Diagnostic pitfall: atypical cerebral venous drainage via the vertebral venous system

We report a case of atypical cerebral venous drainage in a 38-year-old woman with symptoms of benign paroxysmal positional vertigo. Thrombosis of the left internal jugular vein and sigmoid sinus was suspected on the basis of spin-echo and time-of-flight MR findings, but multisection CT angiograms showed a patent sigmoid sinus and predominant drainage via the emissary veins toward the vertebral plexus, with only a minor contribution of the jugular veins. This case illustrates the variability of the venous anatomy in the craniocervical region.     

The craniocervical venous system in relation to cerebral venous drainage

BACKGROUND AND PURPOSE: Passing from the supine to the upright position favors cerebral venous outflow into vertebral venous systems rather than into the internal jugular veins. We sought to determine venous connections between dural venous sinuses of the posterior cranial fossa and craniocervical vertebral venous systems. METHODS: Corrosion casts of the cranial and cervical venous system were obtained from 12 fresh human cadavers, and anatomic confirmation was made by dissection of three previously injected fresh human specimens. MR venography was performed to provide radiologic correlation. RESULTS: The lateral, posterior, and anterior condylar veins and the mastoid and occipital emissary veins were found to represent the venous connections between the dural venous sinuses of the posterior cranial fossa and the vertebral venous systems. This study revealed the nearly constant presence of the anterior condylar confluent (ACC) located on the external orifice of the canal of the hypoglossal nerve. The ACC offered multiple connections with the dural venous sinuses of the posterior cranial fossa, the internal jugular vein, and the vertebral venous system. All these structures were shown by MR venography. CONCLUSION: The lateral, posterior, and anterior condylar veins and the mastoid and occipital emissary veins connect the dural venous sinuses of the posterior cranial fossa with the vertebral venous systems. These connections are clinically relevant, because encephalic drainage occurs preferentially through the vertebral venous system in the upright position. The ACC is a constant anatomic structure that may play an important role in the redirection of cerebral blood in the craniocervical region.     

Venous structures at the craniocervical junction: anatomical variations evaluated by multidetector row CT

The aim of this study was to evaluate the anatomy of and normal variations in the craniocervical junction veins. We retrospectively reviewed 50 patients who underwent contrast-enhanced CT with a multidetector scanner. Axial and reconstructed images were evaluated by two neuroradiologists with special attention being paid to the existence and size of veins and their relationships with other venous branches around the craniocervical junction. The venous structures contributing to craniocervical junction venous drainage, including the inferior petrosal sinus (IPS), transverse-sigmoid sinus, jugular vein, condylar vein, marginal sinus and suboccipital cavernous sinus were well depicted in all cases. The occipital sinus (OS) was identified in 18 cases, including 4 cases of prominent-type OS. The IPS showed variations in drainage to the jugular vein through the jugular foramen or intraosseous course of occipital bone via the petroclival fissure. In all cases, the anterior condylar veins connected the anterior condylar confluence to the marginal sinus; however, a number of cases with asymmetry and agenesis in the posterior and lateral condylar veins were seen. The posterior condylar vein connected the suboccipital cavernous sinus to the sigmoid sinus or anterior condylar confluence. The posterior condylar canal in the occipital bone showed some differences, which were accompanied by variations in the posterior condylar veins. In conclusion, there are some anatomical variations in the venous structures of the craniocervical junction; knowledge of these differences is important for the diagnosis and treatment of skull base diseases. Contrast-enhanced CT using a multidetector scanner is useful for evaluating venous structures in the craniocervical junction.Intracranial veins and venous sinuses converge to form major dural sinuses, the transverse sinus and the sigmoid sinus, which drain into extracranial veins. These major dural sinuses are connected by other venous structures at the skull base. These venous structures form complex venous networks that drain intracranial venous flow into extracranial veins at the craniocervical junction [1]. These venous structures are also known to have an important role as collateral pathways in cases of venoocclusive disease. The typical relationships between the craniocervical junction veins are shown in Figure 1. Knowledge of the anatomical relationships and variations of these veins is necessary not only for radiological diagnosis, but also when considering surgical or endovascular treatment of skull base diseases. Some investigators have previously reported the anatomy of and variations in these veins using anatomical and radiological methods with conventional angiography or contrast-enhanced MRI [2–8]. CT has been recognised as inadequate for evaluations of the posterior fossa owing to artefacts from bony structures; however, recent applications of multidetector row CT (MDCT) enable us to evaluate the posterior fossa with thin-sectional axial images and/or three-dimensional reconstructed images. In this study, the venous structures at the craniocervical junction were evaluated using 32-channnel MDCT, focusing on anatomical variations.Open in a separate windowFigure 1Schematic drawing of the veins at the craniocervical junction. The inferior petrosal sinus (IPS) originates from the posterosuperior aspect of the cavernous sinus (CS), runs along the petroclival fissure and drains into the jugular bulb (JB). Basilar plexus (BP) lies on the clivus with connecting bilateral IPS. The anterior condylar vein (ACV) and lateral condylar vein (LCV) originate from the medial aspect of the JB, forming an anterior condylar confluence (ACC). ACV runs medially through the hypoglossal canal (HGC) and drains into the lateral part of the marginal sinus (MS). MS is contiguous to the medial part of the suboccipital cavernous sinus (SCS). LCV runs posterolaterally and flows into SCS. The posterior condylar vein (PCV) originates from the sigmoid sinus (SS), runs through the posterior condylar canal (PCC) and flows into SCS. SCS lies under the occipital bone surrounding the horizontal portion of the vertebral artery. The occipital sinus (OS) originates from the torcular herophili, confluence of transverse sinus (TS) and straight sinus and drains into the posterior part of MS. MS is the round-shaped sinus surrounding the foramen magnum. MS and the medial part of SCS are connected to the internal vertebral venous plexus (IVVP).     

Why should we report posterior fossa emissary veins?

Posterior fossa emissary veins are valveless veins that pass through cranial apertures. They participate in extracranial venous drainage of the posterior fossa dural sinuses. The mastoid emissary vein, condylar veins, occipital emissary vein, and petrosquamosal sinus are the major posterior fossa emissary veins. We believe that posterior fossa emissary veins can be detected by radiologists before surgery with a thorough understanding of their anatomy. Describing them using temporal bone computed tomography (CT), CT angiography, and cerebral magnetic resonance (MR) venography examinations results in more detailed and accurate preoperative radiological interpretation and has clinical importance. This pictorial essay reviews the anatomy of the major and clinically relevant posterior fossa emissary veins using high-resolution CT, CT angiography, and MR venography images and discusses the clinical importance of reporting these vascular variants.Posterior fossa emissary veins pass through cranial apertures and participate in extracranial venous drainage of the posterior fossa dural sinuses. These emissary veins are usually small and asymptomatic in healthy people. They protect the brain from increases in intracranial pressure in patients with lesions of the neck or skull base and obstructed internal jugular veins (1). They also help to cool venous blood circulating through cephalic structures (2). Emissary veins may be enlarged in patients with high-flow vascular malformations or severe hypoplasia or aplasia of the jugular veins. They are associated with craniofacial syndromes (1, 3). Dilated emissary veins may cause tinnitus (4, 5).We aim to emphasize the importance of reporting posterior fossa emissary veins prior to surgeries that are related to the posterior fossa and mastoid region. Here, we review their embryology and anatomy based on high-resolution computed tomography (CT), CT angiography, and magnetic resonance (MR) venography images.     

静脉性脑梗死MR影像特点

目的回顾总结静脉性脑梗死MRI及MRV影像表现,旨在提高影像诊断水平。方法对15例静脉性脑梗死的MR表现进行了回顾性分析,其中9例临床治疗后复查MR表现明显好转,临床症状明显改善。15例均行常规MRI平扫,其中9例同时进行MR增强及3DCE-MRV,6例行2DTOF MRV。结果 15例脑内多发病灶9例,单发病灶6例,其中2例脑梗死伴出血改变。15例中发生于额叶4例,顶叶6例,颞叶3例,枕叶1例,小脑1例。静脉栓塞部位11例为上矢状窦,1例直窦及左横窦,1例右侧横窦及乙状窦,2例皮层大脑浅静脉。9例行增强扫描,5例病灶内不规则强化,2例脑膜强化,3例无强化.7例MRV均显示栓塞的静脉血流信号丢失或缺损,3例出现异常静脉侧支或引流静脉异常扩张。结论静脉性脑梗死MR影像表现具有特征性,MRI结合MRV可以作为首选的无创检查方法,对静脉栓塞早期诊断和治疗有重要作用。     

Intracranial MR venography in children: normal anatomy and variations

BACKGROUND AND PURPOSE: Little information is available regarding the anatomy of the intracranial veins and sinuses that can be shown on MR venograms of children. The aim of this study was to determine the normal venous anatomy and anatomic variants. METHODS: Fifty children who were referred for investigation of developmental delay and who had normal results of MR imaging of the brain were recruited into the study. The cerebral veins and sinuses, including the occipital sinuses, were assessed by using 2D time-of-flight venography. Particular attention was paid to the anatomy of the venous confluence. RESULTS: Twenty-seven cases had dominant right transverse sinuses, 18 had dominant left transverse sinuses, four had co-dominant transverse sinuses, and one had absence of both transverse sinuses. In 21 (51%) of 41 cases without occipital sinuses, absent or hypoplastic transverse sinuses were found. Nine patients had occipital sinuses. Five (56%) of nine patients with occipital sinuses were younger than 2 years, and patients younger than 2 years accounted for 24% of all patients (12 of 50 patients) in the study. In six (67%) of nine patients with occipital sinuses, absent or hypoplastic transverse sinuses were shown. Two patients had bulbous prominence of the vein of Galen. One had foreshortened superior sagittal sinus, which in turn is drained by two paramedian cortical veins. CONCLUSION: Understanding the normal anatomy of the cerebral venous system and its variants by using MR venography in children provided the background to future studies on anomalous venous structure in malformations of the brain.     

Variations of Intracranial Dural Venous Sinus Diameters from Birth to 20 Years of Age: An MRV-Based Study

BACKGROUND AND PURPOSE:The role of the dural venous sinus system in cerebrovascular pathology and the understanding of normal developmental patterns and sizes of the dural venous sinus system continue to expand. The purpose of this study was to review MR venograms to elucidate developmental patterns and diameters of the major dural venous sinuses from 0 to 20 years of age.MATERIALS AND METHODS:All available MR venograms of patients 0–20  years of age who presented to our institution were retrospectively reviewed. Patient age at the time of image acquisition was noted, and measurements were taken of the diameters of the major dural venous sinuses. The presence of embryonic sinuses including the persistent falcine sinus and the occipital sinus was noted. Dominance patterns of the transverse sinus system were determined. Mean diameters of each sinus were plotted as a function of age. The prevalence of persistent prenatal sinuses and transverse sinus–dominance patterns was compared across ages.RESULTS:A total of 429 MR venograms from 429 patients were reviewed. All dural venous sinuses demonstrated a maximal growth rate from 0 to 7 years of age and reached maximal diameters around 5–10 years of age. The prevalence of falcine sinuses and occipital sinuses trended downward across increasing age categories (P = .09 and, <.0001, respectively).CONCLUSIONS:Dural venous sinuses demonstrate maximal growth between 0 and 7 years of age and reach adult size around 5–10 years of age. Involution of the prenatal sinuses continues to take place after birth into childhood but is largely absent in early adulthood.

Evidence continues to accumulate supporting the idea that the dural venous sinus (DVS) system is a plastic, active player in cerebrovascular pathology rather than a fixed and immutable entity.^1,2 As the role that the DVS system plays in cerebrovascular disease continues to expand, an understanding of the normal developmental patterns of the DVS system becomes increasingly important. The fixed anatomy of the DVS system and the prevalence of certain anatomic variations are relatively well-understood.^3,4 The developmental patterns of individual components of the DVS system from birth into adulthood, however, remain relatively unknown. This study consisted of the following 4 objectives: 1) to elucidate the growth patterns of each dural venous sinus from birth to 20 years of age, 2) to compare the mean size of each dural venous sinus among ages, 3) to compare the prevalence of persistent prenatal sinuses among ages, and 4) to determine the prevalence of transverse sinus–dominance patterns among ages.     

Cerebral MR venography in children: comparison of 2D time-of-flight and gadolinium-enhanced 3D gradient-echo techniques

PURPOSE: To prospectively compare two-dimensional (2D) time-of-flight cerebral magnetic resonance (MR) venography with gadolinium-enhanced three-dimensional (3D) gradient-echo cerebral MR venography in children. MATERIALS AND METHODS: This investigation had investigational review board approval and was Health Insurance Portability and Accountability Act compliant; parental informed consent was obtained. Thirty-seven patients (20 boys, 17 girls) who ranged in age from 4 days to 15 years underwent 2D and 3D MR venography. Two pediatric neuroradiologists compared the visibility of the superior sagittal, straight, transverse, and sigmoid sinuses and the internal jugular veins on images obtained with the two sequences. RESULTS: In 17 (46%) of the 37 patients, the sequences were equivalent in terms of their depiction of venous anatomy. In 19 (51%) of the 37 patients, 3D MR venography was superior to 2D MR venography. Suboptimal enhancement of veins occurred in one (3%) patient at 3D MR venography. Venous anomalies suggested at 2D MR venography but not present at 3D MR venography included flow gaps in the nondominant transverse sinuses of four patients, unilateral transverse sinus atresia in eight, and a narrowed superior sagittal sinus in two. Two-dimensional MR venography results failed to reveal a persistent falcine sinus associated with straight sinus atresia in one patient and suggested transverse sinus thrombosis in two patients in whom 3D MR venography results were normal. Additionally, the extent of dural thrombosis was overestimated at 2D MR venography in one patient. As compared with 3D MR venography, 2D MR venography failed to reveal sigmoid sinus stenosis in one patient and poorly depicted posterior fossa dural sinus anatomy in two patients with dural arteriovenous fistula. CONCLUSION: Three-dimensional MR venography is often superior to 2D MR venography in the delineation of major cerebral venous structures in children. Most of the artifactual loss of vascular signal seen with the use of 2D MR venography occurred in nondominant transverse sinuses.     

Cerebral MR venography: normal anatomy and potential diagnostic pitfalls

BACKGROUND AND PURPOSE: MR venography is often used to examine the intracranial venous system, particularly in the evaluation of dural sinus thrombosis. The purpose of this study was to evaluate the use of MR venography in the depiction of the normal intracranial venous anatomy and its variants, to assess its potential pitfalls in the diagnosis of dural venous sinus thrombosis, and to compare the findings with those of conventional catheter angiography. METHODS: Cerebral MR venograms obtained in 100 persons with normal MR imaging studies were reviewed to determine the presence or absence of the dural sinuses and major intracranial veins. RESULTS: Systematic review of the 100 cases revealed transverse sinus flow gaps in 31% of the cases, with 90% of these occurring in the nondominant transverse sinus and 10% in the codominant transverse sinuses. No flow gaps occurred in the dominant transverse sinuses. The superior sagittal and straight sinuses were seen in every venogram; the occipital sinus was seen in only 10%. The vein of Galen and internal cerebral veins were also seen in every case; the basal veins of Rosenthal were present in 91%. CONCLUSIONS: Transverse sinus flow gaps can be observed in as many as 31% of patients with normal MR imaging findings; these gaps should not be mistaken for dural sinus thrombosis.     

Transtemporal power- and frequency-based color-coded duplex sonography of cerebral veins and sinuses.

PURPOSETo determine the ability of transtemporal power- and frequency-based transcranial color-coded duplex sonography to aid in the assessment of cerebral veins and sinuses, as well as to provide reference data for flow direction and velocity.METHODSUsing a color duplex device equipped with a 2.0/2.5-MHz sector scan, we insonated 120 healthy volunteers and three patients with cerebral venous thrombosis.RESULTSIn subjects 20 to 59 years old, deep middle cerebral veins were identified in 88%, basal veins in 97%, straight sinuses in 60%, and transverse sinuses in 42%. The corresponding values for subjects 60 to 79 years old were 53%, 86%, 23%, and 20%, respectively. Velocities were highest in transverse and straight sinuses, slower in basal veins, and slowest in deep middle cerebral veins. Flow was directed lateromedially in the deep middle cerebral vein, rostrocaudally in the basal vein and straight sinus, and mediolaterally in the transverse sinus. Two patients with straight sinus thromboses showed reversed flow direction in the basal veins, and one patient with superior sagittal sinus thrombosis showed elevated velocities in a deep middle cerebral vein.CONCLUSIONTranstemporal power- and frequency-based color-coded duplex sonography enabled imaging and velocity measurements in deep cerebral veins in subjects 20 to 59 years old, but detection of the straight and transverse sinuses was low. In older subjects, only the basal vein was regularly assessed.     

3D-CE MRA、2D-TOF MRA对颅内静脉窦血栓的诊断价值比较

目的比较3D—CEMRA和2D—TOFMRA对颅内静脉窦血栓的诊断价值。资料与方法8例经临床及影像学随访证实的颅内静脉窦血栓患者及8例健康志愿者分别行3D—CEMRA和2D—TOFMRA检查。由两名放射学医师共同回顾性阅片取得一致意见,病变组分别比较两种MRA技术单独应用MIP和MIP联合MPR、CPR及原始图像对血栓部位、血栓范围、窦腔闭塞及侧支静脉的检出率。对照组仅在MIP和原始图像上观察颅内静脉走行形态、信号强度。结果血栓共累及了20处颅内静脉窦,其中上矢状窦7处,窦汇区、左侧乙状窦及左侧横窦各2处,右侧横窦、右侧乙状窦各3处,右侧颈静脉球1处。在显示颅内静脉窦血栓范围、窦腔闭塞程度及侧支静脉方面,3D—CEMRA优于2D．TOFMRA（P值均〈0．01）。3D—CEMRA采用MIP联合MPR、CPR及原始图像优于单独采用MIP（P值〈0．01）。2D—TOFMRA采用MIP联合MPR、CPR及原始图像和单独采用MIP比较,二者并无明显差异（P值〉0．01）。结论对颅内静脉窦血栓的评价,3D—CEMRA优于2D—TOFMRA,多种后处理技术的联合应用能更好显示血栓的范围、窦腔闭塞的程度和侧支静脉循环。     

The dural venous sinuses: normal intraluminal architecture defined on contrast-enhanced MR venography

Introduction Our objective was to define the appearance and distribution of normally occurring intraluminal structures within the dural venous sinuses on contrast-enhanced MR venography (CE-MRV). Methods Informed consent was obtained from all subjects participating in the study, and the study protocol was approved by the institutional review board of the University Health Network. A group of 56 patients underwent CE-MRV. Intraluminal structures were categorized as an arachnoid granulation (AG) or trabeculation (Willis cord). Willis cords within the transverse and sigmoid sinuses as well as AGs 4 mm or more in size were recorded. Results In 20 of the 56 patients (36%), 29 AGs measuring 4 mm or more were identified within the dural sinuses. All AGs were spherical or ovoid and occurred at sites where a cortical vein joined a dural sinus. Nearly all AGs (28 of 29, 97%) displayed an eccentric internal vein. Willis cords were seen within the superior sagittal sinus in all patients. Willis cords were less prevalent in the remaining dural sinuses. A minimum of one Willis cord was seen in 58 of the 112 transverse sinuses (52%). These cords were 1–2 mm in maximal thickness, uniformly smooth, and commonly partitioned the sinus. Willis cords and AGs (of any size) were not encountered within the sigmoid sinuses or jugular veins. Conclusion CE-MRV elucidates structures normally found within the dural sinuses. These consist of AGs and Willis cords. This report confirms and establishes new criteria for identification of these normally occurring intraluminal structures providing a basis for their differentiation from pathologic entities.     

Arachnoid granulations in the transverse and sigmoid sinuses: CT,MR, and MR angiographic appearance of a normal anatomic variation.

PURPOSETo investigate the imaging characteristics, prevalence, and clinical significance of arachnoid granulations in the transverse and sigmoid venous sinuses.METHODSWe reviewed the imaging findings, clinical signs and symptoms, final diagnoses, and follow-up studies of 32 patients with 41 probable arachnoid granulations.RESULTSOn CT scans, arachnoid granulations appear as well-defined filling defects, wholly or partly within a venous sinus, with the same density as cerebrospinal fluid. MR images show these entities as largely isointense with cerebrospinal fluid in all sequences. Linear variations of signal intensity within the granulations are thought to be fibrous septa or vessels. Calcification was present in 3 granulations and altered both CT density and MR signal intensity. The granulations appear as filling defects at MR angiography and at digital subtraction angiography. In some oblique MR angiographic projections, they appear elliptical and could be mistaken for thrombus. No clinical significance could be given to the existence of any of these arachnoid granulations. They occur in 0.3 to 1 of 100 adults in the population.CONCLUSIONArachnoid granulations in the transverse and sigmoid venous sinuses are common findings seen with thin-section imaging and are usually of no significance.     

Anomalous intracranial venous drainage associated with basal ganglia calcification

We describe the neuroradiologic findings in a 7-year-old boy with anomalous intracranial venous drainage and cerebral calcification. CT scans demonstrated that his scalp mass was a plexus of scalp veins filled through the emissary foramen, and there were cerebral calcifications. Angiography revealed bilateral sigmoid sinus atresia with most of the intracranial venous drainage via the prominent mastoid emissary veins into dilated scalp vein. The possible relationship between cerebral calcification and anomalous intracranial venous drainage is discussed.     

Vascular anomalies, sutures and small canals of the temporal bone on axial CT

PURPOSE: Subtle bony structures, small canals and fine sutures cause sometimes problems in the analysis of CTs of the temporal bone. The aim of this study was: to analyze the visibility of subtle structures and to estimate the incidence of vascular anomalies. PATIENTS AND METHOD: We retrospectively analyzed axial scans of 223 high-resolution CTs of the temporal bone obtained as single slice or spiral CT with 1mm slice thickness. All CTs had clinical indications. Two experienced radiologists studied CTs regarding the visibility of the fine sutures, fissures and small canals and the occurrence of vascular anomalies. RESULTS: The following structures were seen commonly: sphenosquamosal suture (76%), arcuate artery canal (93%), vestibular aqueduct (89%), mastoid emissary vein (82%), singular canal (56%). Not so commonly were observed: tympanosquamosal suture (31%), mastoid canaliculus (28%), lateral sigmoid sinus (28%), petrotympanic fissure (24%), tympanomastoid suture (10%). Seldom we identified: the inferior tympanic canaliculus (6%), high jugular bulb (6%), anterior sigmoid sinus (5%), dehiscent internal carotid artery canal (2%), persistent petrosquamosal sinus (1%), dehiscent jugular bulb (1%). Persistent stapedial artery, aberrant internal carotid artery, dehiscent jugular bulb, high jugular bulb with diverticulum, anterior and dehiscent sigmoid sinus were detected in below 1% of the analyzed temporal bones. The frequency of asymmetry of the jugular foramen, which varied between 3% and 42%, depended on different criterions of size. CONCLUSION: A profound knowledge of normal anatomy and anomalies of the temporal bone avoids misinterpretation as pathological lesions and iatrogenic bleedings.     

MR venography in the pediatric patient

BACKGROUND AND PURPOSE: Little is known about age-related changes in posterior fossa venous anatomy on 2D time-of-flight MR venography (MRV) or about artifacts that limit its accuracy in diagnosing venous occlusive disease. We evaluated pediatric appearances of posterior fossa venous drainage. METHODS: One hundred and eight children with normal MR imaging or minimal congenital anomalies underwent 2D MRV. Transverse sinus dominance and absence and the presence of an occipital sinus were correlated with age. Venous structure conspicuity was compared on source and maximum intensity projection images. RESULTS: Right, left, and codominance of the transverse sinus, respectively, was as follows: at < 25 months, 37%, 21%, and 42%; 25 months to 5 years, 35%, 30%, 35%; and > or =6 years, 50%, 16%, 34%. Transverse sinus dominance was not related to age between the three groups (P=.58, chi-square contingency), but some relationship was observed when patients <6 years were compared to those > or =6 years (P=.032). Chi-square trends showed a mildly positive correlation between age and an absent transverse sinus (P=.026) and a decreasing trend in the presence of an occipital sinus with age (P=.038). Saturation effects due to in-plane/slow flow were worse in patients <25 months; effects in the transverse sinuses or internal jugular veins were miminized with coronal or axial imaging, respectively. CONCLUSION: 2D TOF MRV shows age-related changes in venous anatomy. Caution should be used before posterior fossa venous occlusive disease is diagnosed on the basis of signal intensity loss, especially in neonates and young infants.     

MR imaging of transverse/sigmoid dural sinus and jugular vein thrombosis

Magnetic resonance (MR) imaging was performed on six patients with thrombosis involving the transverse/sigmoid sinus and jugular bulb/vein. Venographic confirmation was obtained in five cases. Thrombi were characterized by increased intraluminal signal on all planes of section and pulse sequences. The change in signal intensity from first to second echo for thrombi was qualitatively less than that found with slow flow. Partial thrombosis in one case was seen as a ring pattern of central intermediate intensity corresponding to the thrombus, surrounded by a peripheral ring of signal void related to flowing blood. The MR findings closely correlated with venography in predicting thrombosis. Evidence of thrombi was not available from CT. Magnetic resonance is well suited for the diagnosis of occlusive disease of the dural venous sinus and jugular bulb.     

2D time-of-flight MR venography in neonates: anatomy and pitfalls

BACKGROUND AND PURPOSE: The dural venous sinuses in neonates differ from those in adults or older children in that the caliber of venous sinuses is smaller and there is skull molding. The aim of this retrospective study is to evaluate the presence of flow gaps in venous sinuses in neonates on 2D time-of-flight (TOF) MR venography (MRV). METHODS: Fifty-one neonates underwent coronal 2D TOF MRV. Nine also had CT venography (CTV) for comparison. In 1 neonate, a further 2D TOF MRV was performed in the sagittal plane; in another neonate, images were captured in the axial plane; and in another, a further coronal TOF MRV with shorter echo time was performed. RESULTS: Flow gap was seen in the posterior aspect of the superior sagittal sinus in 35 of 51 (69%). Focal narrowing of the superior sagittal sinus, in the region of convergence of lambdoid sutures, was detected in 7 of 51 (14%). The right and left transverse sinuses demonstrated flow gap in 13 of 51 (25%) and 32 of 51 (63%) respectively. There was normal filling of contrast on CTV in the superior sagittal sinus, transverse sinus and sigmoid sinus in those cases with flow gap detected on coronal 2D TOF MRV. Right, left, and codominance of the transverse sinuses are as follows: 32 of 51 (63%), 5 of 51 (10%), and 14 of 51 (27%), respectively. The right and left sigmoid sinuses demonstrated flow gap in 7 of 51 (14%) and 8 of 51 (16%), respectively, and the left sigmoid sinus was absent in 1 of 51 (2%). CONCLUSION: The high proportion of flow gap in the venous sinuses of neonates, particularly of the superior sagittal sinus, could be attributed to the smaller caliber venous sinuses, slower venous flow, and skull molding.     

An unusual dural arterio venous fistula in an infant

Dural arteriovenous fistula, (AVF), a rare entity, presents most commonly in adults. An 11-month-old boy presented with symptoms of congenital toxoplasmosis associated with an extensive dural AVF of the torcular Herophili and bilateral occulusion of the transverse and sigmoid sinuses. His intracranial venous drainage had become rerouted via the cavernous sinuses to the ophthalmic veins. The relationship of toxoplasmosis and sinus thrombosis to the pathogenesis of dural AVF and their clinical and radiological features are discussed.     

Craniocervical junction venous anatomy on enhanced MR images: the suboccipital cavernous sinus.

BACKGROUND AND PURPOSE: The suboccipital cavernous sinus, a vertebral venous plexus surrounding the horizontal portion of the vertebral artery at the skull base, provides an alternative pathway of cranial venous drainage by virtue of its connections to the cranial dural sinuses, the vertebral venous plexus, and the jugular venous system. Knowledge of the anatomy of this system facilitates interpretation of images and might reduce the number of false-positive diagnoses of lesions, such as adenopathy or schwannoma. We hypothesized that this circulation could be visualized on contrast-enhanced, fat-suppressed T1-weighted MR images. METHODS: The craniocervical junctions of 14 patients were scanned using fat-suppressed, contrast-enhanced, T1-weighted MR sequences and evaluated for visibility of the following venous structures: suboccipital cavernous sinus, vertebral artery venous plexus, anterior and posterior condylar veins, vertebral venous plexus, internal jugular vein, and the marginal sinus. Both the right and left sides were assessed in at least two planes. The venous diameters were also measured. RESULTS: All the evaluated venous structures were seen routinely in all three planes, with the exception of the posterior condylar vein, known to be variably present, which was seen only one third of the time in the sagittal plane and two thirds of the time in the other planes. The posterior condylar vein also showed the greatest variability in size and symmetry. CONCLUSION: The suboccipital cavernous sinus and most of its associated venous circulation at the skull base are easily identified on contrast-enhanced, fat-suppressed T1-weighted MR images. The posterior condylar vein, known to be variably present, was not well seen in the sagittal plane and displayed the greatest variability in size and symmetry.