334 Neuroanatomy: Draw It to Know It
Spinal Cord Arteries ( Advanced )
Here, we will draw the arterial supply of the spinal cord.
Begin with the extrinsic system: on one side of the page,
draw an axial section through the spinal cord, and on the
other, draw an oblique, coronal section. Indicate that a
single anterior spinal artery descends the anterior median
fi ssure and that a pair of posterior spinal arteries descends
the posterior spinal cord. Next, in the axial cut, show
that generally, the anterior spinal artery supplies the
anterior two-thirds of the spinal cord and that the poste-
rior arteries supply the posterior one-third. Now, on
the coronal side of the diagram, draw the vertebral
arteries. Show that near where they join as the basilar
artery, vertebral artery branches also join to form the
anterior spinal artery. Th en, indicate that each vertebral
artery produces a single posterior spinal artery. Note,
however, that in many instances, the posterior spinal
arteries originate from the PICAs, instead. Also, note
that in addition to these posterolaterally situated arter-
ies, posteromedial spinal arteries can also exist.
Segmental arteries help supply the anterior and poste-
rior spinal arteries throughout their descent. In our axial
diagram, show a source artery and an attached segmental
artery. Th e source arteries and segmental arteries vary
along the superior–inferior length of the spinal canal.
Th roughout the cervical spinal cord, the source artery is
the subclavian artery. Th e segmental arteries in the upper
cervical spinal cord are the spinal segmental branches of
the vertebral arteries, and in the lower cervical spinal
cord, they are the ascending cervical artery (from the
thyrocervical trunk) and the deep cervical artery (from
the costocervical trunk). In the thoracic and lumbar
spinal cord, the descending aorta is the source artery. Th e
segmental branches in the thoracic cord are the posterior
intercostal arteries; in the lumbar cord, they are the
lumbar arteries. Finally, in the sacral spinal cord, the
source artery is the internal iliac artery, most commonly,
and the segmental arteries are the lateral sacral arteries.
Next, indicate that where the segmental artery divides
into ventral and dorsal branches, the dorsal branch is
called the dorsospinal artery, and it forms three types
of radicular arteries. Show that the radicular arteries
(proper) — anterior and posterior — supply the nerve
roots; the radiculomedullary arteries supply the anterior
spinal artery; and the radiculopial arteries supply the
posterior spinal arteries and also the pial network.
Indicate that the pial network is a ring of arterial supply
that surrounds the spinal cord; it has superior–inferior
interconnections that form an arterial meshwork around
the cord. Note that the most important radiculomedul-
lary artery is the artery of Adamkiewicz, which in the
majority of people arises from T9 to T12 but which can
originate anywhere from T8 to L3; it most commonly
originates from the left side of the body. Injury to this
artery can lead to paraplegia. At the C5 to C7 level,
another notable radiculomedullary artery exists — the
artery of the cervical enlargement.
Now, let’s draw the intrinsic arterial territories in axial
view. Th ey divide into the centrifugal and centripetal
systems. Show that the centrifugal system comprises
sulcal arteries from the anterior spinal artery, which
supply the spinal cord from central to peripheral; they
primarily supply the gray matter horns. Th en, indicate
that the centripetal system comprises vasocoronal perfo-
rating arteries from the pial arterial network, which
supply the spinal cord from peripheral to central; they
primarily supply the white matter funiculi.
We will not address the spinal cord venous system,
here, except to note that extensive venous anastomoses
exist that communicate with surrounding venous plex-
uses. Th e low-pressure state and valveless chambers of
the spinal venous system expose the spinal canal to
intrathoracic or intra-abdominal abscesses and neoplas-
tic metastases.^2 , 10 , 11