Zygomatic Root Research Articles

Anatomical Analysis of the Eustachian Tube in the Temporal Bone Through the Middle Fossa Window.

This cadaveric anatomical study aimed to explore precise morphometric measurements of the eustachian tube (ET) and adjacent structures in the middle cranial fossa, focusing on identifying reliable surgical landmarks when traditional markers are compromised due to tumors or trauma. Twenty-two temporal bones from 11 adult cadavers (mean age: 75.70 ± 13.75 yr, range: 40-90 yr; sex: 5 females and 6 males) were dissected bilaterally. Surgical tools, including an operation microscope, endoscope, and digital caliper, were used for meticulous measurements. Parameters such as ET dimensions, distances between key points, and relevant angles were quantified, ensuring precise anatomical data. ET width at the foramen spinosum (FS) level, the midline level, and the eustachian orifice level were measured as 2.18 ± 0.68, 2.42 ± 0.70, and 2.30 ± 0.74 mm, respectively. The distances from the zygomatic root (ZR) to FS, ET, superior semicircular canal (SSC), and internal carotid artery (ICA) were 29.61 ± 2.56, 23.28 ± 2.61, 26.53 ± 2.56, and 32.61 ± 3.69 mm, respectively. The angles between SSC-ZR-ICA and FS-ZR-ICA were measured as 36.57 ± 10.32 and 13.63 ± 3.72 degrees, respectively. No statistical difference was found between right-left or male-female measurements ( p > 0.05). The present study offers invaluable insights for neurotological surgeons performing middle fossa approaches. ET and ZR may serve as crucial reference points, enhancing surgical orientation and minimizing risks during complex procedures. These precise anatomical data may empower surgeons, ensuring safer and more confident middle cranial fossa operations, even in challenging clinical scenarios.

Zygomatic arch root position in relation to dietary type in haplorhine primates.

The zygomatic root, along with other key craniofacial features, is hypothesized to play a crucial role in strengthening the face in response to stresses and strains related to feeding. As such, it has been cited as indicative of dietary specialization among fossil taxa, although it remains unknown how variable zygomatic arch root position is among living primates, and whether its positioning predicts differences in diet. We test whether primates that consume more mechanically challenging foods possess more anteriorly positioned zygomatic roots compared to those consuming less challenging foods. Zygomatic root position, as defined by the zygomaxillare landmark, was identified and recorded from digital images and physical specimens of adult primate crania. Data were collected from 33 haplorhine species (n = 722). Published data were used to assign species to a dietary type based on patterns of overall consumption along with reliance on especially challenging foods. Pairwise comparisons between mechanically challenging (hard and/or tough) and less mechanically challenging (soft) consumers found significant differences (p < 0.05) in the position of the zygomatic root in 17 of 20 pairs, 11 of which supported the prediction that a more mechanically challenging diet is associated with a more anteriorly placed zygomatic root. PGLS analysis found no significant effect of phylogeny on root position. This suggests that a more anteriorly positioned zygomatic root is useful for identifying dietary specialization in some taxa but is not required for consuming a mechanically challenging diet given that other craniofacial and behavioral factors can facilitate the consumption of such foods.

Predicting the Position of the Internal Landmarks of Middle Cranial Fossa Using the Zygomatic Root: An Attempt to Simplify Its Complexity

AbstractSubtemporal–extradural middle cranial fossa (MCF) surgical approach is used to access pathologies involving anterior or posterior part of the petrous bone or its apex. A reliable and precise identification of the important internal landmarks is key to a safe surgery with decreased incidence of morbidity. The zygomatic root (ZR) serves as a reliable reference guide for the surgeon when navigating through the MCF. The aim of the study is to establish an association between the extent of the ZR to the key internal foramina and bony prominences in lateral fossa of the MCF to help the neurosurgeon to safely navigate through the maze of structures of the MCF. The study demonstrates that the ZR is a reliable marker to estimate and predict the position of foramen ovale, foramen spinosum, and trigeminal fossa but not for the position of hiatus of greater petrosal nerve or the arcuate eminence. Successful localization of the foramen ovale, spinosum, and trigeminal fossa would reduce intraoperative time, ensure lesser retraction of brain, and hence reduce patient morbidity while performing surgeries on lesions of/in the internal acoustic canal, petroclival junctions, cerebellopontine angles, basilar artery, or transovale cannulation for the treatment of trigeminal neuralgia.

Predicting the Position of the Internal Landmarks of Middle Cranial Fossa Using the Zygomatic Root: An Attempt to Simplify Its Complexity

Predicting the Position of the Internal Landmarks of Middle Cranial Fossa Using the Zygomatic Root: An Attempt to Simplify Its Complexity

Transmastoid exposure of the labyrinthine segment of the facial nerve: an anatomical study

IntroductionCompression of the labyrinthine segment of the facial nerve by edema has been considered as an important pathology in the majority of the cases of idiopathic facial nerve paralysis. Hence, it is suggested that total decompression of the facial nerve should also include the labyrinthine segment by a middle fossa approach. However, the middle fossa approach requires craniotomy and temporal lobe retraction, which increases the morbidity. The labyrinthine segment of the facial nerve can also be reached through mastoidectomy. However, many ear surgeons are not familiar with this approach due to the lack of anatomical data on this surgical area. ObjectiveTo study the anatomical limitations of decompression of the labyrinthine segment via transmastoid approach. MethodsComplete mastoidectomy was performed in six adult cadavers heads. Dissection was extended in the zygomatic root and posterior bony wall of the external auditory canal to visualize the incudomallear joint completely. The bone between tympanic segment, lateral and superior semicircular canal’s ampullas and middle fossa dural plate was removed. Fine dissection was carried out over tympanic segment of the facial nerve in an anterosuperomedial direction the labyrinthine segment was reached. ResultsAll the mastoids were well pneumatized. Distances between the labyrinthine segment and middle fossa dura, and between the labyrinthine segment and superior semicircular canal, were 2.5 and 4.5 mm on average, respectively. In addition, distances between the middle fossa dura and dome of the lateral semicircular canal, and between the middle fossa dura and tympanic segment were 4.6 mm and 4.3 mm on average, respectively. ConclusionIt is possible to expose the labyrinthine segment of the facial nerve through mastoidectomy by dissecting the bone in the area between the tympanic segment of the facial nerve, middle fossa dural plate and ampullary ends of the lateral and superior semicircular canals.

Anatomic variations of the superficial temporal artery.

The superficial temporal artery (STA) is a terminal branch of the external carotid artery. It is commonly described as coursing posterior to the mandibular condyle and over the posterior zygomatic root (PZR) and then dividing terminally into parietal and frontal branches. However, possible variations of the main trunk of the STA have seemingly been overlooked. This study retrospectively examined the archived head tomography angiograms of 43 patients to determine the morphology and topography of the STA prior to its terminal bifurcation. In 79% of patients, the STA topography related to the mandibular condyle was bilaterally symmetrical, either retrocondylar (65.1%) or laterocondylar (13.6%). The parietal branch was sometimes absent unilaterally (16.3%) or bilaterally (9.3%). In 2/43 cases, the frontal branch of the STA was unilaterally absent. When both terminal branches were present, the bifurcation was retrocondylar or immediately above the PZR when on the PZR, or the terminal division of the STA was high above the PZR. In 88.4% of the STAs, different patterns of kinking and coiling were documented, including retrocondylar kinks (27.9%), laterocondylar kinks (20.9%), kinks placed on the PZR (81.4%) and variably oriented suprazygomatic kinks (32.6%). Five of the 86 STAs were coiled, one retrocondylar, one laterocondylar, and three other placed on the PZR. Two cases showed unilateral pseudoaneurysms of the STA, one above the PZR and the other on the temporomandibular joint. The STA is surgically important; therefore, the number of anatomical studies of the STA should increase.

Zygomatic root abscess: A rare entity not to be forgotten!

Zygomatic root abscess is a rare extracranial extratemporal complication of otitis media. To the best of our knowledge, there are only a few scattered cases of zygomatic root abscesses reported in the literature. We present an unusual case of a zygomatic root abscess in a 24 years old adult. He presented with one month duration of right zygomatic swelling. Otoscopic examination revealed superior and posterior external auditory canal wall sagging with an intact tympanic membrane. High Resolution Computed Tomography (HRCT) temporal bone revealed a rim enhancing lesion lateral to the zygomatic process with fluid filled mastoid air cells. He was managed with antibiotics and staged surgical interventions. He recovered well. Our case serves to shed light on the pathways of infection, clinical manifestations and timely staged surgical intervention in this rare pathology.

Zygomatic-Meatal Perpendicular Projection Lines: Bony Landmarks for Early Identification of the Temporal Horn of the Lateral Ventricle

Localization of the temporal horn of the lateral ventricle (TH) may be required during temporal lobe and ambient cistern surgery. Most available anatomic landmarks for TH localization are based on adjacent cortical landmarks that are inherently variable or subtle. This study aimed to localize the anterior tip of the TH relative to adjacent bony landmarks. The TH was exposed on 21 sides of 11 cadaveric heads via removal of the middle temporal gyrus. Two lines were defined: (1) a perpendicular line to the zygomatic arch projected from the anterior concavity of the posterior zygomatic root (line A), and (2) a parallel line passing through the anterosuperior corner of the external auditory canal (line B). Sagittal distances from lines A and B to a parallel line passing through the anterior recess of the TH (line H) were measured. Mean (standard deviation) distances from lines A and B to line H were 13.3 (2.5) mm and 11.9 (2.2) mm, respectively. Line H was at 53% (8%) of the line A-line B interval measured from line A. The best way to search for the TH was to start approximately 15 mm posterior to line A and progress posteriorly such that a more posteriorly located TH tip would not be missed. The zygomatic-meatal landmark is a reliable tool to localize TH during various approaches. It is independent from the approach trajectory. This landmark may be used as an ancillary tool in conjunction with other cortical landmarks and image guidance.

Minimally Invasive Exposure of the Maxillary Artery at the Anteromedial Infratemporal Fossa.

The maxillary artery (MA) has been described as a reliable donor for extracranial-intracranial high-flow bypass. Existing techniques to harvest MA require brain retraction and drilling of the middle fossa (with or without a zygomatic osteotomy), carrying the potential risks of venous bleeding, injury to the branches of the maxillary or mandibular nerves, muscular transection, or temporomandibular junction disorders. To describe a novel technique to expose the MA without bony drilling and with minimal impact to surrounding structures. A conventional curvilinear incision was performed in 10 cadaveric specimens, prior to elevating the scalp to expose the zygomatic root and lateral orbital rim. The sphenozygomatic suture was followed to the anterolateral edge of the inferior orbital fissure (IOF) to locate and harvest the pterygoid segment of the MA. Topographic anatomy was assessed using surrounding landmarks and 3D Cartesian coordinates to define the surgical area. The number of visible MA branches and their lengths were recorded. The MA was successfully exposed in all specimens. This approach allowed 6 branches of MA to be exposed. The average length of exposure was 23.3±8.3 mm and the average surgical area was 2.8±0.9 cm2. The IOF was 11.5±4.2 mm from the MA. Our technique provides landmarks to identify the distal pterygoid segment of MA as a donor for extracranial-intracranial bypasses without the need for additional craniectomies. Clear anatomical landmarks, including the sphenozygomatic suture, anterolateral edge of IOF, infraorbital artery, and the pterygomaxillary fissure defined a trajectory to efficiently localize the MA with minimal risk to surrounding structures.

Key anatomical landmarks for middle fossa surgery: a surgical anatomy study.

Middle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a "roadmap" of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located. The authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed. The petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC. In middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

Zygomatic abscess complicating coalescent air cell infection and acute otitis media in a pediatric patient with facial swelling and temporomandibular joint subluxation

Acute otitis media is a localized infection. Advanced cases demonstrate local spread and abscess formation in the mastoid, temporomandibular joint, and zygomatic root if anatomy allows. We present a case of acute otitis media complicated by an abscess of a pneumatized zygomatic root extending into the temporomandibular joint treated by incision and drainage.

Microtooth supernumerary included in Zygomatic root

ABSTRACT A supernumerary tooth is one that is additional. The diagnosis is usually made by clinical exam and routine radiographs, and the majority of such teeth are impacted and asymptomatic, without affect others teeth. The supernumerary teeth, can occur included or impacted. An early diagnosis is important in order to implement a suitable plan of treatment and prevent such complications. Ectopic inclusions occur at about 1% of the general population and might be present at many diverse localizations. In this article the authors review the literature around the ectopic inclusions and report a case of an intranasal ectopic supernumerary inclusion. The prophylactic surgical removal of the supernumerary teeth is generally the treatment of choice.

The Middle Temporal Artery: Surgical Anatomy and Exposure for Cerebral Revascularization.

The middle temporal artery (MTA) is the proximal medial branch of the superficial temporal artery (STA), supplying the temporalis muscle along with deep temporal arteries. Its use in vascularized flaps for reconstructive and otologic procedures has been described, yet its potential use in neurosurgery has not been studied. We report a novel technique for exposing the MTA and evaluated its characteristics for extracranial-intracranial cerebrovascular bypass. After a curvilinear frontotemporal incision in 10 cadaveric specimens, the STA was dissected from distal to proximal. The horizontal portion of MTA was found posterolateral to the posterior end of the zygomatic root and was followed proximally until its origin and distally until its 2 terminal branches. The total length, visible branches, and caliber of MTA were measured. The mean total harvested length of MTA was 31.7 ± 5.1 mm, with an average proximal caliber of 1.7±0.4 mm, and distal caliber of 1.3 ± 0.5 mm. There were 4-6 terminal MTA branches. The caliber of the proximal STA trunk was 2.5 ± 0.5 mm. The origin of the MTA was visible with a mean distance of 16.9 ± 4.8 mm inferior to the PEZR. The parotid gland was traversed and a communicating auriculotemporal nerve to the temporal branch of the facial nerve crossed MTA in 2 specimens. MTA can be safely harvested with an anterolateral approach, following its horizontal portion at the level of the zygomatic root, which is constant. The length and caliber of MTA makes it a potential alternative donor vessel or interposition graft for extracranial-intracranial bypass, especially when other donors are unavailable.

Zygomatic Mastoiditis with Extracranial Complications: An Extremely Rare Cause of Cheek Swelling

Zygomatic mastoiditis is an extremely rare cause of an inflamed, swollen cheek. We encountered a 10-year-old girl with left preauricular swelling, pain, and mild trismus. Temporal bone computed tomography revealed a zygomatic root abscess with bone defects and a scanty amount of soft tissue lesion in Prussak’s space. After antibiotic therapy for 2 weeks, her pain subsided, but the swelling persisted. All inflamed air cells, including the lesion in the zygomatic root, were eradicated. The swelling subsided after the surgery. The patient has not experienced any postoperative complications or shown any evidence of relapse for more than 1 year. Key words: Complications ㆍ Mastoiditis ㆍ Zygoma ㆍ Zygomatic process

The Biomechanics of Bony Facial "Buttresses" in South African Australopiths: An Experimental Study Using Finite Element Analysis.

Australopiths exhibit a number of derived facial features that are thought to strengthen the face against high and/or repetitive loads associated with a diet that included mechanically challenging foods. Here, we use finite element analysis (FEA) to test hypotheses related to the purported strengthening role of the zygomatic root and "anterior pillar" in australopiths. We modified our previously constructed models of Sts 5 (Australopithecus africanus) and MH1 (A. sediba) to differ in the morphology of the zygomatic root, including changes to both the shape and positioning of the zygomatic root complex, in addition to creating variants of Sts 5 lacking anterior pillars. We found that both an expanded zygomatic root and the presence of "anterior pillars" reinforce the face against feeding loads. We also found that strain orientations are most compatible with the hypothesis that the pillar evolved to resist loads associated with premolar loading, and that this morphology has an ancillary effect of strengthening the face during all loading regimes. These results provide support for the functional hypotheses. However, we found that an anteriorly positioned zygomatic root increases strain magnitudes even in models with an inflated/reinforced root complex. These results suggest that an anteriorly placed zygomatic root complex evolved to enhance the efficiency of bite force production while facial reinforcement features, such as the anterior pillar and the expanded zygomatic root, may have been selected for in part to compensate for the weakening effect of this facial configuration. Anat Rec, 300:171-195, 2017. © 2016 Wiley Periodicals, Inc.

Zygomatic Root Position in Recent and Fossil Hominids.

The relative position of the zygomatic root to the dentition plays a crucial role in determining the overall strength of the face in response to bite forces. The powerful superficial head of the masseter arises there and the zygomaticoalveolar crest (ZAC) is discussed as a buttressing feature of the face. For instance, a more forwardly or backwardly positioned zygomatic root or a lower or higher vertical distance to the dentition could be indicative for evolutionary adaptations to particular loading regimes which are associated with diet. We therefore examined the morphology of the maxilla using state-of-the-art 3D Geometric Morphometric methods. The data set was reduced to a minimum of relevant measurements and includes five landmarks (pr, ol, zm, lingual and buccal midpoint of second molar alveoli) and three curves with semilandmarks along the lingual and buccal alveolar rim and the ZAC. Results show a stunning overlap in shape variation. We find no clear pattern of shape that would allow separating different hominid groups with confidence, except two extreme forms-Paranthropines and Neanderthals. We also find no clear trend over time. Australopithecines, Habilines, Erectines, and Middle Pleistocene Homo can be very similar to modern humans. Even great apes are within or not far from the central shape distribution of Homo, but they separate clearly from gracile and robust Australopithecines. We discuss the shape factors underlying our data. The geometry studied allows simple measurements and analyses and is thus potentially interesting for classification purposes of extreme forms. Anat Rec, 300:160-170, 2017. © 2016 Wiley Periodicals, Inc.

P.094 Modified Obwegeser temporal approach to the infratemporal fossa: four cases and review of literature

Background: The infratemporal fossa is an anatomically complex region. Lesions that arise in the infratemporal fossa are uncommon; however, their surgical resection remain challenging. Here we present a modified preauricular subtemporal approach initially described by Obwegeser et al. used in four patients with large skull base lesions. Methods: Retrospective case series of 4 patients Results: Four patients with various lesions of the infratemporal fossa (aneurysmal bone cyst, giant cell tumor of the bone, recurrent melanoma and recurrent clival chordoma) underwent surgical resection using the modified Obwegeser approach. A multidisciplinary team cared for patients consisting of maxillofacial surgery, otolaryngology and neurosurgery. After either nasotracheal intubation or tracheostomy, the patient’s jaw was temporarily wired shut. A curvilinear incision was fashioned and the root of zygoma was exposed (masseter attached) and osteotomized followed by inferior mobilization. The mandibular condyle is osteomized next and TMJ disarticulated with temporalis muscle still attached and reflected superiorly. Surgical resection of tumor then proceeded centered around the region bridging the temporal and infratemporal fossae. Reconstruction was carried out using plates and screws. Conclusions: The modified Obwegeser approach can provide safe and direct access to certain infratemporal fossa lesions with good cosmesis and functional outcome for patients without substantially increasing OR time.

Craniofacial modularity, character analysis, and the evolution of the premaxilla in early African hominins

Phylogenetic analyses require evolutionarily independent characters, but there is no consensus, nor has there been a clear methodology presented on how to define character independence in a phylogenetic context, particularly within a complex morphological structure such as the skull. Following from studies of craniofacial development, we hypothesize that the premaxilla is an independent evolutionary module with two integrated characters that have traditionally been treated as independent. We test this hypothesis on a large sample of primate skulls and find evidence supporting the premaxilla as an independent module within the larger module of the palate. Additionally, our data indicate that the convexity of the nasoalveolar clivus and the contour of the alveolus are integrated within the premaxilla. We show that the palate itself is composed of two distinct modules: the FNP-derived premaxillae and the mxBA1-derived maxillae and palatines. Application of our data to early African hominin facial morphology suggests that at least three separate transitions contributed to robust facial morphology: 1) an increase in the size of the post-canine dentition housed within the maxillae and palatines, 2) modification of the premaxilla generating a concave clivus and reduced incisor alveolus, and 3) modification of the zygomatic, shifting the zygomatic root and lateral face anteriorly. These data lend support to the monophyly of Paranthropus boisei and Paranthropus robustus, and provide mounting evidence in favor of a Paranthropus clade. This study also highlights the utility of applying developmental evidence to studies of morphological evolution.

Using the zygomatic root as a reference point in temporal lobe surgery

The zygomatic root (ZR) is an anatomic landmark routinely identified during cranial procedures. Traditionally, it has been used for identification of structures other than temporal lobe anatomy. The aim of this study was to define the structural relationship between the ZR and temporal lobe anatomy and provide a consistent landmark to guide surgical dissection. To our knowledge, there have been no studies demonstrating this relationship. Eighteen DICOM series were analyzed. 2 mm axial MRI slices were reconstructed with the x-axis centered along the zygoma. The posterior point of the ZR that marks the beginning of the groove between the zygoma and temporal bone was identified on all images. Several measures were taken to quantify the relationship of the zygomatic root to surgical landmarks used during temporal lobe surgery. The inferior temporal gyrus was always found just medial to the ZR. The mean distance between the ZR and temporal pole was 2.75 cm on the right and 2.78 cm on the left. The tip of the temporal horn was located on average 2.4 cm (left) and 2.31 cm (right) medial to the ZR. The tip of the temporal horn was found to be an average distance of 1 mm (left and right) posterior and 1.34 cm (left and right) superior to the ZR. All distances were measured orthogonally for each of the x, y, and z axes. The zygomatic root is an easily identifiable and consistent bony landmark that can serve as an adjuvant to neuronavigation for identification of temporal lobe surgical anatomy.

New Practical Landmarks to Determine Sigmoid Sinus Free Zones for Suboccipital Approaches

Literature defines the landmarks to identify the courses and locations of the transverse and sigmoid sinuses on the outer surface of the skull and inner surface of the scalp. These natural landmarks may only be helpful after skin incision and are inadequate to determine the length and size of the skin incision. Still, there is a need to identify palpable landmarks easily to determine the ideal location to open the initial burr hole before an operation. Twenty-eight dried adult human skulls and 2 cadavers were evaluated. The zygomatic root, the inion, and the mastoid process were identified on the external, and the grooves for sigmoid and transverse sinuses, on the internal surfaces. The distances between the 3 landmarks and the midpoints, and the shortest distances of the midpoints to the border of the groove for sigmoid sinus and groove for transverse sinus were measured. Statistically significant differences were evaluated for both sides. Based on the measurements, the defined "artificial landmarks" can be considered safe points that involve no vascular structures and may be used to perform the initial burr hole during posterolateral approaches. Identification of the midpoints and palpation of the defined landmarks easily before the operation render the study feasible and practical unlike with natural landmarks. To avoid venous injury, the midpoints of mastoid-inion line and zygomatic root-inion line can be used safely in skin incision during posterior fossa approaches and craniotomy.