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Fig. 38.8 Axial T2-weighted scans (a–d) and left ICA injection in arterial and early venous phases AP and lateral (e–h) demonstrate a posterior
cingulate AVM with an abnormal small straight sinus that leads to rerouting of venous drainage into the median parietal vein cranially toward the
superior sagittal sinus (arrowheads) and inferiorly via the lateral mesencephalic vein (arrow) and the superior petrosal sinus (small arrows) to the
transverse sinus.
The Infratentorial Veins
197
The longitudinal veins are divided into a midline and a lateral
group. The midline veins run as an anastomotic venous channel
composed of the median anterior pontomesencephalic vein, the
median anterior pontine vein, and the median anterior medullary vein, which is continuous with the anterior spinal vein. The
venous blood flow can run cranially to the posterior communicating vein or the peduncular veins or caudally toward the
spinal veins. The lateral veins are the lateral anterior pontomesencephalic, mesencephalic, and medullary veins, which anastomose with each other and the midline veins. A particularly
important vein in this group is the lateral mesencephalic vein,
which connects the basal vein of Rosenthal with the lateral
brainstem veins and the vein of the medullary fissure. When
the basal vein of Rosenthal is discontinuous, the anterior segment will drain posteriorly to the infratentorial veins via the
lateral mesencephalic vein. In addition, in patients with a vein
of Galen malformation, the lower part of the epsilon sign seen
in lateral angiograms represents the lateral mesencephalic vein,
which serves as a collateral venous drainage route between the
deep venous system and the extracranial veins.
and tentorial sinuses posteriorly, and to the superior petrosal sinus via the petrosal vein laterally. Small bridging veins between
the brainstem veins and the cavernous sinus can also be rarely
seen in angiography.
38.2.5 The Persistent Occipital Sinus
Of the three embryologic meningeal venous plexuses, the posterior plexus undergoes the fewest changes, simply extending
to become the occipital sinus by the 50-mm stage. It serves as a
connection between the torcular and the marginal sinus (at the
level of the foramen magnum) and is continuous with the dorsal internal vertebral venous plexus. The occipital sinus is often
prominent in the newborn and slowly decreases in size as the
jugular bulb maturation occurs during the first year of life.
The presence of an occipital sinus can explain the combination of a hypoplastic transverse sinus with a normal-sized or
even large jugular bulb, as the occipital sinus will use the jugular bulb to drain.
38.2.4 Bridging Veins
The bridging veins cross-connect the subarachnoid and subdural spaces to reach the dural venous sinuses. These bridging
veins collect into the vein of Galen superiorly, to the torcular
38.3 Clinical Impact, Additional
Information and Cases
See ▶ Fig. 38.2, ▶ Fig. 38.3, ▶ Fig. 38.4, ▶ Fig. 38.5, ▶ Fig. 38.6,
▶ Fig. 38.7, and ▶ Fig. 38.8.
The Infratentorial Veins
198
Pearls and Pitfalls
●
The posterior fossa structures drain toward three main collecting structures, depending on the surface. The anterior
(petrosal) surface drains mainly to the superior petrosal sinus. The superior (tentorial) surface drains to the vein of Galen. The posterior-inferior (suboccipital) surface drains to the
torcular and the transverse sinus.
●
The venous configuration explains the posterior fossa venous
congestion in dural fistulas involving the transverse sinus and
torcular.
●
The infratentorial veins anastomose with the vein of Rosenthal via the pontomesencephalic vein and the lateral mesencephalic vein. These anastomoses explain the posterior fossa
drainage of certain carotid-cavernous fistulas.
●
Small bridging veins can exist between the brainstem veins
and the cavernous sinus.
Further Reading
[1] Huang YP, Wolf BS. The veins of the posterior fossa—superior or galenic
draining group. Am J Roentgenol Radium Ther Nucl Med 1965; 95: 808–821
[2] Huang YP, Wolf BS, Antin SP, Okudera T. The veins of the posterior fossa—an-
terior or petrosal draining group. Am J Roentgenol Radium Ther Nucl Med
1968; 104: 36–56
[3] Lasjaunias P, Berenstein A, ter Brugge KG. Surgical Neuroangiography. Vol. 1.
2nd ed. Berlin: Springer; 2006
[4] Rhoton AL, Jr. The posterior fossa veins. Neurosurgery 2000; 47 Suppl: S69–
S92
Section VII
Spine
VII
Fig. 39.1 T2-weighted (a,b,e) and contrast-enhanced T1-weighted (c,d) sagittal (a,b,c) and axial (d,e) MRIs demonstrate an intradural intramedullary
arteriovenous malformation (AVM) in addition to a paravertebral AVM with multiple dilated vessels within the left lateral pedicle of T12 and the
paraspinal tissues, including the musculature at this level on the left. Magnetic resonance angiography (f) demonstrates extensive shunting in both the
cord and the paraspinal soft tissues centered on the T12 level. Case continued in ▶ Fig. 39.2.
The Segmental Spinal Arteries
200
39 The Segmental Spinal Arteries
39.1 Case Description
39.1.1 Clinical Presentation
A 24-year-old female patient complained about progressive
weakness in her left leg. When she was seen, she was unable to
stand on her left leg without support. Sensation, bladder, and
bowel functions were not disturbed. There was evidence of hyperreflexia in her left ankle and knee with clonus and an upgoing left plantar reflex. She had a left-sided skin discoloration
on her lower thoracic region that had been there since birth.
39.1.2 Radiologic Studies
See ▶ Fig. 39.1, ▶ Fig. 39.2.
39.1.3 Diagnosis
Spinal arteriovenous metameric syndrome (Cobb syndrome or
juvenile spinal arteriovenous malformation) at T12.
39.2 Anatomy
The blood supply to a given metamere (which consists of the
vertebral body, the paraspinal muscles, the dura, nerve root,
and spinal cord) is derived from segmental arteries. These segmental arteries are present in the fetus for each of the 31 spinal
segments. This segmental supply remains preserved in the
thoracic and lumbar regions via the intercostal or lumbar arteries. In the upper thoracic region, several segmental arteries
coalesce to form a common feeder, which is the supreme intercostal artery. In the cervical region, this vascular rearrangement
is even more obvious: on each side, three longitudinal anastomotic arteries are established as potential sources of spinal
blood supply; namely, the vertebral artery, the deep cervical artery, and the ascending cervical artery.
The vertebral artery is a chain of intersegmental anastomoses
that connects the cervical segmental arteries, each of which is
able to supply a cervical segment, with the most prominent
being the arcade of the dens. In the upper cervical region, potential sources of metameric blood supply are via anastomoses
Fig. 39.2 Spinal angiography in the anteroposterior view in early (a)
and late (b) arterial phases after injection into the left T12 segmental
artery reveals the paravertebral AVM with arteriovenous shunting
along the segmental artery supplying the skin, paravertebral muscles,
and vertebral body, as well as the origin of a dorsolateral radiculopial
artery (arrow) that supplies a spinal cord AVM. The concurrence of
arteriovenous malformations af fecting multiple compartments of the
same metamere gave rise to the term spinal arteriovenous metameric
syndrome.
Fig. 39.3 Af ter injection into the left ascending cervical artery, the rich
anastomotic network is well visualized. The anterior spinal artery (black
arrow) is supplied by multiple radiculomedullary arteries (white arrows)
that demonstrate retrograde filing to the contralateral vertebral and
deep cervical arteries. The vertebral artery gives rise to the arcade of
the dens (thin double arrows) at the C3 level.
The Segmental Spinal Arteries
201
to the external carotid artery, mainly the occipital artery
(namely, the C1 and C2 anastomoses; see Case 4) and the ascending pharyngeal artery (namely, the hypoglossal artery,
which anastomoses with the C3 collateral of the vertebral artery via the odontoid arterial arch that supplies the dens; see
Case 30). In the sacral and lower lumbar region, sacral arteries
and the iliolumbar artery (which often supply the L5 level) derived from the internal iliac ar teries are the most important
supply to the caudal spine.
In general, the segmental arteries supply all the tissues on
one side of a given metamere, with the exception of the spinal
cord. Because of its embryological origin, each metamere is centered at the level of the vertebral disk, and therefore, each vertebra is supplied by t wo consecutive segmental arteries on both
sides that anastomose extensively both across the midline and
between levels above and below. The latter is formed by an extraspinal longitudinal system that connects the neighboring
segmental arteries longitudinally. The vessels course on the lateral aspect of the vertebra or transverse process. This system
is highly developed in the cervical region, where the vertebral
artery and the deep cervical and ascending cervical arteries
form the most effective chain of longitudinal anastomoses
(▶ Fig. 39.3).
In addition to this extraspinal system, an intraspinal
extradural system is present that constitutes a transverse
anastomosis but also has longitudinal interconnections. The
retrocorporeal and prelaminar arteries are the relevant vessels for the supply of bone and dura and interconnect with
neighboring and contralateral segmental arteries. These anastomoses provide an excellent collateral circulation, and it is
for this reason that numerous segmental ar teries can be visualized by injection of one segmental artery (▶ Fig. 39.3).
The extensive network of ext ra- and intraspinal anastomoses
protects the spinal cord against ischemia related to segmental
arterial occlusion (▶ Fig. 39.4).
The segmental arteries course along the vertebral body
posteriorly, supplying the per iphery of the vertebral body by
perforating arteries. While the muscular branch runs further
posteriorly to the segmental muscles, the spinal branch of
the segmental artery enters the vertebral canal through the
intervertebral foramen and regularly divides into three
branches: an anterior and posterior arter y of the vertebral
canal that supplies the bony spinal column and a radicular
artery that supplies the dura and nerve root at every segmental level.
Fig. 39.4 At various and unpredictable levels, the anterior spinal artery
is reinforced by additional metameric arterial supply. In this young
patient with suspected AVM, injection of the right Th4 artery in early
(a) and late (b) arterial phases demonstrates the anterior spinal artery
and its division into a superior and inferior branch (small black asterisk in
a). In addition, the retrograde filling of additional feeders both superior
and inferior to Th4 (white arrows) is visualized. Via an extensive
collateral supply with longitudinal and transversel paravertebral
anastomoses, and through the anastomotic network of the vasocorona
(small black arrows), additional radiculopial arteries can be seen (black
arrows). The level of the injected segmental artery can be deduced
from the extensive vertebral blush (white asterisk).
Fig. 39.5 The type of feeding artery determines the type of arteriovenous shunt encountered (a–d). In this picture, four different arteriovenous shunts
are depicted, with the arrow pointing to the feeding vessel in each case. In case (a) the shunt is derived from the segmental artery proper, thereby
forming a paravertebral shunt. In case (b), the shunting artery is the radicular artery forming a radicular AVM. In case (c), the feeding vessel is a
radiculomeningeal or dural branch, thereby constituting a dural arteriovenous fistula. Finally, in case (d), the feeding artery is a vessel that would
normally supply the cord, thus constituting a “pial” arteriovenous malformation.
The Segmental Spinal Arteries
202
39.3 Clinical Impact, Additional
Information and Cases
Knowledge of the segmental supply of the spinal cord helps
with understanding the nature of the disease encountered in
the index case: a metameric disease that affects not only the
spinal cord but also muscle, bone, and skin supplied by the affected vessel. Understanding the regional vascular anatomy also
helps to classify different vascular shunts, depending on the
feeding artery, thereby subdifferentiating spinal vascular malformations into paravertebral, radicular, dural, and pial arteriovenous malformations (▶ Fig. 39.5).
During postnatal development, a “pruning” process of the
cord supply takes place that leads to regression of the number of cord-supplying arteries from the segmental arteries.
This process explains why there is not necessarily cord
supply from every single segmental level. Identification of
cord supply is, however, of paramount importance when
embarking on embolization of shunts that are fed by the radiculomeningeal arteries (such as the dural arteriovenous
fistulae of the spine) or on preoperative devascularization of
hypervascularized tumor metastases to the spine, because,
from the segmental level that has to be embolized, vessels
may arise that supply the cord (▶ Fig. 39.6; ▶ Fig. 39.7;
▶ Fig. 39.8).
The rich collateral network that is present in between the
segmental arteries also explains why a proximal ligation embolization of dural arteriovenous shunts will not be successful, as
other dural branches will take over the supply to the shunt with
time if the liquid embolic agent does not reach the proximal
“foot” of the vein (▶ Fig. 39.9).
Fig. 39.6 Vertebral body metastasis from a renal cell cancer is demonstrated in plain coronal (a) and axial (b) CTs. Extensive supply from the bilateral
segmental arteries is visualized on the segmental spinal angiograms (c–f). Before embolizing these lesions, it is important to make sure there is no
cord supply arising from the same segmental level.
Fig. 39.7 In this patient, sagittal (a,b,c) and axial (d,e) T2-weighted (a), T1-weighted (b,e), and contrast-enhanced T1-weighted MRIs demonstrate a
pathologically proven ventral schwannoma. Vertebral angiogram in arterial (f) and capillary (g) phases reveals that the supply to the schwannoma
(black arrow) arose from the same segmental level from which the anterior spinal artery (white arrow) arose. Note the faint tumor blush (arrowheads)
and the displacement of the anterior spinal artery.
The Segmental Spinal Arteries
203
Fig. 39.8 Spinal angiograms in two different patients (a,b) who both
harbor a spinal dural arteriovenous fistula and who have additional
supply to the cord (anterior spinal artery, white arrows) arising from the
same level as the supply to the fistula. Identification of the additional
cord supply is paramount to avoid inadvertent embolization into the
cord supplying vessels.
Fig. 39.9 Injection into the right T7 segmental artery (a) revealed a
dural arteriovenous shunt fed by the radiculomeningeal artery (short
arrow), with the shunting zone (long arrow) underneath the pedicle of
T7. On the T7 injection, a descending dural branch (small arrow) was
noted that anastomosed to the ascending dural branch that arose from
the right T8 segmental artery (b). This case demonstrates the rich
collateral supply to the dura that is the cause for delayed reopening of
dural arteriovenous fistulae in cases of proximal ligation of the feeding
artery.
The Segmental Spinal Arteries
204
Pearls and Pitfalls
●
The segmental artery gives rise at each level to vertebral,
muscular, and paraspinal branches and to a radicular artery
that supplies the meninges of the nerve root sleeve, as well
as the nerve root itself.
●
Supply to the cord may arise from this segmental artery and
has to be identified before embolizing lesions like dural arteriovenous fistulas, paravertebral shunts, or hypervascularized
tumors.
●
The rich anastomotic network between segmental arteries
may lead to inadvertent embolization of neighboring segmental arteries, especially when using liquid embolic material with high penetration capabilities.
Further Reading
[1] Geibprasert S, Pereira V, Krings T et al. Dural arteriovenous shunts: a new
classification of craniospinal epidural venous anatomical bases and clinical
correlations. Stroke 2008; 39: 2783–2794
[2] Krings T, Mull M, Gilsbach JM, Thron A. Spinal vascular malformations. Eur
Radiol 2005; 15: 267–278
[3] Thron AK. Vascular Anatomy of the Spinal Cord: Neuroradiological Investiga-
tions and Clinical Syndromes. Vienna: Springer; 1988
Knowledge of the existence of these anastomoses is important
when employing liquid embolic agents that slowly polymerize
and that may, therefore, open anastomoses, leading to inadvertent occlusion of distant segmental arteries and their daughter
vessels.
Fig. 40.1 Sagittal T2-weighted (a,b) and T1-weighted (c,d) MRIs demonstrate hematomyelia with a localized blood clot in the center of the cord at the
C2 level and no dilated perimedullary vessels. Blood was seen to extend both cranially and caudally along the central canal. The patient was first
treated conservatively. After he regained consciousness, conventional angiography was performed to rule out the remote possibility of a
microarteriovenous malformation. Case continued in ▶ Fig. 40.2.
The Radiculopial and Radiculomedullary Arteries
205
40 The Radiculopial and Radiculomedullary Arteries
40.1 Case Description
40.1.1 Clinical Presentation
A previously healthy 58-year-old male patient had an acute onset of quadriplegia and sensory loss in his upper and lower
limbs, severe headaches, and progressive respiratory dysfunction that required intubation.
40.1.2 Radiologic Studies
See ▶ Fig. 40.1, ▶ Fig. 40.2, and ▶ Fig. 40.3.
40.1.3 Diagnosis
Spinal perimedullary arteriovenous fistula arising from an
unfused segment of the anterior spinal artery.
40.2 Anatomy and Embryology
Although in the embryo each radicular artery gives rise to a
radiculomedullary artery to supply the spinal cord, in postnatal
life, the number of radicular arteries supplying the spinal cord
is reduced after a transformation and fusion process. At a few
unpredictable segmental levels, the radicular artery has a persistent supply to the cord that reaches either the anterior surface via the ventral nerve root or the posterolateral surface via
the dorsal nerve root to form and supply the superficial spinal
cord arteries. Two to 14 (on average, six) anterior radiculomedullary arteries persist as the result of this “pruning process” of
the feeding vessels. The posterior radiculomedullary arteries
are reduced less drastically, mostly to between 11 and 16
vessels.
Several nomenclatures and classifications have been used to
describe spinal cord arteries, which may lead to some confusion. The original classification is based on where the spinal
cord arteries run (i.e., on the posterior, posterolateral, or anterior surface of the spinal cord, thereby constituting the posterior
or posterolateral arteries and the anterior spinal artery). A classification proposed by Lasjaunias differentiates three types of
spinal radicular arteries according to their region of supply:
radicular, radiculopial, and radiculomedullary.
The spinal radicular artery is a small branch, present at every
segmental level, that supplies the nerve root as well as the adjacent dura. The radiculopial arteries supply the nerve root and
the dorsolateral superficial pial system (via the posterior radicular artery). The radiculomedullary arteries supply the nerve
root, the superficial pial system, and the medulla (via the anterior radicular artery). This classification offers advantages for
the interventional neuroradiologist when compared with the
classical differentiation because it stresses the importance of
the anterior supply for the gray matter of the spinal cord parenchyma. Because the anterior spinal artery has radicular, radiculopial, and medullary supply and the radiculopial posterolateral
arteries may have some medullary supply (i.e., part of the posterior horns), this classification may, however, result in misunderstandings. This is why we proposed recently the following
slight modification to the classification to overcome the anatomical confusions: Radicular arteries are vessels that supply
the nerve root and the dura mater but do not supply the spinal
cord. These arteries are present on every single segmental level,
whereas the following two types may or may not be present at
a given segmental level.
Fig. 40.2 Left vertebral artery angiograms in anteroposterior (AP) (a) and lateral (b) views and 3D rotational reconstruction (c,d) visualized a spinal
perimedullary arteriovenous fistula fed by a slightly enlarged anterior spinal artery that arose from the left vertebral artery. At the C2 level, there was a
focal unfused segment of the anterior spinal artery (ASA). The fistula was selectively supplied by one of the two unfused limbs of the ASA at the level
of C2 with a venous (false) aneurysm (arrows) as the point of rupture. Case continued in ▶ Fig. 40.3.
Fig. 40.3 Selective microcatheter injection before (a), plain radiography during (b), and vertebral artery angiograms after (c,d) the embolization
demonstrate deposition of two microcoils that led to occlusion of the shunt, while the ASA was preserved.
The Radiculopial and Radiculomedullary Arteries
206
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