Childs Nerv Syst DOI 10.1007/s00381-014-2612-3
CASE REPORT
Varying clinical and imaging outcomes in patients with spontaneous thrombosis of vein of Galen malformation—a report of two cases Narendra Kumar Jain & Sweta Swaika & Bejoy Thomas & C. Kesavadas & T. R. Kapilamoorthy
Received: 28 September 2014 / Accepted: 22 December 2014 # Springer-Verlag Berlin Heidelberg 2015
Abstract Background Vein of Galen malformations are rare congenital intracranial vascular malformations. The pathophysiological consequences usually manifest as high-output cardiac failure and neurological symptoms secondary to cerebral venous congestion and abnormal CSF flow. Management of these patients is complex. Indications and time to intervene are decided depending upon the age of child, clinical presentation, and multisystemic neonatal scores. Many of these children presenting early and who are not in cardiac failure are expectantly followed up. Spontaneous thrombosis of the vein of Galen malformation is a rare occurrence in these as such rare vascular malformations. Methods This review reports two cases of spontaneous thrombosis of the vein of Galen malformations with varying clinical as well as imaging outcomes. Possible pathophysiologic mechanisms are discussed with review of literature. Results This report highlights the importance of vigilant clinical and imaging follow-up even after spontaneous thrombosis in the vein of Galen malformations. N. K. Jain (*) : S. Swaika : B. Thomas : C. Kesavadas : T. R. Kapilamoorthy Department of Imaging Sciences & Interventional Radiology, Sree Chitra Tirunal Institute for Medical Science and Technology, Trivandrum 695011, India e-mail: [email protected] S. Swaika e-mail: [email protected] B. Thomas e-mail: [email protected] C. Kesavadas e-mail: [email protected] T. R. Kapilamoorthy e-mail: [email protected]
Keywords Vein of Galen malformation . Spontaneous thrombosis . Clinical outcomes . Imaging outcomes
Introduction Vein of Galen malformations (VOGMs) are rare congenital intracranial vascular malformations constituting about 1 % of all intracranial vascular malformations. However, they represent 30 % of all the intracranial vascular malformations presenting in the pediatric age group [1]. These lesions are characterized by fistulous communication between primitive choroidal arteries and an aneurysmally dilated midline venous structure representing median prosencephalic vein which is the embryonic precursor of the vein of Galen [1] The pathophysiological consequences of VOGM usually manifest as high-output cardiac failure and neurological symptoms secondary to cerebral venous congestion and abnormal CSF flow. The severity of the symptoms is variable and dependent on the underlying angioarchitecture of the VOGM as well as the age of the child. Typically, neonates present with congestive heart failure, infants present with hydrocephalus, and the older children or adults present with headache, seizures, and with signs and symptoms of subarachnoid hemorrhage [2]. Management of these patients is complex with currently transarterial endovascular embolization being the preferred treatment. Indications and time to intervene are decided depending upon the age of the child, clinical presentation, and multisystemic neonatal scores. Many of these children presenting early and who are not in failures are also expectantly followed up [3].
Childs Nerv Syst
Spontaneous thrombosis of the vein of Galen malformation is a rare occurrence in these as such rare vascular malformations. A few previous case reports do exist regarding these [6–12]. However, post-thrombosis, these patients may have varying clinical outcomes with some showing complete disappearance of the sac and hydrocephalus while some others may have persisting hydrocephalus and may still require some form of surgical intervention. We report two cases of spontaneous thrombosis of the vein of Galen malformation with varying clinical and imaging outcomes.
Case 1 The first case is a male child, second born of nonconsanguineous parentage at full term by cesarean section for delayed progression of labor. He attained normal developmental milestones till 4 months of age, when the mother noticed progressive increase in the child’s head size. There was no history of seizures, fever, trauma, loss of consciousness, paucity of movements of limbs, or difficulty in feeding. On examination, head circumference was 49 cm; developmental milestones were normal and child was not in cardiac failure. He was evaluated with MRI scan at 4 months of age (Fig. 1a–c) which showed a mural type of vein of Galen malformation with ventriculomegaly. TOF MRA (Figs. 1c and 2a) revealed a single hypertrophied feeder from right posteromedial choroidal artery. There was stenosis of straight sinus with no other significant alternate venous exit for the malformation (Fig. 2c). In view of his clinical and Fig. 1 Initial MRI at the time of presentation: a Sagittal T2 weighted image of brain showing vein of Galen malformation (black arrows) with stenosis of straight sinus (white arrow). b Axial T2 weighted image of brain showing dilatation of both lateral ventricles with periventricular CSF seepage. c TOF MRA image showing single hypertrophied posteromedial choroidal artery feeding the VOGM (arrow). Follow-up MRI: d sagittal T2 weighted image showing hyperintensity within the VOGM (arrows). e Axial T1 weighted image showing hyperintensity within the VOGM suggestive of thrombus (arrows). f Axial T2 weighted image showing increase in lateral ventricular dilatation
angiographic features, the child was followed up. Interval clinical evaluation revealed progressive increase in head circumference. In view of the above, he was planned for treatment and was evaluated by a MRI prior to the planned intervention, which was done 1 year after the initial scan. At this time, his head circumference measured 58 cm and there was mild delay in gross motor milestones. MRI revealed thrombosis of the vein of Galen malformation with increasing hydrocephalus (Fig. 1d–f). There was non-visualization of the single arterial feeder (Fig. 2b). Straight sinus was not visualized (Fig. 2d). He was subsequently followed up with CT scans which revealed progressive calcification and reduction in the sac size. However, there was no reduction in the hydrocephalus (Fig. 3a–b). Clinically, the head circumference was 60 cm and he also had difficulty in bearing its weight. Considering his neurological status and imaging findings, a programmable ventriculoperitoneal shunt was placed (Fig. 3c).
Case 2 The second case is a male child, second born of nonconsanguineous parentage at full term by normal delivery. He cried immediately after birth and had normal birth weight. He developed one episode of neonatal seizure at day 3 of life. His cardiac evaluation was normal with no evidence of failure. He was evaluated with imaging for seizure elsewhere. MRI showed a partially thrombosed vein of Galen malformation (Fig. 4a–b). CT showed a partially calcified lesion with
Childs Nerv Syst Fig. 2 Initial and follow up MRA and MRV of the brain: a Initial TOF MRA revealing hypertrophied posteromedial choroidal feeder. b Follow-up MRA revealing non-visualization of the hypertrophied arterial feeder. c Initial MRV showing dilated vein of Galen and stenotic straight sinus. d Follow-up MRV shows non-visualized vein of Galen sac and the straight sinus
internal hyperdense contents in quadrigeminal cistern suggestive of the partially thrombosed vein of Galen malformation (Fig. 4c–d). He was kept on follow-up. There was no recurrence of seizure. Head circumference and development was normal for age and on follow-up; MRI done at 3 months of age revealed complete disappearance of the vein of Galen malformation with resolution of the hydrocephalus. Only minimal T2 hypointensity was seen in the superior vermian region (Fig. 4e–f). MRA (Fig. 4g) did not reveal any hypertrophied arterial feeder. MRV (Fig. 4h) revealed non-visualization of the dilated Galenic venous sac.
Discussion The vein of Galen malformation arises due to a fistulous communication between primitive choroidal arteries and an aneurysmally dilated midline venous structure representing Fig. 3 Follow-up noncontract axial CT scan of the brain: a (after 2 months) The thrombosed VOGM appears hypodense centrally with peripheral hyperdensity. b (after 4 months) Follow-up axial CT scan shows the thrombosed VOGM is more hyperdense, calcified, and is reduced in size (arrows). c Ventriculoperitoneal shunt tube is seen in situ with dilatation of both lateral ventricles
median prosencephalic vein between 6th to 11th weeks of embryonic life [1]. The median prosencephalic vein, which drains the shunt, lacks a fibrous wall and is largely unsupported, and therefore, it balloons out to a large size. The high flow across the arteriovenous fistula may result in the retention of fetal patterns of venous drainage [4]. Retention of the embryonic pattern of vasculature can explain the presence of several vascular anomalies that are associated with these lesions and may also explain why some of these may have a tendency to spontaneously thrombose. Based on their angioarchitecture, two subtypes of the vein of Galen malformation have been described. The choroidal form which is more common is characterized by a network of vessels with supply from the bilateral choroidal or thalamic arteries, and this vascular supply occurs at the anterior end of the median prosencephalic vein. The mural type is supplied by the branches of choroidal arteries which drain directly through the wall of the persistent median prosencephalic vein [5] In
Childs Nerv Syst
Fig. 4 Initial MRI image of the brain: a Axial FLAIR image showing hyperintensity within the VOGM. b Axial T1 weighted image showing hypointensity within the VOGM with an eccentric isointense area within (arrows). c, d Axial CT images showing hyperdense thrombus within VOGM with peripheral calcifications (arrows). Follow-up MRI at
3 months: e Axial T2 weighted image showing reduction in size of VOGM (arrows). f Coronal T2 weighted image showing hypointensity in the superior vermis with decrease in hydrocephalus. g TOF MRA revealing no evidence of any hypertrophied arterial feeder. h MRV shows non-visualization of the dilated galenic venous sac (arrow)
these cases, obstruction of the exit route is common and these are the ones which are more likely to thrombose spontaneously. Spontaneous thrombosis of the vein of Galen malformations is a rare occurrence, and the exact reasons why they occur are not known. Anomalous and/or stenotic dural sinuses are associated with the vein of Galen malformation [7]. Stenosis can also occur as a result of myointimal proliferation of the venous endothelium in response to rapid and turbulent flow of the shunt. Kavanolov proposed that this thrombosis occurs due to low blood flow and insufficient venous drainage [13]. Based on his studies with animals, Brunelle found that increased pressure and venous flow turbulence lead to progressive myointimal proliferation with hypertrophy of the vein of Galen wall, resulting in gradual venous thrombosis [14]. Few studies have discussed the role of contrast media in promoting thrombosis post cerebral angiography [9]. Hydrocephalus can also accelerate thrombosis of the vein of Galen malformations. Other possible mechanisms which have been proposed are due to compressive effects of surrounding hematoma, postventriculoperitoenal shunting [10], and also following aseptic meningitis [8]. In our first case, the patient had severe stenosis of the straight sinus (Figs. 1a and 2c). More importantly, there were no alternative channels of venous drainage like the falcine
sinus, etc. Also, it was a mural type of the vein of Galen malformation with single feeder from the right posteromedial choroidal artery (Figs. 1c and 2a). These angiographic features were indicators to possibility of spontaneous thrombosis of the malformation. Previously existing hydrocephalus itself could have also promoted thrombosis of the sac by causing compression over the sac. Subsequent MRI had revealed complete thrombosis of the prosencephalic venous sac with nonvisualization of straight sinus and the posteromedial choroidal artery feeder (Figs. 1d–e and Figs 2b, d). However, in spite of the thrombosis of the sac and non-visualization of the only arterial feeder, in this case, the later MRI revealed significant increase in the hydrocephalus and progressive parenchymal thinning (Fig. 1f), for which a child had to be treated by placing a ventriculoperitoneal shunt. CT scans done prior to and after the shunt procedure revealed significant reduction in the size of the sac and progressive calcification from peripheral to the central part of the sac (Fig. 3a–b). In this case, in spite of the thrombosis of the sac, progressive reduction in the size, and calcification of the size, there was a progressive increase in the hydrocephalus. This can be explained to some extent by the fact that hydrocephalus in infants with the vein of Galen malformation is secondary to impaired resorption of CSF due to venous hypertension and not due to aqueductal compression [15, 16]. In infants, as the
Childs Nerv Syst
arachnoid granulations have not yet fully matured, most of the ventricular CSF is reabsorbed across the ventricular ependyma, into the brain parenchyma, for subsequent drainage by the medullary veins. In infants with the vein of Galen malformations, the high venous pressure transmitted to the medullary veins prevents resorption of fluid and thus results in hydrocephalus [4]. Therefore, in our first case, in spite of the thrombosis of the sac, the hydrocephalus might have progressed due to ongoing venous hypertension. In the second case, the sac was partially thrombosed and calcified when first diagnosed (Fig. 4a–d). Morphologically, the shunt appears to be a low flow shunt due to partial thrombosis of the sac as well as ongoing calcification. This child had only mild hydrocephalus at initial imaging. Subsequently, the child remained clinically well with normal developmental milestones and no abnormal increase in head circumference. Follow-up imaging revealed complete disappearance of the sac with resolution of the hydrocephalus. Follow-up MR was normal except for mild T2 hypointensity and SWI blooming in superior vermian region (Fig. 4e–h). In this case, we are not sure about the exact factors which favored spontaneous thrombosis of the malformation as it was partially thrombosed and calcified when first imaged. However, in this case, the child had an excellent clinical and imaging outcome with complete resolution of hydrocephalus. This might have been due to this shunt being a low flow shunt and not severe enough to cause persistent venous hypertension. And also, it can be partly attributed to increasing maturation of arachnoid granulations with increasing age in the infancy, which may provide alternate route for CSF drainage apart from medullary veins. Hurst et al. [7] in their case report observed that postspontaneous thrombosis, these patients had good clinical outcomes. While in the report by Abrao et al. [12] their patient had progressive psychomotor impairment in spite of spontaneous thrombosis of the vein of Galen malformation. Our series shows that in spite of spontaneous thrombosis in the vein of Galen malformations, clinical outcome may actually vary. These may be influenced by other factors like the shunt severity, severity of venous hypertension, preexisting hydrocephalus at the time of thrombosis, and maturity of the venous system. Hence, vigilant clinical and imaging follow-up is recommended even after spontaneous thrombosis in the vein of Galen malformations. Author contributions Narendra Kumar Jain is the first author and planned this study, performed literature review, and wrote the draft. Sweta Swaika contributed to the draft and collected all the images for illustration. Bejoy Thomas proofread the rough draft and offered professional comments. C Kesavadas and TR Kapilamoorthy performed critical review of the article and helped in final editing of the article.
Conflict of interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The authors received no financial support for the research, authorship, and/or publication of this article. Ethical approval Written informed consent was obtained from the patient’s parents for the publication of this case report and brain imaging.
References 1. Raybaud CA, Strother CM, Hald JK (1989) Aneurysms of the vein of Galen: embryonic considerations and anatomical features relating to the pathogenesis of the malformation. Neuroradiology 31:109–128 2. Gold AP, Ransohoff JR, Carter S (1964) Vein of Galen malformation. Acta Neurol Scand Suppl 40:1–31 3. Lasjaunias P, Garcia-Monaco R, Rodesch G, Terbrugge K, Zerah M, Tardieu M, de Victor D (1991) Vein of Galen malformation: endovascular management of 43 cases. Childs Nerv Syst 7:360–367 4. Bhattacharya JJ, Thammaroj J (2003) Vein of Galen Malformations. J Neurol Neurosurg Psychiatry 74:142–144 5. Lasjaunias P, Terbrugge K, Piske R, Lopez Ibor L, Manelfe C (1987) Dilatation of the vein of Galen anatomoclinical forms and endovascular of 14 cases explored and/or treated between 1983 and 1986. Neurochirugie 33:315–333 6. Di Rocco C, Iannelli A, Puca A, Colosimo C Jr (1983) Spontaneous thrombosis of an aneurysm of the great vein of Galen. Eur Neurol 22: 293–299 7. Hurst RW, Kagetsu NJ, Berenstein A (1992) Angiographic findings in two cases of aneurysmal malformation of vein of Galen prior to spontaneous thrombosis: therapeutic implications. AJNR Am J Neuroradiol 13:1446–1450 8. Collins JJ, Fisher WS 3rd (1990) Vein of Galen aneurysm presenting with recurrent aseptic meningitis and subsequent spontaneous thrombosis. Surg Neurol 33:325–328 9. Konus OL, Ilgit ET, Ozdemir A, Onal B (2000) Spontaneous thrombosis of a vein of Galen aneurysmal malformation: possible effects of contrast media. Eur Radiol 10:1456–1458 10. Kuzeyli K, Cakir E, Karaarslan G, Ahmetoglu A, Peksoylu B, Yazar U, Baykal S (2004) Spontaneous thrombosis of vein of Galen aneurysmal malformation after ventriculoperitoneal shunting. J Clin Neurosci 11:439–442 11. Moftakhar P, DanielPor M, Maya M, Alexander MJ (2009) Spontaneous thrombosis of neonatal vein of Galen malformation. Neurosurg Focus 27:E12 12. Abrao GP, Barbosa LA, Sa AT Jr, Caldas JG (2010) Spontaneous thrombosis of a malformation of the vein of Galen. Arq Neuropsiquiatr 68:648–650 13. Konovalov AN, Pitskhelauri DI, Arutiounov NV (2002) Surgical treatment of the thrombosed vein of Galen aneurysm. Acta Neurochirugie 44:909–915 14. Brunelle F (1997) Arteriovenous malformation of the vein of Galen in children. Pediatric Radiol 27:501–513 15. Zerah M, Garcia-Monaco R, Rodesh G, Terbrugge K, Tardieu M, de Victor D, Lajaunias P (1992) Hydrodynamics in vein of Galen malformations. Childs Nerv Syst 8:111–117 16. Sainte-Rose C, La Combe J, Pierre-Kahn A, Renier D, Hirsch JF (1984) Intracranial venous sinus hypertension: cause or consequence of hydrocephalus in infants? J Neurosurg 60:727–736
CASE REPORT
Varying clinical and imaging outcomes in patients with spontaneous thrombosis of vein of Galen malformation—a report of two cases Narendra Kumar Jain & Sweta Swaika & Bejoy Thomas & C. Kesavadas & T. R. Kapilamoorthy
Received: 28 September 2014 / Accepted: 22 December 2014 # Springer-Verlag Berlin Heidelberg 2015
Abstract Background Vein of Galen malformations are rare congenital intracranial vascular malformations. The pathophysiological consequences usually manifest as high-output cardiac failure and neurological symptoms secondary to cerebral venous congestion and abnormal CSF flow. Management of these patients is complex. Indications and time to intervene are decided depending upon the age of child, clinical presentation, and multisystemic neonatal scores. Many of these children presenting early and who are not in cardiac failure are expectantly followed up. Spontaneous thrombosis of the vein of Galen malformation is a rare occurrence in these as such rare vascular malformations. Methods This review reports two cases of spontaneous thrombosis of the vein of Galen malformations with varying clinical as well as imaging outcomes. Possible pathophysiologic mechanisms are discussed with review of literature. Results This report highlights the importance of vigilant clinical and imaging follow-up even after spontaneous thrombosis in the vein of Galen malformations. N. K. Jain (*) : S. Swaika : B. Thomas : C. Kesavadas : T. R. Kapilamoorthy Department of Imaging Sciences & Interventional Radiology, Sree Chitra Tirunal Institute for Medical Science and Technology, Trivandrum 695011, India e-mail: [email protected] S. Swaika e-mail: [email protected] B. Thomas e-mail: [email protected] C. Kesavadas e-mail: [email protected] T. R. Kapilamoorthy e-mail: [email protected]
Keywords Vein of Galen malformation . Spontaneous thrombosis . Clinical outcomes . Imaging outcomes
Introduction Vein of Galen malformations (VOGMs) are rare congenital intracranial vascular malformations constituting about 1 % of all intracranial vascular malformations. However, they represent 30 % of all the intracranial vascular malformations presenting in the pediatric age group [1]. These lesions are characterized by fistulous communication between primitive choroidal arteries and an aneurysmally dilated midline venous structure representing median prosencephalic vein which is the embryonic precursor of the vein of Galen [1] The pathophysiological consequences of VOGM usually manifest as high-output cardiac failure and neurological symptoms secondary to cerebral venous congestion and abnormal CSF flow. The severity of the symptoms is variable and dependent on the underlying angioarchitecture of the VOGM as well as the age of the child. Typically, neonates present with congestive heart failure, infants present with hydrocephalus, and the older children or adults present with headache, seizures, and with signs and symptoms of subarachnoid hemorrhage [2]. Management of these patients is complex with currently transarterial endovascular embolization being the preferred treatment. Indications and time to intervene are decided depending upon the age of the child, clinical presentation, and multisystemic neonatal scores. Many of these children presenting early and who are not in failures are also expectantly followed up [3].
Childs Nerv Syst
Spontaneous thrombosis of the vein of Galen malformation is a rare occurrence in these as such rare vascular malformations. A few previous case reports do exist regarding these [6–12]. However, post-thrombosis, these patients may have varying clinical outcomes with some showing complete disappearance of the sac and hydrocephalus while some others may have persisting hydrocephalus and may still require some form of surgical intervention. We report two cases of spontaneous thrombosis of the vein of Galen malformation with varying clinical and imaging outcomes.
Case 1 The first case is a male child, second born of nonconsanguineous parentage at full term by cesarean section for delayed progression of labor. He attained normal developmental milestones till 4 months of age, when the mother noticed progressive increase in the child’s head size. There was no history of seizures, fever, trauma, loss of consciousness, paucity of movements of limbs, or difficulty in feeding. On examination, head circumference was 49 cm; developmental milestones were normal and child was not in cardiac failure. He was evaluated with MRI scan at 4 months of age (Fig. 1a–c) which showed a mural type of vein of Galen malformation with ventriculomegaly. TOF MRA (Figs. 1c and 2a) revealed a single hypertrophied feeder from right posteromedial choroidal artery. There was stenosis of straight sinus with no other significant alternate venous exit for the malformation (Fig. 2c). In view of his clinical and Fig. 1 Initial MRI at the time of presentation: a Sagittal T2 weighted image of brain showing vein of Galen malformation (black arrows) with stenosis of straight sinus (white arrow). b Axial T2 weighted image of brain showing dilatation of both lateral ventricles with periventricular CSF seepage. c TOF MRA image showing single hypertrophied posteromedial choroidal artery feeding the VOGM (arrow). Follow-up MRI: d sagittal T2 weighted image showing hyperintensity within the VOGM (arrows). e Axial T1 weighted image showing hyperintensity within the VOGM suggestive of thrombus (arrows). f Axial T2 weighted image showing increase in lateral ventricular dilatation
angiographic features, the child was followed up. Interval clinical evaluation revealed progressive increase in head circumference. In view of the above, he was planned for treatment and was evaluated by a MRI prior to the planned intervention, which was done 1 year after the initial scan. At this time, his head circumference measured 58 cm and there was mild delay in gross motor milestones. MRI revealed thrombosis of the vein of Galen malformation with increasing hydrocephalus (Fig. 1d–f). There was non-visualization of the single arterial feeder (Fig. 2b). Straight sinus was not visualized (Fig. 2d). He was subsequently followed up with CT scans which revealed progressive calcification and reduction in the sac size. However, there was no reduction in the hydrocephalus (Fig. 3a–b). Clinically, the head circumference was 60 cm and he also had difficulty in bearing its weight. Considering his neurological status and imaging findings, a programmable ventriculoperitoneal shunt was placed (Fig. 3c).
Case 2 The second case is a male child, second born of nonconsanguineous parentage at full term by normal delivery. He cried immediately after birth and had normal birth weight. He developed one episode of neonatal seizure at day 3 of life. His cardiac evaluation was normal with no evidence of failure. He was evaluated with imaging for seizure elsewhere. MRI showed a partially thrombosed vein of Galen malformation (Fig. 4a–b). CT showed a partially calcified lesion with
Childs Nerv Syst Fig. 2 Initial and follow up MRA and MRV of the brain: a Initial TOF MRA revealing hypertrophied posteromedial choroidal feeder. b Follow-up MRA revealing non-visualization of the hypertrophied arterial feeder. c Initial MRV showing dilated vein of Galen and stenotic straight sinus. d Follow-up MRV shows non-visualized vein of Galen sac and the straight sinus
internal hyperdense contents in quadrigeminal cistern suggestive of the partially thrombosed vein of Galen malformation (Fig. 4c–d). He was kept on follow-up. There was no recurrence of seizure. Head circumference and development was normal for age and on follow-up; MRI done at 3 months of age revealed complete disappearance of the vein of Galen malformation with resolution of the hydrocephalus. Only minimal T2 hypointensity was seen in the superior vermian region (Fig. 4e–f). MRA (Fig. 4g) did not reveal any hypertrophied arterial feeder. MRV (Fig. 4h) revealed non-visualization of the dilated Galenic venous sac.
Discussion The vein of Galen malformation arises due to a fistulous communication between primitive choroidal arteries and an aneurysmally dilated midline venous structure representing Fig. 3 Follow-up noncontract axial CT scan of the brain: a (after 2 months) The thrombosed VOGM appears hypodense centrally with peripheral hyperdensity. b (after 4 months) Follow-up axial CT scan shows the thrombosed VOGM is more hyperdense, calcified, and is reduced in size (arrows). c Ventriculoperitoneal shunt tube is seen in situ with dilatation of both lateral ventricles
median prosencephalic vein between 6th to 11th weeks of embryonic life [1]. The median prosencephalic vein, which drains the shunt, lacks a fibrous wall and is largely unsupported, and therefore, it balloons out to a large size. The high flow across the arteriovenous fistula may result in the retention of fetal patterns of venous drainage [4]. Retention of the embryonic pattern of vasculature can explain the presence of several vascular anomalies that are associated with these lesions and may also explain why some of these may have a tendency to spontaneously thrombose. Based on their angioarchitecture, two subtypes of the vein of Galen malformation have been described. The choroidal form which is more common is characterized by a network of vessels with supply from the bilateral choroidal or thalamic arteries, and this vascular supply occurs at the anterior end of the median prosencephalic vein. The mural type is supplied by the branches of choroidal arteries which drain directly through the wall of the persistent median prosencephalic vein [5] In
Childs Nerv Syst
Fig. 4 Initial MRI image of the brain: a Axial FLAIR image showing hyperintensity within the VOGM. b Axial T1 weighted image showing hypointensity within the VOGM with an eccentric isointense area within (arrows). c, d Axial CT images showing hyperdense thrombus within VOGM with peripheral calcifications (arrows). Follow-up MRI at
3 months: e Axial T2 weighted image showing reduction in size of VOGM (arrows). f Coronal T2 weighted image showing hypointensity in the superior vermis with decrease in hydrocephalus. g TOF MRA revealing no evidence of any hypertrophied arterial feeder. h MRV shows non-visualization of the dilated galenic venous sac (arrow)
these cases, obstruction of the exit route is common and these are the ones which are more likely to thrombose spontaneously. Spontaneous thrombosis of the vein of Galen malformations is a rare occurrence, and the exact reasons why they occur are not known. Anomalous and/or stenotic dural sinuses are associated with the vein of Galen malformation [7]. Stenosis can also occur as a result of myointimal proliferation of the venous endothelium in response to rapid and turbulent flow of the shunt. Kavanolov proposed that this thrombosis occurs due to low blood flow and insufficient venous drainage [13]. Based on his studies with animals, Brunelle found that increased pressure and venous flow turbulence lead to progressive myointimal proliferation with hypertrophy of the vein of Galen wall, resulting in gradual venous thrombosis [14]. Few studies have discussed the role of contrast media in promoting thrombosis post cerebral angiography [9]. Hydrocephalus can also accelerate thrombosis of the vein of Galen malformations. Other possible mechanisms which have been proposed are due to compressive effects of surrounding hematoma, postventriculoperitoenal shunting [10], and also following aseptic meningitis [8]. In our first case, the patient had severe stenosis of the straight sinus (Figs. 1a and 2c). More importantly, there were no alternative channels of venous drainage like the falcine
sinus, etc. Also, it was a mural type of the vein of Galen malformation with single feeder from the right posteromedial choroidal artery (Figs. 1c and 2a). These angiographic features were indicators to possibility of spontaneous thrombosis of the malformation. Previously existing hydrocephalus itself could have also promoted thrombosis of the sac by causing compression over the sac. Subsequent MRI had revealed complete thrombosis of the prosencephalic venous sac with nonvisualization of straight sinus and the posteromedial choroidal artery feeder (Figs. 1d–e and Figs 2b, d). However, in spite of the thrombosis of the sac and non-visualization of the only arterial feeder, in this case, the later MRI revealed significant increase in the hydrocephalus and progressive parenchymal thinning (Fig. 1f), for which a child had to be treated by placing a ventriculoperitoneal shunt. CT scans done prior to and after the shunt procedure revealed significant reduction in the size of the sac and progressive calcification from peripheral to the central part of the sac (Fig. 3a–b). In this case, in spite of the thrombosis of the sac, progressive reduction in the size, and calcification of the size, there was a progressive increase in the hydrocephalus. This can be explained to some extent by the fact that hydrocephalus in infants with the vein of Galen malformation is secondary to impaired resorption of CSF due to venous hypertension and not due to aqueductal compression [15, 16]. In infants, as the
Childs Nerv Syst
arachnoid granulations have not yet fully matured, most of the ventricular CSF is reabsorbed across the ventricular ependyma, into the brain parenchyma, for subsequent drainage by the medullary veins. In infants with the vein of Galen malformations, the high venous pressure transmitted to the medullary veins prevents resorption of fluid and thus results in hydrocephalus [4]. Therefore, in our first case, in spite of the thrombosis of the sac, the hydrocephalus might have progressed due to ongoing venous hypertension. In the second case, the sac was partially thrombosed and calcified when first diagnosed (Fig. 4a–d). Morphologically, the shunt appears to be a low flow shunt due to partial thrombosis of the sac as well as ongoing calcification. This child had only mild hydrocephalus at initial imaging. Subsequently, the child remained clinically well with normal developmental milestones and no abnormal increase in head circumference. Follow-up imaging revealed complete disappearance of the sac with resolution of the hydrocephalus. Follow-up MR was normal except for mild T2 hypointensity and SWI blooming in superior vermian region (Fig. 4e–h). In this case, we are not sure about the exact factors which favored spontaneous thrombosis of the malformation as it was partially thrombosed and calcified when first imaged. However, in this case, the child had an excellent clinical and imaging outcome with complete resolution of hydrocephalus. This might have been due to this shunt being a low flow shunt and not severe enough to cause persistent venous hypertension. And also, it can be partly attributed to increasing maturation of arachnoid granulations with increasing age in the infancy, which may provide alternate route for CSF drainage apart from medullary veins. Hurst et al. [7] in their case report observed that postspontaneous thrombosis, these patients had good clinical outcomes. While in the report by Abrao et al. [12] their patient had progressive psychomotor impairment in spite of spontaneous thrombosis of the vein of Galen malformation. Our series shows that in spite of spontaneous thrombosis in the vein of Galen malformations, clinical outcome may actually vary. These may be influenced by other factors like the shunt severity, severity of venous hypertension, preexisting hydrocephalus at the time of thrombosis, and maturity of the venous system. Hence, vigilant clinical and imaging follow-up is recommended even after spontaneous thrombosis in the vein of Galen malformations. Author contributions Narendra Kumar Jain is the first author and planned this study, performed literature review, and wrote the draft. Sweta Swaika contributed to the draft and collected all the images for illustration. Bejoy Thomas proofread the rough draft and offered professional comments. C Kesavadas and TR Kapilamoorthy performed critical review of the article and helped in final editing of the article.
Conflict of interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The authors received no financial support for the research, authorship, and/or publication of this article. Ethical approval Written informed consent was obtained from the patient’s parents for the publication of this case report and brain imaging.
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