Intravascular Ultrasound in the diagnosis and treatment of chronic cerebrospinal venous insufficiency

Intravascular Ultrasound

Intravascular ultrasound provides benefits that can address many of the deficiencies of venography, surface Duplex examination, CTV and MRV. The most common indications for intravascular ultrasound have been in the evaluation and treatment of arterial disease, notably in the management of coronary artery disease. Its ability to differentiate various tissue characteristics enables one to assess plaque morphology, detect lipid and calcium deposits and elaborate the degree and distribution of calcification within atherosclerotic plaques. It can thus help evaluate the vulnerable soft, un-ruptured plaque. IVUS is useful in characterization of both the vessel wall and the endothelium. It can assess mural and endothelial thickness and clarify whether narrowings are the result of intimal or mural disease.

IVUS has been shown to provide a more accurate assessment of vessel circumference and cross sectional area and thus is useful in detecting critical stenoses. Such elegant analysis of the dimensions of the vessel allows a more accurate selection of balloon size, thus reducing risk of injury and providing more effective angioplasty. IVUS allows improved visualization of intimal thickening after angioplasty. Moreover, IVUS enables the operator to see how well apposed stents are to the intima and thus guides the need for additional angioplasty to reduce separation between intima and stent. This may facilitate endothelialization of the stent.

Although the vast majority of publications on IVUS relate to the coronary arteries, authors have reported on the value of IVUS in many other conditions, both within arteries and veins. (10)

More recently, benefits have been reported in a number of peripheral arterial applications. Some of the same advantages of IVUS have been exploited in the treatment of peripheral atherosclerotic disease (11). Plaque morphology, more accurate determination of vessel size and degree of stenosis, and tissue characterization by IVUS have been added to the information from angioplasty and thus facilitating and enhancing atherectomy and stenting of peripheral, renal and carotid atherosclerosis. (12)

Authors have also been enthusiastic about using IVUS in the deployment of aortic endographs. More accurate measurement of vessel circumference and the sonographic visualization of the location of aortic branches have allowed greater precision in determining both upper and lower landing zones. The addition of IVUS can alter the plans derived by CTA, contradicting CT’s determination that endovascular stenting was either feasible or futile.

IVUS has been shown to facilitate the diagnosis of aortic dissection. It is highly effective in detecting entry points along the dissected aorta. This can facilitate placement of stents and reduce need for operative intervention. Moreover, IVUS has been shown to be an effective guidance method during fenestration procedures. (13-15)

The use of IVUS in cases of traumatic aortic injury has been shown to improve diagnosis, especially in patients with equivocal aortography, by allowing differentiation of ductus diverticulum and pseudoaneurysm. Indeed, it was shown to be superior to aortography in one series of fourteen patients with a sensitivity of 92% and a specificity of 100%. (16)

While much less commonly reported than use in arterial disease, IVUS has shown merit in a variety of venous pathologies and treatments. Because of its portability, IVUS as a guidance method has been recommended for placement of inferior vena caval filters. The ability to precisely determine the circumference of the caval lumen and to localize all renal vein tributaries without contrast media or ionizing radiation has advantages. Filters can be deployed in an intensive care unit, thus avoiding risks of transport of critically ill patients. The ability to perform the procedure without the use of iodinated contrast media is such patients is a distinct advantage.

The use of IVUS for venous disease in patients with renal insufficiency or in patients with potentially life threatening allergies to contrast media has also been reported in management of dialysis grafts and fistulae, and central venous stenosis. (17-18)

Negen and Raju have argued effectively for the use of IVUS in patients with venous disease, notably in chronic iliac vein stenosis and occlusions. They point to the fact that hemodynamic data so helpful in arterial obstructions is often limited or equivocal in venous disease because of small differences. The significance of pull-through pressure gradients is difficult to interpret. Small degrees of pressure differential may indeed be significant, given the large volumes and high compliance. Rather morphological area stenosis of 50% seems to provide some predictive value of clinical improvement after angioplasty. They recognize the rather irregular shape of the iliac vein and the difficulties in using single view diameters to make stenosis measurements. Further they point out that intraluminal abnormalities, such as immobile valves, subintimal edema, and echogenic material, probably representing trabeculae, septa, and webs, cannot be seen by venography which obscures them with dense contrast media. (19-21)

To date I can find nothing in the literature that describes the IVUS findings of CCSVI, nor one that reports on abnormalities of the internal jugular vein and the azygous vein in CCSVI or other diseases.