Anatomical Variations Research Articles

Clinical Significance of Coronary Arterial Dominance: A Review of the Literature.

Coronary dominance describes the anatomic variation of coronary arterial supply, notably as it relates to perfusion of the inferior cardiac territories. Differences in the development and outcome in select disease states between coronary dominance patterns are increasingly recognized. In particular, observational studies have identified higher prevalence of poor outcomes in left coronary dominance in the setting of ischemic, conduction, and valvular disease. In this qualitative literature review, we summarize anatomic, physiologic, and clinical implications of differences in coronary dominance to highlight current understanding and gaps in the literature that should warrant further studies.

Novel Anatomical Variation of Left Coronary Artery Origin at the Sinotubular Junction Level With Coeval Hypoplastic Left Circumflex, Superdominant Right Coronary Artery, and Obstructive Coronary Artery Disease: A Case Report

Novel Anatomical Variation of Left Coronary Artery Origin at the Sinotubular Junction Level With Coeval Hypoplastic Left Circumflex, Superdominant Right Coronary Artery, and Obstructive Coronary Artery Disease: A Case Report

Fractal Analysis of Trabecular Alveolar Bone with Intrabony and Furcation Defects Using Periapical Dental Radiographs

Objective: Fractal analysis (FA) is a non-invasive method that quantitatively measures complex patterned geometric structures present throughout the image. Trabecular morphology of the alveolar bone and the changes occurring in the trabeculae in case of periodontitis can be detected with this method. To examine the periodontal defects in human skull bones using the FA, to compare them with healthy alveolar bone regions. Methods: Furcation and intrabony defects were artificially created in the mandible alveolar bones (n:24). Periapical X-ray images of alveolar bone regions containing teeth with defects were taken using the parallel technique. Fractal analysis was performed by box-counting method using Image J software on images from areas containing healthy and defective trabecular bone. Results: No statistically significant difference was found between the fractal values of healthy tissue and bifurcation defetcs and between the healthy tissue and intrabony defects (p>0.05). Conclusion: Many factors may have affected the outcomes; patient selection, imaging methods, sample size, Region of interest (ROI) selection-location and size, individual and anatomical variations. These variables need to be standardized as much as possible and the limitations of the method need to be improved.

Minimally invasive redo tricuspid valve replacement in patient with persistent left superior vena cava.

The management of cardiopulmonary bypass (CPB) is still challenging in certain circumstances, especially for patients with anatomical variations. This challenge is even harder for reoperations, which are associated with increased morbidity and mortality risk. We describe a minimally invasive, beating-heart redo tricuspid valve replacement in a 71-years old woman with persistent left superior vena cava. Preoperative planning via CT-scan, teamwork and custom-made management of CPB are crucial for reoperations with anatomical variations. The perfusionist has a pivotal role in constructing and managing the CPB. We describe a strategy achieving the benefits of minimally invasive endoscopic and beating-heart surgery (avoidance of resternotomy risk and associated morbidity, right ventricular protection) in reoperative tricuspid surgery with persistent upper left vena cava.

Anatomical Markers Associated With the Presence of Intracranial Aneurysms in Individuals Screened for Aneurysms

BACKGROUND Hemodynamic stress is linked to the development of intracranial aneurysms (IAs) and may be influenced by anatomic variation of intracranial arteries. We assessed diameters and bifurcation angles of intracranial arteries forming the circle of Willis in a cohort of individuals screened for the presence of IAs. METHODS Individuals with and without IAs identified at screening with magnetic resonance angiography were compared. Diameters and bifurcation angles of the following arteries were measured using semiautomatic methods: A1 and A2 segments of the anterior cerebral artery, M1 and M2 segments of the middle cerebral artery, P1 segments of the posterior cerebral artery, posterior communicating artery (Pcom), internal carotid artery, vertebral artery, and basilar artery. We employed univariate general linear models to assess group differences. This included subgroup comparisons between individuals with IAs at specific locations and matched controls, and comparisons on group level between individuals with and without IAs, corrected for age and sex. RESULTS In 94 of the 1049 individuals (9.0%) included, IAs were detected. Individuals with middle cerebral artery IAs had wider ipsilateral M2–M2 bifurcation angles compared with controls (121±25° versus 97±19°; P <0.01). Individuals with anterior communicating artery IAs showed smaller angles for the A1–A2 bifurcation (106±16° versus 120±17°; P  = 0.02), while those with Pcom IAs had wider Pcom–C7 bifurcation angles (147±14° versus 127±17°; P  = 0.02) and smaller diameters below the ipsilateral internal carotid artery top (2.86±0.36 mm versus 3.10±0.33 mm; P  = 0.03) compared with controls. CONCLUSION We found associations between wider M2–M2 bifurcation angles or narrower A1–A2 bifurcation angles and IA presence, consistent with prior literature. Moreover, we uncovered previously unexplored associations, including wider Pcom–C7 bifurcation angles and smaller internal carotid artery diameters in individuals with Pcom IAs. Future research should explore the potential of these markers in predicting IAs in at‐risk populations during follow‐up screenings.

Pulmonary Arterial Anatomical Patterns: a Classification Scheme Based on Lobectomy and 3D-CTBA.

Preoperative evaluation of pulmonary vascular and tracheal routes and variations is of great importance to the surgeon. Three-dimensional computed tomography bronchography and angiography (3D-CTBA) has evolved in recent years with the optimization of 3D reconstruction techniques and artificial intelligence. We aim to apply CT angiography and Exoview 3D reconstruction technology to assess patients' pulmonary arterial tree and its anatomical variants and to try to summarize a set of anatomical typing of the pulmonary arterial tree that is relatively easy and conducive to promoting teaching based on surgical habits of lobectomy. A total of 358 patients hospitalized in the Department of Thoracic Surgery of the First Affiliated Hospital of Soochow University between July 2020 and August 2021 were included in this study. We carefully analyzed the site of emanation, alignment, and number of branches of the pulmonary artery according to a uniform classification method in conjunction with the two-dimensional CT images and transformed them into 3D reconstruction models. Different types of pulmonary artery were observed in 358 cases. We evaluated the complete pulmonary artery tree and counted the number and frequency of major arteries of the pulmonary based on the surgical habits of anatomical lobectomy. The 3D-CTBA technique enables us to adequately assess the anatomy of the pulmonary arteries. Moreover, we provide a practical classification scheme of pulmonary arterial anatomical patterns based on lobectomy and 3D-CTBA. Our data can be used by clinicians in the teaching of pulmonary artery anatomy and the preoperative preparation for anatomical lobectomy.

Simulative investigation of the required level of geometrical individualization of the lumbar spines to predict fractures.

Injury mechanisms of the lumbar spine under dynamic loading are dependent on spine curvature and anatomical variation. Impact simulation with finite element (FE) models can assist the reconstruction and prediction of injuries. The objective of this study was to determine which level of individualization of a baseline FE lumbar spine model is necessary to replicate experimental responses and fracture locations in a dynamic experiment.Experimental X-rays from 26 dynamic drop tower tests were used to create three configurations of a lumbar spine model (T12 to L5): baseline, with aligned vertebrae (positioned), and with aligned and morphed vertebrae (morphed). Each model was simulated with the corresponding loading and boundary conditions from dynamic lumbar spine experiments. Force, moment, and kinematic responses were compared to the experimental data. Cosine similarity was computed to assess how well simulation responses match the experimental data. The pressure distribution within the vertebrae was used to compare fracture risk and fracture location between the different models.The positioned models replicated the injured spinal level and the fracture patterns quite well, though the morphed models provided slightly more accuracy. However, for impact reconstruction or injury prediction, the authors recommend pure positioning for whole-body models, as the gain in accuracy was relatively small, while the morphing modifications of the model require considerably higher efforts. These results improve the understanding of the application of human body models to investigate lumbar injury mechanisms with FE models.

A detailed review of the spinal accessory nerve and its anatomical variations with cadaveric illustration.

The spinal accessory nerve, considered part of the eleventh cranial nerve, provides motor innervation to sternocleidomastoid and trapezius. A comprehensive literature review and two cadaveric dissections were undertaken. The spinal accessory nerve originates from the spinal accessory nucleus. Its rootlets unite and ascend between the denticulate ligament and dorsal spinal rootlets. Thereafter, it can anastomose with spinal roots, such as the McKenzie branch, and/or cranial roots. The spinal accessory nerve courses intracranially via foramen magnum and exits via jugular foramen, within which it usually lies anteriorly. Extracranially, it usually crosses anterior to the internal jugular vein and lies lateral to internal jugular vein deep to posterior belly of digastric. The spinal accessory nerve innervates sternocleidomastoid, receives numerous contributions in the posterior triangle and terminates within trapezius. Its posterior triangle course approximates a perpendicular bisection of the mastoid-mandibular angle line. The spinal accessory nerve contains sensory nociceptive fibres. Its cranial nerve classification is debated due to occasional non-fusion with the cranial root. Surgeons should familiarize themselves with the variable course of the spinal accessory nerve to minimize risk of injury. Patients with spinal accessory nerve injuries might require specialist pain management.

An atlas of anatomical variants of the human calcaneus.

The usefulness of anatomical variation is determined by the knowledge of why nonmetric traits appear. Clear descriptions of the traits are a necessary task, due to the risk of confusing anatomical variants and evidence of trauma. Numerous interpretations of the appearance of calcaneal anatomical variants add to the need of an anatomical atlas of calcaneal nonmetric traits. We have analyzed a total of 886 calcanei; 559 belong to different modern and pre-Hispanic samples, and 327 bones were studied from a reference collection from Athens. In this study, we present the anatomical variations that exist on the calcaneus bone, some of which have rarely been mentioned in previous research. The standardization of methods proposed may be useful to experts working in human anatomy, physical anthropology as well as comparative morphology, due to usefulness of this information during surgery, and bioanthropology to observe and study the lifestyle of past populations.

Aberrant origin of the left vertebral artery: clinical case and scientific literature

The variants in the origin of the trunks of the aortic arch are very heterogeneous. Among them, it is worth highlighting the variants that involve the origin of the vertebral artery and more specifically the left vertebral artery. We present the case of a 62-year-old patient in whom an aberrant vertebral artery was incidentally described in a computed tomography for oncological evaluation. This anatomical variant is asymptomatic in up to 5% of cases and can give rise to clinical problems of a vascular nature.

Acroparesthesias: An Overview.

Acroparesthesia is a symptom characterized by a subjective sensation, such as numbness, tingling, prickling, and reduced sensation, affecting the extremities (fingers and toes). Despite its frequency, data regarding its diagnostic approach and management are scarce. The etiological diagnosis of acroparesthesia is sometimes challenging since it can be due to abnormality anywhere along the sensory pathway from the peripheral nervous system to the cerebral cortex. Acroparesthesia can reveal several diseases. It can be associated with rheumatic complaints such as arthritis or myalgia. Further cautions are required when paresthesia is acute (within days) in onset, rapidly progressive, severe, asymmetric, proximal, multifocal, or associated with predominant motor signs (limb weakness) or severe dysautonomia. Acroparesthesia may reveal Guillain-Barré syndrome or vasculitis, requiring rapid management. Acroparesthesia is a predominant symptom of polyneuropathy, typically distal and symmetric, often due to diabetes. However, it can occur in other diseases such as vitamin B12 deficiency, monoclonal gammopathy of undetermined significance, or Fabry's disease. Mononeuropathy, mainly carpal tunnel syndrome, remains the most common cause of acroparesthesia. Ultrasonography contributes to the diagnosis of nerve entrapment neuropathy by showing nerve enlargement, hypoechogenic nerve, and intraneural vascularity. Besides, it can reveal its cause, such as space-occupying lesions, anatomical nerve variations, or anomalous muscle. Ultrasonography is also helpful for entrapment neuropathy treatment, such as ultrasound-guided steroid injection or carpal tunnel release. The management of acroparesthesia depends on its causes. This article aimed to review and summarize current knowledge on acroparesthesia and its causes. We also propose an algorithm for the management of acroparesthesia.

Adrenal Vein Sampling: Tips and Tricks.

Adrenal vein sampling (AVS) is the standard method for distinguishing unilateral from bilateral sources of autonomous aldosterone production in patients with primary aldosteronism. This procedure has been performed at limited specialized centers due to its technical complexity. With recent advances in imaging technology and knowledge of adrenal vein anatomy in parallel with the development of adjunctive techniques, AVS has become easier to perform, even at nonspecialized centers. Although rare, anatomic variants of the adrenal veins can cause sampling failure or misinterpretation of the sampling results. The inferior accessory hepatic vein and the inferior emissary vein are useful anatomic landmarks for right adrenal vein cannulation, which is the most difficult and crucial step in AVS. Meticulous assessment of adrenal vein anatomy on multidetector CT images and the use of a catheter suitable for the anatomy are crucial for adrenal vein cannulation. Adjunctive techniques such as intraprocedural cortisol assay, cone-beam CT, and coaxial guidewire-catheter techniques are useful tools to confirm right adrenal vein cannulation or to troubleshoot difficult blood sampling. Interventional radiologists should be involved in interpreting the sampling results because technical factors may affect the results. In rare instances, bilateral adrenal suppression, in which aldosterone-to-cortisol ratios of both adrenal glands are lower than that of the inferior vena cava, can be encountered. Repeat sampling may be necessary in this situation. Collaboration with endocrinology and laboratory medicine services is of great importance to optimize the quality of the samples and for smooth and successful operation. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

The relationship of medial sigmoid depression and sigmoid notch morphology with vertical and sagittal growth patterns in Turkish population

Medial sigmoid depression (MSD) is an anatomical variation located just below the deepest point of the sigmoid notch (SN). The etiology of MSD is unknown. It has been reported that increased maximum bite force affects the occurrence of MSD, and vertical growth pattern affects SN morphology. The aim of this study was to investigate the effects of these malocclusions on the presence and morphology of MSD and SN, since bite force can change with vertical and sagittal growth patterns. This is the first study to investigate the effects of vertical growth pattern on the presence and morphology of MSD, and the effects of sagittal growth pattern on SN morphology. Panoramic and lateral cephalometric radiographs of a total of 634 (427 female, 207 male) patients aged from 18 to 35 years (mean 19.58) were included in this retrospective study. MSD and SN shapes, SN depth and width were evaluated on panoramic radiographs. Mann Whitney-U, Kruskal-Wallis and Chi-square tests were used for data analysis. Sagittal and vertical growth patterns were not significantly associated with the presence and shape of MSD (p>0.05). SN depth was greater in individuals with class III malocclusion, and both SN depth and width were lower in hyperdivergent individuals. There was no significant relationship between SN shapes and vertical and sagittal growth patterns (p>0.05). SN depth is affected by both vertical and sagittal growth pattern, and SN width is affected only by vertical growth pattern. The presence of MSD was not associated with growth pattern.

Co-occurrence of patent foramen ovale and Chiari network in a diabetic patient.

The coexistence of congenital cardiovascular anomalies provides valuable insights into the intricate nature of human cardiac anatomy and its potential interactions with underlying health conditions. This case report presents an autopsy analysis of a diabetic patient manifesting both a patent foramen ovale and a Chiari network. A 26-year-old male with a history of type 2 diabetes mellitus was admitted with post cardiac arrest. He died despite resuscitative efforts. Autopsy revealed notable findings including a patent foramen ovale and a Chiari network. Post-mortem biochemical markers indicated elevated HbA1c level and hyperglycaemia. The absence of cryptogenic strokes or paradoxical embolism prompted exploration into potential relationships between these anomalies and metabolic disturbances, and prompts a discussion about whether the observed anatomical variations could potentially serve as risk factors contributing to the patient's death due to complications of diabetes. The co-occurrence of a patent foramen ovale and a Chiari network within a diabetic patient, accompanied by elevated HbA1c level and hyperglycaemia, offers a unique perspective on the convergence of congenital cardiovascular variation and metabolic health. The juxtaposition of these anomalies with biochemical markers underscores the intricate interplay between cardiac morphology and metabolic conditions.

Morphometric analysis of the mastoid process using cone beam computed tomography

The sexual dimorphism of the mastoid process, as demonstrated by cone beam computed tomography (CBCT), is not well examined in forensic anthropology or clinical diagnostics. The mastoid region can be precisely imaged in three dimensions using CBCT, which reveals minute anatomical variations between males and females. These characteristics can help forensic professionals identify the sex of unidentified human remains, helping to solve crimes and aid in the search for missing persons. Moreover, recognising sexual dimorphism in the mastoid process in clinical settings can help with precise patient identification and individualised medical treatments, highlighting the important function of CBCT in both the forensic and medical areas.

Safety and Tolerability of Online Adaptive High-Field Magnetic Resonance-Guided Radiotherapy.

In 2018, the first online adaptive magnetic resonance (MR)-guided radiotherapy (MRgRT) system using a 1.5-T MR-equipped linear accelerator (1.5-T MR-Linac) was clinically introduced. This system enables online adaptive radiotherapy, in which the radiation plan is adapted to size and shape changes of targets at each treatment session based on daily MR-visualized anatomy. To evaluate safety, tolerability, and technical feasibility of treatment with a 1.5-T MR-Linac, specifically focusing on the subset of patients treated with an online adaptive strategy (ie, the adapt-to-shape [ATS] approach). This cohort study included adults with solid tumors treated with a 1.5-T MR-Linac enrolled in Multi Outcome Evaluation for Radiation Therapy Using the MR-Linac (MOMENTUM), a large prospective international study of MRgRT between February 2019 and October 2021. Included were adults with solid tumors treated with a 1.5-T MR-Linac. Data were collected in Canada, Denmark, The Netherlands, United Kingdom, and the US. Data were analyzed in August 2023. All patients underwent MRgRT using a 1.5-T MR-Linac. Radiation prescriptions were consistent with institutional standards of care. Patterns of care, tolerability, and technical feasibility (ie, treatment completed as planned). Acute high-grade radiotherapy-related toxic effects (ie, grade 3 or higher toxic effects according to Common Terminology Criteria for Adverse Events version 5.0) occurring within the first 3 months after treatment delivery. In total, 1793 treatment courses (1772 patients) were included (median patient age, 69 years [range, 22-91 years]; 1384 male [77.2%]). Among 41 different treatment sites, common sites were prostate (745 [41.6%]), metastatic lymph nodes (233 [13.0%]), and brain (189 [10.5%]). ATS was used in 1050 courses (58.6%). MRgRT was completed as planned in 1720 treatment courses (95.9%). Patient withdrawal caused 5 patients (0.3%) to discontinue treatment. The incidence of radiotherapy-related grade 3 toxic effects was 1.4% (95% CI, 0.9%-2.0%) in the entire cohort and 0.4% (95% CI, 0.1%-1.0%) in the subset of patients treated with ATS. There were no radiotherapy-related grade 4 or 5 toxic effects. In this cohort study of patients treated on a 1.5-T MR-Linac, radiotherapy was safe and well tolerated. Online adaptation of the radiation plan at each treatment session to account for anatomic variations was associated with a low risk of acute grade 3 toxic effects.

A cone beam computed tomographic study on foramen transversarium

The foramen transversarium is a vital feature found in the cervical vertebrae of the spine. It serves as a protective passageway for the vertebral artery and vertebral vein, supplying blood to the brain and spinal cord. Any compromise to these structures within the foramen can lead to severe neurological complications, emphasizing its clinical significance. The study was carried out on 83 subjects of typical cervical vertebrae. Among them were 42 males and 41 females. All the foramen transversaria were observed for any anatomical variations. The anteroposterior, transverse diameters of all the foramen transversaria and the distance between the medial margin of uncinate process to the foramen transversarium were measured. The average transverse diameter of typical cervical vertebrae and seventh cervical vertebrae were ± 0.84mm and 5.13 ± 1.22 mm respectively. The average anteroposterior diameters of typical and seventh cervical vertebrae were 4.84 ± 0.69 mm and 3.91 ± 1.17 mm respectively. The distance from medial border of uncinate process to foramen transversaria was 4.28 ± 0.77 mm in typical and 5.44 ± 1.28 mm in seventh cervical vertebrae. The incidence of double bubble foramen in typical cervical vertebrae was reported to be17.5%. The incidence of double foramen transversaria was 12.5% in the seventh cervical vertebrae. Osteophytes were obstructing the foramen transversarium and narrowing it in 25% of vertebrae. In cone beam computed tomography (CBCT), the foramen transversarium plays a pivotal role in precise imaging of the cervical spine. Its significance lies in providing clear visualization of anatomical structures and potential abnormalities, aiding in the accurate diagnosis and treatment planning for various spinal conditions, thus enhancing patient care.

Misdiagnosis or Missed Diagnosis - Hallux Sesamoid Fractures among Active-Duty Females in the United States Air Force: A Case Series

Background: Female service members tend to have a higher level of foot injuries than males. The United States Army spent $103 million in 2017 on fractures in toes and feet. Fractures of the tibial and fibular sesamoids are problem that often can be nonspecific, mainly related to pain at the plantar aspect of the first metatarsal head without an obvious traumatic event. Anatomic variation in these sesamoids exist after ossification which results in the possibility of multipartite sesamoids. Of the multipartite sesamoids, bipartite sesamoids are the relatively common and tripartite sesamoids are quite rare. The overall prevalence of bipartite sesamoids is presumed to be between 7 and 30%, with a majority occurring bilaterally. Methods: We completed a case series on three female active-duty Airmen. All three patients were active with their pain beginning following activity. All three were subsequently misdiagnosed, resulting in at least 6 months of pain prior to diagnosis and treatment. Results: Plain film radiography and subsequent imaging confirmed the diagnosis of a tibial or fibular sesamoid fracture. Following conservative treatment all three patients made a full recovery as confirmed by imaging and self-reported pain levels and they were able to return to full activity. Conclusion: Providers should keep a sesamoid fracture in the differential diagnosis when evaluating active female patients with pain in the area around the base of the great toe, especially in women in the military and others that may do higher levels of physical activity compared to the average patient. While the diagnosis of sesamoid fractures can be challenging, it is standard practice to obtain multiple views if using plain film radiography. Magnetic resonance imaging, weightbearing computed tomography and bone scans can be useful confirmatory studies.

Study of Anatomical Divergences in Facial Artery Endings

Facial artery supplies musculocutaneous tissue, visceral organs, and salivary glands at the upper cervical and facial level. This artery has wide range of anatomical variations in its course. Objective: To find the anatomical divergences in facial artery endings. Methods: It is a cross sectional study conducted at Jinnah international hospital, Abbottabad from January 2023 to July 2023 for duration of 6 months after taking approval from the ethical review committee. A group of 86 people were selected and anatomical course of facial artery was categorized in to four types. Angiographic images of each participant were evaluated by radiologist to categorize the course of facial artery. Results: The average Body Mass Index (BMI) of the participants was 28.3 ± 5.6. The study of angiographic images has concluded that 38.37% (n=33) has Type I course of facial artery, 47.67% (n=41) participants has Type II, 9.3% (n=8) participants has Type III and 4.65% (n=4) has Type IV category (p=0.01. Of the type I category of facial artery, 5 (15.2%) participants met the criteria of type IA, 7(21.2%) has Type IB and 21(63.6%) participants Type IC course of facial artery (p=0.01). Conclusions: This study has concluded that there exists vast variation in the anatomical course of facial artery in local population that streamlines with other studies conducted internationally. Facial artery with a nasal branch with or without alar endings is the most common anatomical variation.

Infraorbital canal variants and its clinical and surgical implications. A systematic review.

Recent literature highlights anomalous cranial nerves in the sinonasal region, notably in the sphenoid and maxillary sinuses, linked to anatomical factors. However, data on the suspended infraorbital canal (IOC) variant is scarce in cross-sectional imaging. Anatomical variations in the sphenoid sinuses, including optic, maxillary, and vidian nerves, raise interest among specialists involved in advanced sinonasal procedures. The infraorbital nerve's (ION) course along the orbital floor and its abnormal positioning within the orbital and maxillary sinus region pose risks of iatrogenic complications. A comprehensive radiological assessment is crucial before sinonasal surgeries. Cone-beam computed tomography (CBCT) is preferred for its spatial resolution and reduced radiation exposure. The aim of this study was to describe the prevalence of anatomical variants of the infraorbital canal (IOC) and report its association with clinical condition or surgical implication. We searched Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS databases from their inception up to June 2023. Two authors independently performed the search, study selection, data extraction, and assessed the methodological quality with assurance tool for anatomical studies (AQUA). Finally, the pooled prevalence was estimated using a random effects model. Preliminary results show that three types are prevalent, type 1: the IOC does not bulge into the maxillary sinus (MS); therefore, the infraorbital foramen through the anterior wall of MS could be used for identification of the ION. Type 2: the IOC divided the orbital floor into medial and lateral aspects. Type 3: the IOC hangs in the MS and the entire orbital floor lying above the IOC. From which the clinical implications where mainly surgical, in type 1 the infraorbital foramen through the anterior wall of MS could be used for identification of the ION, while in type 2, since the lateral orbital floor could not be directly accessed an inferiorly transposition of ION is helpful to expose the lateral orbital wall directly with a 0 scope; or using angled endoscopes and instruments, however, the authors opinion is that direct exposure potentially facilitates the visualization and management in complex situations such as residual or recurrent mass, foreign body, and fracture located at the lateral aspect of the canal. Lastly, in type 3, the ION it's easily exposed with a 0° scope. This systematic review identified four IOC variants: Type 1, within or below the MS roof; Type 2, partially protruding into the sinus; Type 3, fully protruding into the sinus or suspended from the roof; and Type 4, in the orbital floor. Clinical recommendations aim to prevent nerve injuries and enhance preoperative assessments. However, the lack of consistent statistical methods limits robust associations between IOC variants and clinical outcomes. Data heterogeneity and the absence of standardized reporting impede meta-analysis. Future research should prioritize detailed reporting, objective measurements, and statistical approaches for a comprehensive understanding of IOC variants and their clinical implications. Open Science Framework (OSF): https://doi.org/10.17605/OSF.IO/UGYFZ .