The biomechanics, and physiological function of MDBC in dog.

Objective: The myodural bridge (MDB) connects the suboccipital musculature to the spinal dura mater (SDM) as it passes through the posterior atlanto-occipital and the atlanto-axial interspaces. It has recently been proposed that head movement may assist in powering the movement of cerebrospinal fluid (CSF) via muscular tension transmitted to the SDM via the MDB. Methods: The present study utilized dogs as the experimental model to explore the MDB's effects on the CSF pressure (CSFP) during stimulated contractions of the suboccipital muscles as well as during manipulated movements of the atlanto-occipital and atlanto-axial joints. Additionally biomechanical tensile strength tests were conducted. Results: The tensile strength of the collagenous fibers passing through the dorsal atlanto-occipital and atlanto-axial interspaces were 0.16±0.04 MPa and 0.82±0.57 MPa, respectively. Passive head movement, including lateral flexion, rotation, as well as flexion--extension, all significantly increased CSFP. Furthermore, the CSFP was significantly raised from 12.41± 4.58 to 13.45±5.16 mm Hg when the obliquus capitis inferior (OCI) muscles of the examined specimens were electrically stimulated. Head movements appeared to be an important factor affecting CSF pressure, with the MDB of the suboccipital muscles playing a key role in this process. Conclusion: The present study provides direct evidence to support the hypothesis that the MDB may be a previously unappreciated significant power source (pump) for CSF circulation. [ABSTRACT FROM AUTHOR]