Current understanding concerning the human deep cervical fascia (DCF) differs between anatomists, surgeons, and radiologists. One reason has been the varying methodologies used to examine the DCF and the terminology assigned to each layer or potential space formed. Previous knowledge concerning the DCF originally came from cadaveric studies. However, such findings were highly subjective, reliant on the dissectionist�s skill with a scalpel. With the recent advent of radiological imaging and sheet plastination, there has been a re-examination of the fascial layers (investing, pretracheal, and prevertebral) that constitute the DCF. Although there is general consensus regarding the existence of the three layers, there is continuing conjecture over the concise anatomical description of these fascial structures. Recently, the investing (superficial) fascia, as a separate fibrous structure, has been questioned with a small number of plastination studies reporting its absence in the postereolateral regions of the neck. Within the suboccipital region (SOS) it is widely reported that the nuchal ligament, extending from the investing layer, directly connects with the spinal dura mater. However, a recent plastination study by Johnson et al. (2000b) found these fibres to dissipate in the SOS.The question remains as to what fibres directly communicate with the spinal dura? The fibrous connective bridge is reported in some clinical studies to originate from the rectus capitis posterior minor (RCPm) via the SOS. The origin of the connective fibrous bridge is essential in understanding the mechanism in the prevention of the phenomenon of 'infolding' and cervicogenic neck pain? Anteriorly, the investing fascia is regarded as a continuance of a 'fibrous collar' that encapsulates the entire neck, yet if it does not truly exist in the posterior neck region, does it actually exist as a tangible structure in the anterior neck? With regard to the deep midline fascial structures that arise from the pretracheal fascia, the presence of two separate spaces, the retropharyngeal and danger space, divided by the alar fascia in the posterior pharyngeal region, is still debated and is yet resolved in the clinical literature.
The aims of this qualitative study were to: 1. determine the dural ligamentous and tendinous connections in the posterior atlanto-occipital (PAO) interspace region, and establish the morphology of the PAO membrane, 2. determine whether the investing layer of the DCF is a distinct fibrous structure in the anterior neck and examine the relationship with the subcutaneous platysma muscle, and 3. determine the relationship between the RPS and DS in the posterior pharynx region and identify the configuration of the alar fascia. Twenty-seven cadavers were examined at the gross, macro- and, microscopic level. Blunt and sharp dissections were conducted on 12 specimens. Fifteen cadavers were prepared as epoxy sheet plastinates. Light, fluorescent and confocal microscopy was conducted on the sheet plastinations.The findings of the first study demonstrated that small discrete bundles from medial tendinous fibres of RCPm formed a fibrous connective tissue bridge directly with the spinal dura in the SOS (in all 6 median-sectioned plastinated specimens), not the nuchal ligament as commonly reported. The RCPm fascia, in conjunction with lateral contributions from the perivascular sheath, formed the PAO membrane (ligamentum flavum) which was not continuous with the neural arch of C1 as often cited in anatomical texts. The cerebrospinal junction was also demonstrated to be a naturally formed multi-layered structure in all plastinates and not the result of pathological change as widely reported in clinical literature.The Gross dissection findings of the second study supported the traditional view that the investing layer formed a covering over the anterior triangle neck region. However, findings from plastinations, in conjunction with confocal microscopy, demonstrated clearly that the investing layer is formed from the epimysium of superficial muscles in the anterior neck. In the suprahyoid neck, it appeared disjointed with the fascia of the sternocleidomastoid (SCM) fascia isolated from the neighbouring submandibular fascia. In the infrahyoid neck, it was formed by medial fascial extensions from the omohyoid fascia, SCM fascia, and fused at the midline to the infrahyoid fascia, (pretracheal layer) resulting in two ipsilateral compartments. Distal 'finger-like' fascicles of platysma presented with individual epimysial fascia, which gave the false appearance of a thickened investing layer. These findings contravene those of the traditional view that the investing fascia is continuous at the mid-line.The findings of the third study agreed with both those reported in radiological and cadaveric studies respectively, in that the alar fascia was not present above the level of C1 as purported by radiologists, but became more apparent below this level. The alar fascia was observed to be formed from medial extensions of the carotid sheath, with some minor contributions from the lateral slips of the prevertebral fascia posteriorly, and was visible within transverse plastinated slices to the level of C7. However, at the levels of C4 and C6, the alar fascia appeared to fuse with the buccopharyngeal fascia, (posterior pretracheal layer of the DCF), a finding not previously reported. This study demonstrated, through E12 sheeted plastinated sections, that the morphology and topography of the DCF is complex, and a more precise understanding of the anatomy of the DCF and associated potential spaces is paramount clinically in otolaryngology, concerning the cervical fascial pathways of potentially life-threatening commutative pathologies.
| Identifer | oai:union.ndltd.org:ADTP/217372 |
| Date | January 2006 |
| Creators | Nash, Lance Graham, n/a |
| Publisher | University of Otago. Department of Anatomy & Structural Biology |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Lance Graham Nash |
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