A new concept of the fiber composition of cervical spinal dura mater: an investigation utilizing the P45 sheet plastination technique

Abstract

Purpose: Few reports have been published regarding the microanatomy of the dura mater located at the craniovertebral junction (CVJ). In clinic, the precise microanatomy of the CVJ dura mater would be taken into account, for reducing surgical complications and ineffective surgical outcomes. The main objective of the present investigation was to further elucidate the fiber composition and sources of the cervical spinal dura mater.

Methods: The formalin-fixed adult head and neck specimens (n = 21) were obtained and P45 plastinated section method was utilized for the present study. The fibers of the upper cervical spinal dura mater (SDM) were examined in the P45 sagittal sections in the CVJ area. All photographic documentation was performed via a Canon EOS 7D Mark camera.

Results: The posterior wall of the SDM sac at CVJ was found to be composed of stratified fibers, which are derived from three sources: the cerebral dura mater, the occipital periosteum, and the myodural bridge (MDB). The proper layer of the cerebral dura mater passes over the brim of the foramen magnum and enters the vertebral canal to form the inner layer of the SDM, and the fibers originating from the periosteum of the brim of the foramen magnum form the middle layer. The fibers of the MDB are inserted into the SDM and form its outer layer. It was found that the total number of fibers from each origin varied in humans.

Conclusion: At the CVJ, the posterior wall of the SDM is a multi-layered structure composed of three different originated fibers. The cerebral dura mater, the periosteum located at the brim of the foramen magnum, and MDB contribute to the formation of the SDM. The present study would be beneficial to the choice of surgical approach at the CVJ and the protection of the SDB.

Keywords: Craniovertebral junction; Microanatomy; P45 plastination; Spinal dura mater.

Fig. 1

Images evidencing the three sources of the distinct fibers composing the spinal dura mater and an illustrative diagram. Occi, occipital bone; RCPmi, the rectus capitis posterior minor muscle; C1, atlas; hollow arrowhead, cerebral dura mater; solid arrowhead, spinal dura mater; double arrow, spinal dura mater; solid star, the fibers from the occipital periosteum; hollow star, the MDB; hollow arrow, the thickened spinal dura mater

Fig. 2

Images evidencing the fibers of different shapes and thicknesses emanating from the two distinct forms of the occipital bone, sharp vs. blunt. A the fibers from the occipital periosteum and the MDB were few and sparse; B fiber characteristics when the shape of the occipital bone is blunt; C fiber characteristics when the shape of the occipital bone is sharp. Occi, occipital bone, RCPmi, the rectus capitis posterior minor muscle; C1, atlas; hollow arrowhead, cerebral dura mater; solid arrowhead, spinal dura mater; double arrow, spinal dura mater; solid star, the fibers of the occipital periosteum; hollow star, the MDB

Fig. 3

Images evidencing the confluence characteristics of the three types of constituent fibers. A no stratification between the fibers; B the distinct stratification between the fibers; Cthe multiple stratification between the fibers. Occi, occipital bone; RCPmi, the rectus capitis posterior minor muscle; C1, atlas; hollow arrowhead, cerebral dura mater; solid arrowhead, spinal dura mater; double arrow, spinal dura mater; solid star, the fibers of the occipital periosteum; hollow star, MDB; hollow arrow, the thickened spinal dura mater