Hyung-Sun Won

Variable composition of the internal and external branches of the accessory nerve

The purpose of this study was to clarify the composition of the internal and external branches (IB and EB) of the accessory nerve. Fifty‐seven half heads of 34 adult cadavers were used. The IB and EB of the accessory nerve were mixed with the cranial root (CR), vagus nerve, and spinal root (SR). The IB was classified into five types and the EB into four types according to their composition. The IB consisted of only CR in 7.0% of the 57 cases, and of the CR and the vagus nerve in 52.6%; the IB did not exist in 12.3%. The EB was only composed of the SR in 19.3% of cases, the SR and CR in 52.6%, and the SR, CR, and the vagus nerve in 21.1%. There were 14 combinations of IB and EB types. The most common combination was the IB with the CR and the vagus nerve, and the EB with the SR and CR (31.6%). The combination of IB and EB comprising CR and SR, respectively, was not observed. The IB and EB are known to consist of the CR and SR of the accessory nerve, respectively. However, this study shows that there are no IB and EB comprising only the CR and SR, respectively, and the branches have various combinations of the CR, SR, and vagus nerve. Clin. Anat. 27:97–101, 2014.

Classification system for flexor digitorum accessorius longus muscle variants within the leg: clinical correlations.

The flexor digitorum accessorius longus (FDAL), a variant leg muscle, can cause tarsal tunnel syndrome. This study was performed to classify the variants of the FDAL by dissection and to correlate the dissection results with clinical cases of tarsal tunnel syndrome caused by this muscle. Eighty lower limbs of embalmed Korean cadavers were dissected. MR images of two clinical cases of tarsal tunnel syndrome caused by the FDAL were correlated with the dissection results. The FDAL was observed in nine out of 80 specimens (11.3%) and it was classified into three types depending on its site of origin and its relationship to the posterior tibial neurovascular bundle (PTNV) in the leg. In Type I (6.3%), the FDAL originated in the leg and ran superficially along the PTNV, either not crossing (Type Ia, 3.8%) or crossing (Type Ib, 2.5%) the neurovascular bundle. In Type II (6.3%), it originated in the tarsal tunnel. Most FDALs followed a similar course in the tarsal tunnel and the plantar pedis. On correlating the MR images of the clinical cases with this classification, the FDAL corresponded to Types Ia and II. All three types of FDAL can compress the tibial nerve in the tarsal tunnel or the distal leg. Clarification of the topographical relationship between this muscle and the PTNV would help to improve the results of surgery for tarsal tunnel syndrome caused by the FDAL. Clin. Anat. 27:1111–1116, 2014.

Zuckerkandl's tubercle of the thyroid gland: Its location in the anatomical position, and comparative morphology of the same specimens before and after fixation

The aim of this study was to elucidate the definition of the borders and surface of the thyroid lobe in the anatomical position, and to compare the morphology of Zuckerkandls tubercle (ZT) in the fresh and fixed states. One hundred thyroid lobes from 50 fresh Korean cadavers were used. The lateral border of the thyroid lobe could be defined as the most lateral margin of its anterior aspect when in the anatomical position. The posteromedial border was the margin that projected toward the trachea or tracheoesophageal groove. The lateral and posteromedial borders, and the posterior surface between these borders, could be identified in most of the fixed cadavers. The posterolateral border could only be identified in the thyroid lobe if there was compression by the internal carotid artery in cross‐sectioned specimens and CT images. The ZT was identifiable in 85% of both fresh and fixed specimens. It was identified mainly at the posteromedial border of the thyroid lobe when in the anatomical position, and extended to the tracheoesophageal groove or esophagus. In the fresh state, the ZT projected as a rounded cone with a usually semicircular base, but its shape was very variable in the fixed state. In the present study, the ZT was found at the posteromedial border or posterior surface of the thyroid lobe in both the fresh and fixed states, contrary to most previous reports. The location of the ZT should be established in the anatomical position to avoid confusion. Clin. Anat. 28:472–476, 2015.

Distribution of the internal branch of the human accessory nerve

It was recently reported that the internal branch of the accessory nerve not only comprises the cranial root but also various combinations of the cranial root, spinal root, and the vagal component of the vagus nerve. The aim of this study was to demonstrate the anatomical distribution of each component of the internal branch of the human accessory nerve. Ten half-heads and necks of adult cadavers were used. The internal branch of the accessory nerve had three courses: the pharyngeal branch, the descending branch to the thorax, and the recurrent laryngeal nerve. The pharyngeal branch of the internal branch originated mainly from the vagus nerve, rather than from the cranial root of the accessory nerve. All of the components of the internal branch descended to the thorax along the vagus nerve. The recurrent laryngeal nerve comprised the internal branch and the vagus nerve in all specimens, and it was separated into bundles originating from the internal branch and vagus nerve. Both bundles gave off branches to the trachea and esophagus. The laryngeal distribution of the internal branch and vagus nerve was confirmed in the posterior cricoarytenoid, lateral cricoarytenoid, and thyroarytenoid muscles. These three laryngeal muscles were innervated by the cranial root and/or vagus nerve, but the distribution pattern was different in each specimen. Although the vagus nerve and cranial root are morphologically distinct nerves in the cranial cavity, they can be regarded functionally as the same nerve based on their distribution in the laryngeal muscles.

Morphological variations of the deltoid ligament of the medial ankle.

Morphological variations of the deltoid ligament were investigated in this study, with the aim of classifying the different types on the basis of their components. Sixty ankles from 39 cadavers were dissected. The origin and insertion sites of the deltoid ligament were identified, and its length, width, and thickness were measured. The deltoid ligament was divided into two layers, superficial and deep, which respectively comprised four components (tibionavicular, tibiospring, tibiocalcaneal, and superficial posterior tibiotalar ligaments) and two components (anterior tibiotalar and deep posterior tibiotalar ligaments). The tibiospring and tibiocalcaneal ligaments were found in 100% of the specimens, while the prevalence rates of other components lay within the range 63.3–96.7%. The tibionavicular and deep posterior tibiotalar ligaments were the thinnest and thickest, respectively, while the other ligaments had similar thicknesses. The deltoid ligament was classified into types I–IV according to the combinations of these components: all components were present in type I (48.3%), the tibionavicular ligament was absent in type II (36.7%), only the superficial posterior tibiotalar ligament was absent in type III (6.7%), and only the anterior tibiotalar ligament was absent in type IV (8.3%). In conclusion, these results improve knowledge of the morphological and morphometric characteristics of the deltoid ligament and thus provide helpful information for surgical procedures in this region. Clin. Anat. 29:1059–1065, 2016.

Separate muscle bundles of the flexor digitorum superficialis overlying the ulnar nerve.

BACKGROUND The aim of this study was to elucidate the morphological charac-teristics of the muscle bundles of the flexor digitorum superficialis (FDS) attached to the intermuscular aponeurosis (IMA) and any related structure that could potentially compress the ulnar nerve. MATERIALS AND METHODS Fifty embalmed limbs of 34 adult cadavers were studied. RESULTS The FDS arose as multiple separate bundles from the IMA of the lateral surface of the flexor carpi ulnaris in 76% of specimens. Below their origin, these separate bundles became attached continuously as a single mass to form the muscle belly. There were 1, 2, 3, 4 and 5 arising FDS muscle bundles in 28%, 30%, 4%, 10% and 4% of specimens, respectively. The muscle bundles were attached either only superficially (24% of cases) or across the entire width (20% of cases) of the IMA. In 32% of the specimens, bundles arose from the IMA in a combined fashion, being attached to the IMA superficially, deep and across the entire structure. The muscle bundles that arose from the deep part or entire width of the IMA were in contact with the ulnar nerve in 52% of specimens. In 11 (22%) specimens, the deep borders of the lowest muscle bundles close to the ulnar nerve were composed of tendinous fibres that divided from the IMA of the lateral surface of the flexor carpi ulnaris. The distance from the medial epicondyle to the lowest point of the FDS arising from the IMA was 62.0 ± 19.7 mm. CONCLUSIONS The thick tendinous deep border of the lowest muscle bundle of the FDS where it attaches to the IMA is a potential cause of ulnar nerve compression.

The enigmatic subcostal muscle: Anatomical study with application to spine and chest pain syndromes and avoidance of confusion on imaging.

The aim of this study was to revisit the morphological characteristics of the subcostal muscle and to obtain its morphometric data. One hundred and two sides of the thorax from 51 adult cadavers were used. The total number of subcostal muscles in the 102 specimens was 559. The subcostal muscle commonly comprised an aponeurosis at its superior and inferior attachments. This muscle had a thin band‐like shape in 64.2% cases, while in the other 35.8% either its superior or inferior attachment was wider. It was classified into the following four types on the basis of its inferior attachment: in Types I and II it extended to two (79.3%) and three (12.0%) lower ribs, respectively; in Type III it joined adjacent muscles such as the psoas major (2.2%) or quadratus lumborum (0.7%); and in Type IV it was attached to the transverse process (0.4%) or body (3.9%) of the 12th thoracic vertebra and the body of the 1st lumbar vertebra (1.4%). The subcostal muscle was found at the deepest layer of the intercostal space, and mainly presented in the upper and lower parts of the thorax. Its width and height were 18.2 ± 10.9 mm (mean ± SD) and 56.0 ± 13.3 mm, respectively. The distances from the midsagittal line to the superior and inferior attachments of the subcostal muscle were 77.1 ± 13.0 mm and 48.9 ± 13.5 mm, respectively. The results of this study will help to advance current understanding of the subcostal muscle. Clin. Anat. 28:1017–1021, 2015.

Posterior tibiotalar ligament: an anatomic study correlated with MRI.

This study was performed to clarify the morphologic characteristics of two layers of the posterior tibiotalar ligament (PTT) and two bands of the deep PTT (dPTT), and to correlate the dissection findings with MR images. Sixty‐four ankles from 42 cadavers were examined. The origin and insertion sites of the superficial PTT (sPTT) and the two bands of the dPTT were identified, and their length, width, and thickness were measured. MRI was performed on four ankles before serial sectioning or dissection. The serial sections were taken at a thickness of 2 mm. The sPTT was observed in 50 out of 60 dissected specimens (83.3%), taken from 64 ankles of 42 cadavers. The dPTT was observed in all specimens. The sPTT, superficial band of the dPTT (sdPTT), and deep band of the dPTT (ddPTT) arose from the inferior surface of the medial malleolus. The sPTT attached to the posterior process of the talus, and the sdPTT and ddPTT attached to the depression below the articular facet for the medial malleolus. The sPTT and two bands of the dPTT could be distinguished on coronal MR images, where the sPTT appeared as a thin string superficial to the two bands of the dPTT, which were separated as two thick, low‐density strings. In the coronal plane of frozen sections, the outermost sPTT appeared as a thin, white bundle attached to the sdPTT. The PTT is composed of superficial and deep layers, and the dPTT is composed of superficial and deep bands. Clin. Anat. 27:798–803, 2014.

Morphological characteristics of the cranial root of the accessory nerve

There has been the controversy surrounding the cranial root (CR) of the accessory nerve. This study was performed to clarify the morphological characteristics of the CR in the cranial cavity. Fifty sides of 25 adult cadaver heads were used. The accessory nerve was easily distinguished from the vagus nerve by the dura mater in the jugular foramen in 80% of 50 specimens. The trunk of the accessory nerve from the spinal cord penetrated the dura mater at various distances before entering the jugular foramen. In 20% of the specimens there was no dural boundary. In these cases, the uppermost cranial rootlet of the accessory nerve could be identified by removing the dura mater around the jugular foramen where it joined to the trunk of the accessory nerve at the superior vagal ganglion. The cranial rootlet was formed by union of two to four short filaments emerging from the medulla oblongata (66%) and emerged single, without filament (34%), and usually joined the trunk of the accessory nerve directly before the jugular foramen. The mean number of rootlets of the CR was 4.9 (range 2–9) above the cervicomedullary junction. The CR of the accessory nerve was composed of two to nine rootlets, which were formed by the union of two to four short filaments and joined the spinal root of the accessory nerve. The CR is morphologically distinct from the vagus nerve, confirming its existence. Clin. Anat. 27:1167–1173, 2014.

Zuckerkandl Tubercle of the Thyroid Gland: Correlations between Findings of Anatomic Dissections and CT Imaging

BACKGROUND AND PURPOSE: The Zuckerkandl tubercle is located at the posteromedial border of the thyroid lobe, and it may be confused with a neoplasm or other mass. This study was performed to clarify the position and morphologic characteristics of the Zuckerkandl tubercle by dissecting cadavers and to compare the findings with the corresponding CT images obtained in the same cadavers. MATERIALS AND METHODS: One hundred thyroid lobes from 50 fresh cadavers were dissected for this study (20 males and 30 females; mean age at death, 77.3 ± 11.5 years). CT scans were obtained in 10 of the cadavers by using a 128-channel multidetector row CT scanner before dissection. RESULTS: The Zuckerkandl tubercle of the thyroid gland was observed in 83% of the specimens. It was mostly located at the posteromedial border of the thyroid lobe and within the middle two quarters (2nd and 3rd) of the thyroid lobe. The Zuckerkandl tubercle was classified into 3 types based on its direction of extension: posteromedial in 64% of the specimens, posteromedial and superior in 13%, and posteromedial and inferior in 6%. On axial CT, the Zuckerkandl tubercle was usually continuous with the posteromedial part of the thyroid lobe and extended posteromedially to the esophagus. The parts of the Zuckerkandl tubercle that protrude posteromedially and superiorly or posteromedially and inferiorly from the thyroid lobe appeared separated from the thyroid gland by a thin, low-density string on axial CT. CONCLUSIONS: Zuckerkandl tubercles that protrude toward the posteromedial and superior or inferior direction could cause confusion due to their separation when performing diagnoses with CT images.