Emissary Foramina Research Articles

Mastoid emissary vein: Anatomy and clinical relevance in plastic & reconstructive surgery

The mastoid emissary vein (MEV) is an anatomical structure with limited description in the literature and its importance is even less recognized in the plastic surgical field. Investigations in its anatomy and physiology have described its anthropological significance in transition to bipedalism and preferential intracranial venous flow into the vertebral plexus in the upright man. Inadvertant injury of vessels of this size pose a significant problem due not only to difficulty with haemostasis but also from their bidirectional flow and close proximity to the sigmoid sinus where cases of thromboembolism have been described. Recognition of this common anatomical structure and how to manage bleeding from the vessel it is important for the surgeon operating in this area and even more so for the craniofacial surgeon who operates on complex craniosynostotic patients where the MEV may be the sole dominant drainage pathway of the brain. We conducted a study on 106 cadaveric dry skull specimens looking at the incidence, position and caliber of mastoid emissary foramina. 83.7% of skulls were found to have at least one foramen with a mean diameter of 1.64 mm and the largest specimen measuring 7 mm.

Mastoid emissary foramina: an anatomical morphological study with discussion on their evolutionary and clinical implications.

The identification of mastoidal emissary veins is of importance in the neurosurgical practice to diagnose abnormal and normal structures. In the present study, the objectives were to estimate the prevalence rate of mastoidal emissary foramina in the temporal bones of the adult skull and to study their number and morphology. The present study included 48 adult human skulls which were obtained from the gross anatomy laboratory of our institution. The mastoid parts of 96 temporal bones were macroscopically observed for the prevalence, number and morphology of the emissary foramina. It is observed that, the mastoidal emissary foramen was present in 88 temporal bones (91.7%) of our specimens. The foramen was observed single in 60 temporal bones (62.5%), double in 22 bones (22.9%), and triple in 6 temporal bones (6.2%). The mastoidal emissary foramen was absent in 8 (8.3%) temporal bones. The foramen was bilaterally absent in 3 (3.1%) skulls. It was unilaterally absent in 2 (2.1%) skulls and both were on the left side. The mastoidal emissary vein is prevalent in a large number (91.7%) of cases. It was observed that the accessory mastoidal emissary foramina were present in 29.1% of cases. Recognition of the mastoid emissary veins and accessory mastoid emissary veins during the otologic surgery is critical to avoid the significant bleeding. In the neurosurgical practice, the knowledge is important due to variability in the number of mastoidal emissary veins and their connection to the venous sinuses.

The Paracondylar Skull Base: Anatomical Variants and Their Clinical Implications.

The knowledge of the vasculature around the paracondylar region is important in neurosurgical procedures such as the paracondylar and lateral supracondylar approaches. The objectives of the present study were to determine the prevalence of paracondylar emissary foramina in the adult skull bases and to study the morphology of condylar canals and hypoglossal canals. The present study included 48 adult human skulls that were obtained from the gross anatomy laboratory of our institution. The paracondylar region was macroscopically observed for the variant foramina, canals and grooves. It was observed that the paracondylar emissary foramen was present in 16 skulls (33.3%). The foramen was found bilaterally in 7 skulls (14.6%) and unilaterally in 9 skulls (18.7%). The hypoglossal canal was single in 35 (72.9%) skulls, double in 11 skulls (22.9%), and triple in 2 skulls (4.2%). The paracondylar process (2.1%) and the paracondylar groove (2.1%) were seen in 1 skull each. The posterior condylar canal was found to be patent in 19 (39.6%) skulls. The present study observed that, the paracondylar emissary vein is not rare in occurrence as it is observed in 33.3% of cases. The identification of the paracondylar emissary veins and accessory vessels is important to avoid dangerous bleeding during the surgery. The morphological knowledge of the foramina around the paracondylar region is enlightening to the chiropractors, neurosurgeons and radiologists.

Occipital emissary foramina in adult human skulls and their clinical implications

Abstract Background and Aims: Occipital emissary veins are important sources of bleeding during skull base surgeries like suboccipital craniotomies. To prevent such complications it is important to know the topography and incidence of occipital emissary foramina hence the present study aims to find the incidence and location of occipital emissary foramina in adult human skulls of Indian origin. Materials and methods: One hundred human skulls from the collection of Department of Anatomy Mahatma Gandhi Medical College and Research Institute, Pondicherry and other medical colleges in and around Pondicherry were evaluated. The bones were examined for incidence of occipital emissary foramina. Number of emissary foramina and their distance from the margin of foramen magnum were noted. The patency of the foramina was confirmed by passing a probe through it. Results: Out of the 100 human adult skull bones examined 14(14%) of them showed patent occipital formina. Six of these foramina were present on the left side and six on the right side of midline. Double occipital foramina were seen in two skulls (2%). All the foramina were in proximity to foramen magnum than to the external occipital protuberance. The average distance of the occipital emissary foramina from the margin of foramen magnum was 1.13cm on the left side and 1.10cm on the right side. Conclusion: The present study has shown that the occipital emissary foramina occur at a higher frequency than what has been described earlier in literature.

Occipital emissary foramina in human skulls: an anatomical investigation with reference to surgical anatomy of emissary veins

The objectives were to find the incidence and topography of the occipital emissary foramina in skulls of South Indian Region. In the present study, 78 dried adult human skulls were examined. They were analyzed for the gross incidence and position of the occipital emissary foramen. The observations were made in the squamous part of the occipital bone from the posterior margin of the foramen magnum to the external occipital protuberance. From our observations, the occipital emissary foramen was present in 11 (14.1%) skulls. Left sided foramen was observed in 5 cases (6.4%), right-sided foramen in 4 (5.1%) and the median foramen was seen in 2 (2.6%) of the cases. The occipital emissary vein is present in a small percentage (14.1%) of cases. It was also demonstrated that its location is variable as to left, right or midline. Its location was closer to the foramen magnum than to the external occipital protuberance in all the specimens. The morphology of this subject is important to the neurosurgeons and plastic surgeons. The knowledge is of importance in suboccipital craniotomies as this foramen transmits the occipital emissary vein and will keep awareness among the surgeons to avoid the excessive bleeding.

Further data about venous channels in South African Plio-Pleistocene hominids.

Original data about venous channels in South African Plio-Pleistocene hominids are discussed. To assess possible changes in blood volume flow of fossil hominids, we test whether dimensions of three extracranial venous foramina were different between Australopithecus africanus and Australopithecus (Paranthropus) robustus. Moreover, providing further data about the small sample of South African Plio-Pleistocene hominids, we also attempt to re-analyse the incidence of divided hypoglossal canals and four emissary foramina in a very large sample of extant African apes representing all ages, species and subspecies, in A. africanus and in "robust australopithecines". Up to now, only very poor data on extracranial dimensions of venous foramina were available for fossil hominids. However, this topic provides interesting information about the modifications of volume flow during human evolution. Assuming that in fossil hominids, as in humans, dimensions of condylar and mastoid foramina, as well as those of jugular foramina, depended on volume flow through them, we conclude, first, that volume flow through internal jugular veins was comparable in South African australopithecines, extant chimpanzees and humans, and second, that, in comparison with the extant less-encephalized chimpanzees (presumably reflecting the ancestral condition), volume flow was higher through condylar veins in A. (P.) robustus. This increase was responsible for a significantly greater amount of blood drainage from the brain (and consequently an increased arterial blood supply). We support the view that encephalization was the prevailing functional explanation for volume flow increase through condylar veins in A. (P.) robustus, in comparison with its ancestor with its presumably more ape-like degree of encephalization. Considering the incidence of emissary canals and foramina, significant differences between A. africanus, "robust australopithecines" and all the extant African ape species, were tested statistically. Concerning the condylar canal, we did not find differences between "robust australopithecines" and extant African apes. Concerning the incidence of divided hypoglossal canals, mastoid canals, parietal and occipital foramina, no difference was found between extant African apes, A. africanus and "robust australopithecines". High frequencies of either condylar or mastoid canals cannot be regarded as a "pongid condition". Moreover, we did not find convincing data to support the hypothesis that mastoid emissary veins (partly representing a putative "radiator" for cooling the brain) were selected in A. africanus, in comparison with "robust australopithecines".

Use of cranial surface anatomic fiducials for interactive image-guided navigation in the temporal bone: a cadaveric study.

Because of the intricate anatomy of the temporal bone, we examined the feasibility and reliability of cranial surface anatomic fiducials to register computed tomographic images of the temporal bone by using a frameless image-guided system. One-millimeter thick computed tomographic slices and the smallest possible field of view were used to register 10 dry and 10 fresh temporal bones from cadavers. The fiducials used for registration included the umbo of the tympanic membrane, emissary foramina, the asterion, various sutures, the tip of the mastoid process, and Henle's spine. Mean initial fiducial registration error ranged from 0.6 to 0.7 mm, and was reduced to 0.5 and 0.4 mm for the dry cranial and cadaveric studies, respectively, by eliminating or reregistering inexact fiducials. Mean target localization error ranged from 0.91 to 2.44 mm for superficial structures of the temporal bone in the dry cranial specimens and from 0.71 to 1.52 mm for deep structures such as the facial nerve, semicircular canals and ossicles in the cadaveric study. Interactive image-guided navigation in the temporal bone is possible with registration of cranial surface anatomic fiducials. It may be useful to the neurosurgeon and otologist in identifying critical anatomic structures of the temporal bone encountered during the translabyrinthine, retrolabyrinthine presigmoid, and suboccipital approaches.

The emissary foramina: Their value in platyrrhine systematics

AbstractA discriminant analysis was performed on 226 ceboid skulls using data on emissary foramina size and shape. The purposes of the study are to 1) measure the success with which these discriminating variables can distinguish among platyrrhine genera and 2) derive a set of classification functions which will permit the classification of new cases with unknown group membership (i.e., fossil skulls). This technique is able to correctly classify 80% of the 226 ceboid skulls. Support is given to the allocation of Chiropotes, Cacajao, and Pithecia into one morphologically unified subfamily, Pitheciinae. Alouatta, Ateles, and Lagothrix also share many similarities in emissary foramina size and shape and their inclusion into one subfamily, Atelinae, is probably warranted. The distinctiveness of Cebus in these same morphological features is apparent. Possibilities for extending this procedure to study fossil lineages in platyrrhines are discussed.

Cranial asymmetry in Ceboid primates: The emissary foramina

AbstractUntil the last decade or so, relatively little was known of cranial asymmetries in nonhuman primates. Data are slowly, but surely, accumulating for such features as transverse sinus flow, sylvian point angle differences, external brain morphology, etc. Cranial asymmetries are being analyzed and related to such diverse problems as “handedness” and phylogenetic systematics. It has been known for over 200 years that cranial asymmetry exists in some of the cerebral blood flow patterns in man, particularly the internal jugular pathway. Although earlier anatomists assumed this was only characteristic of “higher primates” (meaning man and the great apes), little quantitative data have been available to either support or deny this belief. There is a particular dearth of information for New World primates. The aim of this study is to contribute to the growing literature on cerebral asymmetries by partially filling in this gap in our knowledge of New World primate biology.

SYMMETRICAL OCCIPITAL APERTURES: A CASE REPORT.

The presence of cranial apertures which accommodate emissary vessels has long been recognized (3, 4). The authors believe that the following case report presents a previously undescribed type of symmetrical openings in the occipital bone. Case Report T. F., a 9-year-old white boy, was sent to the Cincinnati Children's Hospital for investigation of possible convulsive disorder. Radiographs of the skull, obtained as a part of his evaluation, demonstrated a pair of almost symmetrical radiolucent defects in the lower half of the squama of the occipital bone, slightly off the midline (Fig. 1). Because the defects appeared developmental in nature, other members of the family were brought in for x-ray examination of the skull. Two younger siblings, the patient's mother, and his paternal grandfather did not demonstrate any abnormal cranial apertures; but his father had identical openings (Fig. 2). Palpation of the heads of the patient and the father failed to identify defects corresponding to those found roentgenographically. Because of the satisfactory clinical course of the patient, in spite of mildly abnormal electroencephalographic findings, we did not feel justified in attempting any angiographic studies to elucidate the nature of the defects. Discussion Matson and Ingraham (5) reported 10 cases of congenital dermal sinus. A bony defect was noted at operation in every instance, but was not always apparent on conventional roentgenographic views. When radiographic findings were present, they usually consisted of single circular smooth midline defects visible particularly in the occipital (Towne) projection. O'Rahilly (6) stated that 73 per cent of 93 cranial meningoceles reported in the literature were occipital and occurred in or near the median plane at varying levels. He concluded that these defects were rarely above the occipital protuberance, sometimes at its level but most commonly between it and the foramen magnum. Boyd (1) reported his findings in 1,478 human skulls and their emissary foramina and concluded that in only 3.5 per cent of specimens were there no emissary foramina. No defects similar to the bilateral occipital ones described above are found in his collection. Boyd reported than in 1.6 per cent of the skulls an emissary foramen was noted in the region of the inion. These were always single with the exception of one specimen in which a single external opening communicated with two smaller ones internally. Kruyff and Munn (2) reported a radiographic incidence of 7.9 per cent of occipital emissary veins in normal children, with the opening in the vicinity of the torcular Herophili. Symmetrical lacunae of the occipital bone were reported by Pommé et al. (8) in a 23-year-old man. In this patient it was possible to palpate two defects “equal in size to a 2 franc piece,”2 the defects being separated by a bony bridge approximately 2 cm in length.

Plain Radiography of the Skull in the Diagnosis of Intracranial Tumours

1. An analysis has been made of the plain radiographic findings in 200 verified cases of intracranial tumour. 2. Sellar changes were found in two groups of lesions: tumours in or near sella, and tumours at a distance from it (metasellar lesions). Of all the abnormal sellar appearances, only two were considered to be of localising value: uniform expansion with little or no thinning of dorsum, and suprasellar calcification. The commonest changes were thinning or erosion of dorsum, and these were common to both groups of lesions. 3. In metasellar lesions showing sellar changes, the degree of sellar destruction and the degree of hydrocephalus are roughly proportionate to one another, but the hydrocephalus in itself is not the cause of the bone destruction. In some of these cases, however, the dilated anterior end of third ventricle comes into close contact with sella, and it is suggested that this may be at least a contributory cause of the sellar changes. 4. Signs of increased intracranial tension, comprising starting of sutures, increased convolutional markings, widening of the occipital emissary foramina, and thinning or erosion of dorsum sellæ, were found in 22·5 per cent. of all cases. 5. Localising signs were found in 30·5 per cent. They included pineal shift, calcification, bone erosion, new bone formation, and widening of the vascular channels.