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Middle meningeal vessels, dural venous sinuses, and emissary veins leave imprints and canals in the endocranium, and thus provide evidence of vascular patterns in osteological samples. This paper investigates whether craniovascular morphology undergoes changes in craniosynostotic human skulls, and if specific alterations may reflect structural and functional relationships in the cranium. The analyzed osteological sample consists of adult individuals with craniosynostoses generally associated with dolichocephalic or brachycephalic proportions, and a control sample of anatomically normal adult skulls. The pattern and dominance of the middle meningeal artery, the morphology of the confluence of the sinuses, and the size and number of the emissary foramina were evaluated. Craniovascular morphology was more diverse in craniosynostotic skulls than in anatomically normal skulls. The craniosynostotic skulls often displayed enlarged occipito-marginal sinuses and more numerous emissary foramina. The craniosynostotic skulls associated with more brachycephalic morphology often presented enlarged emissary foramina, while the craniosynostotic skulls associated with dolichocephalic effects frequently displayed more developed posterior branches of the middle meningeal artery. The course and morphology of the middle meningeal vessels, dural venous sinuses, and emissary veins in craniosynostotic skulls can be related to the redistribution of growth forces, higher intracranial pressure, venous hypertension, or thermal constraints. These functional and structural changes are of interest in both anthropology and medicine, involving epigenetic traits that concern the functional and ontogenetic balance between soft and hard tissues.

Sinus pericranii is a rare vascular anomaly characterized by an abnormal communication between the intra- and extracranial venous systems through a calvarial defect(s). We present three cases of congenital sinus pericranii with facial involvement, emphasizing its cutaneous presentation with diagnostic pitfalls and discuss the multidisciplinary management of this vascular anomaly.

Although the sphenoidal emissary foramen (SEF) and its content are anatomically and clinically relevant, accurate description of them in the modern literature is lacking. This study aimed to examine and describe the SEF and its content (the sphenoidal emissary vein [SEV]). We analyzed 1,000 computed tomography (CT) images, 170 dry skulls, 50 formalin-fixed specimens, and three specimens (heads) following guidelines proposed by Dr. Albert L. Rhoton Jr. MD for latex injection. SEV morphology was determined by histological staining and electron microscopy. The SEF was observed in 46.8% of the CTs studied (25.4% bilateral and 21.4% unilateral), and 45.2% of the dry skulls (18.8% bilateral and 26.4% unilateral). In 9.5% of CTs and 21.1% of dry skulls there was a blind channel in the external surface of the cranial base; since there was no communication with the cranial cavity, it was not considered as the SEF. During the dissections, the SEF was found in seven individuals. In three of them, the SEV was an alternative route for venous drainage of the venous plexus of the foramen ovale. Its walls were composed of collagen fibers and its endothelium contained rhomboid cells resembling those commonly found in the superior sagittal sinus. The presence of the SEF and SEV can anatomically explain the spread of certain cranial base pathologies from or toward Meckel's cave or the cavernous sinus, and should be taken into account during procedures in the middle cranial fossa, percutaneous approaches, odontological procedures, and treatment of dural arteriovenous fistulas. Clin. Anat., 33:767-781, 2020. © 2019 Wiley Periodicals, Inc.

Variations in the venous drainage of the central nervous system can have imaging and clinical findings that mimic pathology, presenting a challenge for neuroimagers and clinicians. Patients with these variants may undergo unnecessary testing, and patients with pathology may receive delayed diagnoses because of overlap with benign findings. Consequently, the accurate identification of venous variations on cross-sectional imaging and angiography and their potential causes are critical for differentiating benign imaging variants from potential pathologic processes requiring further evaluation. For example, in the epidural space, benign dilation of the epidural venous plexus may be mistaken for evidence of a fistula, abscess, or metastasis. Hypoplasia of a dural venous sinus or an arachnoid granulation may mimic venous sinus thrombosis. The superior ophthalmic vein may demonstrate benign dilation in intubated patients, mimicking thrombosis, increased intracranial pressure, orbital varix, inflammatory pseudotumor, or other conditions. Furthermore, certain venous variations, such as the occipital sinus or emissary veins, may complicate surgery or herald pathology and should be reported. In addition, some supposedly benign variations, such as the developmental venous anomaly, can be complicated by pathology. The objective of this review article is to provide a descriptive and pictorial review of common anatomic and physiologic variations in the venous drainage system of the brain, spine, and orbits that can mimic pathology. Neuroimaging findings of related pathologies and differences in clinical presentations will also be discussed to assist in the approach to differential diagnosis.

The vascular networks running into the meningeal layers, between the brain and braincase, leave imprints on the endocranial surface. These traces are visible in osteological specimens and skeletal collections, providing indirect evidence of vascular patterns in those cases in which bone remains are the only source of anatomical information, such as in forensic science, bioarchaeology and paleontology. The main vascular elements are associated with the middle meningeal artery, the venous sinuses of the dura mater, and the emissary veins. Most of these vascular systems have been hypothesized to be involved in endocranial thermal regulation. Although these traits deal with macroanatomical features, much information on their variation is still lacking. In this survey, we analyze a set of craniovascular imprints in two European dry skull samples with different neurocranial proportions: a brachycephalic Czech sample (n = 103) and a mesocephalic Italian sample (n = 152). We analyzed variation and distribution, correlation with cranial metrics, and sex differences in the dominance of the branches of the middle meningeal artery, the patterns of confluence of the sinuses, and the size of the emissary foramina. The descriptive statistics provide a reference to compare specimens and samples from different case studies. When compared with the Italian skulls, the Czech skulls display a greater dominance of the anterior branch of the middle meningeal artery and more asymmetric right‐dominance of the confluence of the venous sinuses. There is no sex difference in the middle meningeal vessels, but males show a greater prevalence of the occipito‐marginal draining system. Differences in the middle meningeal vessels or venous sinuses are apparently not influenced by cranial dimensions or proportions. The mastoid foramina are larger in larger and more brachycephalic skulls, which increases the emissary potential flow in the Czech sample and males, when compared with the Italian samples and females, respectively. The number of mastoid foramina increases in wider skulls. This anatomic information is necessary to develop further morphological and functional inferences on the relationships between neurocranial bones and vessels at the genetic, ontogenetic, and phylogenetic levels.

A B S T R A C T BACKGROUND AND PURPOSE Several studies have found supplemental venous drainage channels in addition to bilateral internal jugular veins for cerebral venous efflux. We performed this study to characterize the supplemental venous outflow patterns in a consecutive series of patients undergoing detailed cerebral angiography with venous phase imaging. METHODS The venographic phase of the arteriogram was reviewed to identify and classify supplemental cerebral venous drainage into anterior (cavernous venous sinus draining into pterygoid plexus and retromandibular vein) and posterior drainage pattern. The posterior drainage pattern was further divided into plexiform pattern (with sigmoid venous sinus draining into the paravertebral venous plexus), and solitary vein pattern (dominant single draining deep cervical vein) drainage. The posterior plexiform pattern was further divided into 2 groups: posterior plexiform with or without prominent solitary vein. RESULTS Supplemental venous drainage was seen ipsilateral to internal jugular vein in 76 (43.7%) of 174 venous drainages (87 patients) analyzed. The patterns were anterior (n = 23, 13.2%), posterior plexiform without prominent solitary vein (n = 40, 23%), posterior plexiform with prominent solitary vein (n = 62, 35.6%), and posterior solitary vein alone (n = 3, 1.7%); occipital emissary veins and/or transosseous veins were seen in 1 supplemental venous drainage. Concurrent ipsilateral anterior and posterior supplemental drainage was seen in 6 of 174 venous drainages analyzed. CONCLUSIONS We provide an assessment of patterns and rates of supplementary venous drainage to internal jugular veins to improve our understanding of anatomical and physiological aspects of cerebral venous drainage.

Objectives The diploic channels appear to be more developed in humans than in nonhuman primates, suggesting they may be relevant in evolutionary biology. This study is aimed at providing a segmentation procedure for diploic channels and CT analysis, a quantitative description of their variation in modern humans, and paleoanthropological case-studies. Materials and Methods CT data were used for the 2D and 3D visualization, rendering, and measure, of diploic channels in modern and fossil hominids. We analyzed 20 modern human skulls and three Neanderthals. The effect of different resolution factors was evaluated. A specific protocol was designed to segment the vascular network and localize the main branches, reducing the noise of the cancellous bone. Results We provide a quantitative description of the frontal, parietal, and occipital diploic networks in modern humans and in three Neanderthals. There is a correlation in the degree of vascularization among the different vault areas. No side differences can be detected. The diploic network is commonly connected with the meningeal artery at the temporal fossa, with the emissary veins at the occipital bone, and with the venous sinuses at the parieto-occipital areas. The channels are more developed in the parietal areas. The three Neanderthals show a vascular development, which is in the lower range of the modern human variation. Conclusions Modern humans display a large variation in their morphological patterns, being the parietal area the most vascularized. The pattern of the diploic channels may be relevant in anthropology, medicine, and paleontology, taking into account their possible involvement in thermoregulation. Am J Phys Anthropol 159:313–324, 2016. © 2015 Wiley Periodicals, Inc.

Although the inferior petro-occipital vein has been recently used for vascular access to the cavernous sinus, few detailed descriptions of its anatomy are in the literature. We aimed to investigate the morphology and relationships of this vessel. Twelve latex-injected cadaveric heads (24 sides) were dissected to identify the inferior petro-occipital vein and anatomic details documented. The petro-occipital vein was identified on 83.3% of sides. Generally this vein united the internal carotid venous plexus to the superior jugular bulb. However, on 10% of sides, the anterior part of this vein communicated directly with the cavernous sinus, and on 15%, the posterior vein drained into the inferior petrosal sinus at its termination into the superior jugular bulb. The petro-occipital vein was separated from the overlying inferior petrosal sinus by a thin plate of bone. On 40% of sides, small venous connections were found between these two venous structures. The vein was usually larger if a nondominant transverse sinus was present. The overlying inferior petrosal sinus was smaller in diameter when an underlying inferior petro-occipital vein was present. On 20% of sides, the posterior aspect of the vein communicated with the hypoglossal canal veins. On three sides, diploic veins from the clivus drained into the inferior petro-occipital vein. The inferior petro-occipital vein is present in most humans. This primarily extracranial vessel communicates with intracranial venous sinuses and should be considered an emissary vein. Knowledge of this vessel's exact anatomy may be useful to cranial base surgeons and endovascular specialists.

Objectives/Hypothesis: CHARGE (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and/or deafness) syndrome is a genetic disorder with prominent otolaryngologic features including choanal atresia and inner ear malformations. Recent experience with venous malformations during cochlear implant surgery prompted this study to define the spectrum of venous abnormalities in CHARGE and their surgical implications in otology. Study Design: Retrospective review of medical and radiologic records from databases of patients with CHARGE syndrome from three tertiary care academic medical centers. Methods: Eighteen patients with CHARGE for whom temporal bone CT scans were available were included in the review. Results: Venous anomalies of the temporal bone were present in 10 of 18 (56%) patients. The most common were large emissary veins (n = 5). In two of these cases, these veins were associated with an ipsilateral a hypoplastic sigmoid sinus or jugular foramen. Other abnormalities included an aberrant petrosal sinus, venous lakes in proximity to the lateral venous sinus, condylar canal veins, and jugular bulb abnormalities, including a high riding bulb obscuring the round window niche and a dehiscent jugular bulb. In four of six patients undergoing cochlear implantation, the course of the aberrant vessel necessitated a change in the surgical approach, either during mastoidectomy or placement of the cochleostomy. Conclusions: Temporal bone venous abnormalities are a common feature in CHARGE syndrome. The pattern of venous abnormality suggests that there is a failure of the sigmoid sinus/jugular bulb to fully develop, resulting in persistence of emissary veins. Recognition of these abnormal venous structures during otologic surgery is critical to avoiding potentially catastrophic bleeding. Laryngoscope, 2012

The petrosquamosal (PSS) is an embryonic emissary vein of the temporal bone in humans and connects the intra- and extracranial venous networks. Few reports in the recent literature provide detailed descriptions of PSSs that are found before or during surgeries. We report the presence of PSS in two patients with chronic otitis media. An abnormal vessel was found originating from the sigmoid sinus of each patient. The vessels coursed anteroinferiorly over the superior portion of the temporal bone and terminated near the posterior part of the temporomandibular joint. The clinical significance of PSS and a brief literature review are presented.

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? Venous ligation surgery has been conducted as a symptomatic treatment, but the effective rate of this surgery was insufficient. We thought that one of the reasons for the low effective rate of this surgery was insufficient for the diagnostic modality. We confirmed that 3D cavernosography was, in comparison with conventional cavernosography, higher in diagnosis precision. OBJECTIVE • To examine the feasibility of three-dimensional (3D) CT cavernosography in the diagnosis of corporal veno-occlusive dysfunction. PATIENTS AND METHODS • The subjects were 55 patients who had failed to respond to phosphodiesterase type 5 inhibitors. We performed pharmacodynamic infusion cavernosometry and cavernosography, using 60 mg papaverine hydrochloride. • Cavernosography was performed at 90 mmHg intracavernous pressure, using a multi-slice CT scan system. The 3D images were reconstructed using aquarius net station, ver.2 computer software. • For comparison with conventional cavernosography, maximum intensity projection (MIP) images were used. A flow of 20 mL/min or being more capable of maintaining 90 mmHg of intracavernous pressure indicated veno-occlusive dysfunction. RESULTS • Forty-five of the 55 patients were diagnosed with corporal veno-occlusive dysfunction. 3D-CT cavernosography revealed drainage veins in all 45 cases, including cavernous veins, dorsal veins, crural veins and other emissary veins. • Compared with 3D-CT cavernosography, observing cavernous veins and the proximal part of the deep dorsal veins using MIP imaging was especially difficult because the origins of the penile veins are often behind the pelvic bone or cavernous body. • Of the patients who seemingly had leakage via the deep dorsal vein, 80.6% did not in fact have leakage via this vein, but had other leakages. The image resolution of 3D-CT cavernosography was significantly higher than that of MIP. CONCLUSION • 3D-CT cavernosography can provide high-resolution images of venous drainage from any angle. We conclude that the images obtained by 3D-CT cavernosography are very helpful for both the diagnosis of corporal veno-occlusive dysfunction and the anatomical study of the human penile venous system.

UMMARY The deep dural sinuses and the veins in the midline in 52 brains of children dying with myelomeningocele were examined. All of these vessels were very abnormal in each case. The abnormal features are described and discussed. When the cerebrospinal fluid pressure is elevated, the transverse sinuses seem to be compressed in children with myelomeningocele. The blood therefore is drained through the emissary veins and then by the skull veins. This explains why the skull veins are engorged with blood in these children in intracranial hypertension. The existence of a wide common facial vein is as easily understood. RESUME Les sinus duraux et les veines du milieu du cerveau dans le myelomeningocele Les sinus duraux profonds et les veines de la ligne mediane de 52 cervaux d'enfants morts avec un myelomeningocele ont ete examines. Tous les vaisseaux etaient tres anormaux dans tous les cas. Les anomalies sont decrites et discutees. Quand la pression du LCR est augmentee, les sinus transverses semblent comprimes chez I'enfant avec myelomeningocele. Le sang est alors draine par les veines emissaires puis les veines du crCne. Ceci explique que les veines du crCne soient remplies de sang chez ces enfants avec hypertension intra-cranienne. L'existence d'une veine faciale commune large est ainsi aisement comprise. ZUSAMMENFASSUNG Die Sinus der Dura und die Venen in der Mittellinie des Gehirns bei der Myelomeningocele Die tiefen Sinus der Dura und die Venen in der Mittellinie des Gehirns wurden bei 52 Kindern untersucht, die an einer Myelomeningocele gestorben waren. Alle diese Gefase waren in jedem Falle sehr abnorm. Die abnormen Erscheinungen werden beschrieben und diskutiert. Wenn der Druck des Liquors erhoht ist, scheinen die quer verlaufenden Sinus bei Kindern mit Myelomeningocele komprimiert zu werden. Das Blut flieBt deswegen uber die emissaren Venen und dann uber die SchUdelvenen ab. So erklart sich, warum die Schadel-venen bei diesen Kindern mit intracranieller Hypertonic mit Blut vollgestaut sind. Auch die Existenz einer erweiterten Vena facialis communis ist so leicht zu verstehen.

A brief general theory is proposed linking the transcephalic DC potential, which is recorded on the midline surface of the head over the frontal and occipital emissary veins, with a certain functional organization of the brain. From this it is proposed that interoceptive or protopathic afferents—carotid sinus, carotid body, vestibular, and visceral—should produce a positive frontal deflection, while exteroceptive or epicritic afferents—tactile, auditory, proprioceptive, gustatory, visual, and olfactory—should produce a negative frontal DC shift. It is proposed that hunger promotes a negative frontal base line, satiety a positive one, and anxiety increases the base-line variance of a group. A relationship is proposed between frontal negativity and body metabolic peaks. It is proposed that a noxious exteroceptive stimulus produces a positive frontal shift, despite its cortical projection. The hypotheses were tested using normal adult male Ss and good agreement between results and predictions was found.

Homozygous mutations in the fibroblast growth factor 3 (FGF3) gene have recently been discovered in an autosomal recessive form of syndromic deafness characterized by complete labyrinthine aplasia (Michel aplasia), microtia, and microdontia (OMIM 610706 - LAMM). In order to better characterize the phenotypic spectrum associated with FGF3 mutations, we sequenced the FGF3 gene in 10 unrelated families in which probands had congenital deafness associated with various inner ear anomalies, including Michel aplasia, with or without tooth or external ear anomalies. FGF3 sequence changes were not found in eight unrelated probands with isolated inner ear anomalies or with a cochlear malformation along with auricle and tooth anomalies. We identified two new homozygous FGF3 mutations, p.Leu6Pro (c.17T > C) and p. Ile85MetfsX15 (c.254delT), in four subjects from two unrelated families with LAMM. The p.Leu6Pro mutation occurred within the signal site of FGF3 and is predicted to impair its secretion. The c.254delT mutation results in truncation of FGF3. Both mutations completely co-segregated with the phenotype, and heterozygotes did not have any of the phenotypic findings of LAMM. Some affected children had large skin tags on the upper side of the auricles, which is a distinctive clinical component of the syndrome. Enlarged collateral emissary veins associated with stenosis of the jugular foramen were noted on computerized tomographies of most affected subjects with FGF3 mutations. However, similar venous anomalies were also detected in persons with non-syndromic Michel aplasia, suggesting that a direct causative role of impaired FGF3 signaling is unlikely.

Objective: The petrosquamosal sinus (PSS) is an emissary vein that connects the transverse sinus and the external jugular vein. Recent studies have shown that a PSS can be identified on high resolution CT scan when it is contained within a bony canal. The persistent PSS is a potential risk of bleeding in middle ear surgery. The aim of this study is to determine the prevalence of the PSS in patients with chronic otitis media.Method: Between February 2011 and January 2012, 61 ears (47 patients) underwent CT scan before surgery for chronic otitis media. Patients younger than 10 years, showing congenital temporal bone anomaly, and having received prior ear surgeries, were excluded. The prevalence of persistent PSS was evaluated using CT scan. During the same period, 66 ears (33 patients) with peripheral facial palsy underwent CT scan. The frequency of a PSS was also examined in these patients.Results: Among the 61 ears with chronic otitis media, a PSS was detected in 12 ears on CT scan (20.0%). Among them, th...

Objective: The petrosquamosal sinus (PSS) is an emissary vein that connects the transverse sinus and the external jugular vein. Recent studies have shown that a PSS can be identified on high resolution CT scan when it is contained within a bony canal. The persistent PSS is a potential risk of bleeding in middle ear surgery. The aim of this study is to determine the prevalence of the PSS in patients with chronic otitis media.

The orbitotemporal venous sinuses accompany the intracranial branches of the stapedial artery. These sinuses are large in primitive primates and drain the extensive territories supplied by the stapedial artery as well as the brain. The orbit is drained by a wide cranio-orbital sinus which empties into the postglenoid emissary vein. Also emptying into the postglenoid vein is the petrosquamous sinus. The latter diverts cerebral blood from the transverse sinus and also drains the temporalis muscle. Emptying into both the cranio-orbital and petrosquamous sinuses are meningeal tributaries, which drain the cranial side wall and the dura mater. The relatively small sinus communicans runs in the angle between the petrosal bone and the cranial side wall. It commences at the postglenoid vein and connects the distal end of the petrosquamous sinus to the pterygoid venous plexus. In humans, the orbitotemporal sinus system is greatly modified. Its remnants persist for the most part as “middle meningeal veins.” The system no longer drains the orbit, the temporal fossa, or the brain. The petrosquamous sinus becomes attenuated or obliterated along part or all of its length. The postglenoid vein vanishes. The cranio-orbital sinus is reduced in diameter and its connection to the orbit is feeble or absent. During development, the posterior end of the cranio-orbital sinus migrates inferiorly along the sinus communicans. In most individuals, this migration ceases at the foramen spinosum, site of the emissary vein of the sinus communicans. Meningeal tributaries are relatively large in humans, and drain principally into the cranio-orbital sinus or sphenoparietal sinus. The sphenoparietal sinus is an evolutionary novelty restricted to hominoids and is frequently developed in only Homo and Pongo. © Wiley-Liss, Inc.

• Retrospective review of medical and radiology records from databases of patients with CHARGE from three tertiary care academic medical centers. • Temporal bone CT of 20 patients with CHARGE were reviewed specifically to assess for venous malformations of the temporal bone. MRI was also viewed when available. Associated temporal bone abnormalities and clinical features were also noted. • Venous malformations of the temporal bone are a common feature in CHARGE that have not previously been appreciated. • While several case series have reported isolated venous anomalies in CHARGE patients, none have previously focused on defining the spectrum of these specific abnormalities and its implications in otologic surgery which these patients undergo. • In particular, collateral emissary veins of the temporal bone including posterior condylar veins, mastoid emissary veins connecting occipital or post auricular veins with the sigmoid sinus and petrosquamosal emissary veins of the temporal bone have been previously noted.6 • One report of patients with petrosquamosal sinuses included a 6-year old female with CHARGE. CT revealed inner ear anomalies and a hypoplastic jugular foramen noted on ipsilateral side of a transmastoid venous canal which joined the internal jugular vein.7 Others noted abnormalities in sigmoid sinus development and jugular bulb diverticulum.3,8 • Reports of skull base anomalies in CHARGE including abnormal basiocciput development and hypoplastic jugular foramen may suggest preceding developmental bony malformations leading to venous malformation, possibly as a compensatory response for required venous drainage.9,10 • Collateral emissary veins should be evaluated as part of the pre-operative assessment for cochlear implant surgery. CT of the temporal bone may reveal venous malformations that require pre-operative identification and possibly an altered surgical approach to mastoidectomy and/or cochleostomy as encountered in this series. • Such abnormalities may not be mentioned in the official radiologic report, so otologic surgeons must look specifically for these findings. Venous Malformations of the Temporal Bone: A common feature in CHARGE David R Friedmann, MD1 Lawrence R Lustig, MD3, John A Germiller MD, PhD5, Misha Amoils3 Christine M Glastonbury4, Bidyut K Pramanik MD2, Anil K Lalwani, MD1 1Department of Otolaryngology-Head & Neck Surgery and 2Department of Radiology, New York University School of Medicine, New York, NY 3Department of Otolaryngology-Head & Neck Surgery and 4Department of Radiology, University of California, San Francisco Medical Center, San Francisco, CA 5Department of Otorhinolaryngology, Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, PA

The TCDC/CO, hypothesis is that slowly changing potentials, source resistances and source currents, measured between electrodes placed over specific diploic/emissary vein distributions on the scalp, largely reflect regional differences in subelectrode CO2 concentrations which are in equilibrium with subjacent cortical differences in metabolism and CO2 production. Studies on humans show that TCDC parameters do show the expected relationships with the effects of regional differences in CO2 concentration. An explicit quantitative formulation of the hypothesis is developed based on the best available measures of all essential parameters, and it in shown that this model permits the correct computation of all TCDC empirical norms under essentially all conditions of measurement. Although it now appears that MIX studies have a substantial theoretical foundation it must be emphasized that the analysis in this paper is based on normative—i.e. averaged—values and cannot yet be applied to isolated TCDC measurements on single subjects.

Until 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.

The venous system of the head and neck of the opossum, Didelphis virginiana, was studied by injecting the veins with a tinctorial mass. Gross dissection spechmens injected with a colored gelatin solution and corrosion specimens prepared by Batson's technique (Batson, '55) were utilized to describe the venous pattern in greater detail than is presently available in the literature. The venous drainage of the superficial structures of the head is principally by way of the V. jugularis externa and its tributaries. Although small emissary veins connect the Sinus cavernosus with the Plexus pterygoideus and the V. maxillaris, the dural venous sinuses drain primarily into the Plexus vertebralis internus and into the V. maxillaris by way of the V. emissaria foraminis retroarticularis. The small V. jugularis interna receives minor connections from the Plexus pterygoideus, the Sinus cavernosus and the Sinus petrosus ventralis as well as anastomotic tributaries from the Plexus vertebralis and the plexus of veins around the hyoid bone. However, the V. jugularis interna serves mainly as a pathway for venous drainage from the deeper structures of the neck and only minimally for draining the brain.