Topographic and anatomical features of muscular and vascular structures in lateral cervical region during prenatal period of human ontogenesis

Background. One of topical areas of morphological research is features of topographic a relationships of the vascular, nervous, muscular, fascial and cartilaginous structures of the neck in prenatal period of human ontogenesis, as data on their formation at different stages of development will improve diagnostic methods of visualization and surgical correction of congenital and acquired pathologies of head and neck. Objective. To find out the peculiarities of synthopia of vascular and muscular structures of the lateral cervical region in human prefetuses. Methods. 9 human prenatal specimens aged 9-12 weeks of prenatal development have been studied by using a set of morphological methods, according to existing bioethical norms. Results. During 9th week of development, bony and musclar boundaries of the lateral triangle of the neck, the carotid vagina, and the components of the vascular-nervous bundle of the neck have been determined. Within the carotid triangle, the external carotid artery is located superficially; it is crossed frontally by the cervical branch of facial nerve and the sublingual nerve. The superior thyroid artery departs from the external carotid artery at the level of the cartilaginous model of the large horns of hyoid bone and passes to the rudiment of thyroid gland. Retropharyngeal space is found at 9th week of development, moderately filled with adipose tissue. The anterior vertebral plate of the cervical fascia forms the bottom for posterior triangle of neck. Conclusion. The lateral cervical region in human prefetuses is represented by a multilayered topographic zone with formed boundaries and contents. Cervical fascia forms carotid vagina within the carotid triangle, and pharyngeal space. The course of blood vessels and nerves within the lateral cervical region is variable. Three-dimensional reconstructions of prefetuses serve as evidence of the early formation of definitive topographic connections within early bony and cartilaginous models in relation to the muscles of the anterior and lateral cervical regions.

Sternocleidomastoid flap for pedicled reconstruction in head & neck surgery- revisiting the anatomy and technique

Background Previous studies on sternocleidomastoid flaps, have defined the importance of preserving sternocleidomastoid (SCM) branch of superior thyroid artery (STA). This theory drew criticism, as this muscle is known to be a type II muscle, i.e., the muscle has one dominant pedicle (branches from the occipital artery at the superior pole) and smaller vascular pedicles entering the belly of muscle (branches from STA and thyrocervical trunk) at the middle and lower pole respectively. It was unlikely for the SCM branch of STA to supply the upper and lower thirds of the muscle. We undertook a cadaveric angiographic study to investigate distribution of STA supply to SCM muscle. Methods It is a cross-sectional descriptive study on 10 cadaveric SCM muscles along with ipsilateral STA which were evaluated with angiography using diatrizoate (urograffin) dye. Radiographic films were interpreted looking at the opacification of the muscle. Results were analyzed using frequency distribution and percentage. Results Out of ten specimens, near complete opacification was observed in eight SCM muscle specimens. While one showed poor uptake in the lower third of the muscle, the other showed poor uptake in the upper third segment of muscle. Conclusion Based on the above findings we suggest to further investigate sternocleidomastoid muscle as a type III flap, as the STA branch also supplies the whole muscle along with previously described pedicle from occipital artery. However, this needs to be further corroborated intra-operatively using scanning laser doppler. This also explains better survival rates of superior thyroid artery based sternomastoid flaps.

Quantitative Prediction of the Location of Carotid Bifurcation and Neurovascular Structures in the Carotid Region: A Cross-Sectional Cadaveric Study

Introduction. The carotid region is encountered in vascular and neurological surgery and carries a potential for vascular and cranial nerve trauma. The carotid bifurcation is an especially important landmark and difficult to predict based on currently established landmarks. This study is a detailed analysis of the carotid region and proposes a novel methodology to predict the height of the bifurcation. Materials and Methods. Superficial and deep dissections were performed on the anterior triangle of the neck to expose the carotid region in twenty-one formalin-fixed donor cadavers. Musculoskeletal and neurovascular structures were assessed in relation to the carotid bifurcation and the medial border of the clavicle (MBC). Results. The carotid bifurcation occurred, on average, 11.4 mm higher on the left ( p < 0.001 ; 95% CI: 9.28, 13.54). The superior thyroid artery ( p < 0.001 ), facial vein ( p < 0.001 ), and cranial nerve XII ( p < 0.001 ) were all more distal on the left side when measured from the MBC while the angle of the mandible and stylohyoid muscle remained symmetric. Left- and right-sided vascular structures were symmetric when measured from the carotid bifurcation. Conclusions. Neurovascular structures within the carotid region are likely to be anatomically superior on the left side while vessels are likely to remain symmetric in relation to the carotid bifurcation. When measured from the MBC, the bifurcation height can be predicted by multiplying the distance between the MBC and mastoid process by 0.65 (right side) or 0.74 (left side). This novel methodological estimation may be easily learned and directly implemented in clinical practice.

Sternocleidomastoid Flap for Pedicled Reconstruction in Head & Neck Surgery- Revisiting the Anatomy and Technique

Background: Previous studies on sternocleidomastoid flaps, have defined the importance of preserving sternocleidomastoid (SCM) branch of superior thyroid artery (STA). This theory drew criticism, as this muscle is known to be a type II muscle, i.e., the muscle has one dominant pedicle (branches from the occipital artery at the superior pole) and smaller vascular pedicles entering the belly of muscle (branches from STA and thyrocervical trunk) at the middle and lower pole respectively. It was unlikely for the SCM branch of STA to supply the upper and lower thirds of the muscle. We undertook a cadaveric angiographic study to investigate distribution of STA supply to SCM muscle.Methods: It is a prospective study on 10 cadaveric SCM muscles along with ipsilateral STA which were evaluated with angiography using diatrizoate (urograffin) dye. Radiographic films were interpreted looking at the opacification of the muscle. Results were analyzed using frequency distribution and percentage. Results:Out of ten specimens, near complete opacification was observed in eight SCM muscle specimens. While one showed poor uptake in the lower third of the muscle, the other showed poor uptake in the upper third segment of muscle. Conclusion: Based on the above findings we propose to re-classify sternocleidomastoid flap as a type III flap as the STA branch also supplies the whole muscle along with previously described pedicle from occipital artery. However, this needs to be further corroborated intra-operatively using scanning laser doppler.

Right External Carotid Artery Originated Right Superior Thyroid Artery in Cadavers of a Medical College in Western Nepal: A Descriptive Cross-sectional Study

Introduction: External carotid artery originated superior thyroid artery are frequently documented in classical anatomical, surgical and radiological textbooks. Knowledge of anatomical variations, proper identification of superior thyroid arteries is very important to avoid major complications during and after neck surgeries. The aim of the study is to find out the prevalence of right superior thyroid artery originating from right external carotid artery in cadavers of a Medical College in Western Nepal. Methods: A descriptive cross-sectional study was carried out at the department of anatomy in Universal College of Medical Sciences, Bhairahawa, Nepal from October 2020 to January 2021 after ethical clearance from the same institution (IRC UCMS, Ref: UCMS/IRC/078/20). Variations in origin of superior thyroid arteries were observed, recorded and photographed. Convenient sampling method was used. Data was analyzed using Microsoft Excel 2016. Point estimate at 90% Confidence Interval was calculated along with frequency and percentage. Results: Out of 30 right superior thyroid arteries of 30 cadavers, 27 (90%) at 90% Confidence Interval (80.22-96.44) originates from right external carotid artery. Conclusions: In our study we observed that almost nine tenths of right superior thyroid arteries originated from the right external carotid artery which was relatively high in comparison to other studies. Thus, Extensive knowledge of variations in origin of superior thyroid artery is important for surgeons prior to various interventional surgeries.

Diagnostic Utility of Mean Peak Systolic Velocity of Superior Thyroid Artery in Differentiating Graves’ Disease from Thyroiditis

Background Differentiating Graves’ disease from thyroiditis can be at times clinically challenging. The gold standard test (thyroid nuclear imaging scan) is expensive, not routinely available, and has radiation exposure. Color Doppler ultrasonography of thyroid represents a suitable alternate which can be used for differentiating these conditions by studying thyroid blood flow parameters. Aim We aimed to investigate the use of thyroid blood flow parameters’ assessment of the superior thyroid artery (STA) and common carotid artery (CCA) with color Doppler ultrasonography for differentiating Graves’ disease from thyroiditis. Materials and Methods This is a cross-sectional study on 111 patients with newly diagnosed thyrotoxicosis (82 with Graves’ disease and 29 with thyroiditis) and 45 years of age and sex-matched healthy controls. All patients underwent detailed clinical and necessary investigations. Color Doppler ultrasonography of the thyroid gland and spectral flow analysis of both superior thyroid arteries was done using standard protocol. Sensitivity and specificity for mean peak systolic velocity of STA (STA-PSV) cut-offs were calculated using receiver operating characteristic curves. Results Patients with Graves’ disease have significantly higher free tri-iodothyronine (FT3) levels, free thyroxine (FT4) levels, antithyroid stimulating hormone receptor antibody (TRAb) levels, and thyroid volume as compared with those with thyroiditis. The mean STA-PSV of patients with Graves’ disease was significantly higher than thyroiditis and control group. Mean STA-PSV greater than 54.3 cm/s had 82.9% sensitivity and 86.2% specificity in diagnosing Graves’ disease. Mean PSV-STA/PSV-CCA ratio of 0.40 was 80.5% sensitive and 86.2% specific for Graves’ disease. Conclusion Mean STA-PSV has high sensitivity and specificity in differentiating Graves’ disease from thyroiditis and can be used routinely in clinical practice as a cheap and invaluable diagnostic tool.

The Superior Laryngeal Nerve and Its Vulnerability in Surgeries of the Neck

Anatomical considerations of the superior laryngeal nerve (SLN), a branch of the vagus, provides information to minimize the potential for iatrogenic intraoperative injury, thereby preventing motor and sensory dysfunctions of the larynx. The present study aims to assess the variation of the SLN and its relationship to the superior thyroid artery (STA) and superior laryngeal artery (SLA). The study was done on 35 formalin-fixed cadavers at Oakland University in 2018–2019. In our study, we found that out of 21 cadavers, 52.4% of the external laryngeal branches (ebSLN) are related posteromedial to the STA, while 47.6% are related anteromedial to it. Out of 14 cadavers, 64.3% of the internal laryngeal branches (ibSLN) are related superoposterior to the SLA, while 35.7% are inferoposterior to it. In most cases, the SLA crosses above the ebSLN while traveling to pierce the thyrohyoid membrane to reach the larynx. The data demonstrate that both the ebSLN and ibSLN display variation in their relationship with the STA and the SLA, respectively. Awareness of these variable relationships is critical for identification and isolation of these structures in order to prevent consequences of nerve injury, primarily a reduction in the highest attainable frequency of the voice and aspiration pneumonia.

Variations in origin of the superior thyroid artery: an update for the head and neck surgeon

Head and neck surgeons must have a thorough knowledge of head and neck vascular anatomy and its variations. This case report documents a variation in the superior thyroid artery encountered during a neck dissection and discusses the surrounding literature. A 55-year-old female with squamous cell carcinoma of the tongue underwent a partial glossectomy, right level I–IV neck dissection and reconstruction with a radial forearm free flap. During the procedure, an arterial branch was encountered arising 2–3cm caudal to the common carotid bifurcation. This variant branch was shown to represent the superior thyroid artery. On review of the literature, various classification systems of the superior thyroid artery origin have been described. Awareness of such anatomical variation is vital for the head and neck surgeon to avoid unexpected complication.

Anatomical Variations in the Origin of Superior Thyroid Artery and its Relation with External Laryngeal Nerve and their Clinical Importance-A Cadaveric Study

INTRODUCTION The major arterial supply of thyroid gland is from superior and inferior thyroid arteries. The superior thyroid artery (STA) usually arises from the external carotid artery. The external laryngeal nerve runs in close proximity to the origin of the superior thyroid artery later leaves the artery by turning medially above or below the upper pole of the thyroid gland. MATERIAL AND METHODS A descriptive study was undertaken on 20 embalmed cadavers. The anterior triangle of neck was dissected bilaterally. The site of origin of STA level of origin in relation to the upper border of lamina of thyroid cartilage and relation of the STA with external laryngeal nerve were observed and noted. RESULTS The STA arises from the external carotid artery in 27.5%, common carotid artery in 62.5%, common carotid bifurcation in 5% and arises by a common trunk with lingual artery at common carotid bifurcation in 5%. The distance from the upper pole to the point where external laryngeal nerve turns medially is more than 10 mm in 50%, less than 10 mm in 25% and 10 mm in 25%. CONCLUSION The variations in the pattern of origin of the superior thyroid artery and its relation to external laryngeal nerve is a very common phenomenon. The head and neck surgeons must be aware of all possible variations to avoid postoperative complications and legal issues.