Prestyloid compartment of the parapharyngeal space: a histological study using late-stage human fetuses

Anatomical studies and early results on endoscopic transoral medial pterygomandibular fold approach to salvage retropharyngeal lymphadenectomy in nasopharyngeal carcinoma

OBJECTIVE

Retropharyngeal lymphadenectomy is challenging. This study investigated a minimally invasive approach to salvage retropharyngeal lymphadenectomy in patients with nasopharyngeal carcinoma.

METHODS

An anatomical study of four fresh cadaveric heads was conducted to demonstrate the relevant details of retropharyngeal lymphadenectomy using the endoscopic transoral medial pterygomandibular fold approach. Six patients with nasopharyngeal cancer with retropharyngeal lymph node recurrence, who underwent retropharyngeal lymphadenectomy with the endoscopic transoral medial pterygomandibular fold technique at the Eye and ENT Hospital of Fudan University from July to December 2021, were included in this study.

RESULTS

The anatomical study demonstrated that the endoscopic transoral medial pterygomandibular fold approach offers a short path and minimally invasive approach to the retropharyngeal space. The surgical procedure was well tolerated by all patients, with no significant post-operative complications.

CONCLUSION

The endoscopic transoral medial pterygomandibular fold approach is safe and efficient for retropharyngeal lymphadenectomy.

Topohistology of the cranial nerves IX-XII at the cranial base and upper parapharyngeal space: A histological study using human fetuses

The topographical relationships among the lower cranial nerves, internal carotid artery (ICA), and internal jugular vein (IJV) in the upper parapharyngeal neurovascular bundle remain obscure. Thus, details of the anatomy were examined in human fetus histology. We observed the horizontal histological sections from 20 midterm (9-18 weeks) and 12 near-term (28-40 weeks) fetuses. At the external skull base, the glossopharyngeal nerve crosses the anterior aspect of the IJV to reach the medially located Hyrtl's fissure in the petrous temporal bone. The nerve crossed the anterior aspect of the ICA medially near or below the first cervical nerve root. Below the hypoglossal nerve canal, the accessory nerve crosses the anterior or posterior aspects of the IJV and moves laterally. During the half-spiral course, the hypoglossal nerve was tightly attached to the posterolateral-anterior aspects of the vagus nerve and surrounded by a common nerve sheath. The glossopharyngeal ganglia sometimes extended inferiorly to the level of the hypoglossal nerve canal but were absent along the inferior course. The inferior vagal ganglion rarely extends above the occipital condyle. The superior cervical sympathetic ganglion occasionally extends above the first cervical nerve root. The IJV (or ICA) descends to the lateral (or medial) margins of the parapharyngeal neurovascular bundle. The glossopharyngeal (or accessory) nerve crosses the ICA (or IJV) to exit the bundle at the base of the skull (or below the hypoglossal nerve canal). The glossopharyngeal and vagus inferior ganglia differ at each site.

Rectus capitis lateralis muscle revisited: a histological study using human fetuses

BACKGROUND

Rectus capitis lateralis muscle (RCLM) is located at the border between the ventral and dorsal muscle groups, but the nerve topographical anatomy around the muscle is obscure.

MATERIALS AND METHODS

We observed the RCLM in histological sections of 12 midterm and 10 near-term fetal heads (9-18 and 26-40 weeks of gestational age).

RESULTS

At midterm, the RCLM wrapped around the inferiorly protruding inferolateral corner of the cartilaginous occipital bone. The muscle was adjacent to, or even continued to, the intertransversarius muscle between the atlas and axis. At near-term, the jugular process of the occipital bone, that is, the RCLM upper insertion, was either cartilaginous or bony, depending on age. The process formed a collar supporting the internal jugular vein from the inferior side. Moreover, the muscle is tightly attached to or inserted into the venous wall itself. The cartilaginous jugular process was adjacent to Reichert's cartilage, and the uppermost muscle fibers passed through a narrow space between these cartilages. The RCLM appeared to accelerate the jugular process elongation, resulting in complete union of the occipital and temporal bones. The ventral ramus of the first cervical nerve passed between the RCLM and rectus capitis anterior muscle to reach the longus capitis muscle. No nerve passed between the RCLM and the obliquus capitis superior muscle (a muscle at the suboccipital triangle).

CONCLUSION

The dorsoventral position of the RCLM seemed to correspond to the scalenus posterior muscle in a laminar arrangement of the cervical axial musculature.

Association between the developing sphenoid and adult morphology: A study using sagittal sections of the skull base from human embryos and fetuses

The developing sphenoid is regarded as a median cartilage mass (basisphenoid [BS]) with three cartilaginous processes (orbitosphenoid [OS], ala temporalis [AT], and alar process [AP]). The relationships of this initial configuration with the adult morphology are difficult to determine because of extensive membranous ossification along the cartilaginous elements. The purpose of this study was therefore to evaluate the anatomical connections between each element of the fetal sphenoid and adult morphology. Sagittal sections from 25 embryos and fetuses of gestational age 6-34 weeks and crown-rump length 12-295 mm were therefore examined and compared with horizontal and frontal sections from the other 25 late-term fetuses (217-340 mm). The OS was identified as a set of three mutually attached cartilage bars in early fetuses. At all stages, the OS-post was continuous with the anterolateral part of the BS. The BS included the notochord and Rathke's pouch remnant in embryos and early fetuses. The dorsum sellae was absent from embryos, but it protruded from the BS in early fetuses before a fossa for the hypophysis became evident. Although not higher than the hypophysis at midterm, the dorsum sellae elongated superiorly after gestational age 25 weeks. In early fetuses, the AP was located on the side immediately anterior to the otic capsule. The AT developed on the side immediately posterior to the extraocular rectus muscles. At late term, the greater wing was formed by membranous bones from the AT and AP. The AT and AP formed a complex bridge between the BS and the greater wing. A small cartilage, future medial pterygoid process (PTmed) was located inferior to the AT in early fetuses. At midterm, one endochondral bone and multiple membranous bones formed the PTmed. The lateral pterygoid process (PTlat) was formed by a single membranous bone plate. Therefore, we connected fetal elements and the adult morphology as follows. (1) Derivative of the OS makes not only the lesser wing but also the anterior margin of the body of the sphenoid. (2) Derivatives of the BS are the body of the sphenoid including the sella turcica and the dorsum sellae. (3) Most of the greater wing including the foramen rotundum and the foramen oval originate from the AT and AP and multiple membranous bones. (4) The PTmed originate from endochondral bones and multiple membranous bones, while the PTlat derive from a single membranous bone.

Fetal development of the carotid canal with special reference to a contribution of the sphenoid bone and pharyngotympanic tube

The bony carotid canal is a tube-like bone with a rough surface in contrast to smooth surfaces of the other parts of the temporal bone petrosal portion (petrosa): it takes an impression of the additional, out-sourcing product. No study had been conducted to evaluate a contribution of the adjacent sphenoid and pharyngotympanic tube (PTT) to the carotid canal. We examined sagittal and horizontal histological sections of hemi-heads from 37 human fetuses at 10 to 37 weeks. At 10 to 18 weeks, the future carotid canal was identified as a wide loose space between the cartilaginous cochlea and the ossified or cartilaginous sphenoid elements (ala temporalis and pterygoid). A linear mesenchymal condensation extending between the cochlear wall and ala temporalis suggested the future antero-inferior margin of the carotid canal. This delineation was more clearly identified in later stages. After 25 weeks, 1) the growing pterygoid pushed the PTT upward and, in turn, the PTT pushed the internal carotid artery (ICA) upward toward the petrosa: 2) a membranous ossification occurs in the dense mesenchymal tissue, the latter of which took an appearance of an anterior process of the petrosa; 3) the bony process of the petrosa involved the ICA inside or posteriorly. The bony carotid canal was made with membranous ossification in the dense mesenchymal tissue between the petrosa and sphenoid. The mother tissue was detached from the sphenoid by the PTT. The ossification of the septum between the ICA and tympanic cavity seemed to continue after birth.

Fetal development of the thoracolumbar fascia with special reference to the fascial connection with the transversus abdominis, latissimus dorsi, and serratus posterior inferior muscles

PURPOSE

The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited.

METHODS

Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm).

RESULTS

At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles.

CONCLUSION

We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.

Umbilicus and the rectus sheath: a study using human fetuses

PURPOSE

The newborn umbilicus is provided by a fibrous ring after closure with a scar at the bottom. Since it is believed to be embedded in the linea alba, a specific connection with the rectus sheath was not yet hypothesized for the umbilicus. However, there are no or few descriptions about the development and growth.

METHODS

We histologically examined 28 fetuses at 8-40 weeks: 6 fetuses at 8 weeks, 12 at 10-14 weeks and 10 at 31-40 weeks.

RESULTS

An initial rectus sheath issued a linear mesenchymal condensation toward the umbilical cord at 10-14 weeks and, an established sheath provided a fibrous band around the umbilical cord at 31-40 weeks. The rectus sheath margins made an acute turn toward the skin at the superior and lateral rims of umbilicus and dispersed into a loose tissue of the cord. In contrast, the sheath margin changed its direction gradually to the superficial side at the inferior rim and inserted at a border between the skin epidermis and a mesothelium-like covering of the cord. The developing umbilical ring contained no or few elastic fibers.

CONCLUSION

Instead of the underdeveloped linae alba, the rectus sheath seemed to be tightly connected with the umbilicus at birth. Rather than an expected elasticity, the rectus muscle contraction was likely to play a critical role in the closure after birth. Via the umbilical ring, the fetal rectus sheath also seemed to tightly connect with the skin at the inferior rim of umbilicus.

Suboccipital myodural bridges revisited: Application to cervicogenic headaches

There seems to be no complete demonstration of the suboccipital fascial configuration. In 30 human fetuses near term, we found two types of candidate myodural bridge: (1) a thick connective tissue band running between the rectus capitis posterior major and minor muscles (rectus capitis posterior major [Rma], rectus capitis posterior minori [Rmi]; Type 1 bridge; 27 fetuses); and (2) a thin fascia extending from the upper margin of the Rmi (Type 2 bridge; 20 fetuses). Neither of these bridge candidates contained elastic fibers. The Type 1 bridge originated from: (1) fatty tissue located beneath the semispinalis capitis (four fetuses); (2) a fascia covering the multifidus (nine); (3) a fascia bordering between the Rma and Rmi or lining the Rma (13); (4) a fascia covering the inferior aspect of the Rmi (three); and (5) a common fascia covering the Rma and obliquus capitis inferior muscle (nine). Multiple origins usually coexisted in the 27 fetuses. In the minor Type 2 bridge, composite fibers were aligned in the same direction as striated muscle fibers. Thus, force transmission via the thin fascia seemed to be effective along a straight line. However, in the major Type 1 bridges, striated muscle fibers almost always did not insert into or originate from the covering fascia. Moreover, at and near the dural attachment, most composite fibers of Type 1 bridges were interrupted by subdural veins and dispersed around the veins. In newborns, force transmission via myodural bridges was likely to be limited or ineffective. The postnatal growth might determine a likely connection between the bridge and headache. Clin. Anat. 32:914-928, 2019. © 2019 Wiley Periodicals, Inc.

Styloglossus muscle: a critical landmark in head and neck oncology

GOAL

To document the role of the styloglossus muscle (SG) in head and neck oncology and at the time of surgical treatment and mandibular preservation surgery for squamous cell carcinoma of the lateral oropharynx (SCCLO).

METHOD

Based on a search conducted within the Pubmed, Embase, and Cochrane databases, using the key words SG muscle, parapharyngeal space and oropharynx, the authors discuss the embryology, physiology, anatomy and radiology of this muscle as well as its role in the oncologic staging surgery of SCCLO.

RESULTS

The most specific radiologic exam to evaluate the involvement of SG muscle in SCCLO is magnetic resonance imaging (MRI). According to the eigth international staging classification systems, radiologic invasion of the SG muscle, at the time of MRI, leads to reclassify as T4a many tumors considered as T1-3 at the time of clinical and/or on computerized tomography evaluation. This must lead to extreme care when comparing oncologic results from series published prior and after the MRI era. When transoral resection of the SG muscle is advocated for SCCLO, one must know that this maneuver brings numerous arterial and venous structures within the operative field. If difficulties to achieve safe margins of resection and/or to control bleeding are encountered, a simple trans cervical maneuver described herein is most useful.

CONCLUSION

The importance of the SG muscle should be emphasized as a touchstone for staging and surgeon's guide to mandibular preservation surgery of SCCLO. The various approaches allowing the control of this muscle and its vascular environment must be taught at the time of initial training.

Denonvilliers' fascia revisited

Although several studies have reported that the peritoneum does not contribute to the formation of a fascia between the urogenital organs and rectum, Denonvilliers' fascia (DF), a fascia between the mesorectum and prostate (or vagina) in adults, is believed to be a remnant of the peritoneum. Remnants of the peritoneum, however, were reportedly difficult to detect in other fusion fasciae of the abdominopelvic region in mid-term fetuses. To examine morphological changes of the pelvic cul-de-sac of the peritoneum, we examined 18 male and 6 female embryos and fetuses. A typical cul-de-sac was observed only at 7 weeks, whereas, at later stages, the peritoneal cavity did not extend inferiorly to the level of the prostatic colliculus or the corresponding structure in females. The cul-de-sac had completely disappeared in front of the rectum at 8 weeks and homogeneous and loose mesenchymal tissue was present in front of the rectum at the level of the colliculus at 12-16 weeks. We found no evidence that linearly arranged mesenchymal cells developed into a definite fascia. Therefore, the development of the DF in later stages of fetal development may result from the mechanical stress on the increased volumes of the mesorectum, seminal vesicle, prostate and vagina and/or enlarged rectum. Therefore, we considered the DF as a tension-induced structure rather than a fusion fascia. Fasciae around the viscera seemed to be classified into (1) a fusion fascia, (2) a migration fascia and (3) a tension-induced fascia although the second and third types are likely to be overlapped.

Fetal anatomy of the upper pharyngeal muscles with special reference to the nerve supply: is it an enteric plexus or simply an intramuscular nerve?

We examined pharyngeal nerve courses in paraffin-embedded sagittal sections from 10 human fetuses, at 25-35 weeks of gestation, by using S100 protein immunohistochemical analysis. After diverging from the glossopharyngeal and vagus nerves at the level of the hyoid bone, the pharyngeal nerves entered the constrictor pharyngis medius muscle, then turned upward and ran superiorly and medially through the constrictor pharyngis superior muscle, to reach either the levator veli palatini muscle or the palatopharyngeus muscle. None of the nerves showed a tendency to run along the posterior surface of the pharyngeal muscles. Therefore, the pharyngeal nerve plexus in adults may become established by exposure of the fetal intramuscular nerves to the posterior aspect of the pharyngeal wall because of muscle degeneration and the subsequent rearrangement of the topographical relationship between the muscles that occurs after birth.

Deep fat of the face revisited

The midfacial deep fatty tissue has been divided into the buccal and parapharyngeal fat pads although the former carries several extensions in adults. Using histological sections of 15 large human fetuses, we demonstrated that the parapharyngeal fat pad corresponds to the major content of the prestyloid compartment of the parapharyngeal space or, simply, the prestyloid fat. The buccal and prestyloid fatty tissues were separated by the medial and lateral pterygoid muscles. In these tissues, superficial parts, corresponding to the lower body and the masseteric extension of the adult buccal fat pad, were well encapsulated and showed the most advanced stage of histogenesis. As the sphenoid bone was not fully developed even in the largest specimens, the temporal, infratemporal, and pterygopalatine fossae joined to provide a large space for a single, large upper extension of the buccal fat pad. In the intermediate part of the extension course, the larger specimens carried a narrower part between the maxilla and the temporalis muscle. The single, upper extension appeared to divide into several extensions, as seen in adults. The periocular fat was clearly separated from the upper extension of the buccal fat pad by the sheet-like orbitalis muscle. A communication between the prestyloid fat and the buccal fat pad likely occurred through a potential space along the lingual nerve immediately superior to the deep part of the submandibular gland. At this site, therefore, the prestyloid fat may be injured or infected when the buccal fat pad is treated surgically.