Chronic Superior Vena Cava Syndrome: Demonstration of Systemic Venous Circulation Inversion and Continuous Venous Blood Shunting Toward the Cerebrospinal Venous Circulation. Physiologic and Clinical implications for Neurodegenerative Disease

Abstract

In superior vena cava syndrome (SVCS), one or more of the major veins are occlused or deeply stenosed. In these cases. Venous blood from the head, neck, chest and upper limbs regularly reaches brachiocephalic veins and the right atrium through collateral vessels. Several angiographic and echocardiographic studies have reported that in the left brachiocephalic venous stenosis venous blood, instead of flowing toward the superior vena cava and taking the compensation circles to reach the heart, reverses its flow direction through the jugular and then the cerebral veins. In the venous system, flows direction is always centripetal one-way, and a completed flow inversion is possible only in presence of venous stenosis associated with a compensatory circle. Thus, we are here hypothesizing that in SVCS inversion of flows into a jugular vein, already clearly described in the literature, is due to the presence of a compensatory circle that finally connects the superior vena cava to the inferior vena cava. Given that jugular and cerebrospinal veins join with full-channel connections to become a single conduit, we hpothesized that the “new” compensatory circle, deriving from the hemodynamic consequences of SVCS, may include the entire cerebrospinal venous system. This hypothesis is corroborated by the current knowledge on the cerebrospinal venous system: it is a unique, valveless, bidirectional flow circuit that freely communicates with superior and inferior vena cava. In the SVCS, venous blood coming from the head, neck and upper extremities may not descend towards the brachiocephalic vein, as expected from literature, but reverses its flow direction towards the jugular vein and the cerebral spinal venous system, to reach the inferior vena cava.This means that constantly, in the SVCS, part of venous blood coming from the head, neck and upper limbs must cross the brain and the spinal cord to finally reach the right atrium, and that there is a direct contact between the venous blood of the superior vena cava and the cerebrospinal venous system. The continuous passage of venous blood from the superior cava system into the cerebrospinal circulation opens new perspectives in understanding the etiopathogenesis of many neurodegenerative diseases. In vena cava stenosis then, the cerebrospinal circle is subjected to an increase both in pressure and in volume overload, thus creating the possibility that infections, emboli or tumors migrate directly from the peripheral tissues to the brain through the venous route (as already demonstrated in literature). From 2010 to now we have operated for plastic enlargement with patches of saphenous vein, 120 patients with congenital stenosis of the superior vena cava system. These compassionate interventions were undertaken as the “last therapeutic chance” of improving a series of severe and invalidating symptoms, completely non-responsive to each and all clinical practise therapy recommended by updated guidelines, and possibily depending on this blood flow inversion in SVCS. Here we are reporting the angiographic findings of the first two patients with vena cava stenosis. In one we describe the inversion of flow from the site of the obstruction towards the cerebrospinal circle, and in the other we describe the passage of venous blood from peripheral tissues to the cerebrospinal circle.