Microanatomy of the dura mater at the craniovertebral junction and spinal region for safe and effective surgical treatment.

Abstract

Few reports have been published regarding the detailed microsurgical anatomy of the dura mater at the craniovertebral junction (CVJ), although many neurosurgeons have had the opportunity to conduct surgeries in this region, such as in cases of Chiari malformation. The authors aimed to evaluate the detailed and precise microsurgical anatomy of the dura mater at the CVJ for safe and effective surgical treatment at this area. This study consisted of dissection of 4 formalin-fixed, continuous, human cadaveric dura maters, extending from the posterior fossa to the C2 level. After removing the occipital bone and C1 laminae, a dural incision was made to harvest the specimen. The following structural and topographical aspects of the dura mater in each region were studied: 1) thickness, 2) morphological characteristics, and 3) vascular structures. The average thicknesses of the dura mater were 313.4 ± 137.0 μm, 3051.5 ± 798.8 μm, and 866.5 ± 359.0 μm in the posterior cranial fossa, CVJ, and spinal region, respectively. The outer layer of the posterior cranial dura mater and the tendon of the rectus capitis posterior minor muscle were connected, forming the "myodural bridge." The dura mater at the CVJ had a well-developed vascular network. These vascular structures were determined to be veins or the venous sinus, and were mainly located around the interface between the inner layer of the cranial dura mater and the rectus capitis posterior minor muscle layer. Regarding the morphological features, the bulging located in the inner layer of the dura mater at the CVJ was determined to be the marginal sinus, and contained a pacchionian granulation that allowed for CSF circulation. In the spinal region, the dura mater was characterized by a single, thick layer enclosing the collagen fibers with almost the same orientation. The dura mater at the CVJ displayed dynamic morphological changes within an extremely short segment. Its characteristic anatomical features were not similar to those in the cranial regions. The dural bulging at the CVJ was determined to be the venous sinus. During surgery in the posterior fossa, CVJ, and spinal cord, different procedures should be used because of the specific microsurgical anatomy of each region.