Publication Summary
I read with great interest the article titled ‘‘No CerebroCervical Venous Congestion in Patients with Multiple Sclerosis’’ by Doepp and colleagues, which challenges the findings of Zamboni and colleagues regarding chronic cerebrospinal venous insufficiency (CCSVI) in multiple sclerosis (MS) patients. The findings of the study challenge the work of Zamboni and colleagues, particularly with regard to the detection of venous reflux in MS patients. I cannot agree with the main conclusion of the article; namely, that the cerebral venous characteristics of MS patients are essentially no different from that of healthy controls. The results of the study do not support this conclusion. Instead, they strongly suggest that MS is associated with some form of cerebral venous abnormality. The results of the study clearly show that when upright, the average flow (318ml/minute) through the internal jugular veins (IJVs) of the MS patients was over twice that in the control group (123ml/ minute). This finding was strongly significant (p < 0.001). Indeed, it appears to be the only statistically significant finding of the study. In order to understand the full implications of the physiological data presented, it is necessary to undertake a hydrodynamic analysis of the results, something that Doepp and colleagues appear to have neglected. Without such analysis, it is all too easy to misinterpret the results. Analysis of the data reveals that when the MS patients were upright, the blood flow rate through the IJVs was 2.5 times greater than that of the healthy controls, despite the fact that the cross-sectional area (CSA) of the IJVs was no greater. Hydrodynamically, this is a highly unusual situation, which raises some interesting questions. Given that the blood flow through the vertebral veins (VVs) in both cohorts was broadly similar, why then should a much greater proportion of the blood draining from the brain in the MS patients choose to flow through the IJVs rather than through other extrajugular pathways? The only plausible answer to this question is that, for some unknown reason, the resistance of the other extrajugular venous pathways must have greatly increased in the MS patients. This can be easily illustrated if one simplifies the extracranial venous network as shown in the Figure. In the Figure, Qt represents the total blood flow rate from the brain; Rijv and Qijv represent the resistance and flow rate through the IJVs; Rvv and Qvv represent the resistance and flow rate through the VVs; Rop and Qop represent the resistance and flow rate through other venous pathways; and DP represents the pressure drop across the whole system. Throughout the system the relationship between the variables is governed by the general equation: Q 1⁄4 DP R (1)
