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Archived Comments for: Assessment of calvarial structure motion by MRI

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  1. Serious flaws in study

    Theodore Jordan, Dept Med Ed, Doctors Hospital, Columbus, OH USA

    12 September 2009

    The study entitled “Assessment of calvarial structure motion by MRI”, claims to have measured a change in calvarial transverse sectional area over time, and is interpreted to represent a change in intracranial fluid volume changes. However, this study has serious flaws in both its design and interpretation. It appears that all measurements were made of the outer most diameter of the tissues of the scalp, and this measurement implies nothing about intracranial dynamics.
    The authors could have been clearer regarding the exact parameters measured. Figure 3 is an example of the MRI image after adjusting grayscale threshold to represent only the two shades of gray and black. The brain matter is represented in gray. The bone of the clavarium is represented as the surrounding black, and surrounding the bone is another area of gray representing the tissues of the scalp. By carefully looking at the very outer pixels of figure 3, it appears that figure 4 is a pixilated representation of the very outer border of the gray-scale scalp tissues of figure 3. Therefore, figure 4 represents neither the inner, nor the outer border of the calvarial bone as imaged on MRI, but rather the very outer border of the tissues of the scalp.
    If the above interpretation of the measured parameters is correct, then this study succeeds in demonstrating that the outer diameter of the scalp may expand and contract over time. Since the late nineteenth century, it has been known that there are vasomotor waves in cutaneous tissue, which swell and recede in response to changes in blood volume. These are known as third-order waves, or Traube-Hering-Mayer waves. This phenomenon has later been associated with the rhythmic changes of the sympathetic nervous system tone and with blood flow dynamics associated with parasympathetically mediated heart rate variability [1].
    In a study using laser flowmetry to measure blood flow dynamics scalp in adults, the rhythmic expansion and contraction of the scalp, known to osteopaths as the ‘cranial rhythmic impulse’ (CRI) was further correlated to be essentally synchronous with the third-order vasomotor phenomenon [2].
    It is of no surprise that the outer diameter of the scalp changes over time. To assume that this represents changes of intracranial dynamics, one would have to assume that the thickness of the scalp does not change. It is unclear why the authors chose to use the outer most border of the MRI scan for this study (representing outermost scalp), rather than using the inner table of the bone of the skull for pixillation and measurement.
    The conclusions that this study “is suggestive of inherent motion in calvarial structure”, and that “the total intracranial area appeared to expand and recede” are invalid conclusions and not supported by the methodology used in this study.


    Theodore Jordan, DO C-NMM
    Dept. Medical Education
    Doctors Hospital, Columbus, OH

    [1] Myers CW et al. A model for the genesis of arterial pressure Mayer waves from heart rate and sympathetic activity. Autonomic Neurosci: Basic and Clin 2001;91:62-75
    [2] Nelson et al. Cranial rhythmic impulse related to the Traube-Hering-Mayer oscillation: comparing laser-Doppler flowmetry and palpation. JAOA 2001;101:163-73

    Competing interests


  2. Solid Methodology: A reply to comment by Dr. Jordan

    Hollis King, The Osteopathic Research Center

    17 September 2009

    The authors appreciate the concern expressed by Dr. Jordan and the opportunity to respond. Dr. Jordan is correct in that his question could have been addressed in the article and rendered his comment unnecessary. The issue raised is technical and based on the threshold settings for ImageJ analysis. The methodology employed in the present study used settings that focused analysis only on the bone, not any gray area outside, or inside the bone. The threshold settings used on all 160 individual images allowed analysis only on dense boney structure. The link provides access to the actual MRI image from which figures 3 and 4 were generated to illustrate the steps in the ImageJ analysis. The outer white ovoid is bone, and all dimensions analyzed were based on the outer edge of the white bone image, which were similar but not exactly the same outer dimensions illustrated in figures 3 and 4. The only difference being the threshold settings which allowed the assessment of the outer bone surface.

    Dr. Jordan is not correct in his analysis of what Figure 3 shows, as the threshold settings do exclude certain intensities of “gray,” such as skin on the external surface of the skull. Based on visual observation of the figures presented in the article it is not possible to ascertain the dimensions Dr. Jordan appears to be addressing. The figures were cropped and resized for publication, which distorts the kind of visual analysis referred to by Dr. Jordan.

    The authors point out that the mean calvarial area difference reported was 122.69 mm2. Even if skin area external to the skull was included in the area analyzed, it is unlikely that such tissue could expand and contract in such a large dimension anywhere on the skull, much less at the level of the calvarial plane imaged in this study.

    In the article, it is clearly stated that we do not yet know what the mechanism of action is for the apparent calvarial structure motion. We simply state it, “…could reflect the change in intracranial fluid volume…” which is a plausible explanation.

    The methodology utilized in this study was solidly based on accepted scientific procedures and not flawed as suggested by Dr. Jordan. The authors stand by the data reported in the article.

    Hollis H. King, DO, PhD, FAAO
    William T. Crow, DO, FAAO
    Rita M. Patterson, PhD
    Vincent Giuliano, MD

    Competing interests

    No competing interests