Spinal artery

General

Single ventral arterial axis

Anterior spinal artery (ASA)
The anterior axis lies within the ventral spinal cleft
forms from a series of radiculomedullary arteries, while the posterior form from radiculopial vessels.

Two dorsal arterial axes— the posterior spinal arteries (PSA).

Branches of the radicular arteries reach the cord by following the dorsal and ventral roots.

Two “watershed” areas within the anterior spinal artery at the level of T1-T3 and T6-T8.

These are regions that lie in between the three main vascular origins, thereby receiving arterial blood both from above and from below; the resulting oppositional flow can lead to cord hypo-perfusion at lower blood pressures.
Due to Caton 2023

less robust anastomoses exists between T4 and T8, rendering these levels susceptible to transient perfusion abnormalities

But clinically not entirely proven

Some explain relative hypovascularity of the mid-thoracic cord reflects metabolic parsimony due to relatively decreased oxygen demand at these levels relative to other cord regions

Spinal artery embryogenesis

These ventral and dorsal axes themselves develop in- utero as paired metameric arteries.

4-6th week gestation:

Fusion

of the anterior metameric pairs ultimately → ASA.
Failure of fusion accounts for the occasional fenestrations seen in the ASA.

Desegmentation: occurs with involution of many metameric arteries.

Simultaneously occurs with fusion
62 metameric vessels initially

dorsal 31 → 10-20 remain
ventral 31 → 4– 8 remain

There is great variability in the degree to which anterior metameric arteries regress, but two relatively constant remnants are named.

The artery of the lumbar enlargement

Larger radiculomedullary artery
Arteria radicularis magna
Artery of Adamkiewicz

Most often arises from the left side.

75% of cases it arises between T9 and T12.

When it arises outside of that area there is usually a second large, persisting metameric artery to be found cranially or caudally.

Artery of Adamkiewicz.

In 75% of patients, the AKA arises between T9 and T12, more commonly on the left.

When its origin is above T8 or below L2, another major contributor to the ASA can be found either cranially or caudally.

In 30-50% of cases, it also contributes significantly to the PSA.
Generally, a pair of arteries arises in the cervical region from the intradural segment of each vertebral artery that fuse to one “Y”-shaped ASA running in the subpial space in the ventral sulcus of the spinal cord (dorsal to the anterior spinal vein) to the terminal film.
The typical hairpin anastomosis between the radiculomedullary arteries and the ASA is found angiographically at the lower thoracic and lumbar levels.

The artery of the cervical enlargement

Entering the C5/ 6 level
arises from

Thyrocervical trunks
Costocervical trunks.
subclavian artery (rarer)

Variation is again frequent

15– 20 weeks gestation

Posterior axes fuses

The radicular arteries

Radicular artery

Radiculospinal branches. (Neuroangio does not talk about radiculospinal arteries instead radicular artery directly becomes radiculopial or radiculomedullary)

Supplies the spinal cord
At each level, the radiculospinal branch may divide into → entering the spinal canal with the corresponding nerve roots

anterior branches
posterior branches

This extrinsic arterial supply is relatively well collateralized, particularly in the cervical region.
Occlusion of the costocervical artery is relatively unlikely to result in anterior spinal infarction, as the deep and ascending cervical arteries will collateralize the anterior spinal axis.
Clinical

Radiculospinal branches form Spinal AVM and perimedullary AVF

Arriving at the cord each radiculospinal artery can be formed into two variants

Radiculopial arteries

Supplies the posterior axis
The terminal branches of the radicular arteries, reaching the pia via the spinal root, form PSA.

Those branches reaching the cord are termed radiculopial arteries and they invade the cord from the pial surface and supply the peripheral parts of the cord with a watershed region at the interface between the white and grey matter.

Vasa coronae.

Small branches from radiculopial and radiculomedullary systems run on the pial surface and encircle the cord.

These give perforating vessels into the superficial white matter of the cord as well as forming a superficial anastomosis with the anterior circulation.

Radiculomedullary artery

An enlarged radicular artery instead of supplying local neural elements, it maintained its embryonic access to the anterior spinal artery.

Supplies the anterior axis
Most of the anterior grey matter of the spinal cord
Anterior part of the posterior grey matter
Elements of the anterior, lateral, and posterior white columns.

Each radiculomedullary artery contributes a superior and inferior ramus to form the anterior arterial axis.
Sulco-commissural arteries penetrate the cord via the ventral commissure in turn giving rise to the radially directed perforating vessels, which supply the cord.

Radiculomeningeal branches.

Supply the nerve root’s dural sheath and contents
Do not supply the spinal cord.
Clinical

Radiculomeningeal branches form arterial supply for Spinal dural AV fistulae

Arterial anastomoses and the ‘conus basket’

The vasa coronae and radial perforating vessels form longitudinal and segmental anastomoses along the cord.

The relative contributions by the radiculopial and radiculomedullary systems vary.

Cervical cord is evenly served
Thoracic cord

Relatively less reliably served
Although the well- known vulnerability of the thoracic cord to ischaemia may also be a function of its venous drainage as discussed next.

Lumbosacral Cord

rely mainly on the central radiculomedullary system

Conus basket

An especially well-developed anastomotic channel between anterior and posterior arterial axes

The ASA tapers as it runs down the anterior surface of the conus and one to two branches join it to the PSA (Martirosyan et al., 2015).

At the level of the conus medullaris.
The artery of the filum terminale is the terminal continuation of the anterior axis below the conus.

Normal arterial supply (Neuroangio)

Supply tree for spinal cord


flowchart TD
    A["Aorta (A)"] --> B["Segmental artery (B)"]
    B --> E["Dorsal spinal artery (E)"]
    E --> K["Ventral division of dorsal<br>spinal artery (K)"]
    K --> Ka["Radicular artery (Ka)"]
    Ka --> O["Radiculopial artery (O)"] & P["Radiculomedullary artery (P)"]
    O --> X["Rami perforantes of<br>the peripheral system (X)"] & S["Posterior spinal<br>artery (S, T)"]
    P --> Q["Anterior spinal artery (Q)"]
    Q --> W["Sulco-commissural<br>artery (W)"]
    W --> Y["Central system of<br>sulcal arteries (Y)"]

Supply tree for meninges


flowchart TD
    A["Aorta (A)"] --> B["Segmental artery (B)"]
    B --> E["Dorsal spinal artery (E)"]
    E --> K["Ventral division of dorsal spinal artery (K)"]
    K --> Ka["Radicular artery (Ka)"]
    Ka --> n1["Epidural fat supply"] & n2["Theca supply"]
    M["Nerve root sleeve<br>dural branch of the<br>ventral division<br>dorsal spinal artery (M)"] --> N["Dural branch of the<br>ventral division<br>dorsal spinal artery (N)"]
    n2 --> M
    n1 --> Lb["Dorsal<br>epidural arcade (Lb)"] & La["Ventral<br>epidural arcade (La)"]

    n1@{ shape: hex}
    n2@{ shape: hex}
    style n1 fill:#FFD600,color:#FFFFFF
    style n2 fill:#2962FF,color:#FFFFFF

Images

The Ka (radicular artery is slightly mis labelled here)

A – aorta	B – segmental artery	Ba – intersegmental arterial anastomosis
C – prevertebral anastomotic network	D – direct vertebral body feeding arteries	E – dorsal spinal artery
F – intercostal/muscular artery	G – pretransverse anastomotic network	H – dorsal division of the dorsal spinal artery
I – post-transverse anastomotic network	J – muscular branches of the post-transverse anastomotic network	K – ventral division of the dorsal spinal artery;
Ka – radicular artery	La – ventral epidural arcade	Lb – dorsal epidural arcade;
M – nerve root sleeve dural branch of the ventral division dorsal spinal artery	N – dural branch of the ventral division dorsal spinal artery	O – radiculopial artery;
P – radiculomedullary artery	Q – anterior spinal artery	R – mesh-like pial arterial network
S, T – posterior spinal artery;	U, V – pial arterial network (a.k.a. vasocorona) anastomoses between anterior and posterior spinal arterial systems,	W – sulco-commissural artery,
X – rami perforantes of the peripheral (centripetal) system,	Y – central (centrifugal) system of sulcal arteries, originating from pial network of the cord; altogether, the pial network and rami perforantes (R+Y) are called the vasocorona or corona vasorum;	Z – rami cruciantes (a.k.a. crux vasculosa, a.k.a. rami anastomotici arcuati)