Multiple coexisting variations of skull and cervical spine anatomy in a symptomatic patient - uncommon or uncommonly noticed? A CT-based case study.

INTRODUCTION: Among many anatomical variations of the skull and cervical spine, some may be an underlying cause of a disease, while others remain clinically silent. The estimated individual prevalences of them differ, but given the available data it is impossible to clarify how frequently they coexist with each other. The following study presents an example of seven anomalies, amongst which at least few have manifested clinically in the examined patient. CASE REPORT: A 35 y.o. Polish woman who suffered from chronic sinusitis was subjected to a computed tomography scan. Mild thickening of the anterior ethmoidal cells' mucosa, bilateral concha bullosa, paradoxical right middle turbinate, bilateral uncinate process pneumatization and arrested pneumatization of sphenoid sinus were found and addressed in context of the reported symptoms. Simultaneously other, clinically silent anatomical anomalies, were found - namely ossification of the anterior petroclinoid ligament, incomplete medial basal canal and bilateral arcuate foramen. CONCLUSION: To the best knowledge of the authors, this case report is the first to present such a coexistence of this many various anatomical anomalies, among which some played a crucial part in the chronic sinusitis experienced by the patient. Concurrence of multiple variations in the same anatomical area or functional unit may exacerbate clinical presentation of a patient. Identifying a single anomaly ought to warrant a thorough investigation into any other potentially existing variants.

Two simultaneous anatomical variations of the cervical spine - a case report discussing the concept of tandem anomalies.

forming a bony opening through which the vertebral artery (VA) enters the vertebral canal. Block vertebra is a synostosis of at least two vertebral bodies that did not separate during the embryological development. It is worth distinguishing it from the Klippel-Feil syndrome, as the latter oftentimes involves other abnormalities (namely skeletal) and is typically diagnosed in childhood. Both variants could potentially lead to an impairment of the blood flow through the VA. Case report: The following case report presents a finding of two anomalies of the cervical spine, found in a 38 y.o. female patient suffering from dizziness. A synostosis of the C4 and C5 vertebral bodies, arches and zygapophysial (facet) joint, was noted by the examining radiologist, with marked narrowing of the intervertebral foramen. Furthermore, second anatomical variation in the form of the complete bilateral arcuate foramen was identified superior to the groove for the VA on the upper surface of the posterior arch of the atlas. Conclusions: To the best knowledge of the authors, this case report is the first to present a co-existing block vertebra and bilateral complete arcuate foramen. Common presence of at least two anatomical variations that could have a synergistic clinical effect could possibly be termed 'tandem anomaly.' Notwithstanding, identification of a single anomaly explaining a patient's symptoms does not absolve the medical professionals from searching for any other potential variations that could also be present and could further influence the clinical picture.

Testicular Metastasis from Renal Cell Carcinoma: A Systematic Review.

Approximately one-third of renal cell carcinoma (RCC) is recognized in its metastatic stage. This systematic review aimed to summarize knowledge on the occurrence and treatment of testicular RCC metastasis. The literature search was performed by two authors independently, with the use of main electronic medical databases (Science Direct, Web of Science, and PubMed) until March 2023 to identify relevant articles that could potentially contribute to this review. Neither language nor publication dates were set as limits. Although we found a total of 51 case reports, only 31 of them contained all the required information. Testicular metastasis in patients with RCC suggests a late stage of the disease. Moreover, it usually does not present typical systemic or specific symptoms except for swelling and enlargement of the affected testis. Knowledge of the possibility of such variants of RCC metastases will allow a clinician to make an appropriate diagnosis and implement adequate treatment without delay, which is crucial in the management of neoplastic disease.

Polyorchidism: An Up-to-Date Systematic Review.

Polyorchidism is a rare male urogenital tract anomaly characterized by at least one supernumerary testis in the scrotum or ectopically. According to data based on our systematic review, 76% of the supernumerary testes (SNTs) were located in the scrotum, and 24% were extra-scrotal (p < 0.001). Among testes located outside the scrotum, 87% were found in the inguinal canal and 13% in the abdominal cavity. In 80% of cases, the diagnosis of SNT was made based on imaging tests, and the remaining 20% of cases were detected incidentally during surgery. The imaging tests performed (US or MRI) resulted in a significantly higher rate of patients who qualified for observation vs. surgical treatment (45% vs. 35%, p < 0.001). The most common conditions associated with SNT were ipsilateral inguinal hernia (15% of cases) and cryptorchidism (15% of cases). Surgery (orchidopexy/orchidectomy) was performed on 54% of patients with SNT, and the decision to observe the SNT was made in a total of 46% of patients (p = 0.001). The therapeutic approach depends on the location of the SNT and the presence of factors that raise suspicion of neoplastic proliferation.

The anatomy of the uterine artery: A meta-analysis with implications for gynecological procedures.

The uterine artery (UA) is an arterial branch of the internal iliac artery in women, usually arising from the anterior division of the internal iliac artery. However, due to the high variability in the anatomy of the UA, embolization of this vessel may be challenging. Therefore, the objective of this meta-analysis was to provide physicians with transparent data on the anatomy of the UA, using the available data in the literature. Databases such as PubMed, Scopus, Embase, Web of Science, and Google Scholar were searched to find all the relevant studies regarding the UA. A total of 16 articles met the required criteria. The UA was found to originate most frequently from the internal iliac artery as the pooled prevalence was set to be 61.72% (95% CI: 41.31%-80.31%). A pooled prevalence of the UA originating from the umbilical artery was established at 13.93% (95% CI: 2.76%-30.44%). A pooled prevalence of the UA originating from the inferior gluteal artery was set to be 5.22% (95% CI: 0.00%-15.44%). In conclusion, we believe that this is the most accurate and up-to-date study regarding the highly variable anatomy of the UA. The UA originates most frequently from the internal iliac artery (61.72%), however, other origins, such as from the umbilical artery (13.93%) or the inferior gluteal artery (5.22%) may occur. It is hoped that the results of the present meta-analysis will be a helpful tool for surgeons performing pelvic or gynecological surgeries.

The thyrocervical trunk: an analysis of its morphology and variations.

The number of studies on the variations of the branching of the TT is scarce, and those works that treat about the different types of the said trunk are oftentimes inconsistent. Therefore, the authors of the present study would like to propose a set of five types of TT, which were created based on observations of 41 computed tomography angiographies (82 TTs). To establish the anatomical variations, their prevalence, and morphometrical data regarding the TT and its branches, a retrospective study was performed. The results of 55 consecutive patients who underwent neck and thoracic computed tomography angiography (CTA) were analyzed. The analysis was performed on a total of 82 TTs of 41 patients, aged 15 to 82 years (mean age: 46 years; SD: 18.4), of which 16 (39.0%) were females, and 25 (61.0%) were males. Initially, 11 types of variations were evaluated, of which types 1-4 constituted 89.0%. Furthermore, a new method of classification of the anatomical variations of the TTs has been established. In this study, the variety of the branching and morphology of the TT was presented, proposing its novel classification based on the five most commonly prevalent types. Types 1 and 2 were the most common, with a prevalence of 26.8% each. This work also provides physicians with crucial data about the morphology of the TT and its branches, which can surely be of use when performing endovascular or reconstructive procedures in the cervical region.

Arthrofibrosis - a myth or true joint disorder?

Authors, mostly specialists on rehabilitation and orthopedic surgery prove that arthrofibrosis is a commonly overlooked phenomenon, which may lead to serious limitation in the range of movement, leading to limitation in patients quality of functioning. The main goal of this article is to emphasize the importance of understanding a such complex condition. Non typical patomechanism, lack of biomarkers dedicated to this dysfunction and general lack of understanding in this pathology causes that risk factors and the most effective strategies remain vastly unknown. Pathophysiology of the arthrofibrosis in the joints is definitely multifactorial, but intense production of collagen seems to be the main factor. Most modern pharmacological methods concentrate on the regulation of collagen fiber production and reducing the inflammation. Inflammation from joint contractures stimulates the proliferation of activated cells that results in the production of extracellular matrix macromolecules to form fibrotic tissue that is deposited into the capsule, thereby resulting in fibrosis. Lack of unified classification scale is caused by relatively high variation of the functions fulfilled by particular joints and each treatment plan should be constructed individually. Quality of surgical treatment and physical therapy play a major role in both prevention and treatment of such complex condition as arthrofibrosis. Both iatrogenic mistakes and overly aggressive manual therapy are some of main factors increasing the risk of this pathological condition. Introducing properly conducted physical therapy treatment in the early stage is crucial to main the range of movement and preventing this significant problem.

The middle anorectal artery: A systematic review and meta-analysis of 880 patients/1905 pelvic sides.

The middle anorectal artery (MAA) is considered to supply the middle and lower parts of the rectum, however, its prevalence and point of origin vary across the literature. Clinical importance of the MAA becomes evident in the total mesorectal excision during the colorectal surgery of rectal cancer in both sexes, as well as interventional radiology procedures utilizing the prostatic vasculature in males. Major electronic medical databases were investigated for terms pertaining to the MAA and its associated variations. Compatible data regarding the artery's prevalence, laterality, origin, and distribution in both sexes was acquired. The risk of bias within the studies was assessed utilizing the AQUA tool. In total, 28 works (n = 880 patients/1905 pelvic sides) were included in this systematic review and meta-analysis, and their publication date ranged from 1897 until 2021. The overall pooled prevalence estimate for the MAA was 59.8% of the patients, and 55.2% of the pelvic sides studied. The vessel was identified more frequently in cadaveric pelvic sides evaluations (79.3%). The artery was found bilaterally more often (56.7%), and most commonly originated from the internal pudendal artery (50.3%). Anastomoses between the MAA and the other anorectal arteries were reported in 78.1%. The MAA is predominantly a present vessel, with various point of origin. Its direct clinical significance is yet to be discovered in larger study samples, providing more detailed and unified reports of its anatomical features, especially regarding its branches.

Pathogenesis and Management of Brugada Syndrome: Recent Advances and Protocol for Umbrella Reviews of Meta-Analyses in Major Arrhythmic Events Risk Stratification.

Brugada syndrome (BrS) is a primary electrical disease associated with life-threatening arrhythmias. It is estimated to cause at least 20% of sudden cardiac deaths (SCDs) in patients with normal cardiac anatomy. In this review paper, we discuss recent advances in complex BrS pathogenesis, diagnostics, and current standard approaches to major arrhythmic events (MAEs) risk stratification. Additionally, we describe a protocol for umbrella reviews to systematically investigate clinical, electrocardiographic, electrophysiological study, programmed ventricular stimulation, and genetic factors associated with BrS, and the risk of MAEs. Our evaluation will include MAEs such as sustained ventricular tachycardia, ventricular fibrillation, appropriate implantable cardioverter-defibrillator therapy, sudden cardiac arrest, and SCDs from previous meta-analytical studies. The protocol was written following the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) guidelines. We plan to extensively search PubMed, Embase, and Scopus databases for meta-analyses concerning risk-stratification in BrS. Data will be synthesized integratively with transparency and accuracy. Heterogeneity patterns across studies will be reported. The Joanna Briggs Institute (JBI) methodology, A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR 2), and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) are planned to be applied for design and execution of our evidence-based research. To the best of our knowledge, these will be the first umbrella reviews to critically evaluate the current state of knowledge in BrS risk stratification for life-threatening ventricular arrhythmias, and will potentially contribute towards evidence-based guidance to enhance clinical decisions.

Cranial diploic channels and their veins - a review of literature.

The current paper is a review of the results attained in the past and current anatomical studies, aimed at understanding the variability and function of the diploic venous system of the human skull. The diploic veins can serve as transit for infections from the scalp to the structures contained within the cranial cavity via the emissary veins, due to their interconnections with the pericranial veins, meningeal veins and dural sinuses. Thereby this clinical aspect has also been discussed.

Anatomy of the deep brachial artery - general overview (cadaveric study) - discussion on terminology.

There are only very few studies on the anatomy of the deep brachial artery - DBA (arteria profunda brachii), both regarding its course, branching pattern and contribution to the cubital rete. Most of the textbooks are based on data which remain unchanged for years. The aim of this article was to summarize the current knowledge on this vessel, based on the anatomical and clinical studies and other sources available including also own cadaveric study. We tried to present also some controversies regarded to the nomenclature of the branches of the DBA.

The course of the main septum in the sphenoid sinuses - evaluation before the FESS.

The purpose of this study was to determine the course of the main septum (MS) in the sphenoid sinuses in the adult population. Materials and Methods: 296 patients (147 females, 149 males), who did not present any pathology in the paranasal sinuses, were included in this retrospective analysis of the computed tomography (CT) scans. Spiral CT scanner (Siemens Somatom Sensation 16) was used in order to glean the images of the paranasal sinuses, using standard procedure, in the option Siemens CARE Dose 4D, without using any contrast medium. Secondary reconstructions of the sagittal and frontal planes were obtained using multi- plans reconstruction (MPR) tool after obtaining transverse planes in the first instance. R e s u l t s: The course of the MS changed the most often from the anterior to the posterior part of the sphenoid sinuses. Such situation took place in 83.78% of the patients, in 32.43% of whom a clear shift to the lateral side was noticed only in the posterior part of the MS: in 18.24% of the patients to the right side, and in 14.19% of the patients to the left side. In 17.57% of the patients the lateral shift was visible in both anterior and posterior parts of the septum, where in 9.46% of the patients it was from the left side to the right, whereas in 8.11% of the patients the shift took place from the right side to the left. The MS had the shape of the letter 'C' in 22.29% of the cases, and 11.82% had the typical shape of the letter 'C,' and in 10.47% of the patients it paralleled the inverted letter 'C' (upside down). Amongst the types of the MS shifting directions the rarest was the MS that resembled the letter 'S' - 11.48% of the patients. In 5.74% of the cases it looked like the typical letter 'S,' and in 5.74% of the cases it was similar to the inverted letter 'S.' Only 16.22% of the cases had the MS that did not change its course nor its shape and ran medially in the sagittal plane from the anterior to the posterior part of the sinuses. Conclusions: In furtherance of reducing the risk of problems occurring during a surgery in the paranasal sinuses, it is prudent to have a CT scan done in all the patients beforehand, due to the high prevalence of the anatomical variations in the sinuses.

The Anatomy of the Convergence of Major Deep Cerebral Veins in the Pineal Region: A Computed Tomography Angiography Study.

BACKGROUND: The anatomy of the veins in the pineal region is one of the most complex areas in the brain because all major deep cerebral veins converge there: the internal cerebral veins (ICVs), the great cerebral vein of Galen (GV), the basal veins (BVs), and the internal occipital veins (IOVs). The aim of this study was to comprehensively describe the anatomy of the veins in the pineal region using computed tomography angiography. METHODS: Head computed tomography angiography scans of 250 adult Polish patients were evaluated. We assessed the location of the junction of 2 ICVs and the presence of a narrowing of the GV and arachnoid granulation at the GV-straight sinus junction. We evaluated the presence, appearance, and termination of the BV, and the presence and termination of the IOV. RESULTS: The study showed that 2 ICVs usually converged posterior to the splenium of the corpus callosum (62.4%). Narrowing of the BV was observed in 51.2% of patients, and the arachnoid granulation was found in 25.2%. The 3 segments of the BV were well visualized in 66% of the studied hemispheres. The BV flowed into the GV in 34.8% of the hemispheres. The IOV was present in 90.2% of the hemispheres and terminated medially in 84.5%. CONCLUSIONS: Because an injury to major deep cerebral veins may result in severe postoperative neurologic deficits, it is essential for neurosurgeons to be familiar with both normal and variant patterns of veins in the pineal region.

A 3D model of the renal vasculature - a joined result of the corrosion casting technique, micro-CT imaging and rapid prototyping technology.

Three-dimensional (3D) printed model of the renal vasculature shows a high level of accuracy of subsequent divisions of both the arterial and the venous tree. However, minor artifacts appeared in the form of oval endings to the terminal branches of the vascular tree, contrary to the anticipated sharply pointed segments. Unfortunately, selective laser sintering process does not currently permit to present the arterial, venous and urinary systems in distinct colors, hence topographic relationship between the vascular and the pelvicalyceal systems is difficult to attain. Nonetheless, the 3D printed model can be used for educational purposes to demonstrate the vast renal vasculature and may also serve as a reference model whilst evaluating morphological anomalies of the intrarenal vasculature in a surgical setting.

Incorporation of the sphenoid sinuses' septum / septa in the carotid canal - evaluation before the FESS.

The purpose of the research was to define the frequency prevalence of the incorporation of sphenoid sinuses' septum / septa in the carotid canal of the adult population. MATERIALS AND METHODS: 296 computed tomography (CT) scans of the patients (147 females, 149 males), who did not present any pathology in the sphenoid sinuses, were evaluated in this retrospective analysis. Spiral CT scanner - Siemens Somatom Sensation 16 - was used to glean the medical images. Standard procedure applied in the option Siemens CARE Dose 4D. No contrast medium was administered. Multiplans reconstruction (MPR) tool was used in order to obtain frontal and sagittal planes from the transverse planes previously received. RESULTS: Bilateral incorporation of the main septum (MS) in the carotid canal was not present in any of the patients, whereas unilateral incorporation was noticed in 21.96% of the patients (17.68% females, 26.17% males). On the right side it occurred in 11.82% of cases (10.88% females, 12.75% males), and on the left side in 10.14% of cases (6.8% females, 13.42% males). Bilateral incorporation of the additional septum (AS) was found in 8.45% of the patients (4.08% females, 12.75% males), whereas unilateral incorporation was noted in 28.37% of the patients. It was seen on the right side in 11.82% of cases (12.93% females, 10.74% males), and on the left side in 16.55% cases (15.65% females, 17.45% males). The most common variant was the incorporation of only one of the septa (either the MS or the AS) in the wall of the carotid canal unilaterally. Such situation took place in 30.07% of the patients (29.25% females, 30.87% males). Incorporation of two septa on the same side was noticed in 4.39% of cases (4.08% females, 4.7% males), and incorporation of three septa in 0.34% of cases (0.7% males). CONCLUSIONS: The anatomy of the paranasal sinuses is varied to a great extent, hence performing a CT scan is crucial before the scheduled surgery, as it may lessen the unforeseeable surgical complications, that may result from the high prevalence of variants in the sinuses.

The height and type of the main septum in the sphenoid sinuses - evaluation before the fess.

The purpose of this study was to examine the height of the main septum (MS) in the sphenoid sinuses and its type, depending on the percentage prevalence of its tissue composition (osseous and membranous) in the adult population. Materials and Methods: A retrospective analysis of 296 computed tomography (CT) scans (147 females, 149 males) of the paranasal sinuses was conducted. The patients did not present any pathology in the sphenoid sinuses. The CT scans of the paranasal sinuses were carried out with a spiral CT scanner (Siemens Somatom Sensation 16) in a standard procedure, in the option Siemens CARE Dose 4D. No contrast medium was used. Having obtained the transversal planes, a secondary reconstruction tool (multiplans reconstruction - MPR) was used in furtherance of gleaning sagittal and frontal planes. R e s u l t s: In all cases, the height of the MS was measured by using a straight line running parallel to the course of the septum (when the MS was regarded as straight) or curved (when the MS was regarded as irregularly shaped). The average height of the MS was 2.1 ± 0.41 cm in the whole research group. Completely osseous MS was found in 32.77% of the patients. In 63.85% of them, the MS was partially membranous. The rarest was the MS which was not even partially ossified - a membranous type, that was observed in 3.38% of the patients. C o n c l u s i o n s: Variant anatomy of the paranasal sinuses may lead to complications encountered during a surgery, hence a CT scan is advised before the planned treatment.

Prevalence and Clinical Implications of the Primitive Trigeminal Artery and its Variants: A Meta-Analysis.

BACKGROUND: The primitive trigeminal artery (PTA) is the most common and the largest persistent carotid-basilar anastomosis. Primitive trigeminal artery variants (PTAVs) are anastomoses between the internal carotid artery and cerebellar arteries. These vessels pose a risk of hemorrhagic or ischemic complications during neurosurgical procedures in the parasellar and intrasellar regions. The aim of this study was to determine the prevalence of both PTA and PTAVs and their clinically important anatomic features. METHODS: Major electronic databases were thoroughly searched for studies on PTA and PTAV. References in the included articles were also evaluated. Data regarding prevalence, laterality, origin, course patterns, and associated anomalies were extracted and pooled into a meta-analysis. RESULTS: A total of 39 studies (110,866 patients) were included in the meta-analysis. The total pooled prevalence estimate of PTA and PTAVs combined was 0.4% (95% confidence interval [CI], 0.3-0.5). Individually, PTA was present in 0.3% of patients and PTAV in 0.2%. Both arteries most often originated from the C4 internal carotid artery and took a course lateral to the dorsum sellae. The anterior inferior cerebellar artery type was the predominant PTAV (72.1%). Basilar artery hypoplasia was found in 42.5% of patients with a PTA. CONCLUSIONS: PTA and PTAVs are rare vessels, but they are clinically important because they can contribute to trigeminal neuralgia. Knowledge of the potential course of these arteries is essential in neuroradiology and neurosurgery, especially in minimally invasive procedures such as the endoscopic endonasal transsphenoidal approach to the pituitary gland and the percutaneous gasserian ganglion procedure.

Sphenoid bone and its sinus - anatomo-clinical review of the literature including application to FESS.

Authors paid attention to anatomy and clinical implications which are associated with the variations of the sphenoid sinus. We discuss also anatomical structure of the sphenoid bone implementing clinical application of this bone to different invasive and miniinvasive procedures (i.e. FESS).

Prevalence and anatomy of the axillary arch and its implications in surgical practice: A meta-analysis.

PURPOSE: The following research aimed to investigate the prevalence and anatomical features of the axillary arch (AA) - a muscular, tendinous or musculotendinous slip arising from the latissimus dorsi and that terminates in various structures around the shoulder girdle. The AA may complicate axillary lymph node biopsy or breast reconstruction surgery and may cause thoracic outlet syndrome. METHODS: Major electronic databases were thoroughly searched for studies on the AA and its variations. Data regarding the prevalence, morphology, laterality, origin, insertion and innervation of the AA was extracted and included in this meta-analysis. The AQUA tool was used in order to assess potential risk of bias within the included studies. RESULTS: The AA was reported in 29 studies (10,222 axillas), and its pooled prevalence estimate in this meta-analysis was found to be 5.3% of the axillas: unilaterally (61.6%) and bilaterally (38.4%). It was predominantly muscular (55.1% of the patients with the AA), originated from the latissimus dorsi muscle or tendon (87.3% of the patients with the AA), inserted into the pectoralis major muscle or fascia (35.2% of the patients with the AA), and was most commonly innervated by the thoracodorsal nerve (39.9% of the patients with the AA). CONCLUSION: The AA is a relatively common variant, hence it should not be neglected. Oncologists and surgeons should consider this variant while diagnosing an unknown palpable mass in the axilla, as the arch might mimic a neoplasm or enlarged lymph nodes.

The total number of septa and antra in the sphenoid sinuses - evaluation before the FESS.

PURPOSE: The purpose of this research is to define the total number of septa and the total number of antra in the sphenoid sinuses (created as a result of the presence of additional septa), as well as the relation between the number of the septa and their location in the adult population. MATERIALS AND METHODS: e study was conducted as a retrospective analysis of the computed tomography (CT) scans of the paranasal sinuses of 296 patients (147 females and 149 males), who did not present any pathology in the sphenoid sinuses. The CT scans of the paranasal sinuses were done with the spiral CT scanner (Siemens Somatom Sensation 16) by using a standard procedure, in the option Siemens CARE Dose 4D, without using any contrast medium. A er obtaining the transverse planes, the frontal and sagittal planes were created using secondary reconstruction tool (multiplans reconstruction - MPR). RESULTS: The analysis of the obtained images in the transverse plane and secondary CT reconstructions has shown the presence of only one sphenoid septum (main septum - MS) in 21.96% of the patients, which divided the sphenoid sinus into two sphenoid antra. In 78.04% of the patients, there were more than one sphenoid septa present in the posterior part of the sphenoid sinuses, hence there were additional septa (AS) present. One AS was present in 22.97% of the patients. The most common variant - two AS - was found in 32.09% of the cases. The presence of more than two AS was found in the following number of patients: three AS in 9.8%, four AS in 7.09%, five AS in 1.69%, six AS in 3.04% and seven AS in 1.01%. The rarest variant was the presence of more than seven AS: eight AS in 0.34% and nine AS also in 0.34%. There were no sphenoid sinuses that would have more than nine AS in the researched material. CONCLUSIONS: Due to the high incidence of the anatomical variants of the paranasal sinuses, a CT scan is recommended in all patients before a planned surgery in order to avoid the potential complications that might arise as a result of the complicated structure of the paranasal sinuses.