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Pneumatisation of the maxillary sinus (MS) is variable. The archived cone-beam computed tomography file of a 54-year-old female was retrospectively evaluated anatomically. Nasal or retrobullar recesses of the MSs (NRMS) were found. The MSs were bicameral. NRMSs extended from the postero-lateral chambers of the MSs into the lateral nasal walls. The right NRMS was reached superior to the middle turbinate and the ethmoidal bulla was applied on its anterior side. The left NRMS had two medial pouch-like ends, one beneath the ethmoidal bulla and the other on the anterior side of the basal lamella of the middle turbinate. Additional anatomical findings were the uncinate bulla, infraorbital recesses of the MS, maxillary recess of the sphenoidal sinus, and atypical posterior insertions of the superior nasal turbinates, maxillo-ethmoido-sphenoidal and ethmoido-sphenoidal. The NRMS is a novel finding and could lead to erroneous endoscopic corridors if not documented before the interventions.

Background: The anatomy of the retrotympanum is highly variable, and surgical access is challenging. In the medial retrotympanum, a descending series of recesses are found: the posterior tympanic sinus, the sinus tympani (ST), and the subtympanic sinus (STS). Most of the previous anatomical studies of the ST evaluated it as a single depression of variable width and depth, without recesses, just on axial sections., Method: The ST was evaluated bilaterally in all the anatomical planes on a lot of 100 cases. Two sagittal anatomical types of the ST were defined and counted: type 0 (saccular ST), with absent postero-inferior recess (PIR) of the ST, and type 1, ST with PIR (bowl-shaped ST)., Results: In 200 sides, 144 type 0 ST (72 %) and 56 types 1 (PIRs) of the ST were found (28 %). On the right/left sides the type 0 ST was found in 74 %/70 % and the type 1, with PIR, in 26 %/30 %. There were no significant correlations between sex and the ST types on both sides. In the general lot, bilaterally symmetrical types 0 were found in 68 %, bilaterally symmetrical types 1 in 24 %, and the bilaterally asymmetrical combination 0+1 in just 8 %., Conclusions: The PIR of the ST is not a scarce anatomical variation in the retrotympanum. It is hidden deep to the ST and difficult to access through the middle ear. It also could retain residual cholesteatoma. A retrofacial approach could access the PIR of the ST if no other anatomical limitations occur., Competing Interests: Declaration of Competing Interest There are no conflicts of interests., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Purpose: The present case report aims to describe the rare coexistence of three variants of the cerebral arterial system diagnosed by computed tomography angiography (CTA)., Methods: A retrospective study on head and neck CTAs was performed on a Greek adult population from the Department of Radiology, University Hospital of Larissa. An interesting case of an 80-year-old male was further investigated., Results: The cerebral arterial circle presented with a combination of three variations. The left anterior cerebral artery (ACA) was fenestrated 1.4 mm proximally to the anterior communicating artery formation. The left posterior cerebral artery (PCA) was also fenestrated, 5.5 mm distally to its origin from the basilar artery. Lastly, the right PCA originated from the ICA supraclinoid segment., Conclusions: This case report highlights an unusual coexistence of A1 and P1 segments fenestration with a fetal PCA, resulting in a unique cerebral circle. A1 segment fenestration has been previously reported as rare, while the PCA fenestration as extremely rare variant. Awareness of these rare variations could aid interventionists in their preoperative assessments., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The vertical level of carotid bifurcation (CB) is commonly indicated at the superior margin of the thyroid cartilage. Few studies observed the CB vertical topography. It was aimed at studying the vertical location of the CB as referred to vertebral and anterior cervical landmarks., Methods: An archived lot of 147 computed tomography angiograms was documented for the vertical level of CB referred to vertebral and anterior cervical landmarks. The topography of the CB in relation to anterior landmarks was classified into seven types: (1) at the superior margin of the thyroid cartilage; (2) between the hyoid and the thyroid cartilage; (3) at the hyoid level; (4) between the hyoid and mandible; (5) subgonial or supragonial CB; (6) lower cervical level; (7) intrathoracic., Results: The most common locations of CB were at C3 (27.21%), C3/C4 (26.19%) and C4 (25.51%). Bilateral symmetry of CB was found in 51.7%, except for C2 and C5/C6. Type 7 was not found, type 3 occurred in 39.12%, type 2 in 24.49%, type 1 in 13.95%, type 4 in 13.61%, type 5 in 6.12%, and type 6 in 2.72% (294 CBs). Bilateral symmetry of anterior types was found in 59.86%. Statistically significant correlations were found between sex and both left and right types and vertebral levels of CB., Conclusions: The vertical topography of the CB is highly variable and has sex-related specificity. This detail should be included in the teaching of anatomy. Surgeons and interventionists should better document the carotid anatomy on a case-by-case basis., (© 2024. The Author(s).)

Functional endoscopic sinus surgery consistently benefits from good anatomical knowledge and modern imaging techniques. Ethmoid air cells migrate in specific topographical sites near the ethmoid. Posterior ethmoid air cells that descend into the maxillary sinus (MS) are ethmomaxillary sinuses (EMSs) that into the superior nasal meatus. Few previous studies found EMSs in 0.68% to 16.48% of cases. An EMS differs from a Haller's infraorbital cell nearing the ethmoidal infundibulum. A posterior ethmoid air cell intercalated between the ethmoid, MS and sphenoidal sinus is a Sieur's cell, but it could also be regarded as an EMS. An EMS should be discriminated from a maxillary recess of the sphenoidal sinus. An EMS could determine Onodi's maxillary bulla into the MS. The false duplicate MS described by Zuckerkandl consists of a MS draining into the middle nasal meatus adjoined by an EMS draining into the superior nasal meatus. These are separated by the ethmomaxillary septum. The latter may be confused with an intrasinus septum of the MS if the drainage pathways are not adequately documented. Therefore, a case-by-case anatomic identification of the pneumatic spaces nearing the MS should be performed before surgical endoscopic approaches of the nose and sinuses., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 by Mutaz B. Habal, MD.)

Purpose: This study aims to assess the anatomical possibilities of the jugular bulb (JB)., Methods: Fifty archived CBCT scans were analyzed., Results: The average distance between the internal acoustic canal (IAC) and the JB was 7.97 mm on both sides (Right: SD = 2.56 mm, range 3.16-13.3 mm; Left: SD = 2.5 mm, range 2.9-13.6 mm). JB walls' pneumatization was classified into eight patterns. Deep petrosal cells (DPCs) prevailed in the lateral wall of the JB. The absence of pneumatization (NP) was commonly found on the left side. The presence of infralabyrinthine and hypotympanic cells varied. Less common types included accessory occipital cells (AOCs), posteromedial tracts (PMTs), and basi-occipital cells (BOCs), which determined a consistent variation of the lateral wall pneumatization patterns. Pneumatization of the medial wall was not observed in 50 right sides and 49 left sides. The inferior wall analysis revealed symmetry in AOC distribution and a predominant occurrence of NP. Cases with hypotympanum (HT) in the lateral wall showed a statistically significant IAC-JB distance increase by an average of 4.67 mm compared to NPs. Specific pneumatizations, particularly HT on the lateral side, have a significant effect on the IAC-JB distance, showing a clear pattern of increasing distance from DPC to NP and then to HT. A significant distance increase in HT pneumatization was noted. There were also recorded instances of JB hypoplasia and hyperplasia, JB diverticula, dehiscent JBs, and high JBs., Conclusion: This study establishes a novel classification of JB pneumatizations to aid in the understanding of the temporal bone anatomy., (© 2024. The Author(s).)

The carotid duct (CD) is a transient embryological structure connecting the 3rd and 4th aortic arches. We found a persisting CD in an adult female case, by studying the computed tomography angiogram. On the left side, the proximal external carotid artery (ECA) agenesis was noted. The CD was inserted into the left subclavian artery and continued upwards to reach the level of the atlas, and then it descended to connect to a normally configured segment of that ECA. It could be speculated that the CD-to-ECA connection was possible via unregressed 1st and/or 2nd aortic arches. The segmental ECA agenesis is extremely rare, while its supply via a persisting patent CD was not reported previously to the authors' knowledge. The variants are extremely important during neck surgery because damaging the CD could determine hemorrhage, as well as ischemia in the ECA territory.

Objective: The tympanic plate typically joins the articular tubercle in the medial glenoid wall. It is aimed to report a peculiar anatomic variant of the latter., Methods: The computed tomography scans of two adult male cases were documented for the anatomical details of the temporomandibular joint., Results: The absence of the tubal processes of the tympanic plates was found bilaterally. The medial glenoid walls were penetrated by posterior or tubal sphenoidal plates extending posteriorly from the sphenoidal spines, 6.6 mm/12.2 mm on the right/left sides in the first case, and 9.8/8.4 mm on the right/left sides in the second case. These plates formed the lateral tubal walls and modified the tubal sulci on the sphenopetrosal fissures into musculotubal pseudo-canals. On the sides of the tubal sphenoidal plates formed in the medial wall of the glenoid fossa additional fissures, an anterolateral sphenotemporal one and a postero-medial sphenotympanic one., Conclusion: As far as the authors know, the tubal plate of the sphenoid bone was not observed previously to participate in the glenoid fossa's medial wall. It could be regarded as a rare anatomic variation.

Morphological and morphometric variants of the anterior communicating artery (AComA) have been described by multiple studies; however, a complete classification system of all possible morphological variants with their prevalence is lacking. The current systematic review with meta-analysis combines data from different databases, concerning the AComA morphological and morphometric variants (length and diameter). Emphasis was given to the related clinical implications to highlight the clinical value of their knowledge. The typical AComA morphology occurs with a pooled prevalence (PP) of 67.3%, while the PP of atypical AComA is 32.7%. The identified AComA morphological variants (artery's hypoplasia, absence, duplication, triplication, differed shape, fenestration, and the persistence of a median artery of the corpus callosum- MACC) were classified in order of frequency. The commonest presented variants were the AComA hypoplasia (8%) and the anterior cerebral artery (ACA) fusion (5.9%), and the rarest ones were the MACC persistence (2.3%), and the AComA triplication (0.7%). The knowledge of those variants is essential, especially for neurosurgeons operating in the area. Given the high prevalence of AComA aneurysms, an adequate and complete classification of those variants is of utmost importance., (© 2024. The Author(s).)

Background: In human anatomy, there are well-known the foramina of the greater sphenoidal wing, the foramen rotundum, the foramen ovale, the foramen spinosum, as well as the inconstant sphenoidal emissary foramen of Vesalius and the foramen of Arnold. Different canals are found in several species of rodents, such as the alisphenoid and sphenopterygoid (SPC) canals., Method: It was re-explored an archived computed tomography angiogram of a 60 y.o. female case., Results: Bilateral superior recesses of the pterygoid fossae (SRPF) and a right SPC were found. The SRPF on each side penetrated the non-lamellar pterygoid root and superiorly reached the sphenoidal sinus wall. Upper fibres of medial pterygoid muscles were inserted into each SRPF. An unexpected SPC was found on the right side. It opened superiorly on the lateral side of the foramen rotundum and inferiorly at a pterygoid foramen in the superior end of the posterior margin of the lateral pterygoid plate. A sphenoidal emissary vein traversed that SPC to drain into the pterygoid plexus., Conclusion: The SRPF and SPC could also be found in humans. As the sphenoidal emissary veins are surgically relevant, they should not be further regarded as exclusively crossing the foramen of Vesalius but also the SPC., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

In most cases, the superior laryngeal artery (SLA) branches from the superior thyroid artery, which, in turn, leaves the external carotid artery. Few dissection studies found previously that the SLA could originate from the lingual artery. We report here probably the first evidence of such a rare anatomical variation found unilaterally in a retrospectively evaluated by computed tomography angiography adult male case. The left SLA left a suprahyoid coil of the lingual artery and continued over the greater hyoid horn to enter the larynx through the thyrohyoid membrane. On both sides, thyroid foramina were found, but only the right one used for the entry of the right SLA. Therefore, the rare SLA origin from the lingual artery can be documented on computed tomography angiograms, which could help during preoperative evaluations and prevent unwanted surgical complications., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background and Objectives : The upper posterior teeth are typically regarded as being exclusively inferior to the maxillary sinus (MS). The expansion of the nasal fossa above the maxillary alveolar base (MAB) needs better investigation. The hypothesis was raised that the MAB in the upper premolar region, which is usually addressed by surgeons for the elevation of the antral floor, is not exclusively beneath the MS. Therefore, we aimed to document the possible upper relations of the MAB as antral, nasal, or both. Materials and Methods : A total of 145 CBCT scans were used to study four types of MAB: type 1-antral; type 2-antral with a palatal recess; type 3-antral and nasal; type 4-nasal. In type 2, the orthoradial width of the alveolar bone, the rectilinear width of the antral floor, and the maximum depth of the palatal recess were measured. For type 3, the MAB width and the straight widths of the antral and nasal segments of the MAB were measured. Results : Type 1 was found in 67.24%, type 2 in 13.45%, type 3 in 16.21%, and type 4 in 3.1% of the 290 MSs investigated. Palatal recesses were found in 11.72% of the MSs on the right side and 15.17% of the MSs on the left side. Types 1 and 2 exhibited strongly statistically significant bilateral symmetry (Pearson's Chi2 = 86.42, p < 0.001). Type 3 correlated equally with contralateral types 1 and 3. The bilateral symmetry for types 1-3 was stronger in the males (Pearson's Chi2 = 47.83, p < 0.001) than in the females (Pearson's Chi2 = 56.96, p < 0.001). There were no statistically significant associations between sex and the unilateral anatomical type. Conclusions : The MAB in the upper second premolar area should not be considered to be exclusively antral during surgeries or in anatomical teaching.

Background: The external carotid artery (ECA) is a major artery of the head and neck. Although numerous studies describe the variability of ECA branches, the course variation of the ECA was seemingly overlooked. It was aimed to study the morphological possibilities of the retromandibular segment of the ECA., Method: A retrospective study was performed on 60 computed tomography angiograms of 26 male and 31 female adult patients. Three types of retromandibular ECA were defined: type 1 - the ECA has a straight course deep to the anatomical plane of the ramus of the mandible; type 2 - the ECA makes a retromandibular loop directed laterally, extending externally to the anatomical plane of the ramus of the mandible; and type 3 - the retromandibular loop directed laterally reaches just behind the posterior margin of the ramus of the mandible., Results: Type 1 was found in just 43.33%, type 2 in 18.33%, and type 3 in 38.33% of 120 sides cases. On the right, type 1 was significantly associated with the male gender, and type 3 with the female gender (Pearson Chi2=10.9, p=0.004). On the left, there were no statistically significant associations (Pearson Chi2=3.5, p=0.153). In 20 cases, the retromandibular course of the ECA was asymmetrical; in 21 cases, type 1 was recorded bilaterally; in 5 cases, type 2 was bilaterally symmetrical; and in 14 cases, type 3 was found bilaterally., Conclusion: These previously undocumented types of ECA are relevant during parotid surgery and should be investigated preoperatively on a case-by-case basis., Competing Interests: Declaration of Competing Interest The authors have no conflict of interest to declare., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

The suprascapular notch represents a depression on the lateral part of the superior border of the scapula, medially to the coracoid process. The current paper presents a systematic review with a meta-analysis of the suprascapular notch morphological variability. Related clinical implications were further discussed as well to emphasize the value of the topic. A total of 31 articles were included in the meta-analysis, which depicted great heterogeneity. Thus, due to the different classification systems, difficulties were faced in creating a complete and united classification. All the problems and pitfalls that arise from each classification system were discussed, and we concluded with the most complete one. The knowledge of the suprascapular notch morphological anatomy is of great importance, especially for orthopedic surgeons, due to its relationship with the suprascapular nerve. Thus, further research in this area is adequate., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Tsakotos et al.)

Background: The ventral enclosure of the thyroid cartilage by a collapsed hyoid bone (CHB) is poorly encountered in previous research. It was aimed to observe whether or not these malformations could be found and detailed anatomically in a consistent lot of computed tomography (CT) files., Methods: Two hundred archived CT angiograms were explicitly observed for the CHB anatomical variant., Results: Different possibilities of CHB were found in 6/200 cases, five males and one female. The symmetrical overlap of the thyroid cartilage by the hyoid body was found in one male case. In three cases, two males and one female, there was asymmetrical overlapping due to tilted hyoid bones. In one male case with such asymmetrical CHD, an ossified anterior longitudinal ligament was noted: the tips of the superior horns of the thyroid cartilage reached lateral to it, thus being retropharyngeal. A different male case had a lowered hyoid with a greater horn fused to the superior horn of the thyroid cartilage, with an interposed ossified triticeal cartilage. In the last male case, the right greater horn collapsed laterally to an ossified triticeal cartilage fused with the thyroid cartilage's superior horn., Conclusions: The CHB is an undeniable anatomical possibility of an atavism that alters conventional anatomical and surgical landmarks. Different anatomical components of the hyoid bone can descend uni- or bilaterally., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

DNA amplifications in cancer do not only harbor oncogenes. We sought to determine whether passenger coamplifications could create collateral therapeutic vulnerabilities. Through an analysis of >3,000 cancer genomes followed by the interrogation of CRISPR-Cas9 loss-of-function screens across >700 cancer cell lines, we determined that passenger coamplifications are accompanied by distinct dependency profiles. In a proof-of-principle study, we demonstrate that the coamplification of the bona fide passenger gene DEAD-Box Helicase 1 (DDX1) creates an increased dependency on the mTOR pathway. Interaction proteomics identified tricarboxylic acid (TCA) cycle components as previously unrecognized DDX1 interaction partners. Live-cell metabolomics highlighted that this interaction could impair TCA activity, which in turn resulted in enhanced mTORC1 activity. Consequently, genetic and pharmacologic disruption of mTORC1 resulted in pronounced cell death in vitro and in vivo. Thus, structurally linked coamplification of a passenger gene and an oncogene can result in collateral vulnerabilities., Significance: We demonstrate that coamplification of passenger genes, which were largely neglected in cancer biology in the past, can create distinct cancer dependencies. Because passenger coamplifications are frequent in cancer, this principle has the potential to expand target discovery in oncology. This article is featured in Selected Articles from This Issue, p. 384., (©2024 The Authors; Published by the American Association for Cancer Research.)

Few previous dissection reports demonstrated the possible course of the maxillary artery (MA) through the temporalis muscle (TM). A dissection study performed a long time ago established a 2% prevalence of this variant. As the variant was not studied on angiograms, we decided to do so. One hundred seventy archived computed tomography angiograms were used on 95 male and 75 female patients. The MA course through the TM was found in 11/170 cases (6.47%) but in 16/340 sides (5.58%). This is because, in 5/11 cases, the variant was bilateral. Therefore, preoperative computed tomography angiography could be helpful when surgical procedures using either the TM or the MA are designed. The course of the MA is variable, either deep or through the TM., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 by Mutaz B. Habal, MD.)

Background and Objectives : Typically, the external carotid artery (ECA) sends off separate anterior branches: the superior thyroid, lingual, and facial arteries. These could, however, form common trunks: thyrolinguofacial, linguofacial (LFT), or thyrolingual. Although known, the LFT variant was poorly detailed previously, and most authors just counted the variant. We aimed to demonstrate the individual anatomical possibilities of the LFT on a case-by-case basis. Materials and Methods : 150 archived angioCT files were used. After applying inclusion and exclusion criteria, 147 files of 86 males and 61 females were kept for this study. Results : In 34/147 cases, LFTs were found (23.12%). Bilateral LFTs were found in 13/34 cases (38.24%) and unilateral LFTs in 21/34 (61.76%) cases. Forty-seven LFTs were thus identified and further studied for different variables. Regarding the vertical topography of LFT origin, type 1a (suprahyoid and infragonial) was found in 28 LFTs (59.57%), type 1b (suprahyoid and gonial) was found in eight LFTs (17.02%), type 3 (suprahyoid and supragonial) was found in two LFTs (4.25%), type 2 (hyoid level of origin) in eight LFTs (17.02%), and type 3 (infrahyoid origin) in just one LFT (2.12%). Types of the initial course of the LFT were determined: type I, ascending, was found in 22/47 LFTs; type II, descending, in 12/47 LFTs; and type III, transverse, in 13/47 LFTs. Regarding the orientation of the first loop of the LFT, 23/47 LFTs had no loop, 4/47 had anterior loops, 1/47 had a posterior loop, 5/47 had superior loops, 5/47 had inferior loops, and 9/47 had medial loops. The position of the LFT relative to the ECA was classified as medial, anterior, or antero-medial. An amount of 12/47 LFTs were anterior to the ECA, 22/47 were antero-medial, 10/47 were medial, 2/47 were inferior, and 1/47 was lateral. Regarding their general morphology, 23/47 LFTs had a rectilinear course, 22/47 had loops, and 2/47 were coiled. A case-by-case presentation of results further demonstrated the diversity of the LFT. Conclusions : In conclusion, the morphology and topography of the LFT are individually specific and unpredictable. It can be anticipated case-by-case by surgeons on CT or MR angiograms.

Background and Objectives : The adult superficial middle cerebral vein (SMCV) commonly drains into the middle cranial fossa. However, different embryonic types persist, in which the SMCV drains into the lateral sinus. The basal type of SMCV coursing on the middle fossa floor is a scarce variant. Materials and Methods : During a retrospective study of archived computed tomography angiography (CTA) and magnetic resonance angiography (MRA) files, three rare adult cases of the basal or sphenopetrosal type of SMCV were found and further documented. Results : In the first case, which was evaluated via CTA, the basal type of SMCV formed a sagittal loop. It continued on the middle fossa floor, over a dehiscent tegmen tympani, to drain into the lateral sinus. In the second case, documented via MRA, the basal type of SMCV's anterior loop was in the coronal plane and closely related to the internal carotid artery and the cavernous sinus. It continued with the basal segment over a dehiscent glenoid fossa of the temporomandibular joint (TMJ). In the third case, documented via CTA, the initial cerebral part of the SMCV had a large fenestration. The middle fossa floor coursed within a well-configured sulcus of the SMCV and received a tributary through the tympanic roof. Its terminal had a tentorial course. Conclusions : Beyond the fact that such rare variants of the SMCV can unexpectedly interfere with specific approaches via the middle fossa, dehiscences of the middle fossa floor beneath such variants can determine otic or TMJ symptoms. Possible loops and fenestrations of the SMCV should be considered and documented preoperatively.

The maxillary artery (MA) leaves from the external carotid artery and further courses through the infratemporal fossa to reach the pterygopalatine fossa. It typically has an ascending course either on the lateral or on the medial side of the inferior bundle of the lateral pterygoid muscle. While studying retrospectively, the computed tomography angiogram of an adult male case with peculiar tortuosities of the MA was documented. The left MA described a large inferior sagittal loop applied on the mandible's ramus's inner cortical in the pterygomandibular space's upper part. That loop reached 1.66 cm inferior to the mandible's notch and 0.5 cm superior to the mandibular foramen and was applied on the mandible's lingula (spine of Spix). That MA continued to the pterygomaxillary suture, and a second superior coronal loop was found applied on the posterior wall of the maxillary sinus, reaching the inferior orbital fissure. It is therefore mandatory to take good care in the decortication of the mandibular ramus or during osteotomies of the ramus. When an inferior loop of the MA approaches the spine of Spix, bleeding when an inferior alveolar nerve block is performed seems hardly avoidable., Competing Interests: The authors have no conflict of interest to declare., (Copyright © 2024 by Mutaz B. Habal, MD.)

Fibers of the lateral pterygoid muscle (LPM) occasionally originate on the posterior surface of the maxilla. Anatomic exploration of an adult patient's cone beam computed tomography files revealed a previously unreported unilateral anatomic variant of the LPM. The variant consisted of a distinctive muscular slip that originated on the tuberosity of the maxilla and coursed postero-laterally through the notch of the mandible to insert on an accessory pterygoid fovea on the outer condylar pole. This maxillomandibular muscle was lateral to the inferior head of the LPM. Therefore, it could contribute to the antero-inferior displacement and medial rotation of the mandibular condyle during the movements of the temporomandibular joint. The maxillomandibular muscle should be added to the extensive spectrum of anatomical variations of the LPM; however, prevalence studies should assess whether its maxillary attachment is the rule or the exception., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 by Mutaz B. Habal, MD.)

Background: Anatomical variants of the left renal vein (LRV), such as the retroaortic (RLRV) and circumaortic (CLRV) course, are of surgical importance. Different morphological and topographical possibilities of the RLRV could occur. It was aimed at documenting the anatomical variables of the RLRV., Method: A retrospective study on 375 computed tomography angiograms was performed. Five different anatomical types of LRV were documented: preaortic types 1 and 2 and retroaortic types 3-5., Results: In 344/375 cases, preaortic LRVs were found. In 31/375 cases, different types of RLRV were found: type 3a - single RLRV, 41.94%; type 3b - single RLRV with bifid caval end, 9.68%; type 3c - single RLRV with trifid caval end, 3.23%; type 4a - CLRV with extrahilar origin, 29.03%; type 4b - CLRV with renal sinus origin, 12.9%; type 5 - triple LRV (one preaortic LRV and two RLRVs), 3.23%. Reference vertebral levels were recorded for the prevertebral segment of the RLVR. The vertebral level of type 3a varied from the L1/L2 disc to the upper third of the L4 vertebra. Type 3b was found in 3/31 RLRV cases; in one of these, the hemiazygos vein was inserted by two roots into the LRV and its upper caval end trunk. There was a significant statistical association between type 3b and the vertebral level, all cases being centered on the middle third of the L4 vertebra., Conclusions: New morphological possibilities of the LRV were distinguished, and a new anatomical classification system of the RLRV results. The RLRV variant should be documented case-by-case as it has its anatomical variables., Competing Interests: Declaration of Competing Interest There are no conflicts of interests., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Background and Objectives: The microanatomy of the superior cerebellar artery (SCA) is clinically significant. We, thus, aimed at patterning unilateral and bilateral possibilities of SCA origin. Materials and Methods: In total, 205 archived records of computed tomography and magnetic resonance angiograms were used. There were defined types of SCA origin from the basilar artery (BA): "0"-absent SCA, "1"-preterminal, "2"-collateral SCA, with SCA appearing as a terminal branch of BA, and "3"-SCA from the posterior cerebral artery (PCA) of the cerebral type. Fenestrations and duplications of SCA were recorded. Bilateral combinations of types were recorded as follows: A (1 + 0), B (1 + 1), C (1 + 2), D (1 + 3), E (1 + duplicated SCA), F (2 + 2), G (2 + 3), H (3 + 3), I (3 + duplicated SCA), J (1 + fenestrated SCA). Results: Type 0 SCAs were found in 0.25%, type 1 in 71.29%, type 2 in 19.06%, and type 3 in 9.41%. Absent and fenestrated SCAs were each found in a single case. The most frequent combinations were B (58.05%), C (13.17%) and F (13.17%). Bilateral symmetrical types occurred in 70.7% of cases. Fetal types of PCA and the artery of Percheron modified the BA ends. Combinations of C, F, and G changed the BA ends or tips; thus, different subtypes resulted in five BA bifurcation patterns, including five BA trifurcations and one BA quadrifurcation. BA trifurcation was also found in cases with duplicated SCAs. Conclusions: The SCA has various anatomical possibilities of origin and bilateral combinations that are not presented in anatomical lectures. Details on the specific end of the BA should be gathered on a case-by-case basis.

Background: Dandy's superior petrosal vein (SPV) anatomy is highly relevant for neurosurgeons. The SPV drains into the superior petrosal sinus (SPS), closely related to the trigeminal and internal auditory pores., Method: The archived enhanced MRI files of a male patient were studied., Results: An infratentorial ring-shaped (RS) SPV was found on the petrosal surface of the right cerebellar hemisphere. It was inserted in the SPS above the internal auditory pore, postero-lateral to the trigeminal pore. The anterior arm of that venous ring received a delicate supratrigeminal plexus of veins from the pontine surface and continued as a single venous trunk on the cerebellar surface., Conclusion: Such previously unreported RS-SPV is of utmost importance to be identified before subtemporal transtentorial and retrosigmoid approaches for different neurosurgical reasons., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

(1) Background: Twisted carotid bifurcations (CBs) lead to lateralized external carotid arteries (ECAs). Such variants are usually reported on a case-by-case basis. We aimed to study the anatomical possibilities of the axial spin of CB. (2) Methods: Determinations were made bilaterally on a retrospectively assessed sample of 150 cases, 88 males and 62 females. The following types of the axial spin of the CB were determined: type CK1-CB in the coronal plane, with ICA lateral of ECA; type CK3-CB in the coronal plane, with ECA lateral of ICA; the oblique type OK1, with the ECA antero-medial of ICA; the oblique type OK3a, with the ICA antero-medially; the oblique type OK3b, with the ICA postero-laterally; the sagittal type SK2a, with ECA anterior of ICA. (3) Results: In the overall group of 300 CBs, type OK1 was found in 40%, type OK3a in 1%, type OK3b in 2%, type CK1 in 9%, type CK3 in 5.67%, and type SK2a in 42.33% of the bilateral BC group. The types SK2a (46.67%) and OK1 (33.33%) prevailed on the right side. The types OK1 (46.67%) and SK2a (38%) prevailed on the left side. There was no statistically significant association between gender and left or right subtypes. A very strong symmetry existed between the left and right sides (Pearson Chi2 = 53.93 p < 0.001) for types OK1 and SK2a. Asymmetrical types were found in different bilateral combinations. (4) Conclusions: The spin of the CB is relatively symmetrical bilaterally, especially for the variants with the ECA antero-medial or anterior to ICA.

Purpose: Fenestrations of posterior cerebral artery are exceedingly rare and, therefore, deserve being reported., Methods: During an educational dissection, a peculiar anatomical variant of the posterior cerebral artery (PCA) was found., Results: During an educational dissection targeting the right cerebellopontine angle, a peculiar variant of the right PCA was found. The respective posterior communicating artery inserted posteriorly into the junction of the P1 and P2 segments of the PCA. The P1 segment was thinner than the P2 segment. That junction was superior to the oculomotor nerve and was fenestrated, with a thin postero-medial arm facing the cerebral peduncle, and a larger antero-lateral arm formed by the distal end of the P1 segment and the proximal end of the P2 segment., Conclusions: To the authors' knowledge, fenestrated P1-P2 junctions of PCA were not found previously by dissection. The evidence presented here recommends such variations not to be ignored., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background and Objectives : The carotid bifurcation (CB) is presented in most anatomy textbooks as having a unique location at the upper margin of the thyroid cartilage. Although a number of case reports have provided evidence of the possibility of carotid artery location either lateral or medial to the greater hyoid horn, these reports have not established specific anatomic possibilities and prevalences. Materials and Methods : We retrospectively analysed a batch of 147 CT angiograms for 12 types of carotid-hyoid relationships and classified the bilateral combination possibilities of these types. Results : In 168/294 sides there were no carotid-hyoid relationships. Type I, external carotid artery (ECA) medial to the greater horn of the hyoid bone (GHHB), was observed in 0.34%; type II, internal carotid artery (ICA) medial to GHHB, in 0.34%; type III, ICA and ECA medial to GHHB, in 1.02%; type IV, common carotid artery (CCA) medial to GHHB, in 1.02%; type V, CB medial to GHHB, in 0.34%; type VI, ECA lateral to GHHB, in 20.41%; type VII, ICA lateral to GHHB, was not recorded; type VIII, ECA and ICA lateral to GHHB, in 3.74%; type IX, CCA lateral to GHHB, in 8.5%; type X, CB lateral to GHHB, in 6.46%; type XI, ECA lateral and ICA medial to GHHB, in 0.34%; and type XII, ICA lateral and ECA medial to GHHB, in 0.34%. Bilateral symmetry was found in 70.74% of cases, including the null types without carotid-hyoid relationships as well as types IV, VI, VIII, IX, and X. There was a highly significant association between the left and right variants of the carotid-hyoid relationship. Conclusions : Mechanical compression of the hyoid bone on the carotid arteries has various undesirable effects on the ICA and cerebral circulation. Underlying these are several variational anatomical patterns of carotid-hyoid relationships, which can be accurately documented on CT angiograms. A case-by-case anatomical study is better than assuming the carotid anatomy learned from textbooks.

Background: The force a muscle exerts is partly determined by anatomical parameters, such as its physiological cross-section. The temporal muscle is structurally heterogeneous. To the authors' knowledge, the ultrastructure of this muscle has been poorly specifically studied., Methods: Five adult Wistar rats weighting 350-400 g were used as temporal muscle donors. Tissues were specifically processed and studied under transmission electron microscope., Results: On ultrathin cuts, the general ultrastructural pattern of striated muscles was observed. Moreover, pennate sarcomeres were identified, sharing a one-end insertion on the same Z-disc. Bipennate morphologies resulted when two neighbor sarcomeres, attached on different neighbor Z-discs and separated at that end by a triad, converged to the same Z-disc at the opposite ends, thus building a thicker myofibril distinctively flanked by triads. Tripennate morphologies were identified when sarcomeres from three different Z-discs converged to the same Z-disc at the opposite ends., Conclusions: These results support recent evidence of sarcomeres branching gathered in mice. Adequate identification of the sites of excitation-contraction coupling should be on both sides of a myofibril, on bidimensional ultrathin cuts, to avoid false positive results due to putative longitudinal folds of myofibrils., Competing Interests: Declaration of Competing Interest The authors have no conflict of interests to declare., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Astrocytes (AS) are the most abundant glial cells in the central nervous system (CNS). They have various morphologies and numerous (50-60) branching prolongations, with roles in the maintenance of the CNS function and homeostasis. AS in the optic nerve head (ONH) have specific distribution and function and are involved in the pathogenesis of glaucoma and other neural diseases, modify their morphologies, location, immune phenotype, and ultrastructure, thus being the key players in the active remodeling processes of the ONH.

Anatomical variations of the cerebral vasculature are frequently encountered. The archived magnetic resonance angiogram of a 62-year-old male patient was studied anatomically on planar slices and 3-dimensional volume renderings. Numerous anatomical variants were found in that single case. In the vertebrobasilar system were found: the proximal basilar artery fenestration, with a unilateral origin from that fenestration of an anterior inferior cerebellar artery, and the unilateral origin of the superior cerebellar artery from the P1 segment of the main posterior cerebral artery (PCA). There were also unilateral variants of the right internal carotid artery (ICA): a subvariant of an accessory PCA leaving the ICA as a hyperplastic anterior choroidal artery and united to the main PCA by a short communicating branch, distinctive of the posterior communicating artery in that side (unilateral double PCA); a right bihemispheric anterior cerebral artery (ACA) but with complete agenesis of the contralateral A1 ACA segment; from the right ACA continued an anatomically normal ipsilateral A2 segment and a short transverse contralateral A2 that, in turn, sent off long pericallosal and callosomarginal arteries; and fenestrated origin of the left pericallosal artery. Therefore, an arterial variant in one of the main cerebral circulations could not exclude anatomical variants in the other cerebral circulatory beds., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 by Mutaz B. Habal, MD.)

(1) Background. The anatomical variations of the vertebral arteries (VAs) have a significant impact both in neurosurgery and forensic pathology. The purpose of this study was to evaluate the variational anatomy of the vertebral artery. We evaluated anatomical aspects regarding the V1 and V2 segments of the VA: origin, course, tortuosity, hypoplasia, and dominance, and established the prevalence of each variation. (2) Methods. We conducted a systematic search in PubMed and Google Scholar databases, up to December 2022. Sixty-two studies, comprising 32,153 vessels, were included in the current meta-analysis. We used a random-effects model with a DerSimonian-Laird estimator. The confidence intervals were set at 95%. The heterogeneity between studies was assessed using I 2 . The funnel plot and Egger's regression test for plot asymmetry were used for the evaluation of publication bias. Statistical significance was considered at p < 0.05. (3) Results. The most common site for the origin of both VAs was the subclavian artery. The aortic arch origin of the left VA had a prevalence of 4.81%. Other origins of the right VAs were noted: aortic arch (0.1%), right common carotid artery (0.1%), and brachiocephalic trunk (0.5%). Ninety-two percent of the VAs entered the transverse foramen (TF) of the C6 vertebra, followed by C5, C7, C4, and least frequently, C3 (0.1%). Roughly one out of four (25.9%) VAs presented a sort of tortuosity, the transversal one representing the most common variant. Hypoplasia occurred in 7.94% of the vessels. Left VA dominance (36.1%) is more common, compared to right VA dominance (25.3%). (4) Conclusions. The anatomy of the VA is highly irregular, and eventual intraoperative complications may be life-threatening. The prevalence of VA origin from the subclavian artery is 94.1%, 92.0% of the VAs entered the TF at C6, 26.6% were tortuous, and 7.94% were hypoplastic.

The anterior communicating artery (AComA) normally joins the anterior cerebral arteries (ACAs) when they change their directions from horizontal to vertical. Each postcommunicating segment of the ACAs commonly sends off the callosomarginal artery (CMA) and continues as the pericallosal artery. While documenting the archived computed tomography angiogram of a 61-year-old male patient, a rare anatomic variant was found to be associated with a previously unreported one. Both ACAs had symmetrical horizontal and vertical segments, but the AComA was absent from the usual location. The right ACA continued as CMA without sending off a pericallosal artery. A median artery of corpus callosum (MACC) left from the horizontal segment of the left ACA. Then the left ACA continued as CMA. At 1.9 cm from its origin, the MACC was united to the right CMA by a high, interhemispheric AComA. Therefore, an AComA should be regarded as absent only after documenting the bilateral anastomoses within the interhemispheric fissure. A third interhemispheric main artery, such as a rarely occurring MACC, could be accurately documented by computed tomography angiogram to avoid unpleasant intraoperative hemorrhage or to establish a personalized endovascular route to the anterior cerebral system., Competing Interests: The authors declare no conflict of interest., (Copyright © 2023 by Mutaz B. Habal, MD.)

Purpose: Anatomic variations at the junction of primitive internal carotid and basilar arteries are exceedingly rare. We aimed at reporting such rare variants involving the posterior communicating artery (PComA) and the P1 segment of posterior cerebral artery (PCA)., Methods: The circle of Willis was dissected in an adult cadaver after removal of the cranial vault and cerebral hemispheres., Results: The basilar end was rotated axially to the right. The P1 segment of the right PCA was fenestrated and occupied the interpeduncular fossa. The right PComA passed over the oculomotor nerve to join the anterior arm of the P1 fenestration. On the opposite side, the PComA coursed supero-medially to the oculomotor nerve and it had a partly duplicated posterior end, with two arms, medial, larger, and lateral, thinner, inserting successively into the left PCA., Conclusion: Extremely rare anatomic variations of the circle of Willis should not be ignored when endovascular or microneurosurgical specific approaches are intended., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background: The posterior cerebral artery (PCA) leaves from the distal end of the basilar artery (BA) and is joined to the internal carotid artery (ICA) by the posterior communicating artery (PComA)., Method: The archived computed tomography angiogram of a 67 y.o. male patient was studied anatomically., Results: Anatomically normal PCAs left the BA. Both anterior choroidal arteries were found but the right one was hyperplastic. As the latter distributed parieto-occipital and calcarine branches, it was regarded as an accessory PCA. It was laterally to the normal one, inferior to the vein of Rosenthal., Conclusion: The terms "accessory PCA" and "hyperplastic anterior choroidal artery" describe the same morphology. Rare anatomical variants could benefit from a homogenous terminology., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

(1) Background : The external jugular vein (EJV) descends on the sternocleidomastoid muscle to drain deep into the subclavian vein. Anatomical variations of the EJV are relevant for identification of the greater auricular nerve, flap design and preparation, or EJV cannulation. (2) Methods : Different publications were comprehensively reviewed. Dissections and three-dimensional volume renderings of peculiar cases were used to sample the review. (3) Results : Different anatomical possibilities of the EJV were critically reviewed and documented: fenestrations and double fenestrations, true or false duplications, triplication, absence, aberrant origin or course, or bifurcation. Tributaries of the EJV, such as the facial and posterior external jugular veins, are discussed. The internal jugular vein termination of the EJV is also presented. (4) Conclusions : Care should be taken when different morphological features of the EJV are encountered or reported.

Background and Objectives. The occipital artery (OA) is a posterior branch of the external carotid artery (ECA). The origin of the OA is commonly referred to a single landmark. We hypothesized that the origin of the OA could be variable as referred to the hyoid bone and the gonial angle. We thus aimed at patterning the vertical topographic possibilities of the OA origin. Materials and Methods. One hundred archived computed tomography angiograms were randomly selected, inclusion and exclusion criteria were applied, and 90 files were kept (53 males, 37 females). The cases were documented bilaterally for different levels of origin of the OA origin: type 1-infrahyoid; type 2-hyoid; 3-infragonial; 4-gonial; 5-supragonial; 6-origin from the internal carotid artery (ICA). Results. The incidence of unilateral types in the 180 OAs was: type 1-1.11%, type 2-5.56%, type 3-40.56%, type 4-28.33%, type 5-23.33% and type 6, ICA origin of the OA-1.11%. There was found a significant association between the location of the left and right origins of the OAs (Pearson Chi2 = 59.18, p < 0.001), which suggests the presence of a strong symmetry of the origins. Bilateral symmetry of the vertical types of the OA origin was observed in 56.67% of cases; in 43.33% there was bilateral asymmetry. Conclusions. The ICA origin of the OA is an extremely rare variant. For surgical planning or prior to endovascular approaches the topography of the OA origin should be carefully documented, as it may be located from an infrahyoid to a supragonial level.

Background and Objectives : Anatomical variations of the arterial circle of Willis (cW) are common. A posterior cerebral artery (PCA) fed mostly or exclusively from the internal carotid artery is a fetal PCA (FPCA), partial (p-FPCA), or full/complete (f-FPCA), respectively. Because FPCA occurs in different anatomical configurations of the cW sides, we aimed to document in detail these morphological possibilities of FPCA within the cW. Materials and Methods : FPCAs were documented on a retrospective set of 139 computed tomography angiograms. Results : FPCAs were found in thirteen cases, nine males and four females. In 7/13 cases there were two modified sides of the cW. In 5/13 cases there were three altered sides of the cW. Another case with FPCA showed four altered sides of the cW. In 10/13 cases, FPCA was unilateral and in the other three cases it was bilateral. Compared to the overall group, unilateral p-FPCAs were found in 1.43%, while unilateral f-FPCAs were found in 5.75%. A bilateral p-FPCA-f-FPCA combination was found in 0.71% and a bilateral f-FPCA-f-FPCA combination occurred in 1.43%. An anatomically isolated ICA was found in just one case with bilateral f-FPCA (0.71%). In 7/13 FPCA cases there were arterial variants exclusively in the posterior cW. In the other 6/13 FPCA cases, there were variants in both anterior and posterior circulation. There were no statistically significant associations of FPCA with sex or age. The higher prevalence of right-sided FPCA was not statistically significant. Conclusions : Anatomical assessments of cW should be performed on a case-by-case basis, as they may correspond to different cW morphologies.

Commonly, the trigeminal and abducens nerve course to the middle cranial fossa, beneath the tentorial border (posterior petroclinoid dural ligament) and, respectively, beneath Grüber's petrosphenoidal ligament, in Dorello's canal. It is hereby reported a rare unilateral association of anatomic variants which was found when the brain computed tomography angiography of a 56-year-old male patient was observed. On the left side, the tentorial border was ossified above the petrous apex, resulting in a tentorial bar 1.96 cm long that transformed the trigeminal pore into a completely ossified one. On that side was also found an ossified petrosphenoidal ligament determining a completely ossified Dorello's canal. On the opposite side a 2.9 mm long clinoid bar extended from the posterior clinoid process to the anterior one. Although these bars are not common in humans they should be documented in computed tomography in cases with associated trigeminal neuralgia and abducens nerve palsy.

The lingual surface of the mandible's body is commonly indicated as presenting the submandibular and sublingual fossae, which are separated by the mylohyoid line. The mylohyoid line attaches to the mylohyoid muscle (MM). Less attention has been paid to the 'mylohyoid boutonnières', which allow the 'sublingual buttons' to pass through the mylohyoid muscle in the submandibular space. The cone-beam computed tomography files of patients were routinely examined for anatomical studies. Two cases were found with unexpected morphologies of the mandible's body - the mylohyoid lines were incomplete anteriorly, and herniated sublingual tissue determined an additional fossa inferior to that line in the premolar region. That fossa was termed the 'accessory submandibular fossa'. It determined on coronal slices a 'sand watch' contour of the mandible's body. With such a peculiar morphology, the mandible is more prone to fracture. Moreover, when inserting endosseous implants, the procedure should be carefully personalised in such rare cases.

The superficial middle cerebral vein (SMCV) commonly drains in the cavernous sinus. Its different drainage variants include preserved segments of the primitive tentorial sinus. In any of these variants, the terminal venous segment of SMCV passes on the base of the skull. The archived computed tomography angiograms of a 58-year-old female case were documented anatomically. On the left side was found the sinus of the lesser sphenoidal wing converging with the middle meningeal vein to form a venous channel located within the Sylvian fissure at 4 mm laterally to the cavernous sinus and trigeminal cavum. That venous channel was thus termed the 'laterocavernous vein'. It drained posteriorly within the superior petrosal sinus. This aberrant vein could interfere unpleasantly with pterional neurosurgical approaches for the Sylvian fissure, cavernous sinus or trigeminal ganglion., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

The external carotid artery divides terminally into the superficial temporal and maxillary arteries (MA), deep to the base of the neck of the mandible. Arterial fenestrations are commonly found in the vertebrobasilar and internal carotid systems but are rarely encountered, or reported, in the external carotid artery system. The archived computed tomography angiograms of a 70-year-old male patient were observed anatomically. Inferior to the posterior end of the lateral pterygoid muscle was found a fenestrated segment of the MA, oriented mediolaterally. The middle meningeal artery left the superior arm of that fenestration. The inferior arm of the fenestration gave off a temporoalveolar trunk, further divided into posterior deep temporal and inferior alveolar arteries. The MA fenestration and the temporoalveolar trunk are rare variations of the MA at the entrance in the infratemporal fossa. These make the MA prone to iatrogenic lesions during different surgical procedures addressed to this region., Competing Interests: The authors reports no conflicts of interest., (Copyright © 2022 by Mutaz B. Habal, MD.)

Background: The lymphatic structure of the eye is still under debate. It is mainly assumed that the retina is primarily drained by prelymphatics and not by lymphatics per se. We aimed to identify lymphatics in the rat retina., Methods: Eyes from ten Wistar rats were paraffin-embedded and the lymphatic marker podoplanin (D2-40) was investigated., Results: We identified in the rat retina a blunt-end network of lymphatic endothelial vessels. It consisted of circumferential vessels within the outer and, respectively, inner plexiform layers, connected by radial dichotomous vessels. Moreover, D2-40 expression was found within the choroid, ciliary body, and extraocular muscles., Conclusions: This in situ evidence is strongly supported by the recent in vitro demonstration of the expression of lymphatic markers in retinal endothelial cells. Further studies of comparative histology should use specific lymphatic markers to test whether other species besides rats have proper retinal lymphatics., Competing Interests: Disclosure statement The authors have no conflict of interests to declare., (Copyright © 2022 Elsevier GmbH. All rights reserved.)