Critical infections in the head and neck: A pictorial review of acute presentations and complications

Non-traumatic head and neck emergencies include several disease processes such as infectious, inflammatory, and malignant. Infections are among the most common pathological processes that affect the head and neck, and are particularly important due to their acute, severe, and potentially life-threatening nature. Radiologists need to be well acquainted with these entities because any delay or misdiagnosis can lead to significant morbidity and mortality. Having a general understanding of such diseases is crucial, their prevalence, clinical presentation, common causative pathogens, route of spread, potential complications, and multimodality radiological appearance. Furthermore, understanding the relevant anatomy of the region, including the various fascial planes and spaces, is essential for radiologists for accurate image interpretation and assessment of potential complications. Our aim is to review the most common severe infections affecting the head and neck as well as other rare but potentially life-threatening infections. We will also describe their imaging features while focusing on the anatomy of the regions involved and describing their potential complications and treatment options.

Sudden Death: A Practical Autopsy Approach to Unexplained Mediastinitis Due to Fatal Untreated Neck Infections-A Systematic Review

Neck infections are often prone to being underestimated and can manifest insidiously. The spread of infection can lead to translocation into thoracic areas, causing descending necrotizing mediastinitis (DNM). However, the application of the post-mortem approach in such cases is not well-described in the literature. A literature review was carried out according to the PRISMA methods. Nine papers were included in the final review, revealing different levels of involvement of neck layers that can be linked to different causes. Expertise with respect to the anatomy of the fasciae and spaces of the neck enables an understanding of the pathogenesis of DNM. However, a clear autoptic description was not provided in any of the articles. Therefore, we also employed a practical post-mortem approach to cases of death due to DNM. It is fundamental for pathologists to identify the exact head and neck structures involved. Providing dissectors with support from an otolaryngologist could be useful. This paper could help address such difficult cases.

Simple Universal Whole-Organ Resin-Embedding Protocol for Display of Anatomical Structures

Whole-organ plastic resin casting is a very useful method for preserving rare pathological specimens for forensic/anatomical studies and for teaching/research purposes. Many techniques have been proposed over time, but most of them use special non-commercially available resin mixtures, lengthy protocols, and are overall not easily implemented in any anatomy/pathology department that might need such a procedure for rapid organ preservation. Here, we utilized anatomical sections of the human brain, heart, kidneys, spleen, large intestine, and lungs from on-display organs that were fixed for more than 1 year in 10% neutral-buffered formalin and from a freshly processed cadaver for teaching purposes in our Human Anatomy Department, and we optimized a fast-processing protocol without the use of any clearing agents, which yields solid, clear, cylindrical resin casting blocks. The resulting protocol, which takes no longer than 4 days, proves that at least three commonly used epoxy resins from hobby shops can be utilized without any restrictions, and the use of resin or glycerin vacuum-forced impregnation even offers two choices of intrinsic contrast, depending on the nature of the preparation. A number of innovations have been included here and compared to existing publications, such as the use of a system of permanent fixation plexiglas rods that maintain the organ in the desired position and become invisible in the final block, the use of UVC sterilization of the tissue to ensure a long shelf life of the block, and the utilization of cheap cylindrical polypropylene food containers as casting molds. Altogether, we present a simple resin-embedding protocol that can be made available to any department/institution without the need for expensive materials and specially trained personnel.

The Alar Fascia and Danger Space: A Modern Review

PURPOSE

Given the advancements in dissection modalities over the last decade, what is the current understanding of the alar fascia and its clinical implications as an access point into the danger space (DS)? The aim of the study is to provide an updated review of the alar fascia and danger space.

METHODS

A comprehensive search of the alar fascia and danger space was performed through PubMed databases up to August 2022. Thirty-two sagittal E12 sheet plastination slices of the head and neck were analyzed under a stereomicroscope to assess the morphology and continuity of the retropharyngeal, alar, and prevertebral fasciae (PVF and their respective potential spaces).

RESULTS

Recent advancements have provided evidence that the alar fascia is a true fascial layer between the retropharyngeal and danger spaces within the deep cervical region. Although its composition, histological features, and borders remain topics of controversy, the alar fascia is comprised of dense connective tissue and may serve as a physical barrier to prevent the spread of infection into the danger space. Complications arising from deep neck infections that invade the danger space include mediastinitis, necrotizing fasciitis, and empyema.

CONCLUSION

A proper understanding of the anatomy, structure, function, and potential spaces is crucial to assessing the alar fascia and danger space routinely in clinical practice, especially when imaging.

The Posterior Atlantooccipital Membrane: The Anchor for the Myodural Bridge and Meningovertebral Structures

INTRODUCTION

Sheet plastination has provided evidence that the posterior atlantooccipital membrane attaches to the dura's posterior sleeve at the cerebrospinal junction. These findings contradict the traditional anatomical description of this membrane extending from the atlas' posterior arch to the foramen magnum.

METHODS

A total of 16 plastinated cadavers were studied to evaluate the in situ and gross configuration of the posterior atlantooccipital membrane. Fifteen cadavers underwent sheet plastination, and one head was hemisected and plastinated. In all specimens, stereomicroscopy was used to evaluate the posterior atlantooccipital membrane and related structures within the intervertebral and epidural spaces.

RESULTS

In all 16 specimens, the posterior atlantooccipital membrane extending from the occiput, merged with the craniocervical dura mater, and formed a membrane-dura complex that ended at the level of the third cervical vertebra. The superior and inferior myodural bridge coalesced with their respective vertebrodural ligaments and fused with the posterior atlantooccipital membrane at their respective interspaces.

CONCLUSION

The median aspect of the posterior atlantooccipital membrane does not directly communicate with the posterior arch of the atlas. Instead, the posterior atlantooccipital membrane converges with the craniocervical dura mater and terminates at the level of the third cervical vertebra. This membrane-dura complex serves as a common attachment site for the myodural and vertebrodural structures.

Nontraumatic Head and Neck Emergencies

Head and neck imaging is an intimidating subject for many radiologists because of the complex anatomy and potentially serious consequences of delayed or improper diagnosis of the diverse abnormalities involving this region. The purpose of this article is to help radiologists to understand the intricate anatomy of the head and neck and to review the imaging appearances of a variety of nontraumatic head and neck conditions that bring patients to the emergency department, including acute infectious and inflammatory diseases and acute complications of head and neck neoplasms. These conditions are presented in five sections on the basis of their primary location of involvement: the oral cavity and pharynx, neck, sinonasal tract, orbits, and ears. Important anatomic landmarks are reviewed briefly in each related section.Online supplemental material is available for this article.^©RSNA, 2019.

Anatomical and histological study of the alar fascia

INTRODUCTION

The alar fascia remains one of the most variably described fascial structure in the human body. Much disagreement persists in the literature and mainstream anatomical texts about its anatomy, function, and clinical significance. It is generally described as a coronally oriented fascial sheet separating the retropharyngeal space anteriorly from the danger space posteriorly. The current study aimed to confirm the presence of the alar fascia and delineate its anatomical characteristics, connections, and potential function through gross dissection and microscopic analysis. Possible clinical and surgical implications are considered.

METHODS

Twelve (12) cadaveric necks were dissected and examined histologically. Smooth muscle (αSMA), nerve (S100 protein), and myosin proteins were identified immunohistologically to characterize the composition and possible functions of the alar fascia.

RESULTS

The alar fascia was found in all specimens spanning between the carotid sheaths. Morphologically, it was not a delamination or derivative of the prevertebral fascia. It extended from the base of the skull to the upper thoracic level (T2) where it fused with the visceral fascia. No midsagittal connection was found between the alar and visceral fasciae. Immunohistochemically, the alar fascia was positive in focal areas for αSMA and S100 proteins but negative for fast and slow myosin.

CONCLUSION

The alar fascia is an independent and constant coronal fascial layer between the carotid sheaths. It contains neurovasculature and may limit the spread of retropharyngeal infections into the thorax as well as facilitate normal physiological functions of the cervical viscera.

The intercarotid or alar fascia, other cervical fascias, and their adjacent spaces - a plea for clarification of cervical fascia and spaces terminology

Due to varying descriptions and terminology of fascias of the neck, medical advice relying on this basic knowledge is insufficient. Our goal was to provide a precise anatomical description of cervical fascias and spaces with special focus on the intercarotid fascia, or the alar fascia. One hundred bodies donated to science embalmed with Thiel's method were investigated, cervical fascias were dissected layer by layer, and the results were documented by photography, with a focus on the intercarotid fascia. In addition, we performed a review of recent literature concerning cervical surgical interventions, radiological diagnostic pathways, and basic anatomical works focusing on core information on anatomical relations of cervical fascias and spaces. In another 10 bodies donated to science, the spaces of the neck were injected with coloured latex under ultrasound guidance, dissected, and documented by photography. The intercarotid fascia was a constantly developed connective tissue interconnecting the carotid sheath of both sides. In 52 of 100 specimens (52%) it crossed to the opposite side without any fusion to the ventrally situated visceral fascia. Fusion with the visceral fascia was found in 48%, either at the lateral border of the pharynx or on its dorsal side. The results of our dissections strengthen the precise description of the cervical fascias provided by Grodinsky and Holyoke in 1938. Spaces can be confirmed as described by Hafferl in 1969. The international anatomical and ENT societies should codify a unified anatomical terminology of the cervical spaces and fascias to prevent varying interpretations in the future.

Early stages of development of the alar fascia (human specimens at 6-12 weeks of development)

In recent years, there has been much discussion concerning the cervical fasciae. The aim of this study is to confirm and to describe the development of the alar fascia as well as its relationship with nearby structures. Histological preparations of 25 human embryos (6-8 weeks of development) and 25 human fetuses (9-12 weeks of development) were studied bilaterally using a conventional optical microscope. Our study confirms the existence of the alar fascia and permits three stages to be established during its development. The initial stage (1st), corresponding to the 6th week of development (Carnegie stages 18-19), is characterized by the beginning of the alar fascia primordium in the retroesophageal space at the level of C7-T1. In the formation stage (2nd), corresponding to the 7th and 8th weeks of development (Carnegie stages 20-23), the alar fascia primordium grows upwards and reaches the level of C2-C3. In the maturation stage (3rd), beginning in the 9th week of development, the visceral, alar and prevertebral fasciae can be identified. The alar fascia divides the retrovisceral space (retropharyngeal and retroesophageal) into two spaces: one anterior (between the alar fascia and the visceral fascia and extending from C1 to T1, named retropharyngeal or retroesophageal space according to the level) and the other posterior (between the alar fascia and the prevertebral fascia, named danger space). We suggest that this latter space be named the retroalar space. This study suggests that alar fascia development is related to mechanical factors and that the alar fascia permits the sliding of the pharynx and the oesophagus during swallowing.

The Fascial Layers Attached to the Skull Base: A Cadaveric Study

OBJECTIVE

A profound understanding of the relationship between the deep cervical fasciae and the skull base is essential for skull base surgery. To our knowledge, there has been little research on the relationship between the deep cervical fasciae and inferior surface of the skull base; thus, this study aims to examine the fascial network of the skull base.

METHODS

Two cadaveric heads are dissected to reveal the fascial network of the skull base and 19 sides of cadaveric heads were used to reveal an anatomical variant of the pterygospinous and pterygoalar ligaments/muscles.

RESULTS

The interpterygoid fascia is attached to the skull base along the sphenopetrosal fissure and tympanosquamous suture. The tensor vascular styloid fascia extends from the inferior border of the tensor veli palatini and covers the tympanic bone and styloid apparatus laterally. The pharyngobasilar fascia attaches to the pharyngeal tubercle on the inferior surface of the basilar part of the occipital bone and petro-occipital synchondrosis. In the middle of the clivus, we found thick fibrocartilaginous tissue and the prevertebral fascia fused to this area. Fascia of the longus capitis, the tensor-vascular styloid fascia, and stylopharyngeal fascia extend laterally and form the complex fascial network around the internal jugular vein and the internal carotid artery. The carotid sheath attaches anteriorly to the vaginal process and posteriorly to the fibrocartilaginous tissue around the jugular foramen and carotid canal.

CONCLUSIONS

This study comprehensively exposes the fascial network of the skull base. Our cadaveric dissection findings support those from previous imaging-anatomical studies. Precise knowledge of these fascial layers is essential for accurate diagnosis and understanding the spread of disease, as well as helping skull base surgeons safely perform challenging procedures.

Histological study of the thin membranous structure made of dense connective tissue around the esophagus in the upper mediastinum

BACKGROUND

The structure of the fascia in upper mediastinum has already been reported from gross anatomical viewpoints by Sarrazin. But it is necessary to understand meticulous anatomy for thoracoscopic or mediastinoscopic surgery. So herein, we investigate histologically the thin membranous structure made of dense connective tissues.

METHODS

Semi-sequential transverse sections of the mediastinum were obtained from three cadavers. Hematoxylin and eosin staining, Elastica van Gieson staining, and Masson trichrome staining were performed to identify the presence and location of the thin membranous structure made of dense connective tissues.

RESULTS

The "visceral sheath" and "vascular sheath," as previously described by Sarrazin, were observed histologically. These two thin membranous structures do not surround the esophagus and trachea cylindrically. In addition, the "visceral sheath" on the right side of the upper mediastinum was unclear in comparison to the left side. The "visceral sheath" (on the left side) gradually became unclear, and seemed to almost disappear; the esophagus was found to be very close to the thoracic duct on the caudal side of the bifurcation of the trachea. Although the left recurrent nerve was located inside the "visceral sheath" in all cadavers, the left recurrent nerve lymph nodes were located inside the "visceral sheath" in cadaver 1 and between the "visceral sheath" and "vascular sheath" in cadaver 3.

CONCLUSION

The "visceral sheath" around the esophagus in the upper mediastinum was histologically demonstrated; however, the findings were not constant.

Anatomical and histological study of the deep neck fasciae: does the alar fascia exist?

PURPOSE

The aim of this study was to determine whether the alar fascia is a distinct layer of the deep cervical neck fasciae. The present study also aimed to elucidate the anatomical limits of this fascia.

METHODS

Neck dissections of ten adult cadavers were performed, layer by layer, in the retropharyngeal region, under a powered operating microscope. Detailed dissections revealed the anatomical limits of the deep neck fasciae. Histological descriptions were also performed on large tissue samples collected from three cervical dissections.

RESULTS

In the ten dissections, three layers of fascia were identified and dissected in the retropharyngeal region: a visceral fascia, a prevertebral fascia and an alar fascia. The alar fascia appeared like a connecting band derivative of the visceral fascia, between both vascular sheaths. It fused completely with the visceral fascia anteriorly at the level of T2 and with the prevertebral fascia posteriorly at the level of C1. No sagittal connection between the visceral fascia and the prevertebral fascia was identified. The stained histological sections confirmed the presence of the visceral and prevertebral fasciae at the oropharyngeal level, with a third intermediate layer closely connected with the visceral fascia.

CONCLUSION

The alar fascia is a layer of the cervical neck fascia connected with the visceral fascia from C1 to T2 levels. The anatomical limits of this alar fascia and its relationships with the internal carotid artery are important in the surgical management and the prognosis of deep neck infections and retropharyngeal lymph node metastases.