Anatomical study of the so-called “retromolar gland”: Distinguishing normal anatomy from oral cavity pathology

The sublingual branch of the lingual nerve: Anatomical study and suggestion for a new terminology

The lingual nerve carries somatosensory fibers from the anterior two-thirds of tongue. The parasympathetic preganglionic fibers arising from the chorda tympani also travel with the lingual nerve in the infratemporal fossa to synapse in the submandibular ganglion to innervate the sublingual gland. However, only a few studies have investigated the specific nerve that innervates the sublingual gland and surrounding tissue i.e., the so-called sublingual nerve. Therefore, this study aimed to clarify the anatomy and definition of the sublingual nerves. Thirty sides from formalin fixed cadaveric hemiheads underwent microsurgical dissection of the sublingual nerves. The sublingual nerves were found on all sides and categorized into three branches, i.e., branches to the sublingual gland, branches to the mucosa of the floor of the mouth, and gingival branches. Additionally, branches to the sublingual gland were subcategorized into types I and II based on the origin of the sublingual nerve. We suggest that the lingual nerve branches should be categorized into five branches, i.e., branches to the isthmus of the fauces, sublingual nerves, lingual branches, posterior branch to the submandibular ganglion, and branches to the sublingual ganglion.

The clinical anatomy of the accessory submandibular gland: a comprehensive review

An accessory submandibular gland is a rare variation. As such, there is limited literature regarding the embryology, anatomy, variations, clinical imaging, and pathology of the accessory submandibular gland. In this article, we review the existing literature on the accessory submandibular gland from clinical and anatomical perspectives. The goal of this review is to provide comprehensive knowledge of this variation which can be useful for oral and maxillofacial/head and neck surgeons, radiologists, and anatomists. Within this review, the embryologic origin as well as the anatomy of the accessory submandibular gland is detailed. Several imaging modalities which can be used to visualize the accessory submandibular gland are outlined as well as its variations. Lastly, this review investigates several reported clinical considerations regarding the accessory submandibular gland including sialoliths, Wharton's duct obstruction, and pleomorphic adenoma.

Lip pleomorphic adenomas: case series and literature review

BACKGROUND

Pleomorphic adenoma (PA) is the most frequent benign salivary gland tumor, but a lip PA is rare. Although this tumor may be definitively diagnosed by imaging or a tissue biopsy if it is reasonably large, PAs on the lip are relatively small, and they present findings that are similar to those of other lip lesions, which can make a preoperative diagnosis difficult.

METHODS

We analyzed all PAs in the oral region and lesions on the lips treated in our department over the past 20 years, and we discuss them together with the relevant literature.

RESULTS

We found that 11.8% (n=6) of the PAs occurred on a lip (upper lip: 9.8%, lower lip: 2.0%), and ~1% of all mass lesions of the lips were PAs. The average size of the lip PAs was 1.5±0.7 cm (range, 0.7-2.2 cm). For preoperative diagnostic assistance, ultrasonography (US) (n=4), magnetic resonance (MR) (n=3), or no imaging (n=2) was used. An excisional biopsy was performed in all cases, and to date, no recurrence or malignant transformation has been observed.

CONCLUSIONS

Lip PA is relatively rare. Because almost all of these lesions are small, a preoperative diagnosis is more difficult compared to palatal lesions. This tumor is also prone to long-term neglect and has the potential for recurrence and malignant transformation. It is thus necessary to perform an excision that includes the capsule and surrounding tissues, and careful postoperative follow-up should be continued.

A large sublingual glandular branch of the lingual nerve: a rare case report

While the route, location, and pathology of the lingual nerve has been detailed extensively in reports in the literature, its terminal branch to the sublingual gland is often overlooked. It is known, via both gross and histological observation, that the sublingual glandular branch terminates at the posterior aspect of the sublingual gland. Upon routine cadaveric dissection of a male cadaver, one of the lingual nerve branches was found to terminate at the anteroinferior portion of a herniated sublingual gland. This specific course has not previously been discussed or reported via gross or histological observation. Therefore, a timely review of the lingual nerve’s terminal sublingual glandular branch’s anatomy and clinical significance pertaining to this case is warranted. Surgeons who treat patients with submental masses should be aware of the anatomy of this nerve and the potential variance described here in order to avoid postprocedural complications.

Surgical anatomy of the lingual nerve for palate surgery: where is located and how to avoid it

PURPOSE

To describe the anatomic relationship of the lingual nerve with the lateral oropharyngeal structures.

METHODS

An anatomic dissection of the lateral oropharyngeal wall was conducted in eight sides from four fresh-frozen cadaveric heads. Small titanium clips were placed along the lingual nerve and the most anterior and medial border of the medial pterygoid muscle. Radiological reconstructions were employed for optimal visualization; the coronal view was preferred to resemble the surgical position. The distance between the lingual nerve and the medial pterygoid muscle at its upper and lower portion was measured radiologically. The trajectory angle of the lingual nerve with respect to the pterygomandibular raphe was obtained from the intersection between the vector generated between the clips connecting the upper and lower portion of the medial pterygoid muscle with the vector generated from the lingual nerve clips.

RESULTS

The mean distance from the upper portion of the medial pterygoid muscle and superior lingual nerve clips was 10.16 ± 2.18 mm (mean ± standard deviation), and the lower area of the medial pterygoid muscle to the lingual nerve was separated 5.05 ± 1.49 mm. The trajectory angle of the lingual nerve concerning to the vector that describes the upper portion of the most anterior and medial border of the medial pterygoid muscle with its lower part was 43.73º ± 11.29.

CONCLUSIONS

The lingual nerve runs lateral to the lateral oropharyngeal wall, from superiorly-inferiorly and laterally-medially, and it is closer to it at its lower third.

Clinical anatomy of the inferior labial gland: a narrative review

Objective

In this article we review the literature on the inferior labial gland from a clinical and anatomical perspective.

Background

Regardless of its importance in clinical practice, there are no medical literature that comprehensively reviewed the inferior labial gland.

Methods

A database search using PubMed and Google Scholar was conducted. The following keywords were used in the search: "lower labial salivary gland", "lower labial gland", "inferior labial salivary gland", AND "inferior labial gland".

Conclusions

The human labial glands are types of minor salivary gland that continuously secrete small amounts of mucous and serous substances to maintain oral health. The inferior labial glands are innervated by the inferior labial branch of the mental nerve, and the inferior labial branch of the facial artery is the main arterial supply to the lower lip. Although they only have an auxiliary role in saliva production compared to the major salivary glands, minor salivary glands provide a certain amount of lubrication in the oral cavity by the continuous outflow of saliva. The inferior labial gland not only promotes moisturization in the oral cavity but also secretes substances with antibacterial effects, which is important for the function of the oral cavity. A recent study showed that the rate of salivary secretion from the inferior labial glands does not change with age, and in some cases the inferior labial glands are used for diagnosing intractable diseases such as Sjogren's syndrome and cystic fibrosis. In addition, since the inferior labial glands themselves can be the site of cyst and/or neoplasia development, we should be careful to distinguish them from other diseases. Elucidation of the anatomy, physiology, and pathology of the inferior labial glands, is important for understanding human health and diseases.

An anatomical and histological study of mental nerve branches to the inferior labial glands

PURPOSE

In this study, we aimed to reveal the detailed anatomy of mental nerve branches to the inferior labial glands.

METHODS

Embalmed cadaveric heads were used in this study and the mental nerve branches to the inferior labial glands were dissected. Branches to the glands were then excised for histological observation.

RESULTS

On all sides, the inferior labial glands were innervated by small branches arising from mental nerve branches that innervated the lower lip. No nerve branches to the inferior labial gland crossed the midline. Histological observation found that the tissue to the inferior labial gland were composed primarily of nerve fibers with a small number of surrounding vessels. Histological findings in examined specimens were consistent.

CONCLUSION

The inferior labial glands were innervated by small branches of the mental nerve to the lower lip.

Mouse Mandibular Retromolar Taste Buds Associated With a Mucus Salivary Gland

We have characterized a recently rediscovered chemosensory structure at the rear of the mandibular mucosa in the mouse oral cavity originally reported in the 1980s. This consists of unorganized taste buds, not contained within troughs, associated with the ducts of an underlying minor salivary gland. Using whole-mount preparations of transgenic mice expressing green fluorescent protein under the promoter of taste-signaling-specific genes, we determined that the structure contains taste bud clusters and salivary gland orifices at the rear of each mandible, distal to the last molar and anterior to the ascending ramus. Immunohistochemical analysis shows in the retromolar taste buds expression of the taste receptors Tas2R131 and T1R3 and taste cascade molecules TrpM5, PLCβ2, and GNAT3, consistent with type II taste cells, and expression of GAD1, consistent with type III taste cells. Furthermore, the neuronal marker, calcitonin gene-related peptide, in retromolar mucosa tissue wrapping around TrpM5+ taste buds was observed. RT-PCR showed that retromolar taste buds express all 3 mouse tas1r genes, 28 of the 35 tas2r genes, and taste transduction signaling genes gnat3, plcb2, and trpm5, making the retromolar taste buds similar to other lingual and palate taste buds. Finally, histochemistry demonstrated that the mandibular retromolar secretory gland is a minor salivary gland of mucous type. The mandibular retromolar taste structure may thus play a role in taste sensation and represent a potential novel pharmacological target for taste disorders.

Imaging of Malignant Minor Salivary Gland Tumors of the Head and Neck

Minor salivary gland carcinomas (MSGCs) are nonminor tumors in the head and neck region and account for about half of all salivary gland carcinomas. Imaging evaluation based on the anatomy of minor salivary and mucous glands in the head and neck region as well as invasion patterns in each site helps in identifying optimal treatment modalities and planning suitable treatment strategies. MSGCs can be divided radiologically into localized and invasive subtypes on the basis of the clinical utility of such categorization. Characteristic invasion patterns of the invasive type include deep submucosal extension, bone marrow infiltration, and perineural spread, which are difficult to assess clinically. MSGCs easily invade adjacent structures because of their submucosal location and may spread along the muscles, nerves, periosteum, and dura mater. Moreover, the tumor may spread into the bone marrow without obvious bone destruction. In addition to imaging classification, examining the anatomy and distribution of the minor salivary glands, including the palatal, lingual, buccal, labial, and retromolar glands, as well as other mucous glands, including the glands of the sinonasal cavity and nasopharynx, lacrimal glands, ceruminous glands, laryngeal glands, and tracheal glands, facilitates MSGC diagnosis and tumor extension assessment. The authors review the precise anatomy of the minor salivary and mucous glands in the head and neck region, discuss the MSGC imaging classifications, and describe how to evaluate the extent of MSGCs in each site on the basis of the imaging classification and invasion patterns. ^©RSNA, 2020.

Lymphatic System of the Head and Neck

ABSTRACT

An intimate knowledge of the lymphatic drainage of the head and neck is needed by the clinician examining and diagnosing patients with lesion of this region.It is considered that approximately 150 to 300 lymph nodes are located in the neck region. The classification of cervical lymph nodes by Rouvière has long been most widely referenced in textbooks and articles because it covers most of the lymph nodes of the head and neck region. Anatomical review of the lymphatic system of the head and neck helps surgeons understand and treat the patients who have any cancers and cancer metastasis in and around the head and neck regions. Regardless, comprehensive review of the lymphatic system of the head and neck has been rarely discussed. This paper details the anatomy of the lymphatics of these regions by reviewing related publications, books, official reports from the academic society and also describes the clinical manifestations and levels used in staging of the various lymph nodes with illustrations and computed tomographic images.

How to avoid iatrogenic lingual nerve injury in the retromolar area: an anatomical study of retromolar pad and lingual nerve

PURPOSE

This study aimed to investigate the relationship between the retromolar gland and pad, and the relationship between the LN and retromolar gland/pad to establish a new landmark for avoiding LN injury.

METHODS

Sixty-two lingual nerves from fresh-frozen cadavers were used for this study. The age of the specimens at the time of death ranged from 57 to 98 with a mean of 76.5 years. The mucous incision was made into the medial border of the retromolar pad and the submucosal tissue depth of the initial incision was bluntly dissected to expose the lingual nerve. When the LN was identified, the mucosa overlying the retromolar pad was removed to expose the retromolar gland to confirm if the retromolar pad corresponds to the retromolar gland.

RESULTS

On all sides, the lingual nerve was found to course medial to the retromolar pad and inferior to the inferior border of the superior pharyngeal constrictor muscle to enter the sublingual space via the pterygomandibular space. The retromolar pad corresponded to the retromolar gland on all sides. This demonstrated that the retromolar pad is an overlying mucosa of the retromolar gland. No LN was found to travel through the retromolar gland.

CONCLUSION

We suggest that the retromolar pad can be used as a new landmark for avoiding iatrogenic LN injury.

A new treatment for lingual nerve injury: an anatomical feasibility study for using a buccal nerve pedicle graft

PURPOSE

Lingual nerve (LN) palsy is a serious complication in dentistry and repaired by direct suture or a free graft technique. To our knowledge, there has been no study using a (long) buccal nerve (BN) graft as a donor for LN repair. Therefore, we aimed to clarify the location of the BN and investigate if it is feasible to reroute the BN to the LN.

METHODS

Twenty-four sides from 12 fresh-frozen Caucasian cadaveric heads were used in this study. The mean age at death was 73.9 ± 13.4 years. The LN was dissected on the floor of the oral cavity medial to the third molar tooth. Next, the mucosa with the buccinator muscle, pterygomandibular raphe, and superior pharyngeal constrictor muscle on the retromolar area was retracted anteriorly to widen the pathway of the LN. Finally, the BN was cut and transposed to the LN through this widened pathway to its feasibility.

RESULTS

The mean diameter of the BN and vertical distance from the horizontal part of the retromolar trigone to the BN was 1.47 ± 0.32 mm and 18.53 ± 6.21 mm, respectively. On all sides, the BN was able to be transposed to the LN without tension.

CONCLUSION

Such a technique might be used for the patients with LN injury and who have lost sensation of the tongue.

Anatomy of the lingual nerve: Application to oral surgery

The purpose of this research is to obtain morphological information about the traveling route, branching pattern, and distribution within the tongue of the lingual nerve, all of which are important for oral surgical procedures. Using 20 sides from 10 Japanese cadaveric heads, we followed the lingual nerve from its merging point with the chorda tympani to its peripheral terminal in the tongue. We focused on the collateral branches in the area before reaching the tongue and the communication between the lingual and hypoglossal nerves reaching the tongue. The collateral branches of the lingual nerve were distributed in the oral mucosa between the palatoglossal arch and the mandibular molar region. Two to eight collateral branches arose from the main trunk of the nerve, and the configuration of branching was classified into three types. More distally, the lingual nerve started to communicate with the hypoglossal nerve before passing the anterior border of the hyoglossus muscle. Nerve communications were also found in the main body and near the apex of the tongue. A thorough understanding of the collateral branches near the tongue, and the communication with the hypoglossal nerve inside the tongue, will help to prevent functional disorders from local anesthesia and oral surgical procedures associated with the lingual nerve. Clin. Anat. 32:635-641, 2019. © 2019 Wiley Periodicals, Inc.