Supramastoid Crest Research Articles

Radiologic exploration of the morphometric and morphological features of the carotid canal

ObjectivesThe carotid canal is a foramen located in the petrous part of the temporal bone. Detailed knowledge about the anatomy of the base of the skull is important, as many surgeries are done there for various malignancies and aneurysms. The aim of this study was to collect various morphometric measurements of the carotid canal to aid neurosurgeons with various surgical approaches to easily locate the second fragment of the internal carotid artery. MethodsA retrospective study was done, and 500 CT scans on both sides of the skull were analysed. Various morphometric parameters related to the carotid canal were measured. The shape of the carotid canal was also noted. Statistical analysis was done for all the parameters. ResultsThe mean anteroposterior diameter and width of the carotid canal was 0.535 and 0.683 cm, respectively. The mean distance of the carotid canal from the external acoustic meatus, zygomatic arch, and mandible was 2.27, 3.28, and 2.34 cm, respectively. The mean distance of the carotid canal from the midline of the base of the skull was 2.97 cm. The mean angle between the zygoma root, external aperture of the carotid canal, and external acoustic meatus was 27.08°. The mean angle between the external acoustic meatus, external aperture of the carotid canal, and supramastoid crest was 26.74°. The carotid canal was round in most cases (50.5%). ConclusionThese measurements will aid neurosurgeons to identify various surgical approaches to easily locate the second part of the internal carotid artery, and they can serve as a reference to guide surgeries at the base of the skull.

Skull morphometric variability related to offshore and inshore ecotypes of the common bottlenose dolphin (Tursiops truncatus) from northwestern Mexico

AbstractThe distribution of common bottlenose dolphins Tursiops truncatus is associated with environmental factors, which influence morphological adaptations. In the present study, we examined the cranial characteristics of this species from the Pacific Northwest of Mexico to detect the main variations using geometric morphometric analysis. From stable isotope concentrations (δ13C), we identified 24 specimens of the inshore coastal ecotype and 18 of the offshore ecotype. Maturity was determined using the degree of fusion of the maxillae and premaxillae. Allometry was detected in the skull lateral region, indicating that the relationship between shape and size is maintained in adults. After eliminating the allometric effect by discarding the smallest individuals, morphometric comparisons indicated differences between the ecotypes that were associated mainly with the intersection between the frontal bone and zygomatic process, the anteriormost point in the curvature of the zygomatic process, and the meeting of the suture between squamosal and exoccipital bones, with the supramastoid crest to anteriormost in the curvature of the temporal crest of the intersection between the parietal and interparietal. No significant differences were found in the ventral view. The cranial differences between both Tursiops truncatus ecotypes could be mainly associated with the different types of feeding.

STUDY OF ANATOMICAL VARIATION OF ASTERION IN HUMAN DRY SKULLS AND ITS SURGICAL IMPORTANCE

Asterion is the meeting point of temporal, occipital, and parietal bones on the posterolateral surface of the skull. This point is surgically important in various posterior cranial fossa surgeries since it is a smaller delicate area where many vital structures are present. The Neurosurgeons have been doubtful about its accuracy due to population-based differences in its morphology and its location with relationship to sigmoid and transverse sinuses. In this study 100 (54 male & 46 female) adult skulls were measured to accurately the type of asterion, its distance from important bony landmarks, and also the nearby venous sinuses were measured. Our study revealed that type II (absence of sutural bones) is the commonest type when compared to type I (presence of sutural bones) asterion. The asterion was 4.82 ± 0.58 cm from the apex of the mastoid process on the right side and 4.70 ± 0.70 cm on the left. It was higher in males than in females, p-value being statistically significant (P = 0.00 & P = 0.02 for right & left sides respectively). The distance of asterion from supramastoid crest is 4.22 ± 0.73 cm on the right and 4.23+/-0.58 cm on the left. The distance in males is higher than in females. The position of the asterion in relation to transverse sinus was at the level of the transverse sinus in 74.67% of cases, and inferior to the asterion in 22.41%, and superior to the asterion in 2.92%. The measure taken reveals that the asterion is located either at the level or below the level of the transverse sinus in the majority of the cases. This information is useful to neurosurgeons to minimize the risk during posterior cranial fossa surgeries. This study is useful for anthropologists, forensic science experts for the determination of the sex of the skull along with other parameters.

Dentigerous cysts with exostosis of the temporal bone in horses – A new variant diagnosed by computed tomography

SummaryThe dentigerous cyst or temporal teratoma in horses is a well‐known congenital malformation that occurs in the temporal region and usually contains dental tissue. This case report describes two horses with a previously unreported variant of the dentigerous cyst associated with an exostosis arising from the temporal bone. The principal clinical sign was a draining tract opening at the margin of the right pinna in both horses. There was no evidence of an ectopic tooth on the radiographs or at ultrasonographic examination. Computed tomography combined with positive contrast sinography of the draining tract revealed bone formation arising from the supramastoid crest of the right temporal bone extending towards a cyst‐like structure but without direct connection in both cases. This bone formation was located at a site on the supramastoid crest, close to the external acoustic meatus, where ectopic teeth may also occur. Both cysts were removed surgically with a good long‐term outcome.

Temporal Bone Landmarks of the Transversesigmoid Sinus Junction: An Anatomical Study in Dried Human Skulls

Objective: To investigate the accuracy in localization of the anterosuperior margin of TSSJ by using the intersection point between the squamosal and parietomastoid sutures (A point) and the intersection of the squamosal suture and supramastoid crest (B point) as bony landmarks.Materials and Methods: The A and B points were marked on the inner surface of a skull by using the transillumination technique. The anatomical relationship between the projected A point, B point, and groove of TSSJ was investigated in 60 dried Thai human skulls (120 sides).Results: Of the 120 sides, the projected A points were located exactly on the anterosuperior margin of the TSSJ in 38 (31.7%) instances and adjacent (above and below) the anterosuperior margin in 82 (68.3%) cases. Of the 118 sides with identifiable supramastoid crests, the projected B points were located precisely on the anterosuperior margin of TSSJ in 60 (50.8%) cases and above the anterosuperior margin of the TSSJ in 57 (48.3%) cases. Hence, the projected B point was a more reliable bony landmark for localizing the anterosuperior margin of the TSSJ when compared with the projected A point (p = 0.003, OR 2.2, and 95% CI =1.3-3.8).Conclusion: The B point is a more reliable temporal bone landmark for localization of the TSSJ than the A point. In temporal craniotomy, an initial burr hole at the B point is relatively safe and carries a very low risk of inadvertent venous sinus injury.

The branching pattern of the middle temporal artery and the relation with the temporal fascia.

Although the middle temporal artery is used for maxillofacial and otological flap surgeries, the anatomical knowledge of the artery is insufficient to corroborate its usage. This study has investigated the interrelationship between the artery and the temporal fascia to enhance its availability. The middle temporal artery was dissected in ten cadavers, and its spatial relations with the temporal fascia and muscle and the adjacent structures were examined. The middle temporal artery arose behind the mandibular head or neck and in front of the external acoustic meatus. It penetrated the temporal fascia external to the junction between the zygomatic process and the supramastoid crest. The artery gave off a thin branch in the space between the superficial and the deep layers of the fascia and is divided into two branches piercing the deep layer to supply the temporalis. The anterior branch anastomosed with the deep temporal artery; furthermore, it gave off the slender ramus coursing on the base of the zygomatic process to communicate with the masseteric artery. The posterior branch passed along the supramastoid crest, gave off a slender ramus and ascended in the groove of the temporal bone. The branching pattern of the middle temporal artery and its positions relative to the temporal fascia and the landmark structures are helpful in identifying the artery, designing favourable flaps and avoiding unfavourable bleeding during surgery. They are also beneficial in developing the clinical usage of the artery.

Radiologic analysis of the location, shape and size of the external aperture of the carotid canal in children

This retrospective computed tomography (CT) study was aimed to assess the growth dynamic of the external aperture of the carotid canal (EACC) in children aged between 1 and 20years. Two hundred patients (sex 100 females/100 males, average age 10.50 ± 5.77years) with good head CT image quality were included in this study. CT images of the patients were used to obtain data related to the location, shape and dimension of EACC. EACC shapes were identified as oval shaped, round shaped, and tear-drop shaped in 58.3% (233 sides), 24% (96 sides) and 17.8% (71 sides), respectively. EACC length, disEACC-MSP (distance between EACC and midsagittal plane), and EACC width did not change from the prepubescence period; while, the disEACC-SC (distance between EACC and supramastoid crest) seemed to reach adult size in the postpubescence period. Linear functions for EACC length and width were calculated as: y = 5.453 + 0.091 × years, and y = 5.398 + 0.059 × years, respectively. The regression equations of the measured parameters representing the growth dynamic of EACC in children can be helpful to estimate its size, location and angulation, which suggest that the dimension and distances to certain anatomical landmarks seemed to reach adult size in different developmental periods. In this context, the findings of this study may seem to emphasize the importance of preoperative radiological evaluation on skull base, related to EACC, for multidisciplinary surgeon teams during childhood surgeries in terms of patients' positioning, and the selection of appropriate surgical approach.

Description of Cephalic Index in Female Indian and Chinese Malaysian

Cephalic index is an important parameter in evaluating racial and sexual differences, is measured by establishing a ratio between the breadth and the length of the head calculated as 100 times the maximum breadth of the head measured at the greatest diameter of the cranial vault above the supramastoid crest divided by the maximum length of the head measured from the most prominent point on the glabella to the opisthocranion. The aim of the research was to differentiate the cephalic index between female Indian and Chinese Malaysian studying in Padjadjaran University. This research was a descriptive study with total samples are 35 comprise of 13 females Indian and 22 females Chinese. The sampling technique used was stratified random sampling. The subjects were measured for head length and head breadth by using a spreading caliper. The result of the research shows that 22 female Chinese surveyed has an average cephalic index of 85.861(hyperbrachycephalic) with a standard deviation of 3.717. Meanwhile, the 13 female Indian surveyed has an average of 81.768 (brachycephalic), with a standard deviation of 3.205. The conclusion of this research is that there is a significant difference of cephalic index between females Indian and Chinese Malaysian.

Reliability of Supramastoid Crest in Sex Determination by Logistic and Probit Regression

Sex determination is vital for the identification of an individual. Success in the sex determination is limited as often fragmentary remains are available for forensic identification. In the present study, 60 adult human skulls of North Indian individuals were studied to assess the reliability of the prominence of supramastoid crest(a non-metric trait) in sex determination, so that sex can be determined from fragmentary crania. The prominence of the supramastoid crest was compared with the casts prepared and standardized by Australian National University. The data was statistically analysed by Logistic and Probit regression models. Subsequent to analysis, it was found that the prominence of supramastoid crest correctly classified 75% of the sample.

A new Eomysticetid (Mammalia: Cetacea) from the Late Oligocene of New Zealand and a re‐evaluation of ‘Mauicetus’ waitakiensis

AbstractThe published Oligocene record of mysticetes (baleen whales) is dominated by toothed mysticetes in addition to the Eomysticetidae, the earliest known chaeomysticetes known only from the Oligocene. Formally recognized eomysticetids include examples from the Oligocene of South Carolina, USA (Eomysticetus), and Japan (Yamatocetus). A new fossil from the upper Oligocene Otekaike Limestone including a partial skull, periotic, tympanic bulla, mandible and some postcrania is here described as Tohoraata raekohao gen. et sp. nov. Tohoraata confirms the presence of an eomysticetid in New Zealand. Tohoraata raekohao is characterized by delicate frontal with numerous supraorbital foramina and sulci, relatively long exposure of the frontal and parietal along a transversely narrow intertemporal region, greatly enlarged temporal fossa, massive and anteriorly directed zygomatic process lacking a supramastoid crest, and a periotic with superior process reduced to a low ridge with anterior and posterior apices. Cranial and postcranial fusion of elements, development of muscle attachments and osteohistology demonstrate that the T. raekohao holotype is an adult or possible subadult. Features of the tympanic bulla including a relatively wide bulla with a medial lobe that is transversely much wider than the lateral lobe, and a slightly posterolaterally facing exoccipital, permit referral of the fragmentary ‘Mauicetus’ waitakiensis of Marples into the genus Tohoraata, resulting in Tohoraata waitakiensis comb. nov. Description of T. raekohao and resolution of the relationships of the hitherto problematic Tohoraata waitakiensis indicates that several eomysticetids were present in the Southern Ocean during the Late Oligocene.

A novel reference coordinate system to locate the inferomedial point of the transverse-sigmoid sinus junction.

A coordinate system was previously developed to identify landmarks on the skull surface to help locate the transverse-sigmoid sinus junction in order to reduce surgical morbidity in retrosigmoid craniotomy; however, in practice we found that this system has important flaws. To develop and evaluate a novel reference coordinate system to precisely locate the inferomedial point of the transverse-sigmoid sinus junction (IMTS) and evaluate the effect of gender and skull side (left or right). Forty-two adult skulls (84 sides) were obtained for analyses. The X-axis was defined by point A (where the upper edge of the zygomatic arch joins with the frontal process of the zygomatic bone) and point B (where the upper edge of the zygomatic arch blends posterosuperiorly into the supramastoid crest). The Y-axis was defined by the line perpendicular to the X-axis and extending across the tip of the mastoid. The x and y coordinates of IMTS (IMTS-x and IMTS-y) were measured in this coordinate system. There were 20 male skulls and 22 female skulls. The mean IMTS-x measurements were significantly higher on the right side compared with the left side in both males and females. For the left skull side, the mean IMTS-y measurements were significantly lower in females compared with males. This novel reference coordinate system may be a reliable and practical method for identifying the IMTS during retrosigmoid craniotomy. There are significant differences in location of the axes with regard to gender and skull side.

Role of squamosal suture as a consistent landmark for middle fossa approach craniotomy: an anatomical study.

Objective To establish a consistent surface bony landmark for a middle fossa approach (MFA) lateral craniotomy represented by the squamosal suture (SS). Methods In 60 dried skulls, we assessed the relation between the SS and the external auditory canal (EAC). The lateral portion of the middle cranial fossa floor was also assessed for a possible relation with the anteroposterior diameter (APD) of the squama temporalis (ST). Clinically, we applied our findings on the SS in MFA for different lesions. Results A vertical line at the EAC divided the ST into the anterior part constituting 61% of the APD (i.e., two thirds) and the posterior part forming 39% (i.e., one third). The average ST height was 35.92 mm. The SS posterior limit at the supramastoid crest was located just anterior to the external projection of the petrous ridge in 35 skulls (58%) and exactly corresponded to it in 25 skulls (42%). The APD of the ST equals on average 97% of the APD of the lateral middle cranial fossa. Optimum exposure of the middle fossa was obtained without any further craniotomy extension. Conclusion The SS serves as a consistent natural surface bony landmark for MFA. Optimum craniotomy, two thirds anterior to the EAC and one third posterior, is obtained following SS as a landmark.

The lower border of the zygomatic arch could be a better landmark for the middle fossa dura: Cadaveric dissection study

BackgroundDural injury and CSF otorrhea is a serious complication during mastoidectomy especially in low level dura. ObjectivesAim of the study is to determine a reliable landmark for the middle fossa dura to minimize risk of dural injury and CSF otorrhea during mastoidectomy. By answering the question which is considered as a more fixed landmark for the dura; the supramastoid crest or the lower border of the zygomatic arch? MethodsA cadaveric study was done on 204 temporal bone specimens in the temporal bone lab at the Ain Shams University Specialized Hospital.A correlation between the level of the supramastoid crest and the level of the zygomatic arch was done.A correlation between the level of the dura and the level of the supramastoid crest in the area of mastoid antrum was done.A correlation between the level of the dura and the level of the zygomatic arch was done. ResultsIn 20.6% of specimens, the dura lies at a lower level than the level of the supramastoid crest but in 2.9% of specimens the dura lies at a lower level than the lower border of the zygomatic arch. ConclusionIt is better to consider the lower border of the zygomatic arch as a reliable landmark of the middle fossa dura in the area of the antrum than to consider the supramastoid crest as a landmark for the dura. It is better to consider imaginary line directed posteriorly from the lower border of the zygomatic arch as a superior limb of the Macewen triangle.

Mini-mastoidectomía para anastomosis hipogloso-facial con sección parcial del nervio hipogloso

Introducción:La anastomosis hipogloso-facial es la técnica de elección para la reparación de la parálisis facial cuando no se dispone de un cabo proximal sano del nervio facial. La técnica de anastomosis mediante fresado mastoideo y sección parcial del hipogloso minimiza la atrofia lingual sin sacrificar resultados a nivel facial.Método:La porción mastoidea del nervio facial transcurre por la pared anterior de la AM, a un promedio de 18+/-3 mm de profundidad respecto de la pared lateral. Se debe reconocer la cresta supramastoidea, desde la cual se marca una línea vertical paralela al eje mayor de la AM, 1 cm por detrás de la pared posterior del CAE El fresado se comienza desde la línea medio mastoidea hasta la pared posterior del CAE. Una vez encontrado el nervio facial en el tercio medio del canal mastoideo, el mismo es seguido hacia proximal y distal.Resultados:El abordaje descripto permite acceder al nervio facial intratemporal en su porción mastoidea, y efectuar un fresado óseo sin poner en riesgo al nervio o a estructuras vasculares cercanas. Se trata de un procedimiento técnicamente más sencillo que los abordajes amplios habitualmente utilizados al hueso temporal; no obstante su uso debe ser restringido mayormente a la anastomosis hipogloso-facial.Conclusión:Esta es una técnica relativamente sencilla, que puede ser reproducida por cirujanos sin mayor experiencia en el tema, luego de su paso por el laboratorio de anatomía.

Variation and modalities of growth and development of the temporal bone pneumatization in Neandertals

The temporal bone is used frequently to determine taxonomic affinities as it contains several features that differentiate Neandertals from anatomically modern Homo sapiens. However, only little information is available about temporal bone pneumatization in Neandertals. This study provides descriptions and comparisons of the disposition and the extensiveness of the pneumatization of the temporal bone in large samples of Neandertal specimens of different geological and developmental ages (25 individuals and 33 temporal bones from the sites of Engis, Krapina, La Chapelle aux Saints, La Ferrassie, La Quina, Pech de l'Azé, and Spy). Although temporal bone pneumatization shows some individual variability, a similar pattern of distribution is found in all adult Neandertal individuals from Krapina and Western Europe. Pneumatization is restricted mainly to most parts of the petromastoid areas. We also retrace for the first time the modalities of growth and development of this pneumatization in Neandertals. Finally, this study provides new information about possible correlations between the extension and position of temporal bone pneumatization and some of the morphological features used to characterize the temporal bone of the Neandertals. These latter features include the relatively low and short temporal squama, the robust zygomatic process with a relatively marked lateral projection, the strong supramastoid crest, the significant thickness of the tympanic part of the temporal bone, and the relatively small mastoid process and large juxtamastoid eminence. Our results suggest that the development of pneumatization in Neandertals is related to available space and to temporal bone morphology. Moreover, it appears that the development of pneumatization does not play an active role in determining the morphology of the apomorphic features of the temporal bone in Neandertals.

Surface and Superficial Surgical Anatomy of the Posterolateral Cranial Base: Significance for Surgical Planning and Approach

We have performed an anatomic study, 15 using fixed cadaveric preparations, with the goal of identifying surface landmarks that will reliably locate the underlying transverse and sigmoid sinus complex. Simple morphometric relationships were first determined on both sides of each specimen to yield 30 sides measured. The following relationships were determined: 1) zygoma root-asterion, 2) asterion-mastoid tip, 3) zygoma root-suprameatal spine (Henle's spine), 4) asterion-suprameatal spine, 5) mastoid tip-suprameatal spine. The relationship of the asterion to the transverse-sigmoid junction was determined by bone removal. Also, the distances from the asterion to the sigmoid sinus-superior petrosal sinus junction and the superior margin of the transverse sinus were studied. Surface and marks were found to have definitive relationships to underlying anatomic substrates in all specimens studied. The critical relationships that were concluded from this study can be described in terms of two easily identified lines between bony surface structures. A line drawn from the zygoma root to the inion, i.e., the superior nuchal line, reliably located the rostrocaudal level of the transverse sinus in all specimens. Although the asterion did not consistently fall on this line, the transverse-sigmoid junction could reliably be placed at the anteroposterior level of the asterion. Further, a line drawn from the squamosal-parietomastoid suture junction to the mastoid tip reliably defined the axis of the sigmoid sinus through the mastoid. We also found that the junction of the squamosal and parietomastoid sutures lay over the anterior border of the upper curve of the sigmoid sinus. The anterior portion of the supramastoid crest correlated with the level of the middle fossa. These surface relationships all have significance for posterolateral approaches to the cranial base. Since performing this study, these relationships have been found reliable for operative planning in our clinical cases.

Temporal bone: three-dimensional CT. Part I. Normal anatomy, techniques, and limitations.

Three-dimensional (3D) surface renderings of the temporal bone were created from routine axial computed tomographic (CT) images in 15 subjects and in cadaver specimens. The displayed anatomy was correlated with these specimens, as well as with images from the routine study. Six sets of viewing angles were derived for optimal display of surgically important surface landmarks, such as the suprameatal triangle and supramastoid crest. The 3D CT images were found to be of excellent quality and permitted a global view of the temporal bone surface anatomy. Bone depletion artifacts ("pseudoforamina") posed a potentially serious problem in evaluating the tegmen and wall of the sigmoid sulcus, being present in eight of 20 cases. Three-dimensional CT may be a useful adjunct to routine temporal bone imaging.

Thickness of the lateral surface of the temporal bone in children.

The placement of implantable auditory prostheses in children has raised questions concerning the thickness of the temporal bone in the region of implantation. The purpose of this study is to describe the thickness at specific sites of the lateral surface of the temporal bone in children of different ages. One hundred twenty-five intact temporal bones from 83 children of known sex, race, and age between birth and 20 years were measured. Thickness was measured with a specially designed micrometer at specific locations from a fixed reference point by use of a surface projected grid for site identification. Thickness was plotted against age on scattergraphs for each site, and regression analysis revealed a bimodal linear relationship. Sites medial to the temporalis muscle were the thinnest; sites associated with the posteroinferior insertion of the temporalis muscle, along the supramastoid crest, were the thickest. However, wide interindividual variability was the rule.

SUBTEMPORAL AND SUBOCCIPITAL MYOPLASTIC CRANIOTOMY

In no branch of surgery is the maneuver of opening and closing the wound more important or more arduous than in cranial surgery. We desire to describe a simple operative technic which in our hands has proved to be superior to the conventional subtemporal and suboccipital procedures. MYOPLASTIC SUBTEMPORAL CRANIOTOMY The myoplastic subtemporal craniotomy technic permits rapid exploration through a wide unobstructed opening and provides a firm, safe restoration. The steps of the procedure follow in detail. 1. A curved incision, as indicated in the insert in figure 1, is made in the scalp without wounding the pericranium. This incision skirts the superior temporal line to which the fascia of the temporal muscle is attached. This ends anteriorly at or just behind the hair line. Posteriorly the incision is swung slightly forward on the supramastoid crest, which lies at the level of the superior border of the zygoma. The superior