Assessment of cerebral venous return by a novel plethysmography method
Paolo Zamboni, MD, Erica Menegatti, PhD, Paolo Conforti, MD, Simon Shepherd, PhD, Mirko Tessari, VT, Clive Beggs, PhD
Magnetic resonance imaging and echo color Doppler (ECD) scan techniques do not accurately assess the cerebral venous return. This generated considerable scientific controversy linked with the diagnosis of a vascular syndrome known as chronic cerebrospinal venous insufficiency (CCSVI) characterized by restricted venous outflow from the brain. The purpose of this study was to assess the cerebral venous return in relation to the change in position by means of a novel cervical plethysmography method.
This was a single-center, cross-sectional, blinded case-control study conducted at the Vascular Diseases Center, University of Ferrara, Italy. The study involved 40 healthy controls (HCs; 18 women and 22 men) with a mean age of 41.5 ± 14.4 years, and 44 patients with multiple sclerosis (MS; 25 women and 19 men) with a mean age of 41.0 ± 12.1 years. All participants were previously scanned using ECD sonography, and further subset in HC (CCSVI negative at ECD) and CCSVI groups. Subjects blindly underwent cervical plethysmography, tipping them from the upright (90°) to supine position (0°) in a chair. Once the blood volume stabilized, they were returned to the upright position, allowing blood to drain from the neck. We measured venous volume (VV), filling time (FT), filling gradient (FG) required to achieve 90% of VV, residual volume (RV), emptying time (ET), emptying gradient (EG) required to achieve 90% of emptying volume (EV) where EV = VV-RV, also analyzing the considered parameters by receiver operating characteristic (ROC) curves and principal component mathematical analysis.
The rate at which venous blood discharged in the vertical position (EG) was significantly faster in the controls (2.73 mL/second ± 1.63) compared with the patients with CCSVI (1.73 mL/second ± 0.94; P = .001). In addition, respectively, in controls and in patients with CCSVI, the following parameters were highly significantly different: FT 5.81 ± 1.99 seconds vs 4.45 ± 2.16 seconds (P = .003); FG 0.92 ± 0.45 mL/second vs 1.50 ± 0.85 mL/second (P < .001); RV 0.54 ± 1.31 mL vs 1.37 ± 1.34 mL (P = .005); ET 1.84 ± 0.54 seconds vs 2.66 ± 0.95 seconds (P < .001). Mathematical analysis demonstrated a higher variability of the dynamic process of cerebral venous return in CCSVI. Finally, ROC analysis demonstrated a good sensitivity of the proposed test with a percent concordant 83.8, discordant 16.0, tied 0.2 (C = 0.839).
Cerebral venous return characteristics of the patients with CCSVI were markedly different from those of the controls. In addition, our results suggest that cervical plethysmography has great potential as an inexpensive screening device and as a postoperative monitoring tool.
MrSuccess wrote:How expensive could the test be ?
In addition, our results suggest that cervical plethysmography has great potential as an inexpensive screening device and as a postoperative monitoring tool.
PointsNorth wrote:Here is full link:
Hopefully this works . . . If not I'll try a tinyurl.
Cerebral venous outflow resistance and interpretation of cervical plethysmography data with respect to the diagnosis of chronic cerebrospinal venous insufficiency
C Beggs*⇓, S Shepherd* and P Zamboni†
+ Author Affiliations
*Medical Biophysics Laboratory, University of Bradford, UK
†Vascular Diseases Centre, University of Ferrara, Italy
Correspondence: C Beggs PhD
, Medical Biophysics Laboratory, School of Engineering, Design & Technology, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK.
While chronic cerebrospinal venous insufficiency (CCSVI) can be characterized using cervical plethysmography, much remains unknown about the haemodynamics associated with this procedure. The aim of the study was therefore to gain a deeper understanding of the observed haemodynamics.
Forty healthy controls and 44 CCSVI patients underwent cervical plethysmography, which involved placing a strain-gauge collar around their necks and tipping them from the upright (90o) to supine position (0o) in a chair. Once stabilized, they were returned to the upright position, allowing blood to drain from the neck. A mathematical model was used to calculate the hydraulic resistance of the extracranial venous system for each subject in the study.
The mean hydraulic resistance of the extracranial venous system was 10.28 (standard deviation [SD] 5.14) mmHg.s/mL in the healthy controls and 16.81 (SD 9.22) in the CCSVI patients (P < 0.001).
The haemodynamics of the extracranial venous system are greatly altered in CCSVI patients.
Why does this measurement matter?
Hydraulic resistance is affected in large part not only by cross-sectional area of a vein (narrower in a stenosis), but also by the geometry of the vein (whether it bends and how much, whether it is flattened and by how much). Ambient temperature, along with thickness (of blood) are also factors. The thinner the blood, the lower the resistance.
If there is a higher resistance to blood flow in veins, as a result of CCSVI, that matters more than a similar narrowing would in arteries, because pressure is way lower in veins than it is in arteries.
For blood to have the same overall flow rate, at the vein end of things, as it does in the arteries, there must be lower resistance in veins, to compensate for the lower pressure.
That's why neck veins are bigger and more voluminous than neck arteries, and why collateral veins matter. Gravity, and whether a person is prone or upright also changes the pressure, therefore the need for low resistance. The overall result is that veins need low hydraulic resistance, so they won't slow the flow. You need it more when you are lying down.
If it is higher in CCSVI than in normals, that will be a problem for those patients.
(Why do 'MS' patients ever lie down? Some do because they cannot get up.)
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