Anatomical Variations

Background: The thoracic duct (TD) is the largest lymphatic vessel responsible for returning lymph and chyle to the venous system. Its terminal anatomy shows notable variability, which has clinical implications for surgeries and interventions in the cervical and thoracic regions. Objective: To systematically review anatomical studies on the terminal portion of the TD, identifying and categorizing variations in its termination site. Methods: A systematic review of nine anatomical studies involving 406 human cadavers was conducted. Data on the TD termination sites were extracted and analyzed to assess variability and prevalence. Results: The venous angle, defined as the junction of the left internal jugular and subclavian veins, was the most frequent termination site, observed in approximately 63% of cases. The left internal jugular vein and left subclavian vein were less commonly reported as termination sites, accounting for 18% and 2% of cases, respectively. The remaining cases showed a variety of anatomical variations or lacked a clear dominant pattern. Conclusions: Significant variability exists in the terminal anatomy of the TD, emphasizing the need for clinicians to be aware of these differences to reduce surgical risks. Further research with larger samples and modern techniques is warranted to enhance anatomical understanding and improve clinical outcomes.

Anatomic variants of the muscles of the hand have important clinical implications. We report a case of bilateral extensor digitorum brevis manus (EDBM), a rare muscle found on the dorsum of the wrist and hand in an adult female formalin-fixed cadaver. In both hands the muscle inserted proximally in the dorsal surface of the distal radius and finished inserting in the common extensor tendon of the middle finger. The anatomic and clinical implications of this variant are discussed here.

The cephalic arch is a unique anatomic structure. Multiple variants of its usual morphology and termination have been described in the literature. We present 2 cadaveric cases of variants of the cephalic arch; firstly, a morphologic variant, where the cephalic arch divided in two and joined the axillary vein, and secondly, a cephalic arch that drained directly into the external jugular vein. The variants of the cephalic arch are associated with arterio-venous fistulas malfunction, thus the proper anatomic knowledge is essential for both diagnosis and treatment of this condition.

The human body presents a variety of structural patterns and arrangements, known as anatomical variation. These variations usually have no effect on human health, but some variations may cause surgical faults due to an unusual or variant anatomy that attributed to patient injury. Anatomical variations related to the clinical training is not considered in most of anatomy courses in early medical education. It is crucial for surgeon and physician to know and understand the anatomical variation for effective diagnosis and treatment. It is important to introduce teaching and evaluating the anatomical variations in the medical curricula and postgraduate training of radiological and surgical programs. This review is written to highlight some variant anatomy that can affect the outcome of a surgical procedure and clinical practice.

Background: The vertebral arteries originate from the root of the neck as the first branches of the subclavian arteries. Variations of vertebral arteries are congenital anomalies occurring during embryonic development. Anatomic variations of the left vertebral artery are clinically symptomless and recognized incidentally during angiographic assessments or imaging techniques so the diagnosis of these anomalies is a serious challenge. Anomalous origin of vertebral arteries may lead to neurologic disorders. It is, thus, important to identify variations of the large vessels of the aortic arch when planning neck and cervical spine interventions and diagnostic radiology. For this reason, we would like to present this rare case of left vertebral artery showing a different origin. Case report: In this work, we describe a 60-year-old female patient with headache, lethargy and blurred vision. We employed magnetic resonance angiography for both the brain and neck. There was no lesion in the brain. Incidentally, we found that the root of the left vertebral artery was anatomically aberrant. The left vertebral artery arose from the nearest section of the left external carotid artery, next to the bifurcation of the left common carotid artery, which is a rare variation. Conclusion: Understanding the state of anomalous variations of the origin of the vertebral artery might have crucial implications in angiographic and surgical procedures. It is beneficial to perform more screening with noninvasive studies like neck magnetic resonance angiography in clinical cases with potential symptoms coexisting with other diseases in order to predict possible future problems in intracranial and extracranial interventions.

Introduction: Ultrasound is the most reliable imaging modality for thyroid evaluation due to the limitations in the clinical examination of this gland. Thyroid gland developmental anomalies are rare. Most of its variations are due to the persistence of the thyroglossal duct and the absence of the isthmus. The aim of this study was to determine the incidence of pyramidal lobe and agenesis of the thyroid isthmus in Nnewi population using ultrasound. Materials and method: A total of 321 subjects resident in Nnewi, including 167 males and 154 females, were randomized. A written consent was obtained from all patients. The subjects were aged between 18 and 35 years. This was a prospective cross-sectional study. Thyroid glands were scanned using a 2-dimensional ultrasound machine with a 7.5 MHz transducer; model Siemens Sonoline Prima which was made in Japan for Siemens Medical System Incorporated, ultrasound Group, Issaquah, WA, 98029-7002, USA. Results: The study revealed no incidence of...

The Circle of Willis (CoW) is a critical arterial network at the base of the brain that maintains cerebral blood flow during vascular compromise. Although classically described as a complete ring, anatomical and imaging studies show variations in approximatel y 40-68% of individuals, which can significantly affect neurosurgical and cerebrovascular procedures. A 2025 classification system identifies four main CoW configurations: Type I (complete, ~60%), Type II (posterior communicati ng artery hypoplasia or aplasia, ~20%), Type III (anterior communicating or anterior cerebral artery hypoplasia or aplasia, ~10%), and Type IV (fetaltype posterior cerebral artery, ~10%). Meta-analyses confirm that posterior circulation variants are most common, with notable population differences, including higher prevalence in South Asian cohorts. Clinically, these variations limit collateral circulation and increase the risk of ischemic complications during surgery. Advances reported in 2025-such as robotic surgical planning, intraoperative 4D flow MRI, artificial intelligence-based risk prediction, and adaptive deep brain stimulation-support safer, anatomy-guided interventions. Routine preoperative vascular imaging and individualized surgical planning are essential to optimize neurovascular outcomes.

The Flexor digitorum brevis (FDB) muscle of the plantar aspect of the foot typically forms four tendons that insert into the lateral four toes. Although variations in tendon number and insertion patterns are common (13-83% worldwide), they are critically understudied with respect to biomechanical implications, especially in populations with high prevalence for variation (77.3% in South Asians). The present case report describes the unilateral absence of the fourth FDB tendon of a 60-year-old male cadaver of South Asian origin using comprehensive morphometric analysis using digital callipers: muscle belly length measured 82.20 mm and widths varied (proximal: 9.10 mm, midpoint: 11.4 mm, distal: 5.92 mm); the remaining three tendons measured 79.09 mm, 65.24 mm, and 56.77 mm. This quantitative documentation adds to limited morphometric data available for South Asian populations and provides population-specific reference values crucial to surgical planning as well as demonstrating a need for biomechanical analysis and standardized clinical assessment protocols in high-variation populations.

Introduction: The vascular variations in the human body are very common. In the region of the neck, variations of The Carotid Arteries Position, Branches may be seen. Study Design: In Present study, we report a rare Positional Variation of External carotid [ECA] artery in relation with the internal carotid artery [ICA]. The External carotid artery was seen Antero lateral to the internal carotid artery at the bifurcation of the common carotid artery [CCA]. The clinical significance, embryological reasons of the variation is discussed. Such variations must be given utmost importance before planning for any neck surgeries to avoid post operative complications.

The kidneys of two adult female Leopardus pardalis were analysed to study their
morphology and vascularization. The kidneys presented an outer renal cortex and an
inner medulla, with the pelvis and renal crest visible in longitudinal and transverse sections
and were simple and unipapillary. The locations and measurements of both kidneys, as
well as the renal arteries and veins, are presented.

Agenesis of the thyroid isthmus was observed in an adult male cadaver during a routine dissection at the anatomy laboratory of the Faculty of Medicine and Odontostomatology (FMOS) in Bamako. The two thyroid lobes were completely separated from each other. The left lobe presented the pyramidal lobe. The supra and infra-isthmic arches were absent, the upper right and left thyroid arteries did not anastomose, as did the lower right and left thyroid arteries. On the right side, the superior laryngeal and crico-thyroid arteries were born by a common trunk which came from the external carotid artery by a common trunk with the lingual and superior thyroid arteries.

The posterior femoral cutaneous nerve is a sensitive nerve that rises from S1-S3, usually giving off cutaneous branches for the gluteal region, perineum, the posterior region of the thigh and leg. The sciatic nerve is the largest nerve in the human body, rising from L4-S3, and divides into the tibial and common fibular nerves, innervating the muscles from the posterior compartment of the thigh. Anastomosis between the sciatic nerve and the posterior femoral cutaneous nerve is rare. During dissection of the right gluteal region on a male cadaver fixed with 10% formalin, we observed an anastomosis between both nerves, while the common fibular nerve perforated the piriformis muscle, dividing it in two muscle slips. Both nerves trajectories were within the regular pattern after this communication. Our aims were to describe this unusual case of anastomosis and perform a literature review on the variations of the sciatic nerve, while also discussing their clinical significance.

Background: Severe external root resorption, especially in teeth with unusual root anatomy, poses a diagnostic and treatment challenge. CBCT, calcium hydroxide, and MTA are effective in addressing these cases. Case Presentation: A 10-year-old boy presented with a two-rooted maxillary central incisor and severe root resorption following trauma. Cone-beam computed tomography (CBCT) confirmed necrotic pulp and severe external root resorption in both maxillary central incisors. The right central incisor exhibited chronic apical periodontitis, while the left had a chronic apical abscess. Treatment involved long-term calcium hydroxide therapy and placement of mineral trioxide aggregate (MTA) apical plugs. Results: At the six-month follow-up, the patient's teeth were clinically and radiographically stable, with no signs of pain, inflammation, or ongoing resorption. The left central incisor demonstrated successful healing, while partial healing was observed in the right maxillary central incisor. Conclusion: This case illustrates the value of CBCT for diagnosis and the success of calcium hydroxide and MTA in treating severe root resorption.

Molars often have complex root structures with multiple canals, and if one or more of these canals is missed during treatment, bacteria can remain trapped, leading to infection and pain. One of the most frequent causes of root canal treatment failure is difficulty in finding extra canals, especially in molar teeth. This case series exemplifies the importance of radiographs and magnification techniques in the detection and effective endodontic therapy of a mid-mesial canal in the mandibular first molar tooth.

Objective: To present the incidence, morphology, and the relationships of the accessory head of the flexor pollicis longus (Gantzer`s) muscle (AHFPL) in a recent Turkish population. Methods: The study was performed on 52 upper extremities of 26 adult Turkish cadavers in the Department of Anatomy, Ege University Faculty of Medicine, Izmir, Turkey in 2005. In our dissections, the prevalence and anatomical morphology of the AHFPL including muscle shape, origin and insertion point, and its relation to the anterior interosseous nerve (AIN) was examined. Results: The AHFPL muscle was found in 27 upper extremities (51.9%). It was bilateral in 10 cadavers (74%), and unilateral in 7 cadavers (26%). The muscle shape was spindle in 19 (70.4%), and papillary in 8 (29.6%). The AHFPL originated from the coronoid process of the ulna in 22 upper extremities (81.5%), and the medial epicondyle of the humerus in 5 cases (18.5%). The AIN passed anterior to the AHFPL in one case (3.7%), lateral in 3 (11.1%), posterolateral in 8 (29.6%) and posterior in 15 (55.6%) cases. Conclusion: The knowledge of the morphology and the topography of the AIN and AHFPL is important for understanding the mechanism of the AIN syndrome. The results of this study show the mechanical compression due to the AHFPL may be a cause of the pronator and AIN syndromes.

A pair of parotid glands, mostly serous salivary glands situated infront and beneath each ear canal, to empty their secretions through parotid duct into the
mouth's vestibule. Each gland is located in front of the temporal bone's mastoid process and behind the mandibular ramus. The group of salivary tissues that
are located directly in front of the Stensen's duct or main parotid duct is known as the accessory parotid gland. Accessory Parotid gland has a significant role
in surgical removal of parotid gland i.e. the reoccurance of the tumor may result from a parotidectomy that fails to remove an accessory parotid gland that is far away. A rare case of accessory parotid gland without secondary duct was found during our routine dissection which is at left side of the face and is superior to the parotid duct. A precise understanding about parotid gland and accessory parotid gland may play vital role in planning for surgical intervention like parotidectomy which helps to prevent the reoccurrence of tumors.

During a routine anatomical dissection of a 70-year-old male cadaver, we found that this specimen had an unusual branching pattern of the third part of the
axillary artery. On the right side, the third part of the axillary artery had a common trunk originating from it. The common trunk gave rise to four arteries: the subscapular artery medially and the anterior and posterior circumflex humeral arteries laterally. In contrast, the common trunk continued as the profunda brachii artery (deep brachial artery). It is terminated by dividing into two arteries, the middle collateral and the radial collateral arteries.

Anatomical variations in the renal and urinary systems, though often asymptomatic, hold significant clinical and surgical relevance. Variants such as bifid
ureter, aberrant renal vessels, and polycystic kidneys may complicate diagnostic and operative procedures if unrecognized.
During a routine cadaveric dissection conducted in the Department of Rachana Sharir, anatomical variations were noted in a formalin-fixed 72 yrs old male
cadaver of Indian origin. Following reflection of the posterior peritoneum and removal of overlying fascia and fat, the kidneys, ureters, renal vessels, and
surrounding structures were carefully examined and documented. The cadaver presented with four notable renal anatomical variations: (1) Incomplete Bifid
Ureter (Left Side, Unilateral): a unilateral left-sided incomplete bifid ureter, with two ureteric branches fusing 3.5 cm from the renal pelvis; (2) Multiple
Tributaries of the Left Renal Vein: three distinct tributaries—designated as LRV1, LRV2, and LRV3—were observed draining the left kidney. These tributaries
converged to form a single venous trunk, which subsequently drained into the inferior vena cava. (3) Early Division of the Left Renal Artery: the left renal
artery was noted to bifurcate into segmental branches prior to its entry into the renal hilum, indicating an early prehilar division and (4) Bilateral polycystic
kidneys, each containing 10–15 cysts, varying from 0.5 to 3.5 cm in depth, with dark, viscous fluid content. The coexistence of multiple renal anatomical
variations in a single individual is rare and underscores the importance of awareness in clinical and surgical settings. Thorough anatomical knowledge is crucial in preventing iatrogenic complications during renal surgeries, transplants, or radiological interventions. Cadaveric studies remain invaluable for understanding such variations.

The cephalic arch is a unique anatomic structure. Multiple variants of its usual morphology and termination have been described in the literature. We present 2 cadaveric cases of variants of the cephalic arch; firstly, a morphologic variant, where the cephalic arch divided in two and joined the axillary vein, and secondly, a cephalic arch that drained directly into the external jugular vein. The variants of the cephalic arch are associated with arterio-venous fistulas malfunction, thus the proper anatomic knowledge is essential for both diagnosis and treatment of this condition.

Accessory spleen or splenunculus is a congenital ectopic tissue with incidence rate ranging from 10-30% in autopsy series. Most commonly situated near splenic hilum and supplied by splenic artery. Developmentally, it is due to failure of fusion of splenic nodules in the dorsal mesogastrium. Although most of the time it is an incidental finding, awareness of its presence is important since it may mimic lymphadenopathy and tumor during diagnostic procedures. We report a rare case of accessory spleen in the posterior wall of omental bursa with vascular supply from left gastric artery.

The anatomical relationship between saphenous nerve (SN) and the great saphenous vein (GSV) should be taken into account to avoid injuries to the SN during surgical harvesting of the GSV. The relationship of SN with GSV is highly variable in the lower leg region and there is no comprehensive dataset available on the positioning and distance of the SN with GSV in the lower leg region. The main goal of our study was to analyze the positioning and distance of GSV with SN in the lower leg region. A systematic literature search using PRISMA guidelines was performed in databases such as MEDLINE, PubMed, SciELO, and Cochrane reviews using search terms such as "Saphenous nerve" "Great saphenous vein" "distance" AND "lower leg region", which yielded 1248 article links. Of the fourteen studies that met the inclusion criteria comprising 592 lower limbs are in a range of 26-101 years age. Our pooled analysis revealed that the distance of SN with GSV in the lower third of the leg using a random effects model with Hartung-Knapp adjustment was 0.27 cm (95 % CI; τ 2 =0.0049), indicating a relatively consistent anatomical proximity between these two structures. However, substantial heterogeneity was observed among the studies (I 2 = 97.6%, Q=254.3, p < 0.0001), suggesting significant variability in the reported distances. With regards to positioning of the SN with GSV, pooled estimate of our study revealed that the SN lies anterior to GSV in 31.4% cases, and in 33.1 % cases posterior to it. The predominance of SN lying deep to GSV aligns with 35.5 %, reflecting vulnerability of SN in surgical interventions of the GSV. Our data gives more representative values on the spatial relationship of SN with GSV in the lower leg region, and this information would be of great advantage for surgeons to avoid injury to the SN which can lead to sensory disturbances in the lower leg region and even the SN neuroma.

Various types of variations have been associated with the proximal attachment of the biceps brachii muscle (BBM). The bulk of the reports, been studies done on Caucasian subjects. This is a case report on the supernumerary and variant heads of the proximal part of BBM in three young male adult Nigerian cadavers. Supernumerary occurrence of the head of BBM noted was that of 3 heads and this occurred unilaterally. Another variation noted in another subject was that of the origin of the short head of biceps brachii (SHB) from the acromion and from the supraglenoid tubercle, which also occurred unilaterally. These findings were compared with other documented reports.

The aorta serves as the systemic outflow tract from the heart and it is subject to anatomical variation in the adult, in part, to a complicated set of temporospatial and morphogenetic interactions. The occurrence of an aberrant right subclavian artery (arteria subclavia dextra lusoria, ARSA) is reported to occur with a frequency of approximately 0.1-25.0%. We report the occurrence of ARSA in a cadaver from a 91-year-old male during a routine dissection of the thorax. Features included a bicarotid trunk, normal left subclavian, but a right subclavian that branched from the terminal portion of the descending aorta. The ARSA was positioned in a retroesophageal and retrotracheal location. However, the person was asymptomatic with respect to the ARSA during his life according to medical records. Animations were generated to demonstrate the spatial relationships of the ARSA in this individual. Additional animations were generated to depict embryological relationships that were likely asso...

The rare congenital anomaly of ribs was found incidentally during routine osteology classes. This type of abnormality of first rib May leads to compression of Neurovascular bundle and causes thoracic outlet syndrome. We are reporting a case of Synostosis of first rib, which we come across during osteology classes at Department of Anatomy, KBNIMS, Gulbarga, Karnataka, India. The specimen showed fusion of first rib with sternum on both sides which is very rare. As far as the literature referred there was no such kind of anomaly reported. Knowledge of such anomalies is an important to know, especially for surgeons and radiologists for interpretation.