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

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.

Identification of Deep Cervical Fascial Layers During Anterior Cervical Spine Exposure

BACKGROUND

Anterior approaches to the cervical spine are among the most common exposures by which neurosurgeons and orthopedic surgeons access the prevertebral space and ultimately the cervical disk and vertebral bodies. There is a paucity of literature describing the microanatomic fascial planes of the neck with respect to anterior cervical approaches.

OBJECTIVE

To delineate the microanatomic connections of the cervical fascial planes pertinent to anterior cervical exposure.

METHODS

Using a cadaveric model, original illustrations, the Visible Human Project, and an original surgical video, we demonstrate a stepwise method for identifying the correct planes for anterior cervical exposure.

RESULTS

A step-by-step method for identifying the anterior cervical fascial planes intraoperatively is demonstrated.

CONCLUSION

A comprehensive understanding of anterior cervical microsurgical anatomy is vital for performing a methodical yet efficient approach to the prevertebral space while minimizing retraction and iatrogenic injury to the surrounding neurovascular structures.

MRI of acute neck infections: evidence summary and pictorial review

Infection of the deep neck spaces is a life-threatening acute illness that requires prompt diagnosis and treatment. Magnetic resonance imaging (MRI) offers unsurpassed soft tissue discrimination and is therefore well suited for imaging neck infections. Recently, the feasibility, diagnostic accuracy, and clinical significance of this method have been documented in patients with acute neck infections. This review article summarizes the scientific evidence, provides a practical guide to image acquisition and interpretation, reviews the most common imaging findings, and discusses some difficult diagnoses and pitfalls in acute neck infections, to help both radiologists and clinicians in managing these critically ill patients.

Upgraded hydrodissection and its safety enhancement in microwave ablation of papillary thyroid cancer: a comparative study

OBJECTIVES

To study the efficacy and safety of an improved hydrodissection protocol based on the perithyroidal fascial space during microwave ablation for papillary thyroid carcinoma (PTC).

METHODS

The data of 341 patients (94 men and 247 women, median age 41 years old, 25%-75% interquartile range 34-53 years old, nodule maximum diameter 0.2-1.9 cm) who underwent microwave ablation for PTC were retrospectively reviewed. Among them, 185 patients underwent traditional hydrodissection and served as a control group, and 156 patients underwent improved hydrodissection based on perithyroidal fascial spaces, constituting the improved group. Improvements in safety were analyzed by comparing complications between the two groups. The characteristics of hydrodissected spaces, complications, and follow-up results were recorded.

RESULTS

Hydrodissection was successfully performed in all enrolled patients according to the protocol. The incidence of hoarseness caused by recurrent laryngeal nerve injury, the most common complication in thermal ablation of thyroid nodules, was significantly lower in the improved group than in the control group (1.9% vs. 8.1%, p = 0.021). The median hoarseness recovery time in the improved group was shorter than that in the control group (2 months vs. 3 months, p = 0.032). During follow-up, no local recurrence was encountered in either group. The tumor disappearance rate was not significantly different between the two groups (69.9% vs. 75.7%, p = 0.228).

CONCLUSIONS

Improved hydrodissection based on perithyroidal fascial spaces had better protective effects than traditional hydrodissection.

The carotid sheath: Anatomy and clinical considerations

Objectives

The distinctive bilateral carotid sheaths (CS) reside in the neck region and form part of the deep cervical fasciae. Aspects of the CS anatomy are controversial, most notably its specific attachment sites and fascial makeup, which are key determinants for the spread of tumours and infections and surgical planning. This review aimed to organise the pertinent aspects relating to CS anatomy and pathology, explore their clinical relevance and highlight areas of disagreement in the literature.

Methods

A narrative review identified key papers relating to CS anatomy, histology, embryology, pathology and clinical and surgical significance using PubMed and Google Scholar. This was supported by a systematic review focused on the fascia forming the CS which was conducted using PubMed, Web of Science and Core Collection which yielded 22 papers.

Results

and Discussion: The CS surrounds the internal carotid artery, internal jugular vein, cranial nerves IX - XII, lymph nodes and nervous plexuses as they course from the jugular foramen superiorly down along into the mediastinum inferiorly. There are contradicting descriptions regarding the CS attachments at the extracranial skull base and within the mediastinum. Author descriptions of the CS fasciae are complex, varied and incongruent. Pathologies affecting the CS include malignancies of the nerves, vascular lesions and utilisation of the CS space as a corridor for the spread of deep neck infections.

Conclusion

This paper collates and presents pertinent anatomical and clinical aspects regarding the CS. A proper knowledge of the CS anatomy and structural relationships will optimise surgical approaches and orientation when operating within the region.

Imaging assessment of deep neck spaces infections: an anatomical approach

Despite the widespread use of antibiotics, deep neck infections are still a relevant clinical problem and can cause severe and potentially life-threatening complications. Imaging plays a pivotal role into the clinical management of deep neck infections, allowing identification of the source of infections, definition of the precise extension of the disease and early diagnosis of local or distant complications. The complex anatomy of deep neck spaces may hide the actual extent of disease: the knowledge of neck anatomy enables radiologists to rapidly evaluate expected routes of spread of infections and to effectively communicate crucial information to surgeons. Computed Tomography is the most used imaging modality for assessing primary site of infection, extent of disease and local complications. Magnetic resonance imaging may be used as a second level imaging modality for individuating intracranial or spinal complications. The present work aims to review the imaging of deep neck spaces infections, focusing on relevant anatomy and clinical scenarios, underlining practical teaching points for each of them. Familiarity with deep neck spaces anatomy and knowledge of most common routes of spread of infections allow the radiologist to make a prompt diagnosis and to look for early signs of potential complications.

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.

Paediatric Deep Neck Infection—The Risk of Needing Intensive Care

Deep neck infections are potentially dangerous complications of upper respiratory tract or odontogenic infections. The pathophysiology, clinical presentation, and potential spreading depend on the complex anatomy of the neck fascia. These infections can lead to severe pathological conditions, such as mediastinitis, sepsis, and especially airway impairment with difficult management. Because of the risk of life-threatening emergency situations and the possible impacts on the overall health status of affected children, their early recognition is of utmost importance. Torticollis, drooling, and stridor are the most common signs of advancing disease. Children presenting with these symptoms should be admitted to the paediatric intensive care unit for vital function monitoring, where the airway could be readily secured if function is compromised.

Surgical anatomy of the upper esophagus related to robot-assisted cervical esophagectomy

Robot-assisted cervical esophagectomy (RACE) enables radical surgery for tumors of the middle and upper esophagus, avoiding a transthoracic approach. However, the cervical access, narrow working space, and complex topographic anatomy make this procedure particularly demanding. Our study offers a stepwise description of appropriate dissection planes and anatomical landmarks to facilitate RACE. Macroscopic dissections were performed on formaldehyde-fixed body donors (three females, three males), according to the surgical steps during RACE. The topographic anatomy and surgically relevant structures related to the cervical access route to the esophagus were described and illustrated, along with the complete mobilization of the cervical and upper thoracic segment. The carotid sheath, intercarotid fascia, and visceral fascia were identified as helpful landmarks, used as optimal dissection planes to approach the cervical esophagus and preserve the structures at risk (trachea, recurrent laryngeal nerves, thoracic duct, sympathetic trunk). While ventral dissection involved detachment of the esophagus from the tracheal cartilage and membranous part, the dorsal dissection plane comprised the prevertebral compartment harboring the thoracic duct and right intercosto-bronchial artery. On the left side, the esophagus was attached to the aortic arch by the aorto-esophageal ligament; on the right side, the esophagus was bordered by the azygos vein, right vagus nerve, and cardiac nerves. The stepwise, illustrated topographic anatomy addressed specific surgical demands and perspectives related to the left cervical approach and dissection of the esophagus, providing an anatomical basis to facilitate and safely implement the RACE procedure.

Selection of the surgical approach for lesions with parapharyngeal space involvement: A single-center experience on 153 cases

BACKGROUND

The parapharyngeal space (PPS) can harbor a variety of tumors that can be approached through a wide spectrum of surgical routes. A decisional algorithm on the surgical approach to resect PPS lesions was tested in terms of reliability by retrospectively applying it to a large series of patients.

METHODS

Patients treated at the Unit of Otorhinolaryngology - Head and Neck Surgery of the University of Brescia, Italy, for tumor or tumor-like lesions involving the PPS between October 1986 and July 2019 were included in the retrospective analysis. Tumor characteristics, clinical presentation, diagnostic work-up, type of resection, surgical approach, and oncologic and morbidity outcomes were reviewed. Reliability of the algorithm was calculated as the number of cases in which the expected approach was confirmed/total number of cases × 100.

RESULTS

The analysis included 153 patients. Most lesions (64.1%) were benign. The most frequent complaint at presentation was unilateral oropharyngeal medialization (47.1%), followed by neck/parotid swelling (41.2%). Ninety-two (61.3%) lesions were excised through an enucleation/extracapsular dissection. Wide-margin resection and compartmental resection were performed in 17 (11.3%) and 41 (27.3%) patients, respectively. A single-corridor approach was employed in 132 (87.4%) cases. Combinations of multiple corridors were adopted in 19 (12.6%) patients. Reliability of the decision-making algorithm was 91.2%. Capsular integrity and margin status affected prognosis of pleomorphic adenomas and PPS malignancies, respectively.

CONCLUSION

The proposed decision-making algorithm can reliably guide approach selection, which should primarily aim at ensuring intact-capsule excision of benign lesions suspicious for pleomorphic adenomas and clear-margins resection of PPS malignancies.

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.