Paraspinal arteriovenous fistula: Stuttgart classification based on experience and a review of the literature

Abstract

The term “paraspinal arteriovenous shunts” (PAVSs) summarizes an inhomogeneous variety of rare vascular disorders. PAVSs have been observed as congenital or acquired lesions. The clinical course of PAVSs may be asymptomatic or present with life-threatening symptoms. Based on a collection of individual cases from three institutions and a literature evaluation, we propose the following classification: PAVSs that are part of a genetic syndrome are separated from “isolated” PAVSs. Isolated PAVSs are subdivided into “acquired”, “traumatic” and “congenital” without an identifiable genetic hereditary disorder. The subgroups are differentiated by the route of venous drainage, being exclusively extraspinal or involving intraspinal veins. PAVSs associated to a genetic syndrome may either have a metameric link or occur together with a systemic genetic disorder. Again extra-vs intraspinal venous drainage is differentiated. The indication for treatment is based on individual circumstances (e.g. myelon compression, vascular bruit, high volume output cardiac failure). Most PAVSs can be treated by endovascular means using detachable coils, liquid embolic agents or stents and derivates.

Introduction

Spinal vascular malformations can in general be classified into arteriovenous malformations (AVM) and the more common arteriovenous shunts (AVSs). AVSs account for 60–80% of all spinal vascular disorders.¹ In 1926, Foix and Alajouanine described the clinical features of what was later called “spinal dural arteriovenous fistula”.² Another 60 years later, Kendall and Logue understood the underlying vascular pathology, pointing out that the majority of “intradural spinal AVMs” were actually the venous drainage of dural AVSs located on a nerve root sleeve.¹ Over the last 20 years, different efforts have been made to subdivide AVSs with respect to their location, their venous drainage pattern, and their etiology to gain better understanding of their pathophysiology.^3–5 In 2003, Rodesch and Lasjaunias proposed a classification scheme for spinal cord AVSs (SCAVSs), separating them into four different groups according to their localization and relationship to the dura: paraspinal, epidural, dural and intradural.⁴ Furthermore, SCAVSs, in their opinion, can be described according to the type of shunt involved (direct fistula vs nidus) and their potential relationship with genetics, vascular biological features and angiogenesis.

Dural AVSs have been the subject of many investigations, as they are the most common type of spinal AVSs.⁶ Paraspinal AVSs (PAVSs), also termed paravertebral shunts, on the contrary, are rare lesions, presenting with a female predominance. There frequency is below 5% of the incidence of spinal dural arteriveonous fistulas. Rodesch and Lasjaunias described paraspinal (or parachordal) AVSs as malformations arising along the embryonic notochord.⁴ In contrary to epidural and intradural shunts, the AVS of PAVSs is located outside the spinal canal. Nevertheless, PAVSs can cause neurological symptoms due to cord compression by ectatic draining veins, venous congestion or by arterial steal due to reflux in the epidural of perimedullary venous system.

The literature consists of singular case reports and only a few case series. Understanding the angioarchitecture of different subtypes of PAVSs is important for estimating the course of the disorder and planning of the treatment. Based on a review of the literature and our experiences, we propose a simple classification exclusively for paraspinal shunts, illustrating it by representative cases. To our knowledge, no classification dealing exclusively with PAVSs exists in the literature.

Methods and materials

A search for articles on Pubmed (National Library of Medicine) was conducted to find studies dealing with paravertebral shunts and their diagnosis, classification and treatment from December 1980 to March 2016. The following keywords were used: “spinal arteriovenous fistula/shunt”, “paraspinal arteriovenous fistula/shunt”, “paravertebral arteriovenous fistula/shunt” or “vertebro-vertebral fistula/shunt”. Additional articles were found by searching the reference list of relevant articles. PAVSs were defined as AVSs located paravertebral with extraspinal, epidural or perimedullary venous drainage.

In addition, the records of the three participating hospitals were reviewed and patients with AV shunts outside but adjacent to the spinal canal were identified. All available examinations were reviewed by senior neuroradiologists and representative cases were chosen for illustrating the developed classification for PAVS.

Case based classification of paraspinal AV shunts

Isolated paraspinal AV shunts

Most of the paraspinal arteriovenous shunts can be categorized as isolated shunts without associated genetic, hereditary disorders. We subdivided this group according to their etiology in acquired, traumatic and congenital PAVSs, the later without identifiable genetic, hereditary disorder according to the proposed classification (Table 1). Table 2 summarizes the cases 1 to 5 to illustrate our classification scheme.

Table 1. .

Classification scheme of paraspinal arteriovenous shunts, mainly divided into their origins (isolated or associated with a metameric link or genetic disorder) and their drainage pathways

Stuttgart lassification of PAVSs
Isolated
Acquired
Extraspinal venous drainage
Intraspinal venous drainage
Traumatic
Extraspinal venous drainage
Intraspinal venous drainage
Congenital without identifiable genetic hereditary disorder
Extraspinal venous drainage
Intraspinal venous drainage
Associated
Metameric link
Extraspinal venous drainage
Intraspinal venous drainage
Systemic genetic dysplasia
Extraspinal venous drainage
Intraspinal venous drainage

PAVS, paraspinal arteriovenous shunt.

Table 2. .

Overview of the example cases illustrating the Stuttgart classification for PAVSs compared to the classification according to Iizuka et al³

Case number	Age	Clinical presentation	Location of shunt	Assumed etiology of the PAVS	Venous drainage	Therapy	Clinical outcome	Stuttgart classification	Classification according to Iizuka et al3
1	62 years	Pulsatile tinnitus, dizziness	Cervical	Unknown	Paraspinal venous plexuses	None	Persisting clinical symptoms	Iolated acquired PAVS, extraspinal venous drainage	Isolated extradural arteriovenous shunt
2	78 years	Progressive paraparesis	Lumbar	Trauma	Paraspinal and epidural venous plexuses	Transarterial Onyx embolization	Clinical improvement	Isolated traumatic PAVS, intraspinal venous drainage	Isolated extradural arteriovenous shunt
3	7 years	Audible bruit on the back	Thoracic	Congenital	Paraspinal and epidural venous plexuses	Coiling	Complete occlusion after 4 years, symptoms completely resolved	Isolated congenital PAVS without genetic hereditary disorder, intraspinal venous drainage	Isolated extradural arteriovenous shunt
4	44 years	Progressive paraparesis (due to medullary AVM), no symptoms associated with the PAVS	Sacral	Klippel–Trénaunay syndrome	Paraspinal venous plexuses	None	Paraparesis improved after endovascular treatment of the medullary AVM, PAVS asymptomatic	Associated PAVS with a metameric link, extraspinal venous drainage	Associated PAVS with metameric link
5	50 years	Clumsiness oft the right hand	Cervical	Neurofibromatosis	Paraspinal and epidural venous plexuses	Coiling	Complete occlusion after 6 months, symptoms completely resolved	Associated PAVS with systemic genetic disorder, intraspinal venous drainage	Associated PAVS with systemic dysplasia

AVM, arteriovenous malformation; PAVS, paraspinal arteriovenous shunt.

Acquired paraspinal AV shunts

Acquired PAVSs occur spontaneously in late adolescence or adulthood. According to the literature, 44% of the PAVSs cannot be linked with a history of trauma.⁷ Most acquired PAVSs show an epidural or paraspinal venous drainage.^8–12 Vertebrojugular or vertebrovertebral AVSs are a subtype of PAVSs, predominantly draining into paraspinal venous plexuses or epidural veins.

Depending on the location of the PAVSs, neurological symptoms can vary from minor disorders as audible bruit to serious symptoms as radiculopathy or paraparesis (Figure 1). A gradual onset of symptoms is typical for this subgroup of PAVSs, although it should also be considered that a so-called “acquired” PAVSs could be hardly differentiated from a formerly asymptomatic congenital PAVS. Dilated epidural veins and feeding arteries cannot only cause myelon compression but also bony erosions. Schmidt et al reported two patients with osseous erosions of the adjacent vertebrae.¹⁰

Figure 1.

Time-of-flight MRA of a 62-year-old patient presenting with a pulsatile tinnitus of the left ear, dizziness and no history of trauma, showing arterialization of the left transverse sinus (a). Digital subtraction angiography confirms two different arteriovenous shunts, an arteriovenous shunt of the skull base [(b), injection of the ascending pharyngeal artery, black arrow] and a vertebrovertebral shunt (white arrow) originating from the right vertebral artery, the latter draining via paraspinal venous plexuses in the ipsilateral internal jugular vein (c, d). Both shunts were not treated yet, because the patient refused any kind of therapy. MRA, MR angiography.

Subarachnoid hemorrhage is a rare complication of PAVSs, probably due to sudden occlusion of perimedullary draining veins or rupture of arterialized veins.¹³ It can be accompanied by severe neurological symptoms such as paraparesis, bladder and sphincter dysfunction. Our literature search revealed only four patients, who suffered subarachnoid hemorrhage from a spontaneous PAVS.^13–15

Traumatic paraspinal AV shunts

Traumatic PAVSs are caused or associated with a regional trauma of different severity.^15–18 Most often, traumatic PAVSs are located at the cervical level and are shunts between the vertebral artery and the paraspinal venous plexus or the jugular veins. Symptoms vary depending on the location and volume of the shunt and comprise an audible bruit, motor weakness, sensory disturbance, radiculopathy, pulsatile tinnitus or headache (Figure 2).^15–17,19

Figure 2.

A 78-year-old female patient suffering from progressive paraparesis. The sagittal T₂ weighted images (a, b) show intramedullary oedema and serpingineous leptomeningeal veins indicating a spinal AVS. The contrast-enhanced MR angiography (c) reveals a primary shunt into the epidural and paraspinal venous plexuses. DSA of the third lumbar radicular artery on the left confirms a paraspinal AVS that drains primarily into the segmental epidural spinal venous plexus (d) and into a leptomeningeal vein of the longitudinal venous drainage of the spinal cord (e). AVS, arteriovenous shunt; DSA, digital subtraction angiography.

Besides vertebrovertebral or vertebrojugular PAVSs, only a few traumatic paraspinal shunts are reported in the literature. Cognard et al published the case of a 17-year-old girl, presenting with a history of progressive lower back pain, which begun 6 months after she had fallen from a horse. Spinal angiography revealed a PAVS, supplied by an iliolumbar artery and a branch of the medial sacral artery. The shunt showed venous drainage via the ascending lumbar vein to the epidural and perimedullary veins, causing a backward shift of the conus medullaris due to the space-occupying effect.²⁰

Congenital paraspinal AV shunts without identifiable genetic hereditary disorder

Paraspinal AV shunts also occur in children.^{13, 21} Congenital PAVSs with and without a detectable genetic disorder can be distinguished. If diagnosed shortly after birth without history of trauma, a congenital origin of the paraspinal shunt can be assumed. Most of the reported children had first been submitted, because of a continuous heart murmur over the paraspinal or parasternal area (Figure 3). Neurological symptoms due to spinal venous congestion or compression of the spinal cord are extremely rare.²² Congestive heart failure secondary to a high shunt volume has been reported in only one patient.²³

Figure 3.

Large calibre arteriovenous shunt from the descending aorta to the vena cava inferior in a 7-year-old boy with an audible bruit on his back. Venous congestion of the para-and intraspinal veins (a, b). The arteriovenous connection was occluded with coils in 2012 (c). A follow-up DSA, 4 years later confirmed the persistent occlusion of the paraspinal arteriovenous shunt (d). DSA, digital subtraction angiography.

Paraspinal AV shunts associated with genetic disorders

Only a small number of case reports describe PAVSs related to an underlying genetic disease. Depending on the stage in cellular evolution when the vascular cells are affected, two different groups of PAVSs associated with a genetic disorder can be distinguished: non-hereditary lesions that share a developmental metameric link and hereditary lesions caused by a mutation in the vascular germinal cells (Table 1).²⁴

Paraspinal AV shunts with metameric link

Spinal arteriovenous metameric syndrome (SAMS) is a very rare disease including spinal vascular malformations of non-hereditary genetic metameric origin, which affect the spinal cord as well as other tissues originating from the same metamere. The cause of the development of multiple malformations in parts or all tissues of the same metamere lies in a disturbed mesodermal cell migration during embryogenesis due to the mutation of mother cells. SAMS can involve the spinal cord, adjacent bone, subcutaneous tissues, and tissues of the epidural or paraspinal space and the skin.²⁵ According to the largest series of cases published by Niimi et al in 2012, the fistulous variant of SAMS is even rarer than the nidus form (86%). Among 28 cases presented, 13 showed a paraspinal involvement, although it remains unclear whether there were fistulous malformations in the paraspinal region.²⁶

The most important representative of this group of diseases is the Cobb syndrome, an association of a skin lesion with a spinal vascular malformation at the level corresponding to the respective dermatome.²⁷ Moreover, overgrowth syndromes such as the Klippel–Trénaunay syndrome and CLOVES syndrome, which also seem to have a metameric link, can be accompanied by vascular malformations (Figure 4).²⁸ Alomari et al reported six cases of CLOVES syndrome with complex spinal–paraspinal high flow lesions.²⁹

Figure 4.

A 44-year-old male patient with Klippel–Trénaunay syndrome. He presented with progressive paraparesis due to a medullary arteriovenous malformation, supplied by the anterior spinal artery, which carries a fusiform aneurysm (a). The supply of the AV-malformation and the aneurysm were occluded with coils in order to eliminate the associated bleeding risk (b), achieving a significant reduction of the arteriovenous shunt. While the clinical symptoms were caused by the spinal AVM, injection of the right common iliac artery shows an asymptomatic paraspinal arteriovenous shunt with paraspinal venous drainage (c–e). This AV-shunt remains asymptomatic and, therefore untreated. The condition of the patient stabilized, he walks with a cane. AVM, arteriovenous malformation.

Paraspinal AV shunts associated with genetic dysplasia

Several genetically inherited conditions are known to be associated with vascular anomalies, most notably neurofibromatosis (Figure 5) and hereditary hemorrhagic telangiectasia (Rendu–Osler–Weber disease).^{4, 11,30} The latter is characterized by an early affection of the vascular cells in the germinal stage.⁴ Besides, a few case reports concerning PAVSs in patients with fibromuscular dysplasia exist in the literature.^{28, 30}

Figure 5.

A 50-year-old female patient with neurofibromatosis. Clumsiness of her right hand and a suspected intraspinal neurofibroma (a) led to a surgical exploration of her cervical spine. During this operation, no neurofibroma but intraspinal arterialized veins were found. The injection of the right vertebral artery showed several fusiform dilatations of this artery and an arteriovenous shunt to the para-and intraspinal veins (b, c). Both, the aneurysms and the arteriovenous shunts were occluded with detachable coils (d). Follow-up MRI, 6 months later confirmed the complete disappearance of the intraspinal veins (e).

Discussion

Numerous classifications for spinal AVSs have been published, since the first AVSs around the spinal cord were described in the late 19th century by Hebold and Gaupp.^5,31–40 These classifications divide spinal AVSs into subgroups on the basis of morphological criterion which, according to Rodesch and Lasjaunias, create unfortunate confusion due to subjective interpretation of angiographic data or imprecise description. Thus, in 2003 Rodesch and Lasjaunias proposed a classification scheme for spinal AVSs, categorizing them according to (1) their precise localization, (2) the type of shunt involved (fistula or nidus) and (3) their potential association with genetic alterations, vascular biological features, and angiogenesis. Thereby, they took an additional step separating extradural shunts in extradural/epidural and PAVSs.⁴

In our opinion, a classification system for PAVSs is worthwhile, as they represent an independent entity of AV shunts, which can be distinguished from extradural or epidural AV shunts by differences in their arterial supply and their venous drainage pattern. Subdivision could help to draw information about natural course, treatment options and outcomes together and, thereby could help to determine therapy strategies in the future.

Table 3 summarizes the available literature for PAVSs, classifying them according to the proposed classification for PAVSs. In the literature, the isolated PAVSs are much more common than the associated ones. Only a few case reports and small case serious with coherence of hereditary genetic or metameric origin and paraspinal shunts exist.^28,43–45

Table 3. .

Review of the literature

Author	Year	No. of cases	Assumed etiology of the PAVS	Clinical presentation	Location of shunt	Venous drainage	Therapy	Stuttgart classification	Classification according to Iizuka et al3
Alomari et al29	2011	6	Syndromal (CLOVES syndrome)	Weakness of upper extremity, back pain, urinary incontinence, leg weakness	Thoracic, lumbar	Paravertebral, epidural	Surgery, embolization (material unknown)	Associated PAVS with metameric link, extra- and intraspinal drainage	Associated PAVS with metameric link
Ashour et al41	2015	2	Congenital	Heart murmur	Cervical	Epidural	Coils + occlusion device	Isolated congenital PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Briganti et al30	2014	29 (review)	Spontaneous (4), syndromal (NF; 10), trauma/iatrogen (15)	Inferior limb weakness, pulsatile bruit, cervical pain, tinnitus	Cervical	Paravertebral	Balloon, coils, transarterial glue, surgery	Isolated acquired (4)/traumatic (15) PAVS, extraspinal drainage; associated (10) PAVS with systemic genetic dysplasia, extraspinal drainage	Isolated PAVSs along the segmental nerve, type a (vertebrovertebral shunts)
Chen et al11	1996	1	Spontaneous	Leg weakness	Thoracic	Epidural	Transarterial glue	Isolated acquired PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Cognard et al20	1995	1	Trauma	Pain, radicular hypoesthesia	Sacral	Ascending lumbar vein	Balloon occlusion	Isolated traumatic PAVS, extra- and intraspinal drainage	Isolated extradural arteriovenous shunt
Farhat et al31	2015	2	Congenital	Heart murmur	Cervicothoracic (1), thoracic (1)	Epidural	None	solated congenital PAVS, intraspinal drainage	solated extradural arteriovenous shunts
Fotso et al42	2006	1	Congenital	Heart murmur	Thoracic	Epidural	Coils	Isolated congenital PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Hui et al23	1993	2	Congenital	Leg spasm, underweight, heart murmur	Cervical (1), Thoracic (1)	Paravertebral, epidural, perimedullary	Transarterial glue (2), coils (1)	Isolated congenital PAVS, extra- and intraspinal drainage	Isolated extradural arteriovenous shunts
Kähärä et al8	2003	1	Spontaneous	Pain, bladder dysfunction	Sacral	Epidural	Transarterial glue	Isolated acquired PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Niimi et al26	2005	5	Congenital	Heart murmur	Thoracic (4), Lumbar (1)	Paravertebral,  epidural	Transarterial glue (4), coils (1)	Isolated congenital PAVS, extra- or intraspinal drainage	Isolated extradural arteriovenous shunts
Schmidt et al10	2008	3	Spontaneous	Pain, no neurological symptoms	Thoracic (1), Lumbar (1), Sacral (1)	Epidural	Transarterial onyx	Isolated acquired PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Toi et al14	2011	1	Trauma	Pain, paraplegia, bladder and sphincter dysfunction	Sacral	Perimedullary	Transarterial glue + surgery	Isolated traumatic PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Yamaguchi et al9	2008	1	Spontaneous	Tetraparesis, bowel dysfunction	Cervical	Epidural	Transarterial glue	Isolated acquired PAVS, intraspinal drainage	Isolated extradural arteriovenous shunt
Yeh et al15	2014	5	Trauma (3), Spontaneous (2)	Headache, pulsatile tinnitus, neck pain, subarachnoidal hemorrhage (2)	Cervical (vertebro-vertebral PAVSs)	Paravertebral	Covered stent (3), coils (3)	Isolated acquired (2) or traumatic (3) PAVS, extraspinal drainage	Isolated extradural arteriovenous shunts

NF, neur ofibromatosis; PAVS, paravertebral arteriovenous shunt.

Cases were classified according to the Stuttgart classification and the classification according to Iizuka et al³.

Iiizuka et al reported a case of high-flow paraspinal osseous epidural AVF, presenting a classification for epidural/paraspinal AVMs/AVFs at the same time. In this classification, they further subcategorized the isolated epidural/paraspinal AVMs/AVFs in (a) paraspinal AVFs along the segmental nerve route, (b) vertebral bone AVMs, (c) slow flow epidural AVFs and (d) other extradural AVFs/AVMs. In contrast, our classification scheme is based on the supposed origin of the PAVS and its potential relationship to an underlying disease with respect to the venous drainage pattern. This way of classifying PAVSs is more consistent and, thereby superior to the one proposed by Iizuka et al whose classification is a mixture of morphological aspects, etiology and drainage characteristics.³

Anatomy and pathophysiology

The vascular anatomy of spine and myelon is relevant for the understanding of the pathophysiology of PAVS and the potential complications of their treatment.

PAVSs arise from segmental arteries and are located either at the main trunk or its branches.⁴ Every segmental artery supplies all the tissues on one side of a given metamere with exception of the spinal cord. The segmental arteries are connected via a system of extradural longitudinal and transversal anastomoses. In the cervical region, the vertebral arteries together with the deep cervical and ascending cervical arteries form the effective chain of longitudinal anastomoses.^{39, 46} Therefore, vertebrovertebral fistulas should also be rated among the group of PAVS.⁴ The venous drainage of the spinal cord parenchyma is effected through intrinsic veins of the parenchyma in the anterior and posterior median spinal veins. Theses longitudinal collectors drain into the epidural venous plexus through radicular veins. The epidural venous plexus is connected with the paraspinal venous system, namely the intercostal or segmental veins, the ascending lumbar vein, and the vertebral and deep cervical veins.⁴⁶ Normally, the paravertebral veins drain into the azygos and hemiazygos venous system but can in presence of a PAVS also lead to venous congestion in the epidural venous plexus and even the perimedullary veins.

The reason of retrograde venous flow in the spinal venous system was widely discussed in literature.^47–49 In anatomic studies the existence of venous valves was already excluded for the spinal venous system.⁵⁰ Quite the contrary, an antireflux mechanism was discovered, consisting of narrowing and zigzagging of the radicular veins while crossing the dura.⁴⁶ Gilian hypothesized that a failure in the antireflux mechanism of the epidural space as a result of chronic venous hypertension could be a possible explanation for the reflux into the epidural and perimedullary venous system.⁵⁰

Clinical presentation

Symptomatic PAVSs most often present with reflux into the epidural venous system with venous hypertension in the epidural veins or even venous congestion. The latter could be a result of venous stenosis, pouches or thrombosis due to longstanding high-flow shunts.^{14, 26} Compressive myelopathy, isolated nerve root compression or infrequently steal of blood flow with high-output cardiac failure are possible clinical symptoms, however, there is no classical presentation.^{3, 10,14,26,27,51,52}

Congenital PAVSs often cause a murmur as the only symptom, especially before the age of 10.⁵³ Therefore, the need for treatment in this subgroup of PAVSs is discussed controversial, especially because the natural course of this rare entity is unknown and epidural venous engorgement occurs infrequently.²¹ Nevertheless, there seems to be a tendency towards prophylactic treatment in asymptomatic children to avoid the possible development of congestive heart failure, which in fact is an infrequent if not inexistent phenomenon.⁵⁴

In contrast, traumatic and acquired PAVSs may present with local pain, but also severe symptoms for example paraparesis is possible and therefore, immediate treatment should be favored.^{11, 53}

The natural course of the different subtypes of PAVSs is still.

Treatment

The indication for treatment of PAVSs is based on clinical signs and symptoms. Incidentally detected PAVSs with exclusive extraspinal drainage often remain untreated. Reasons for treatment include intraspinal drainage with congestion or compression of the myelon, intraspinal hemorrhage, vascular bruit, local pain or a high-output cardiac failure.

Endovascular as well as surgical treatment aims at a complete interruption of the pathological arteriovenous connection.

Before the development of endovascular methods, surgery of PAVSs was the only option. Due to unsatisfactory results, neurosurgical therapy is now only indicated in the case of compressive extradural hematoma.^{8, 12} Endovascular embolization became, meanwhile, the accepted first line treatment method for PAVSs.^{23, 26,55,56}

Given the frequently present anastomoses and direct arterial supply to the myelon in the surrounding territory of PAVSs, particle embolization should be avoided. No matter if polyvinyl alcohol or one of the more technical embolization particles [e.g. Embozene Microspheres, Boston Scientific (Marlborough, MA)] is used, the control of the distribution of these particles can be difficult and any inadvertent occlusion of the pial supply of the myelon may result in a major neurological deficit. Vessel occlusion after particle embolization is frequently not permanent, especially with polyvinyl alcohol, and recurrences can be more difficult to treat than the original lesion.

For small calibre single hole or plexiform arteriovenous connections, we prefer nBCA/Lipiodol (e.g. Glubran2, GEM) rather than ethylene-vinyl alcohol copolymer (Onyx; Medtronic). During the glue injection, arterial reflux should be avoided but a well-controlled and limited venous passage with occlusion of the draining vein adjacent to the shunt is the aim.

In a large calibre shunt, the propagation of any liquid embolic agent can be difficult to control. For the time being, coil occlusion is the preferred technique, if needed in combination with liquid embolic agents. Both selective obliteration of the shunt as well as parent artery occlusion can be part of the treatment strategy.

In selected PAVSs, a reconstruction of the artery from which the supply of the PAVSs arises can be achieved using telescoping porous stents, stent grafts or flow diverters. The vertebral artery is the preferred vessel for this treatment strategy.

Conclusion

PAVSs occur isolated or associated with genetic disorders. Isolated PAVSs are either acquired, due to trauma or congenital. PAVSs associated with a genetic disorder have a metameric link or a systemic genetic background. The route of venous drainage, mainly responsible for the symptoms, is either extraspinal or intraspinal.

The presented classification system can intuitively be used and the subclassification of this complex and rare type of AVS may lead to better understanding of the clinical course and, therefore, can help to reliably determine treatment strategies in the future. Currently, the indication for and technique of endovascular treatment is based on individual clinical and anatomical criteria. With this classification, a standardized nomenclature is proposed, which could also help to create a comprehensive database in the future.