Investigation of meningomyovertebral structures within the upper cervical epidural space: a sheet plastination study with clinical implications.

BACKGROUND CONTEXT: Over the past two decades, soft-tissue structures communicating with the dura mater within the epidural space have become the focus of many anatomical and histopathologic studies. The relationship between these bridging structures has yet to be evaluated in situ. PURPOSE: This is the first study that used E12 sheet plastination to investigate the epidural space of the upper cervical spine in situ and its associated bridging structures. Given the complexity of this space, this study may prove useful to clinical anatomists and surgeons who operate within this region. STUDY DESIGN: Anatomical and microscopic analyses of structures that communicate with the dura mater within the upper cervical region were carried out. METHODS: Gross dissection in conjunction with microscopy was used to evaluate bridging communications of the upper cervical spine in 10 cadavers. To evaluate the in situ arrangement of these structures, E12 sheet plastination was used on 13 cadavers. RESULTS: In all 23 specimens, suboccipital fascia coalesced with the dorsal meningovertebral ligament of the atlas, and inserted directly into the posterior surface of the dura as a single but separable laminar layer. At the level of the atlantoaxial interspace, suboccipital fasciae combined and coalesced with the dorsal meningovertebral ligament of the atlas and the axis. These structures inserted into the posterior surface of the dura mater as a single but separable layer. Microscopy validated these findings and E12 sheet plastination revealed the in situ organization of these soft-tissue structures. E12 sheet plastination also provided new information on dural arrangement at the craniocervical junction, which was observed to be composed of periosteum from the occiput but consisted mainly of deep fascia from the rectus capitis posterior minor. CONCLUSIONS: E12 sheet plastination has provided in situ visualization of bridging structures within the cervical epidural space and offers new insight into these structures, as well as the composition and arrangement of the posterior atlantooccipital membrane and cerebrospinal dura at the craniocervical junction. This study aims to expand on the anatomical understanding of the upper cervical region while defining structures that may reduce neurosurgical complications, and aid in the understanding of the pathophysiology of certain neurogenic disorders.

Defining the Morphology and Distribution of the Alar Fascia: A Sheet Plastination Investigation.

OBJECTIVES: This study aims to delineate the morphology, integrity, and distribution of the alar fascia using dissection and E12 sheet plastination. This is the first study that employs E12 sheet plastination to investigate the alar fascia and its adjacent potential spaces. METHODS: Twenty-nine manual dissections and 3 sets of E12 sheet plastinations were used to examine the posterior pharyngeal region for the architecture and distribution of the alar fascia. Specimens were examined from the inferior nuchal line to C6. RESULTS: The alar fascia originated as a well-defined midline structure at the level of C1 and could be identified down to C6. There was no evidence of the alar fascia between the inferior nuchal line and the base of the skull. Notably, the alar fascia permitted resistance to manual traction. CONCLUSIONS: E12 sheet plastination allowed for visualization of the alar fascia's superior attachments within the deep cervical region. Resistance to traction suggests that the alar fascia may be more than just a loose fibroareolar matrix. The findings in this study suggest an alternative point of entry into the danger space. Understanding the continuity of this fascial layer is critically important with regard to the pathophysiology of deep neck space infections.

Does the investing layer of the deep cervical fascia exist?

BACKGROUND: The placement of the superficial cervical plexus block has been the subject of controversy. Although the investing cervical fascia has been considered as an impenetrable barrier, clinically, the placement of the block deep or superficial to the fascia provides the same effective anesthesia. The underlying mechanism is unclear. The aim of this study was to investigate the three-dimensional organization of connective tissues in the anterior region of the neck. METHODS: Using a combination of dissection, E12 sheet plastination, and confocal microscopy, fascial structures in the anterior cervical triangle were examined in 10 adult human cadavers. RESULTS: In the upper cervical region, the fascia of strap muscles in the middle and the fasciae of the submandibular glands on both sides formed a dumbbell-like fascia sheet that had free lateral margins and did not continue with the sternocleidomastoid fascia. In the lower cervical region, no single connective tissue sheet extended directly between the sternocleidomastoid muscles. The fascial structure deep to platysma in the anterior cervical triangle comprised the strap fascia. CONCLUSIONS: This study provides anatomical evidence to indicate that the so-called investing cervical fascia does not exist in the anterior triangle of the neck. Taking the previous reports together, the authors' findings strongly suggest that deep potential spaces in the neck are directly continuous with the subcutaneous tissue.

Configuration of the connective tissue in the posterior atlanto-occipital interspace: a sheet plastination and confocal microscopy study.

STUDY DESIGN: The connective tissue structures in the posterior atlanto-occipital region were investigated using E12 sheet plastinations and confocal microscopy. OBJECTIVES: To define the relationship between rectus capitis posterior minor (RCPm), posterior atlanto-occipital (PAO) membrane, nuchal ligament, and the spinal dura in the PAO interspace. SUMMARY OF BACKGROUND DATA: It has been speculated that connections between the dura and muscles and/or ligaments in the PAO interspace may transmit forces from the cervical spine joint complexes to the pain-sensitive dura, generating cervicogenic headaches. Anatomic structures involved in these connections include the RCPm, PAO membrane, and nuchal ligament. However, there is little information about the nature of these connections and the relationships between these anatomic structures. METHODS: The study used a combined approach, consisting of the gross anatomic dissection of nine cadavers and the E12 sheet plastination method for thirteen adult human cadavers, five of which were further examined using confocal microscopy. RESULTS: The study demonstrates that (1) the tendinous fibers from the medial and deep part of the RCPm muscle are continuous antero-inferiorly with the spinal dura; (2) the PAO membrane is part of the RCPm fascia and tendon and the perivascular sheathes; (3) antero-inferiorly the PAO membrane fuses with the spinal dura rather than the atlas; and (4) the nuchal ligament does not exist in the PAO interspace. CONCLUSIONS: The connective tissue structures that connect the spinal dura to the RCPm muscle in the PAO interspace are the RCPm fascia and tendinous fibers and perivascular sheathes.

Skin ligaments: regional distribution and variation in morphology.

Skin ligaments (SL) (L. retinacula cutis) are present extensively in the face, hands, feet, and in breast tissue, but have seldom been reported elsewhere in the body. The traditional histological view of the subcutaneous region is that it comprises a matrix of loose connective tissue devoid of fibrous specializations. The purpose of this study was to determine the structure and distribution of skin ligaments. Eight embalmed cadavers (3 males, 5 females, 69-90 years of age) were used in this study. Tissue was prepared using the E12 plastination technique. Macroscopic and microscopic examination demonstrated the widespread presence in the limbs and most of the rest of the body of fibrous strands linking the base of the dermis and the superficial fibers of the underlying deep fascia. The morphology and distribution of these skin ligaments were similar in the individuals examined. Variations in the structure of the skin ligaments depended on the presence of underlying muscle, neurovascular bundles, intermuscular septa and adipose tissue. We conclude that skin ligaments are complex fibrous structures that are present over most of the body. They form an extensive peripheral network in the subcutaneous fat. These 'ligaments' seem to provide an anchorage of skin to deep fascia that is flexible and yet resistant to mechanical loading from multi-directional forces. The use of the E12 plastination technique coupled with fluorescent confocal microscopy has been of benefit in visualizing and delineating SLs from other soft tissue structures in three planes.