Published online before print April 28, 2005, 10.1148/radiol.2353041427
(Radiology 2005;235:1011-1017.)
© RSNA, 2005
Cerebral MR Venography in Children: Comparison of 2D Time-of-Flight and Gadolinium-enhanced 3D Gradient-Echo Techniques1
Nancy Rollins, MD,
Claro Ison, MD,
Tony Reyes, RT and
Jon Chia, MS
1 From the Departments of Radiology, Children’s Medical Center (N.R., C.I., T.R.) and University of Texas Southwestern Medical School (N.R.), 1935 Motor St, Dallas, TX 75235; and Philips Medical Systems, Best, the Netherlands (J.C.). Received August 16, 2004; revision requested October 21; revision received October 27; accepted November 22. Address correspondence to N.R. (e-mail: nancy.rollins@childrens.com).
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ABSTRACT
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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.
© RSNA, 2005
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INTRODUCTION
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The major veins draining the brain are often studied by using a two-dimensional (2D) time-of-flight magnetic resonance (MR) venography sequence (1,2). However, the depiction of smaller venous structures and venous structures that have slower flow may be limited by saturation effects (1–3). Relatively recent reports (4–7) suggest that gadolinium-enhanced three-dimensional (3D) MR venography may be superior to 2D MR venography in the depiction of normal dural venous anatomy, thrombotic disease, and nonthrombotic venous stenoses in adults. Thus, the purpose of our study was to prospectively compare 2D time-of-flight cerebral MR venography with gadolinium-enhanced 3D gradient-echo MR venography in children.
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MATERIALS AND METHODS
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This prospective study was approved by the investigational review board of the University of Texas Southwestern Medical School. Parental informed consent was obtained, and the study conformed to Health Insurance Portability and Accountability Act guidelines. Although technical support for optimization of the protocols used to perform MR venography was provided by an author (J.C.) who is an employee of Philips Medical Systems, the other authors controlled the inclusion of all data and the conclusions reached. There was no financial support for this investigation. Thirty-seven patients (20 boys and 17 girls) who ranged in age from 4 days to 15 years (mean age, 4.6 years) and who had been referred for MR imaging underwent both 2D and 3D MR venography. There was a myriad of clinical indications for MR imaging; no patient underwent MR imaging solely for the purpose of obtaining the MR venography data. The most common indications were seizures (in eight patients) and chronic recurrent headache (in seven patients); four of the seven patients with headache had pseudotumor cerebri. Five patients had macrocephaly or known hydrocephalus, five had an intracranial tumor or had previously undergone resection of an intracranial tumor, and four had an intracranial vascular malformation. Closed head injury and mastoiditis were clinical indications in three patients each, one patient had a tongue mass, and one had neuroblastoma and was suspected of having dural metastases.
MR Imaging
MR imaging was performed with superconducting 1.5-T MR units (Intera Version 9.0; Philips, Best, the Netherlands) and standard head coils. Routine MR imaging included the following sequences: sagittal and transverse T1-weighted spin echo (repetition time msec/echo time msec, 450/11; number of signals acquired, two), transverse and/or coronal T2-weighted fast spin echo (3200–4500/90–120; number of signals acquired, three to four), and transverse fluid-attenuated inversion recovery (repetition time msec/echo time msec/inversion time msec, 8000/120/2300). Other pulse sequences were performed as clinically indicated. Two-dimensional MR venography was performed in the coronal plane by using the following parameters: 23/5.1; flip angle, 50°; section thickness, 2 mm; gap, –0.6 mm; matrix, 320 x 512; and field of view, 24 cm with a caudal saturation slab. Image acquisition time was 4 minutes 12 seconds.
Three-dimensional MR venography was timed to achieve maximum enhancement of major venous structures. The dose of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) was 0.2 milliliters per kilogram of body weight. In patients with an indwelling inserted central line or peripheral intravenous line smaller than 21 g, the contrast agent was manually injected as fast as possible. When feasible, the contrast agent was injected with a power injector (Spectris; Medrad, Indianola, Pa) at a rate of 2 mL/sec. A 10–20-mL flush of normal saline followed the contrast agent injection. A fluoroscopically triggered 2D sequence (3.7/1.04; flip angle, 40°; section thickness, 8 cm; field of view, 30 cm) was performed in the sagittal plane during injection of the gadolinium chelate. When the gadolinium chelate was visually detected in the sagittal sinus by the technologist (T.R.), the coronal 3D gradient-echo sequence was initiated with the following parameters: 6.0/2.0; flip angle, 35°; matrix, 320 x 512; field of view, 24 cm; 0.8-mm overcontiguous sections with segmented central k-space ordering; and image acquisition time, 2 minutes 11 seconds.
Image Interpretation
Maximum intensity projections (MIPs) were created at the MR operator console for 2D and 3D MR venography data sets. The MIP images were viewed in the sagittal, transverse, and coronal planes by two pediatric neuroradiologists (N.R. and C.I., working in consensus) with 18 and 2 years of experience, respectively. Images were interpreted on commercially available Sun Microsystems (Santa Clara, Calif) software–based picture archiving and communication system workstations (Magic View Version 42B; Siemens, Erlangen, Germany). Source data from 3D MR venography were transferred to a commercially available 3D workstation (Easy Vision, Philips; or Vitrea Version 3.2.4, Vital Images, Plymouth, Minn) for creation of shaded surface renderings.
The continuity and visibility of the superior sagittal, transverse, sigmoid, and straight sinuses and the internal jugular veins (IJVs) were compared between the 2D and the 3D MR venograms. When an area of signal loss or luminal narrowing was seen equally well with both sequences, the 2D and 3D MR venograms were judged as equal. When 2D MR venograms suggested an area of signal loss or absence of a venous structure but 3D MR venograms showed a patent and continuous corresponding venous structure, the 3D MR venograms were judged to be superior. When narrowing of a venous structure was qualitatively more severe on the 2D MR venograms than on the 3D MR venograms, the 3D MR venograms were judged to be superior. When enhancement of regional vascular structures impeded visualization of a major cerebral vein on the 3D MR venograms but the venous structure was clearly seen on the 2D MR venograms, the 2D MR venograms were considered to be superior.
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RESULTS
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In the Table, the findings at 2D MR venography are compared with those at 3D MR venography. In 17 (46%) of 37 patients, venous anatomy was normal and depicted equally well with both techniques. The superior sagittal sinus, the straight sinus, the transverse sinus, and the sigmoid sinus were patent and continuous, as were the IJVs. In one patient, there was suboptimal enhancement of the venous structures, and 2D MR venography was considered to be superior to 3D MR venography in this case. In 19 patients (51%), 2D MR venography results suggested variations in venous anatomy or venous disease that were not confirmed with 3D MR venography. Areas of signal loss referred to as flow gaps (3) were seen in a transverse sinus at 2D MR venography in four patients with otherwise normal venous anatomy (Fig 1a); such flow gaps were within the nondominant transverse sinus in three of the four patients. In these four patients, 3D MR venography results indicated that the transverse sinuses were patent and continuous (Fig 1b).
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Figure 1a. Artifactual loss of signal intensity (flow gap) seen within a nondominant transverse sinus at 2D MR venography in 10-year-old girl. (a) Coronal MIP from 2D time-of-flight MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows a left dominant transverse sinus. There is a flow gap (arrow) within the right nondominant transverse sinus. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows no flow gap within the right transverse sinus.
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Figure 1b. Artifactual loss of signal intensity (flow gap) seen within a nondominant transverse sinus at 2D MR venography in 10-year-old girl. (a) Coronal MIP from 2D time-of-flight MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows a left dominant transverse sinus. There is a flow gap (arrow) within the right nondominant transverse sinus. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows no flow gap within the right transverse sinus.
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One patient had congenital absence of both transverse sinuses with small sigmoid sinuses; venous drainage occurred via a large occipital sinus (Fig 2). In this patient, 2D MR venography and 3D MR venography were considered to be equivalent in depicting venous anatomy, although the level of confidence with which the diagnosis of congenital absence of the transverse sinuses was made was considerably higher at 3D MR venography. Moreover, fenestration of the straight sinuses was most conspicuous on the shaded surface rendering from the 3D MR venography data set, and the possibility of thrombus within the torcula was excluded.
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Figure 2a. Congenital absence of transverse sinuses in 13-year-old boy. (a) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows large occipital sinus (thick arrow). There are no transverse sinuses. Small sigmoid sinuses (thin arrows) are seen. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows occipital sinus (short arrow). Note the fenestrated distal straight sinus (long arrow). (c) On posterior projection from the shaded surface rendering in b, the fenestration (long arrow) is better seen. Short arrow indicates occipital sinus.
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Figure 2b. Congenital absence of transverse sinuses in 13-year-old boy. (a) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows large occipital sinus (thick arrow). There are no transverse sinuses. Small sigmoid sinuses (thin arrows) are seen. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows occipital sinus (short arrow). Note the fenestrated distal straight sinus (long arrow). (c) On posterior projection from the shaded surface rendering in b, the fenestration (long arrow) is better seen. Short arrow indicates occipital sinus.
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Figure 2c. Congenital absence of transverse sinuses in 13-year-old boy. (a) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows large occipital sinus (thick arrow). There are no transverse sinuses. Small sigmoid sinuses (thin arrows) are seen. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows occipital sinus (short arrow). Note the fenestrated distal straight sinus (long arrow). (c) On posterior projection from the shaded surface rendering in b, the fenestration (long arrow) is better seen. Short arrow indicates occipital sinus.
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In two other patients, 2D MR venography failed to reveal the persistent occipital sinuses that were seen at 3D MR venography. In eight patients, 2D MR venography results suggested absence of a transverse sinus but 3D MR venography results indicated that these sinuses were hypoplastic but patent (Fig 3). In addition to suggesting absence of a transverse sinus in two of the four neonates evaluated (ie, patients 2 and 3), 2D MR venography results did not fully depict the caliber of the posterior third of the superior sagittal sinus in these two neonates (Fig 4). In another neonate (patient 21), no straight sinus was seen at 2D MR venography; 3D MR venography revealed a persistent falcine sinus and hypoplasia of the straight sinus (Fig 5).
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Figure 3a. Inability to distinguish transverse sinus atresia from hypoplasia with 2D MR venography in 3-year-old boy. (a) On coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set, the left transverse sinus (arrow) is not seen. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows a small-caliber left transverse sinus (arrow).
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Figure 3b. Inability to distinguish transverse sinus atresia from hypoplasia with 2D MR venography in 3-year-old boy. (a) On coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set, the left transverse sinus (arrow) is not seen. (b) Coronal shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows a small-caliber left transverse sinus (arrow).
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Figure 4a. Artifactual loss of signal intensity within superior sagittal sinus at 2D MR venography in 4-month-old boy. (a) On sagittal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set, the posterior aspect (arrows) of the superior sagittal sinus is not seen owing to in-plane flow. (b) On sagittal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set, the superior sagittal sinus is patent. The apparent filling defect (curved arrow) is due to a high bifurcation of the superior sagittal sinus. Note the inferior sagittal sinus (short arrows), improved visualization of the internal cerebral veins (long arrow), and the normal bulbous appearance of the vein of Galen (arrowhead).
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Figure 4b. Artifactual loss of signal intensity within superior sagittal sinus at 2D MR venography in 4-month-old boy. (a) On sagittal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set, the posterior aspect (arrows) of the superior sagittal sinus is not seen owing to in-plane flow. (b) On sagittal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set, the superior sagittal sinus is patent. The apparent filling defect (curved arrow) is due to a high bifurcation of the superior sagittal sinus. Note the inferior sagittal sinus (short arrows), improved visualization of the internal cerebral veins (long arrow), and the normal bulbous appearance of the vein of Galen (arrowhead).
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Figure 5a. Congenital venous anomaly missed at 2D MR venography in 4-day-old girl. (a) Sagittal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows no straight sinus. (b) Sagittal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows focal atresia of a hypoplastic straight sinus (long arrow) and a large falcine sinus (short arrow) that connects the vein of Galen with the superior sagittal sinus.
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Figure 5b. Congenital venous anomaly missed at 2D MR venography in 4-day-old girl. (a) Sagittal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows no straight sinus. (b) Sagittal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows focal atresia of a hypoplastic straight sinus (long arrow) and a large falcine sinus (short arrow) that connects the vein of Galen with the superior sagittal sinus.
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Four patients (patients 19, 24, 35, and 37) were suspected of having thrombosis of a transverse sinus on the basis of increased intravascular signal intensity on fluid-attenuated inversion recovery images (Fig 6a). In two of these patients, 2D MR venography revealed patent transverse sinuses, while in the other two patients, 2D MR venography results suggested transverse sinus thrombus (Fig 6b). Three-dimensional MR venography revealed patent transverse sinuses in three of these four patients (ie, patients 19, 24, and 35) (Fig 6c), while the remaining patient (patient 37) was found to have thrombosis of the transverse and sigmoid sinuses at both 2D and 3D MR venography. However, 3D MR venography better delineated the caudal extent of the thrombus in that patient (Fig 7). Three-dimensional MR venography revealed segmental occlusion of both IJVs in two of the four patients; both IJVs in the other two patients were patent and continuous.
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Figure 6a. Flow-related enhancement in transverse sinus simulating dural sinus thrombosis in 20-month-old girl. (a) Transverse fluid-attenuated inversion recovery MR image (8000/120/2300) shows increased signal intensity within the left transverse sinus (arrow). (b) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows an apparent filling defect (arrow) in the middle region of the left transverse sinus. (c) Coronal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows that the left transverse sinus is patent and dominant.
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Figure 6b. Flow-related enhancement in transverse sinus simulating dural sinus thrombosis in 20-month-old girl. (a) Transverse fluid-attenuated inversion recovery MR image (8000/120/2300) shows increased signal intensity within the left transverse sinus (arrow). (b) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows an apparent filling defect (arrow) in the middle region of the left transverse sinus. (c) Coronal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows that the left transverse sinus is patent and dominant.
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Figure 6c. Flow-related enhancement in transverse sinus simulating dural sinus thrombosis in 20-month-old girl. (a) Transverse fluid-attenuated inversion recovery MR image (8000/120/2300) shows increased signal intensity within the left transverse sinus (arrow). (b) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows an apparent filling defect (arrow) in the middle region of the left transverse sinus. (c) Coronal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set shows that the left transverse sinus is patent and dominant.
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Figure 7a. Comparison of 2D and 3D MR venography in delineation of dural sinus thrombosis in 6-year-old boy. (a) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows absence of flow in the right transverse and sigmoid sinuses. The thrombus appears to extend into the right IJV (arrow). (b) With coronal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set, there is better definition of the caudal extent of the thrombus. The right IJV (arrow) is patent.
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Figure 7b. Comparison of 2D and 3D MR venography in delineation of dural sinus thrombosis in 6-year-old boy. (a) Coronal MIP from 2D MR venography (23/5.1; flip angle, 50°; section thickness, 2 mm) data set shows absence of flow in the right transverse and sigmoid sinuses. The thrombus appears to extend into the right IJV (arrow). (b) With coronal MIP from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set, there is better definition of the caudal extent of the thrombus. The right IJV (arrow) is patent.
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The four patients with pseudotumor cerebri had no venous disease or disorder that was identifiable at 2D MR venography. In one of these patients, 3D MR venography revealed a stenosis in the sigmoid sinus that drained the dominant sinus (Fig 8). Two of the 37 study patients had occlusive disease of the posterior fossa dural sinuses that was associated with intracranial vascular malformations; 3D MR venography was judged to be superior to 2D MR venography in depicting restricted venous drainage in these patients. In three patients, suboptimal timing of the gadolinium chelate bolus resulted in enhancement of overlapping arterial structures or of prominent posterior condylar veins that obscured the junction between the sigmoid sinus and the IJV; these problems were solved by electronically removing the overlapping structures at the 3D workstations.
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Figure 8. Oblique shaded surface rendering from 3D MR venography (6.0/2.0; flip angle, 35°; section thickness, 0.8 mm) data set in 3-year-old boy shows right dominant transverse sinus and a stenosis of the sigmoid sinus (arrow); the stenosis was not apparent at 2D MR venography.
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DISCUSSION
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The larger venous structures draining the brain may be studied noninvasively at MR imaging by using phase-contrast techniques, time-of-flight techniques, and contrast material–enhanced 3D sequences (1–7). Phase-contrast MR angiography is limited by gradient imperfections, eddy currents, and long acquisition times and potential lack of sensitivity to slow flow if the selected velocity encoding is incorrect (2,6). Two-dimensional time-of-flight MR venography suffers from progressive signal loss caused by slow-flowing protons and by the flow of protons parallel to rather than perpendicular to the imaging plane; both of these phenomena result in spin saturation (3). Gadolinium chelate reduces the spin saturation and is best administered as a bolus to avoid enhancement of chronically thrombosed venous structures; enhancement of such structures may simulate the appearance of a patent venous sinus (6). Techniques for bolus injection of gadolinium chelate with subsequent acquisition of images with a 3D rapid gradient-echo sequence have been described previously for the imaging of intracranial venous anatomy in adults (5,6).
However, the use of a power injector in the pediatric population is often limited by the presence of a surgically implanted or percutaneously inserted central line or small peripheral intravenous cannulas, through which power injections are contraindicated at our institution. In children who had one of these lines, we did not insert an additional intravenous catheter but chose instead to manually inject the contrast agent through the indwelling venous catheter. The slower injection of the contrast agent may result in suboptimal enhancement of the venous structures, a problem we observed most often in small infants with small-gauge intravenous lines in the extremities. However, diagnostic 3D MR venograms were acquired even in the smallest infants when the contrast agent was injected through 24-gauge intravenous lines.
The use of automated detection of contrast agent in the cavernous carotid artery and subsequent triggering of the 3D gradient-echo sequence with elliptic centric ordering of phase encoding to ensure that the center of k-space is collected at a time when a high concentration of contrast material is intravascular has been shown to yield a high vessel-to-background signal intensity (8). We did not use automated detection of the gadolinium chelate or triggering of the 3D MR venographic acquisition because these features are not available with our MR units. Predicting the time to maximum contrast agent accumulation in the dural venous sinuses after intravenous administration of a gadolinium chelate is problematic in young children with rapid heart rates. Hence, we used a 2D MR fluoroscopic sequence, during which the technologist began performing 3D MR venography once contrast material was observed in the superior sagittal sinus.
The transverse sinuses are the major conduits of cerebral venous drainage. There are anatomic variations in the appearance of the transverse sinuses at 2D MR venography that may simulate the appearance of thrombus (3,6). Ayanzen et al (3) observed flow gaps in the nondominant transverse sinuses in 30% of healthy patients, mostly adults, who underwent 2D MR venography performed in the coronal plane and commented that these flow gaps could potentially be indistinguishable from dural sinus thrombosis. In a study with adults that involved 2D and 3D MR venography, Farb et al (6) noted that flow gaps seen in nondominant transverse sinuses at 2D MR venography were sometimes not visible when 3D MR venographic sequences were performed after intravenous administration of a gadolinium chelate. In the pediatric population described herein, flow gaps seen within the nondominant transverse sinuses of four patients at 2D MR venography were not present after the gadolinium chelate was administered. As Farb et al (6) suggested, we therefore suggest that the presence of flow gaps at 2D MR venography should be considered an indication to proceed to 3D MR venography before the diagnosis of thrombus within a transverse sinus is made.
Previous reports have also indicated that 3D contrast-enhanced gradient-echo techniques enable better differentiation between atretic and hypoplastic sinuses than does 2D MR venography (4). The insensitivity of 2D MR venography to a low volume of flow or slow flow through a hypoplastic transverse sinus may result in overestimation of the prevalence of transverse sinus atresia. In one large study of pediatric patients involving normal routine MR imaging, 2D MR venography revealed atresia of a transverse sinus in about 13% of patients (9). In the patient population reported herein, 2D MR venography results suggested the absence of one transverse sinus in eight patients in whom 3D MR venography revealed hypoplastic transverse sinuses. Of the 37 patients we evaluated, none had unilateral transverse sinus atresia.
Congenital absence of both transverse sinuses is rare, having been reported in less than 1% of healthy children, and may be misdiagnosed as dural sinus thrombosis (9). In our study, the level of confidence with which the diagnosis of transverse sinus atresia rather than thrombosis was made in patient 20 was strengthened on the basis of 3D MR venography results (Figure 2). In one of the patients in the present study, absence of the straight sinus was seen but could not be diagnosed with any level of certainty at 2D MR venography; 3D MR venography revealed a persistent falcine sinus associated with hypoplasia of the straight sinus.
In the setting of pseudotumor cerebri, a normal 2D MR venogram does not exclude nonthrombotic veno-occlusive disease (7). A recent report (7) describing the use of gadolinium-enhanced 3D MR venography in adults with idiopathic intracranial hypertension suggests that this method is more sensitive to the presence of nonthrombotic stenoses of the transverse and sigmoid sinuses in adults than 2D MR venography. In the four pediatric patients in our study who had pseudotumor cerebri, 2D MR venography findings were normal. In three of the patients with pseudotumor, 3D MR venography findings were also normal, while one patient had an apparent stenosis of the sigmoid sinus that drained the dominant transverse sinus. The frequency with which posterior fossa dural sinus stenosis, as seen with 3D MR venography, occurs in the pediatric population and the clinical and hemodynamic importance of venous stenoses have not been studied in children. As part of an ongoing investigation at our institution, patients with pseudotumor and age-matched control patients are being evaluated with 3D MR venography.
Limitations of this study relate to the lack of blinded interpretation by the neuroradiologists, the small number of patients studied, and the low incidence of thrombotic venous disease. Further comparison of 2D and 3D MR venography in pediatric patients suspected of having or known to have dural sinus thrombosis is needed before definitive conclusions can be drawn about which technique is preferable in this clinical setting. However, in this prospective nonblinded study, gadolinium-enhanced 3D gradient-echo MR venography performed by using segmented central k-space ordering appeared to be superior to 2D time-of-flight MR venography in the depiction of major draining veins in infants and children. At our institution, 3D gadolinium-enhanced MR venography is performed when there is a high clinical suspicion of disease of the major cerebral venous structures or when 2D time-of-flight MR venography results suggest clinically important disease.
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FOOTNOTES
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Abbreviations: IJV = internal jugular vein,
MIP = maximum intensity projection,
3D = three-dimensional,
2D = two-dimensional
See Materials and Methods for pertinent disclosures.
Author contributions: Guarantor of integrity of entire study, N.R.; study concepts and design, all authors; literature research, N.R., C.I., J.C.; clinical studies, all authors; data acquisition and analysis/interpretation, all authors; manuscript preparation, definition of intellectual content, editing, and final version approval, all authors
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REFERENCES
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ABSTRACT
INTRODUCTION
