CENTRAL NERVOUS SYSTEM VASCULAR MALFORMATIONS

8/13/2019 CENTRAL NERVOUS SYSTEM VASCULAR MALFORMATIONS

1/11

Current Management in Child Neurology, Third Edition Central Nervous System 2005 Bernard L. Maria, All Rights Reserved Vascular Malformations in Pediatric PatientsBC Decker Inc Pages 595605

CHAPTER90

CENTRAL NERVOUS SYSTEMVASCULARMALFORMATIONSQUOC-ANH THAI, MD

JOHN L. MORIARITY, MD

RAFAEL J. TAMARGO, MD, FACS

Cerebral vascular malformations are divided into fivetypes: (1) arteriovenous malformation (AVM), (2) duralarteriovenous fistulas (AVF), (3) cavernous malformation(CM), (4) venous angioma, and (5) capillary telangiecta-sia. Typically, only AVMs, AVFs, and CMs become symp-tomatic and require neurosurgical care; venous angiomasand capillary telangiectasias often are found incidentally.AVMs, AVFs, and CMs, however, differ dramatically andwill be discussed separately. The vein of Galen malforma-tion is a special case of a dural AVF and will be discussedseparately. Spinal AVMs and AVFs will also be discussedseparately due to the different anatomic, pathologic, andclinical considerations associated with them.

Some of these lesions occur predominantly in adult pop-ulations. Often, less is known about the natural history andbest management of these lesions in pediatric patients.Whenpossible, we have focused our discussion on evidence frompediatric patients, but in many instances we will discuss thebehavior and treatment of these lesions in adults in the hopethat it sheds light on the same entities in pediatric patients.

Cerebral Arteriovenous Malformations

Cerebral AVMs are characterized by direct communicationbetween one or more arterial feeders and one or more

draining veins without an intervening capillary bed. Unlikethe dural AVFs discussed below,cerebral AVMs reside insidethe brain (although they often extend to the surface) andare intermingled with gliotic brain tissue. Cerebral AVMsappear grossly as a tangle of vessels but often have an iden-tifiable center or nidus. AVMs are high-flow lesions thatcause multiple pathologic changes in the involved vesselsand thus create tendency toward hemorrhage.

On the basis of a review of adult autopsy series and largeclinical studies, Berman and colleagues at ColumbiaUniversity (2000) estimated the annual incidence of cere-bral AVMs to be roughly 1 per 100,000 and the prevalenceto be 10 per 100,000. Owing to a smaller number of stud-

ies, prevalence rates specific to the pediatric population aremore difficult to obtain.In a series of 4,122 pediatric autop-sies reviewed by Pinar and colleagues at Brown Universityin 1998,however, 2% (82) of patients were found to harborone of the five types of cerebral vascular malformations,with AVMs accounting for 15% (12) of these 82 lesions.

Clinical Presentation

Cerebral AVMs most often present between the third andfifth decades of life with acute hemorrhage, seizure disor-der, or nonhemorrhagic neurologic deficit. In 1996,Humphreys and colleagues at the Hospital for Sick

Children can be afflicted with a variety of intracranial lesions, including arteriovenous malformations (AVMs), cavernous mal-formations (CMs), vein of Galen malformations,and dural arteriovenous fistulas (AVFs). Certain types of spinal cord AVMsalso are known to occur in children and young adults, especially intradural spinal AVFs and juvenile AVMs. These lesions dif-fer dramatically in their anatomy, pathophysiology, treatment, and prognosis. They are best managed in a multidisciplinarysetting by neurosurgical, neuroendovascular, and neurocritical care teams.


2/11

596/The Hospitalized Child

Children reviewed their experience with 160 children har-boring cerebral AVMs. Consistent with others, they foundthat a significant number of their patients (80%) presentedwith acute hemorrhage. Because children with AVMs seemto present more often with hemorrhage, the peak age forhemorrhage from an AVM is lower, possibly between 15

and 20 years old. Clinically, a child suffering from an AVMhemorrhage will complain of sudden,severe headache andmay develop other signs or symptoms, including nausea,vomiting, seizures, or neurologic deficit. On the basis ofHumphreysseries, hemorrhage from an AVM in the pedi-atric population may carry a higher mortality than inadults. The overall mortality in the group presenting withacute hemorrhage was 21% (27 of 126), whereas multipleadult series report roughly 10% overall mortality fromhemorrhage. This is possibly secondary to the increasedincidence of posterior fossa (brainstem and cerebellar)lesions in children. Humphreys and colleagues reported

23% (36 of 160) posterior fossa lesions in their pediatricseries, while Jomin and colleagues (1985) found only 5%(8 of 150) in their adult series. According to another seriesby Humphreys that focused only on posterior fossa AVM,the reported mortality rate was 35% (1998).

Overall, AVMs represent the most common cause ofintracranial hemorrhage in the pediatric population, butprospective data for the annual risk of hemorrhage arelacking.In adults, the annual risk of hemorrhage is roughly2 to 4%, irrespective of a history of prior hemorrhage.

Evaluation and Diagnosis

Although cerebral AVMs are often first detected with com-puted tomography (CT) or magnetic resonance imaging(MRI), the gold standard for diagnosis and anatomicdefinition is cerebral angiography. Because many childrenpresent with acute intracranial hemorrhage, most willinitially obtain a CT scan, which can demonstrate an acutethrombus or calcified vessels, if present. Addition ofcontrast is of little utility but, if done, can reveal dilatedarterial or venous vessels. MRI can detect AVMs by thepresence of multiple flow voids (areas of low signal) rep-resenting blood vessels in the malformation. Magneticresonance angiography (MRA) may or may not demon-strate an AVM because it is gated to reveal arterial-typeflow,but AVMs often have intermediate flow that is neithertruly venous nor arterial.

Although AVMs are detectable with these other imag-ing modalities, all surgical, endovascular, and stereotacticradiotherapy management decisions are based on a four-vessel (internal carotid and vertebral arteries) and oftenexternal carotid angiogram. This defines the vascularanatomy of the lesion and allows for possible endovascu-lar embolization prior to either surgical resection or stereo-tactic radiotherapy(Figures 90-1 and90-2).

Treatment

The ideal treatment for a cerebral AVM is total surgicalresection. In selected cases, surgery is preceded by endovas-cular embolization of the AVM to aid surgical resectionand limit intraoperative bleeding. Small AVMs in surgi-cally difficult locations, however, are best treated with

stereotactic radiotherapy. Although AVMs can be treatedwith stereotactic radiotherapy, this approach results indelayed obliteration of the AVM (over months) as the ves-sels respond to the radiation injury. As a result, the patientremains at risk for hemorrhage for a substantial amount oftime after treatment.Furthermore,there may be risks asso-ciated with radiotherapy. Kaido and colleagues at the NaraMedical University in Japan described a 14-year-old patientwho developed a glioblastoma multiforme (GBM) 6.5 yearsafter radiotherapy for AVM. For these reasons, stereotacticradiotherapy is reserved for AVMs deemed surgically inac-cessible due to depth or involvement of eloquent tissue.

Outcome

With better endovascular, radiotherapeutic, and surgicaltechniques, outcomes continue to improve for childrenwith cerebral AVMs. Currently,overall mortality is roughly10 to 15%,with 50 to 60% of children who undergo surgeryregaining normal neurologic function. Although seizuresare less often part of the clinical picture in children withAVMs (versus adults),10 to 20% of children with AVMs willhave a seizure disorder and require antiepileptic drugs.

Finally, pediatric patients appear to be at higher risk thanadults for recurrence of their AVM,even after negative post-

treatment angiograms. Lindqvist and colleagues from theKarolinska Hospital in Stockholm reported in 2000 thatpediatric patients are more likely than adults to experiencerecurrence of their AVM years after radiosurgical oblitera-tion. Additionally, Kader and colleagues at the AlbertEinstein College of Medicine reported five pediatric cases ofrecurrent AVMs years after negative postoperative angio-graphy.These results suggest delayed posttreatment imagingstudies may be warranted in the pediatric population.

Intracranial AVFs

Intracranial dural AVFs are high-flow lesions consisting ofarteriovenous shunting found outside the brainparenchyma,either in the subarachnoid space or dura. Thisis in contrast to cerebral AVMs, which reside in the brainand are intermingled with gliotic brain tissue. The arterialsupply of AVFs is from dural arteries and the venousdrainage is through either dural sinuses or leptomeningealvenous channels.A dural sinus is a venous channel locatedbetween the leaflets of the dura mater (eg, sagittal sinus,transverse sinus, sigmoid sinus). Even though the exactcause of AVFs is unknown,it is widely believed these lesions



3/11

are acquired, occasionally secondary to sinus thrombosis

and recanalization. The thrombosis allows fistulous con-nections to develop between meningeal and dural vessels,thus causing high-flow arteriovenous shunts to becomeestablished.The high-flow shunts and retrograde flow causevenous dysfunction and put the patient at risk for venousrupture and ischemia due to severe venous congestion.

In 1997, Lasjuanias described three types of pediatricAVFs on the basis of the patients age at presentationand type of shunting: neonatal, juvenile, and adolescent.The neonatal AVF results from a congenital malforma-tion of the dural sinuses. The juvenile type is associatedwith multifocal, high-flow shunts without sinus malfor-mation and often is associated with secondary occlusionof the jugular bulb. The adolescent type is associatedwith slow flow and is located along the cavernous sinusor sigmoid sinus.

Sinus pericranii is an extracranial vascular malformationthat should be distinguished from AVFs, because these arenot fed by arterial feeders. Rather, they represent a group ofvascular malformations involving the extracranial andintracranial venous systems,which usually involve the supe-rior sagittal sinus and sometimes the transverse sinus. Theselesions are thought to be congenital, presenting in young

infants as a soft, reducible, fluctuant mass on the scalp.

Because these venous malformations are directly connectedto the intracranial sinuses, any changes in head position oractivities that induce a Valsalva maneuver will change thesize of the lesion.Diagnosis of a sinus pericranii depends onthe physical exam and CT or skull radiograph showing adefect in the skull beneath the lesion. Angiograms will showthe lesion only if digital subtraction and delayed images aretaken. Treatment is recommended mostly for cosmetic rea-sons or, occasionally, because of risk of hemorrhage fromtrauma. In these cases, a craniotomy or craniectomy withcranioplasty is performed, followed by complete oblitera-tion of the abnormal communications.


The neonatal AVF occurs in neonates and infants and pre-sents with symptoms of elevated intracranial pressure(ICP),such as emesis, limited up-gaze,bulging fontanelles,irritability, or neurologic deficits. The malformation of thedural sinus results in a giant dural lake that enlarges andcommunicates with other sinuses. Patients with a moremidline sinus malformation tend to be more symptomatic.If the venous outlet undergoes thrombosis, the patient canpresent with a hemorrhage or a venous infarction.

FIGURE 90-1. A, Coronal, gadolinium-enhanced magnetic resonance imaging (MRI) demonstrates a right frontal arteriovenous malformation

(AVM) extending to the cortical surface. B, Anterior view of right internal carotid angiogram in the same patient reveals the internal carotid artery

(large arrow head), the anterior cerebral artery (small arrow head), and the middle cerebral artery (black arrow). The AVM nidus (white arrows) is fed

largely by branches of the middle cerebral artery.

A. B.

Central Nervous System Vascular Malformations / 597



4/11


The juvenile, or high-flow, AVF also can present inneonates or infants. Because these AV shunts are high-flow,neonates can present with congestive heart failure (CHF) sim-ilar to that seen in patients with vein of Galen malforma-tions. Unlike the CHF seen in neonates with vein of Galenmalformations,however,heart failure in juvenile AVF patients

is often mild and more easily managed medically. This usu-ally allows intervention to be delayed until the child grows,thereby reducing the morbidity and mortality that canaccompany the treatment of neonates with vein ofGalen mal-formations. The natural history of juvenile AVF is to produceprogressive venous occlusive phenomena. This can interferewith the drainage of the high-flow shunts as well as the healthybrain.The patients symptoms depend on the extent of venouscongestion and the ability of the cavernous sinus to accom-modate the venous outflow from the cortical venous systemof the brain, thereby circumnavigating the dural shunt.Untreated, the patient may gradually develop neurologic

deficits,seizures, and mental retardation. Intervention is rec-ommended when the juvenile AVF causes macrocephaly,headaches, slowed development,or hemodynamic disorders.

Adolescent AVFs are similar in appearance and pre-sentation to those seen in the adult population. The nat-ural history of these lesions is highly variable. Many pur-sue a benign course, but some cause sudden andaggressive neurologic deficits. The clinical behavior ofadolescent (and adult) AVFs is determined by lesion loca-tion,patterns of arterial supply, and venous drainage. The

venous drainage is the most important factor determin-ing symptoms. Venous dysfunction due to high pressureof direct and retrograde flow can cause increased ICP, sig-nificant neurologic deficits, and fatal hemorrhage. If var-ious venous drainage systems can accommodate corticaloutflow from normal brain, symptoms may be minor or

absent. Symptoms other than hemorrhage or focal neu-rologic deficits rarely warrant radical treatment.


In the acute setting of a new neurologic deficit, mostpatients will be evaluated with CT. Even though CT mayallow proper diagnosis of a vascular anomaly, it is impor-tant to recognize that these lesions need to be further eval-uated with MRI and MRA.Although MRI (and MRA andmagnetic resonance venography [MRV]) shows the majorvascular channels, as with AVMs, the gold standard fordiagnosing and assessing the anatomy of dural AVFs is four-

vessel angiography that includes the external carotid circu-lation.The angiogram also provides important informationabout intracranial circulation and allows for preoperativeplanning by the surgeon and the neurointerventionalist.

Treatment

There are two treatment modalities for pediatric duralAVFs: (1) endovascular embolization and (2) surgicalresection.Substantial improvements in both endovascularand surgical techniques have made treating dural AVFs


FIGURE 90-2. A, Large, bilateral, thalamic arteriovenous malforma-

tion (AVM) on contrast-enhanced, axial magnetic resonance imaging

(MRI). B, Coronal view of magnetic resonance angiography (MRA) in the

same patient reveals the extensive, bilateral nidus of the lesion.

A. B.


5/11


safer and more effective. Currently, pediatric dural AVFsare managed using a multidisciplinary approach involvingneurointerventionalists and neurosurgeons. The goal ofsurgical intervention is the interruption or excision of thepathologic dural leaflet or the obliteration of the arterial-ized venous connection. Despite improvements in surgical

technique, risks are associated with surgical intervention.Therefore, the neurointerventionalist typically firstattempts to embolize the arterial feeders. If the emboliza-tion is able to sufficiently treat the dural AVF, then surgeryis avoided. If the embolization cannot sufficiently discon-nect or reverse cortical venous reflux drainage by the duralAVF, then surgical intervention is considered.

Outcome

Outcome data on pediatric dural AVFs are limited becausethey are rare. The clinical progression of a neonatal type ofdural AVF may be relentless, and the outcome poor

because of venous infarction and hemorrhage.The patientwith a juvenile dural AVF can have a good outcome iftreated early and effectively.If the patient has multifocal AVshunts, treatment is difficult and the outcome can includeseizures, neurologic deficits, and global retardation. Themost important factor in the outcome of neonatal andjuvenile AVFs, however, is the extent of the patients heartfailure. If the CHF can be managed effectively, the outcomecan be quite good. Managing the childs CHF allows thepatient to grow and gain weight, thus allowing the inter-ventionalist to use more dye during the angiographic pro-cedure and to more easily access the arterial feeders.

The adolescent dural AVF is similar to the adult type;therefore,adult numbers are reviewed here.In 1969, Newtonand colleagues reviewed angiograms of patients withintracranial AVMs during a 6-year period and found thatdural AVFs constitute 10 to 15% of all intracranial AVMs.The most important factor determining the outcome is thevenous drainage. Untreated, the majority behave benignly,but some experience rapid neurologic deterioration withvenous ischemia and hemorrhage. In 2000, Kawaguchi andcolleagues reported results on 12 patients who had previ-ously undergone embolization but then became sympto-matic and underwent surgical removal of their dural AVF.They reported no surgical mortality or lasting morbidityand achieved symptomatic resolution in all patients.Substantial gains have been made in the outcomes of pedi-atric dural AVFs. As endovascular and surgical equipmentand techniques continue to improve, so will outcomes.

Cavernous Malformations

CMs are angiographically occult vascular malformations thatconsist of sinusoidal vascular channels lined by a single layerof endothelial cells. These vascular channels lack a full com-

plement of normal vessel wall components and are embed-ded in loose connective tissue stroma. The lesion may besurrounded by gliotic tissue,but there is generally no neuraltissue within the lesion.The channels are filled with blood invarious degrees of thrombosis and degradation, leading tothe characteristic mulberry appearance of these malfor-

mations grossly and their reticulated appearance on MRI.CMs constitute roughly 10% of all cerebral vascular

malformations and are present in about 5% of the popu-lation,according to a review of 24,535 autopsies conductedby Otten and colleagues in Geneva in 1989. As with AVMs,there are fewer studies focusing on the pediatric preva-lence of CMs. If one looks at a number of large clinicalseries, however, pediatric patients (age < 18 years) com-prise roughly 20% of the patient population. In our seriesof 68 patients at the Johns Hopkins Hospital, for example,13 patients (19%) presented at or before 18 years of age.

CMs are found throughout the central nervous system

and appear to be distributed in proportion to the amountof tissue in each region. Therefore, roughly 80% are foundin the supratentorial compartment (hemispheres and deepnuclei), 20% are found in the infratentorial compartment(brainstem and cerebellum), and a very small number(< 1%) are found within the spinal cord.

CMs can occur in either a sporadic or familial form.Familial cases account for 20 to 50% of all cases, are trans-mitted in an autosomal dominant fashion, and have beenlinked to chromosome 7. Although clinically indistin-guishable from sporadic cases, familial cases are more likelyto harbor multiple lesions. In our series, 85% (11 of 13) of

familial patients had multiple lesions, compared with 25%(14 of 55) of sporadic cases.


Most patients with CMs present in their fourth decade, butthe mode of presentation varies widely,and there are insuf-ficient data to discern any difference between the clinicalpresentation in adults and children. Most series reportheadache, seizure, focal neurologic deficit, and hemor-rhage as major symptoms. Seizures, occurring in 25 to50% of patients, are often the primary complaint thatprompts clinical evaluation. In our series at Johns Hopkins,33 patients (49%) presented with seizures. In prospectivefollow-up of the patients without a seizure history, wefound a 4.8% per patient-year risk of developing seizures.

Prospective CM hemorrhage rates found in the litera-ture are roughly 1 to 3% per patient-year. Similarly, analy-sis of our series yielded a prospective hemorrhage rate of3.1% per patient-year.


MRI is the imaging modality of choice for detecting CMs.In contrast, CT has poor sensitivity and specificity for these



6/11


lesions, and their low flow and lack of large feeding ordraining vessels render them largely undetectable by MRA.The relative merits of these different imaging modalitieswere best illustrated by Rigamonti and colleagues at theBarrow Neurological Institute (1987), who studied 10patients with pathologically verified CMs. In these 10

patients, MRA was negative in four, revealed an avascularmass in three, and revealed subtle venous pooling or cap-illary blush in the remaining three. In the same 10 patients,three CT scans were negative,and a total of 14 lesions weredetected in the remaining seven scans. This is in contrastto MRI, which demonstrated a CM in every patient andrevealed 27 lesions overall.

The MRI appearance of CMs was divided into fourtypes by Zabramski and colleagues at the BarrowNeurological Institute in 1994. The classic appearance(type II) is one of a mixed-signal, reticulated core (likenedto popcorn) surrounded by a low-signal rim(Figure 90-3).

Other possible appearances of CMs on MRI include ahomogeneous, hyperintense core (type I), a markedlyhypointense lesion (type III), and punctate, poorly visual-ized hypointense foci (type IV).

Treatment

Surgical resection is the mainstay of therapy for sympto-matic CMs.Endovascular treatment cannot be used becauseof the lack of filling of these lesions on angiography. The effi-cacy of stereotactic radiotherapy is still questionable due toa lack of long-term follow-up in most series and a belief thatthe biology of these lesions differs from that of AVMs,mak-

ing them inherently less amenable to radiation treatment.Deciding to treat a CM surgically, however, requires

comparing the natural history of the lesion with the risksof surgery. In general, CMs follow a more benign coursethan AVMs, and episodes of hemorrhage are (dependingon location) not usually associated with a catastrophicneurologic deficit. Therefore, patients whose CMs havebeen identified incidentally can be monitored with serialMRIs, reserving surgical intervention for those developinga neurologic deficit,medically intractable seizures, or radi-ographic evidence of rapid growth or extralesional hem-orrhage (blood extending beyond the rim of the lesion).

Cases of brainstem or spinal cord CMs present specialtreatment dilemmas. These lesions are in eloquent regionswhere even a small hemorrhage can be clinically devastat-ing. For the same reason, however, surgical excision can beassociated with significant postoperative morbidity.Currently, the high morbidity associated with hemorrhagein these regions leads many surgeons to recommend resec-tion after multiple hemorrhagic events. Although largeprospective studies have not addressed the issue, some ret-rospective analyses have indicated a benefit to early surgi-cal resection of brainstem and (especially) spinal cord CMs.

Outcome

In general, patients with CMs fare better clinically thanpatients with AVMs. Unfortunately, most of our clinicaldata comes from mixed (adult and pediatric) series. In aseries of 173 patients with CM,followed prospectively fora mean of 2.5 years per patient, Porter and colleagues at the

University of Toronto (1997) recorded no fatal episodes ofintracranial hemorrhage.Overall,34% (59 of 173) of theirpatients presented with, or experienced during follow-up,an episode of neurologic deficit. Roughly one-third ofthese patients recovered completely, one-third recoveredpartially, and one-third experienced no significantimprovement. In this study, lesions located in the basalganglia, thalamus, brainstem, or spinal cord were associ-ated with a higher rate of lasting neurologic deficit,a find-ing that mirrors our experience.

The risk of surgical intervention depends on the loca-tion of the lesion but is relatively low for most CMs. In a

study of 94 patients who underwent 97 operations,Amin-Hanjani and colleagues at Massachusetts General Hospital(1998) reported persistent, disabling neurologic compli-cations in four cases and no mortality as a result of surgery.They also reported an overall neurologic outcome of excel-lent to good for 87 (90%) of the surgical procedures.

Surgery performed to treat medically intractableseizures secondary to a CM also carries a high success rate.Most series, including our own, indicate a complete cessa-tion of seizures in more than 95% of patients.

Vein of Galen MalformationThe vein of Galen is a short (1 to 2 cm), large-diametervenous confluence that collects multiple tributaries fromthe deep venous system of the brain. It then drains directlyinto the straight sinus, which is superior and posterior tothe pineal gland. Malformations of the vein of Galen oftenare referred to as vein of Galen aneurysms, as they resultin dilation of the vein of Galen.In the following discussion,however, we will refer to these lesions as vein of Galenmalformations. We do this for two reasons. First,intracranial aneurysms are arterial lesions with entirelydifferent pathology and treatment. Second, vein of Galenmalformations are vascular malformations that involvedirect arteriovenous shunting.

Vein of Galen malformations were first comprehen-sively described by Jaeger, Forbes, and Dandy at JohnsHopkins in 1937. Since that time, this lesion has been sub-jected to multiple classification schemes. Each scheme dif-ferentiates between direct AVFs into the vein of Galen(considered the true vein of Galen malformation) andsimple dilation of the vein of Galen secondary to anothervascular malformation. Even for lesions representing trueAVFs, however, the name vein of Galen malformation is



7/11

FIGURE 90-3. A, Enhanced, axial T1-weighted magnetic resonance imaging (MRI) reveals low signal lesion of left medial temporal lobe. As is typ-

ical for cavernous malformations (CMs), no enhancement with contrast is noted. B, Axial T2-weighted image of same lesion reveals typical reticu-

lated core and low signal (hemosiderin) ring surrounding lesion.

A. B.


likely a misnomer. A study of 23 cases by Raybaud and col-leagues (1989) concluded that such lesions actually repre-sent the persistence of the median prosencephalic vein ofMarkowski. Normally, this vessel exists only transientlyduring intrauterine development and then regresses as the

paired internal cerebral veins replace all but its most cau-dal portion. The vein of Galen malformation, Raybaudand colleagues argue,represents the aberrant persistence ofthis vein of Markowski and its arterial tributaries, thuscreating a high-flow AV communication.

Overall, vein of Galen malformations are rare vascularmalformations, with only a few hundred cases having beenreported in the literature since Jaegers original description.If one considers only pediatric cerebrovascular malforma-tions, however, vein of Galen malformations constitute asignificant proportion of reported lesions. In a study byLong and colleagues at the University of Minnesota (1974),vein of Galen malformations made up 33% of all giantAVMs found in infancy or childhood.


The clinical presentation of vein of Galen malformationsdepends on the patients age. Neonates (0 to 1 month)usually present with high-output CHF requiring aggressivemedical management. Infants (1 to 12 months) often pre-sent with hydrocephalus, compensated CHF, and occa-sional seizures or focal neurologic deficits. Patients whopresent between 1 and 5 years of age have even less severe

CHF, whereas patients older than 6 years often presentwith parenchymal or subarachnoid hemorrhage as well asneurologic deficits and seizures.


In addition to clinical signs of CHFhydrocephalus,seizures,and possible auscultation of a cranial bruitveinof Galen malformations can be detected using multipleimaging modalities. Ultrasound is a useful screening toolboth in utero and during the neonatal period. The additionof Doppler ultrasonography allows better differentiationbetween vascular and nonvascular midline structures.Ultrasonography also allows one to follow the progress ofocclusive surgical or endovascular therapy.

CT also is able to detect vein of Galen malformations.On CT, these lesions appear as rounded, low-densitymasses lying in the region of the quadrigeminal plate (thedorsum of the midbrain) and the pineal gland. If there isthrombus within the dilated vein of Galen, however, thelesion can appear radiodense on CT (Figure 90-4A).Calcification can be present, and if intravenous contrast isadministered, the aneurysm as well as any large feedingarteries will appear enhanced.

Compared with ultrasound and CT, MRI affords muchgreater anatomic detail in evaluating a vein of Galen mal-formation. The malformation itself, its arterial feeders,andvenous drainage will all appear as low signal flow voidson MRI (Figure 90-4B). MRA and MRV allow for some



8/11


anatomic definition of arterial feeders, venous drainage,and the degree of thrombosis within the dilated vein.

Despite the anatomic information yielded by MRI,conventional cerebral angiography remains the gold stan-dard for anatomic definition and treatment planning incaring for patients with vein of Galen malformations

(Figure 90-4C).

Treatment

Treatment of vein of Galen malformations depends inlarge part on the patients age at diagnosis and medicalcondition. With improvement in ultrasonographic tech-niques, the diagnosis is often made during the prenatalperiod. In this instance, the fetus also must be assessed forevidence of other anomalies and distress. Once this infor-mation is obtained, the parents must be thoroughly coun-

seled as to the nature of the disorder and the potential forsignificant morbidity or mortality.

In addition, it is important to stress to the parents thatthere are no known genetic factors involved in the disor-der and that no predisposing environmental factors havebeen identified. In addition,prenatal diagnosis also allows

for time to ensure the baby is delivered at a hospital withcapable neurosurgical, neuroendovascular, and neonatalcritical care teams. The prenatally diagnosed patient maybe delivered vaginally,as there are not strict indications forcesarean section in cases in which both the baby and themother are medically stable and no cephalopelvic dispro-portion exists. After delivery, the decision to intervene isbased on clinical manifestations, including CHF, hydro-cephalus, seizures, or developmental delay. If the patientremains asymptomatic, some would recommend close


FIGURE 90-4. A, Axial computed tomography (CT) demonstrates an

area of high radiodensity (arrow) corresponding to thrombus in the

dilated vein of Galen. B, Sagittal magnetic resonance imaging (MRI)

reveals a large flow void representing the dilated vein of Galen.

C, Lateral view of vertebral artery angiogram reveals multiple arterial

feeders to the vein of Galen malformation.

A. B.

C.


9/11

follow-up only,whereas others would recommend electiveangiography and obliteration at about 6 months of age.

At whatever age a patient presents, multiple treatmenttechniques have been described for vein of Galen malfor-mations.Although technically very different, all approachesshare the common goal of obliterating the anomalous AV

communication. This has been attempted surgically bycareful exposure and clipping (occlusion) of all arterialfeeders, thus initiating thrombosis of the aneurysm.Because of high surgical morbidity and improvements inendovascular technique, however, the endovascularapproach has largely supplanted surgery in the treatment ofvein of Galen aneurysms. Multiple endovascular routeshave been described, but currently, transarterial access viafemoral puncture is the most commonly used.This usuallyinvolves deposition of occlusive material (coils, balloons,acrylic glue) into the malformation to achieve completeobliteration. This is best achieved gradually with multiple

endovascular procedures to avoid possible hemorrhage orcardiac decompensation that can accompany abrupt clo-sure of vein of Galen malformations.

Outcome

In general, vein of Galen malformations carry a high mor-bidity and mortality depending on the flow characteristicsof the lesion and the medical condition of the patient.Neonates presenting with severe CHF fall into the groupwith the worst outcome. In a review of 70 neonatal cases,Johnson and colleagues (1987) found an overall mortalityof 91% (64 of 70) with little or no difference between med-

ical, surgical, and endovascular management.More recentselected endovascular series, however, present a slightlymore promising picture. Friedman and colleagues (1993)

reported no mortality and 45% morbidity in 11 neonates;Lasjuanias and colleagues (1991) reported 8% mortalityand 75% morbidity in 13 neonates; and Circillo and col-leagues (1990) reported 25% mortality and 50% morbid-ity in eight neonates.

Spinal Cord AVMs and AVFs

Background and Clinical Presentation

Spinal cord AVMs and AVFs are a heterogeneous group oflesions that are much rarer than intracranial AVMs. Aswith their intracranial counterparts, all spinal cord AVMsshare the unifying trait of a direct AV connection in oraround the spinal cord.The heterogeneity in this group hasled to multiple classification attempts. InTable 90-1, weclassify these lesions (as initially proposed by Rosenblumand colleagues at the National Institutes of Health [NIH]

in 1987) into four types on the basis of the differentanatomy, location, and extent of the anomalous AV con-nection. For the remainder of this section, we will expandupon the information summarized inTable 90-1.

Spinal AVFs are extradural spinal cord AVMs. Theselesions represent a direct AVF between an extradural radic-ular artery (branch to the nerve root) and an intraduralmedullary vein. These lesions account for 60 to 80% of allspinal cord AVMs. Because they occur almost exclusivelyin older adults, however, they will not be discussed further.

Intradural spinal AVMs are further subdivided intointradural AVFs, glomus intramedullary malformations,

and juvenile intramedullary AVMs. Intradural AVFs consistof an anomalous connection between the anterior spinalartery and vein. These lesions reside outside the pia mater

TABLE 90-1. Spinal Cord Arteriovenous Malformations*

Type Anatomy Clinical Presentation Pathophysiology Age Gender Treatment Comments

Dural AVF Radicular artery-to- Progressive myelora- Venous hypertension 4070 Male Surgery Most common spinal

medullary vein fistula on diculopathy in spinal cord cord AVM

superior aspect of dorsal

nerve root sleeve

Intradural Fistula between anterior Progressive myelopathy Compression, steal 5 40 Equal Small = surgery Higher flow in larger

AVF spinal artery and vein in or subarachnoid venous hypertension Large = endo- lesions requiressubarachnoid space hemorrhage vascular embolization

Glomus AVM without spinal cord. Acute myelopathy or Hemorrhage, 2050 Equal Surgery Pathologically similar

AVM Usually has multiple pain (progressive compression, to intracranial AVM

feeders pattern much less steal

common)

Juvenile Large AVMs that can involve Pain or progressive Compression, 530 Equal Endovascular Extremely rare and

AVM spinal cord, extramedullary myelopathy steal, carry a poor prognosis

space, and adjacent hemorrhage

vertebral bodies

*Classified according to Rosenblum B, et al, NIH, 1987.

AVF = arteriovenous fistula; AVM = arteriovenous malformation.




10/11


and the spinal cord, frequently at the level of the conusmedullaris. Intradural AVFs often present in adolescentsor young adults with progressive myelopathy but also havebeen reported to cause spinal subarachnoid hemorrhage.

Glomus malformations are the spinal cord equivalent ofthe intraparenchymal, cerebral AVMs. These lesions reside

within the spinal cord and involve a compact tangle of ves-sels (or nidus) with multiple arterial feeders and drain-ing veins. They most frequently occur in the cervical cordof adults between 20 and 50 years of age and often presentwith hemorrhage, causing acute myelopathy.

Juvenile AVMs are extremely rare lesions that afflict ayounger population than do the other three types of spinalcord AVMs. In general, patients present between 5 and30 years of age with pain or progressive neurologic deficit.These lesions occupy entire segments of the spinal cordand canal and often extend into the adjacent vertebral body.

Evaluation and DiagnosisAs is the case with many vascular lesions, the gold stan-dard for diagnosis and classification of spinal cord AVMsand AVFs is selective spinal angiography. Other imagingmodalities, however, also can point to the diagnosis and arehelpful in treatment planning. Chief among these is MRI.On MRI, spinal cord AVMs (depending on the type andsize) often can be revealed by flow voids representinginvolved vessels, compression or expansion of the spinalcord, evidence of hemorrhage, or areas of spinal cordedema or infarction. MRI is also helpful in indicating theprecise spinal level involved, allowing for planning of the

surgical approach.A combination of MRA and MRI, how-ever, are the central modalities used in the diagnosis ofthese lesions. Currently, both CT and conventional myel-ography are contraindicated in the presence of a spinalAVM or AVF because of the risk of puncturing a drainingvein with the needle.

Treatment

The goal of treating any spinal cord AVM is to eradicate theanomalous AV connection. Depending on the type ofAVM, this is currently best achieved by surgery, endovas-cular therapy(see Table 90-1), or a combination of thetwo.The best approach to intradural AVFs depends on thesize of the lesion. In smaller lesions, surgery is preferred,as endovascular cannulation of the feeding vessels is diffi-cult and risky. Larger lesions, however, are best treated viathe endovascular route in many instances. In general, glo-mus AVMs are primarily treated surgically, with endovas-cular embolization playing an adjunctive role. In the caseof juvenile AVMs, the extent of the lesion often makes sur-gical excision impossible or prohibitively morbid. For thisreason, endovascular therapy is considered the primarymode of therapy for these difficult lesions.

Outcome

Outcome after treatment of a spinal cord AVM dependslargely on the type and extent of the lesion. The primarymode of therapy for intradural spinal AVF depends on thesize of the lesion.Smaller lesions are best treated surgically,as the small feeding vessels are difficult to approach

endovascularly. For larger lesions, the primary treatmentmodality is endovascular. These lesions are relatively rareand were only first described in 1977, so there are still toofew patients treated to make strong statements about long-term outcome. In most series, however, the majority oflesions can be obliterated, and most patients either stabi-lize or improve clinically following treatment. In 1993,Mourier and colleagues in France reported on 35 patientswith intradural spinal AVFs. Overall,79% (27 of 34 treatedpatients) were completely obliterated and 91% (31 of 34treated patients) were clinically improved or unchangedafter treatment.

Glomus AVMs are primarily treated surgically but notwithout morbidity and mortality. Yasargil and colleaguesin Zurich (1984) reported a mortality of 5% and clinicaldeterioration in 20% of patients, and Rosenblum and col-leagues at the NIH (1987) reported 2% mortality and neu-rologic deterioration in 14%.

Juvenile AVMs are difficult to treat by any means, andcomplete obliteration or removal is often impossible.Both the endovascular and surgical approaches havebeen attempted. Because of the extent of the lesion andits intimate involvement of the spinal cord, surgical exci-

sion carries a high morbidity. For these reasons, mostfavor endovascular palliation. As reported by Bao andcolleagues at Beijing Hospital (1997), however, 74% (17of 23) of their patients with juvenile AVMs requiredrepeat endovascular treatment because the lesionrecurred.

Suggested Readings

Humphreys RP, Hoffman HJ, Drake JM,Rutka JT. Choices in the

1990s for the management of pediatric cerebral arteriove-

nous malformations. Pediatr Neurosurg 1996;25:27785.

Moriarity JL Jr, Steinberg GK. Surgical obliteration for vein of Galenmalformation: a case report. Surg Neurol 1995;44:36570.

Moriarity JL,Wetzel M, Clatterbuck RE, et al.The natural history

of cavernous malformations: a prospective study of 68

patients. Neurosurgery 1999;44:116673.

Rosenblum B, Oldfield EH, Doppman JL, Di Chiro G. Spinal

arteriovenous malformations: a comparison of dural arteri-

ovenous fistulas and intradural AVMs in 81 patients. J

Neurosurg 1987;67:795802.

terBrugge KG. Neurointerventional procedures in the pediatric

age group. Childs Nerv Syst 1999;15:7514.



11/11


Practitioner and Patient Resources

Neurosurgery 4 Kids

Primary Childrens Medical Center

100 N. Medical Drive, Suite 2400

Salt Lake City, UT 84113

Phone: (801) 588-3400

http://www.neurosurgery4kids.com/vascular_malformations.htmThis site offers a comprehensive service in the management of all

types of vascular malformations of the brain and spinal cord.

Chicago Institute of Neurosurgery and Neuroresearch

Phone: (800) 411-2466

http://www.cinn.org/ibsc/pediatric/vascular.html

This page describes a program that provides a multidisciplinary

team approach needed tosuccessfully treat these complex and

complicated disorders.

http://www.neurosurgery4kids.com/vascular_malformations.htmhttp://www.cinn.org/ibsc/pediatric/vascular.htmlhttp://www.neurosurgery4kids.com/vascular_malformations.htmhttp://www.cinn.org/ibsc/pediatric/vascular.html

Documents

CENTRAL NERVOUS SYSTEM VASCULAR MALFORMATIONS