know from previous works that, using velocity criteria alone, TCD with pulsed wave probe may miss up to 17% of M l stenoses of any degree and up to 20% of intracranial vertebral and basilar 50% stenoses. With the use of transcranial color-coded (TCCD) ultrasonography, we can define the direction of the vessel and calculate the Doppler shift together with angle incidence with better estimate of velocities. TCCD may better define the exact site of the junction of the two verterbral arteries and the origin of the basilar artery, allowing a better identification of this part of the vertebrobasilar system, often the site of abnormality. TCCD can also solve the problem of inverted direction of flow due to tortuosity of vertebral artery, allowing vision of the whole artery course. Recently we experienced contrast-enhanced TCCD both in vertebrobasilar and MCA study: this method allows complete vision of intracranial arteries overcoming the difficulties of insufficient temporal bone window and a deeper and clearer identification of vertebrobasilar system. With contrast-enhanced TCCD we were able to identify intracranial stenoses in seven patients (4 vertebrobasilar, 3 MCA). This finding was confirmed by digital arteriography.
|Journal||Italian Journal of Neurological Sciences|
|Issue number||5 SUPPL.|
|Publication status||Published - 1998|
ASJC Scopus subject areas
- Clinical Neurology