Published online before print January 26, 2012, doi: 10.3174/ajnr.A2991
AJNR 2012 33: E30

K. Dolic^a and K. Marr^a
aBuffalo Neuroimaging Analysis Center
State University of New York

R. Zivadinov^b,c
bBuffalo Neuroimaging Analysis Center
State University of New York
^cThe Jacobs Neurological Institute, Department of Neurology
University at Buffalo, State University of New York
Buffalo, New York

We read with interest the article entitled “Positional Venous MR Angiography: An Operator-Independent Tool to Evaluate Cerebral Venous Outflow Hemodynamics,” originally published in the American Journal of Neuroradiology on-line on November 3, 2011.¹

We believe that the authors did not consult relevant references previously reporting some of the key issues investigated by their study; the authors state that strictures of the jugular veins are common in healthy subjects at the level of the craniocervical junction in the supine position, which has already been noticed in previous work.^2–4 In these studies, a high incidence of venous stenoses at the level of the lateral mass of the atlas (C1) and at the level of the inferior thyroid gland (C6/C7), in a cohort of healthy subjects and patients with multiple sclerosis (MS), was a physiologic finding (mostly due to compression of the adjacent structures) on the basis of the test-retest reproducibility results.⁴ It was reported by Niggemann et al¹ that criterion 3 on Doppler sonography⁵ represents a “proximal (superior) stricture of the IJV [internal jugular vein],” whereas criterion 3 referred to the “high resolution B-mode evidence of proximal IJV stenoses.” The term “proximal” refers to relationship to the heart, indicating that stenosis is considered at the level of the thyroid or lower IJV area, not the upper craniocervical junction area.

Furthermore, the authors compared the IJV strictures in the supine-versus-upright position, which is not possible because in the supine position, the main venous extracranial outflow is through IJVs, so the signal-intensity flow in the IJVs in the upright position is very low or absent. This makes reliable determination of vein morphology changes difficult.⁵ On the basis of their results, which probably represent physiologic findings,^2–4 they make a conclusion regarding the validity of the use of MR venography stenosis findings as a criterion for detection of chronic cerebrospinal venous insufficiency. In our opinion, this is an erroneous and misleading statement because previous reproducibility studies have shown that stenoses at the reported levels of C1/C6/C7 present with high variability in both patients with MS and healthy controls.⁴

Although the authors mentioned briefly that veins are prone to collapse, they do not discuss this in light of their findings, especially with respect to change toward the upright position, as previously described.^2–4 In addition, by using only the 2D time-of-flight technique, they were not able to alleviate some of the usual MR venography artifacts and provide more detailed flow information. It was previously reported that assessment of reflux into the venous system by MR venography is not reliable even at 3T.^2–4 In addition, criterion 1 on Doppler sonography⁵ represents reflux in the supine and upright position, not the supine or upright position, as reported by the authors. Also, the low strength of their MR imaging machine, 0.6T, and thicker sections used, 3.5 mm, which led to poor contrast and spatial resolution in comparison with standard MR imaging devices with 1.5–3T strength and section thicknesses of 1.5 mm, could have influenced their results considerably.

References

1. Niggemann P, Seifert M, Förg A, et al. Positional Venous MR Angiography: An Operator-Independent Tool to Evaluate Cerebral Venous Outflow Hemodynamics. AJNR Am J Neuroradiol 2011;33:246–51
2. Hojnacki D, Zamboni P, Lopez-Soriano A, et al. Use of neck magnetic resonance venography, Doppler sonography and selective venography for diagnosis of chronic cerebrospinal venous insufficiency: a pilot study in multiple sclerosis patients and healthy controls. Int Angiol 2010;29:127–39 » Medline
3. Zivadinov R, Galeotti R, Hojnacki D, et al. Value of MR venography for detection of internal jugular vein anomalies in multiple sclerosis: a pilot longitudinal study. AJNR Am J Neuroradiol 2011;77:138–44
4. Zivadinov R, Lopez-Soriano A, Weinstock-Guttman B, et al. Use of MR venography for characterization of the extracranial venous system in patients with multiple sclerosis and healthy control subjects. Radiology 2011;258:562–70 » Abstract/FREE Full Text
5. Zamboni P, Galeotti R, Menegatti E, et al. Chronic cerebrospinal venous insufficiency in patients with multiple sclerosis. J Neurol Neurosurg Psychiatry2009;80:392–99 » Abstract/FREE Full Text

Reply

Published online before print January 26, 2012, doi: 10.3174/ajnr.A3008
AJNR 2012 33: E31

P. Niggemann^a and M. Seifert^a
aDepartment of Radiology
University of Bonn
Bonn, Germany

A. Förg^b
bPrivatpraxis für Upright MRT
Aschheim, Germany

H.H. Schild^c and H. Urbach^c
cDepartment of Radiology
University of Bonn
Bonn, Germany

T. Krings^d
dDepartment of Neuroradiology
Toronto Western Hospital
Toronto, Canada

We appreciate the opportunity to respond to criticisms of our article by Dolic et al.

Dolic et al state that the internal jugular veins (IJVs) show a normal variation in caliber due to compression from adjacent structures and suggest that we mistook these for strictures. To avoid this mistake, we chose only to take reductions of diameter of more than 90% into account. Variations in caliber due to external compression can be seen on Fig 2 at the craniocervical level, and they did not meet our definition of a stricture. The difference between these caliber variations and strictures as shown in Figs 3 and 4 is obvious and needs no further explanation. However, as Dolic et al pointed it out and as we wrote, our findings are not to be considered pathologic because no patient with multiple sclerosis was investigated.

We are well aware of the methodologic differences between duplex sonography and MR venography and their respective limitations, as stated in our work. We do agree that the reduced flow in the IJV in the upright position makes it difficult to acquire sufficient signal intensity to perform MR venography and that correlation with duplex sonography is needed.

Dolic et al rebut our discussion of the criteria for chronic cerebrospinal insufficiency. Although some formulations might not be optimal, they did not influence our findings and confirm the need to correlate positional MR venography findings with those in duplex sonography.

In their letter, they condemn that we do not discuss the reasons for the collapse of the IJV throughout and suggest citing their own works. Because the physiology of the cerebral venous outflow system is well-known, we referred to excellent pioneer works covering this topic. The strength of our work is that, contrary to other recent rather theoretic works, we can actually demonstrate in an objective way the physiologic changes in the cerebral venous blood outflow system.

Finally, they question the ability to acquire a reliable MR venography at 0.6T and point out that high-field magnets are less prone to artifacts in MR venography. This is undoubtedly true, and it will never be possible to acquire images of equal quality in a 0.6T compared with a 3T magnet. Due to machine design, it is, however, impossible to perform positional MR venography in high-field magnets.

We maintain that positional MR venography is a promising new tool for showing the cerebral blood outflow system and is suitable for detecting morphologic variances in the outflow system. However, its usefulness in patients with suspected CCVSI has yet to be investigated, and a correlation with duplex sonography in these patients is mandatory.