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

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

Salvatore J.A. Sclafani, MD, FSIR

American Access Care Physicians

Professor of Radiology, Surgery and Emergency Medicine

State University of New York Downstate Medical School

Brooklyn, New York

Introduction

Chronic Cerebrospinal venous insufficiency (CCSVI) is a clinical syndrome that results from outflow resistance of the veins that drain the brain and the spine. It presents with chronic fatigue and temperature intolerance, short term memory deficiencies and problems of concentration and executive processing, headaches, spasticity and vision deficiencies, among others (1-3). CCSVI is most commonly seen in patients with multiple sclerosis (4), but these symptoms have been reported in patients with jugular stenoses and occlusions caused by radical neck surgery, vascular access catheters, tumor compression, hypercoagulable states, and trauma and without antecedent cause. (5-8)

The primary venous conduits that constitute the cerebrospinal venous circuit include the right and left internal jugular vein (IJV), the right and left vertebral veins and the azygous vein. These are the major outflow veins of the brain and the spinal cord draining venous blood from the dural sinuses and from the vertebral plexus and spinal veins. There are also secondary outflow veins, namely the innominate veins and the superior vena cava. Augmentation of the primary outflow veins can result from obstruction of the "inflow" veins that are connected to the primary veins. These include the left renal vein that is connected to the hemiazygous vein and the left common iliac vein that is connected to the ascending lumbar vein.

The recommended diagnostic algorithm utilizes Doppler ultrasound of the deep cerebral veins, the IJVs and the vertebral veins in both the erect and supine positions to assess the hemodynamic consequences of outflow derangement and B-mode ultrasound to detect structural abnormalities. Doppler hemodynamic manifestations include reversal or absence of flow and loss of normal postural control in the erect position. A variety of B-mode abnormalities can be seen, including occlusions, stenoses and hypoplasias, thickened, elongated and immobile valves, septum and membranes. The detection of at least two of five criteria correlates highly with the presence of CCSVI. (9)

Magnetic resonance venography (MRV) and computed tomographic venography (CTV) have been used by some to screen for CCSVI. These examinations allow non-invasive visualization of the entirety of the veins of the neck, but in addition can detect stenoses, hypoplasias and occlusions of these veins. Moreover these imaging methods allow visualization of the central chest veins and the dural sinuses prior to venography. Additionally, some efforts have been made to quantify flow selectively in each of these critical veins.

Venography remains the Gold Standard for the visualization of the jugular veins, as well as of the azygous vein, a vein that cannot be imaged satisfactorily by MRV, CTV or Ultrasound. To its advantage, venography can also visualize the secondary veins, such as the left renal vein, the left common iliac vein and the ascending lumbar vein. Venography can also assess subjectively flow, stasis and reflux in these veins. To its advantage, the catheter study enables subsequent treatment by angioplasty of stenoses of these veins.

However, each of these imaging modalities has deficiencies that can negatively influence treatment decisions. Surface ultrasound cannot visualize well the confluens of the internal jugular vein and the subclavian vein because of the impediment of the clavicle. Angling the transducer into the chest may underestimate disease in this area. This is a critical deficiency because the area under the clavicle is the most common location for pathology in CCSVI. Similarly, the upper cervical jugular vein and the jugular bulb cannot be visualized by ultrasound because of the limited acoustical window resulting from the spine, mandible and skull. Moreover it is clear that ultrasound can evaluate completely neither the azygous vein nor the brachiocephalic veins. In addition assessing the degree of stenosis is unreliable by ultrasound.

MRV and CTV cannot evaluate intraluminal pathology, such as the immobile valves, webs, septations, membranes and duplications. As with ultrasound, they cannot evaluate satisfactorily the azygous and hemiazygous veins even though they are able to identify the compression syndromes of the renal vein and the iliac vein. Furthermore they often detect spurious stenoses that are not confirmed by venography. These stenoses may represent transient phasic narrowings or may result from diminished flow above true stenoses commonly located at the confluens region of the vein.

Similarly venography also has difficulties identifying the intraluminal pathology because density of the injected contrast may obscure these findings. Moreover venographic determination of the size of the veins is rather subjective and may mislead without multiple projections that would be necessary to assess this characteristic. The IJV is often not a circular object; rather it is oval or complex in shape. Thus determination of the diameter of the vein if often arbitrary and often underestimates or underestimates the proper size of balloon for angioplasty. In light of the high pressures necessary to disrupt this internal pathological stenosis, proper sizing is crucial to avoidance of injury to the vein by overdilatation or early recurrent stenosis by underdilatation.

All of the luminographic studies, such as venography, MRV and CTV, suffer from their "snapshot" nature. Outflow obstruction of the jugular veins results in slow flow or stasis. Because there is an alternative cerebral outflow via the vertebral veins, decompression results in diminished IJV volume these thin walled IJVs that can collapse against rigid structures such as the spine, the carotid artery and neck musculature. Accurate depiction of these veins requires multiple views, such as imaging during inspiration and expiration, during flexion and extension, and during rotations of the neck. These maneuvers cannot be done in real time by MRV and CTV and doing them during venography is time-consuming to the operator and results in increased radiation dose to the patient.