Veins of the Brain · 437 11

Fig. 11.16 Veins of the base

	Anterior	of the skull
	cerebral v.
	Deep
	middle
	cerebral v.
	Striate vv.
	Basal v.
	(of Rosenthal)
	Internal
	cerebral vv.
	Great cerebral v.
	(of Galen)

Venous blood from deep regions of the brain, including the basal ganglia and thalamus, drains into the paired internal cerebral veins and the paired basal veins of Rosenthal. The internal cerebral veins are created by the confluence of the vein of the septum pellucidum (septal vein) with the thalamostriate vein. These four veins, coming from the two sides, join behind the splenium to form the great vein of Galen. From here, venous blood drains into the straight sinus (sinus rectus) and then into the confluence of the sinuses (confluens sinuum, torcular Herophili), which is the junction of the straight sinus, the superior sagittal sinus, and the transverse sinuses of the two sides (Figs. 11.14­16).

Dural Sinuses

The superficial and deep veins of the brain drain into the cranial venous sinuses formed by double folding of the inner dural membrane (Fig. 11.17). Most of the venous drainage from the cerebral convexities travels from front to back in the superior sagittal sinus, which runs in the midline along the attachment of the falx cerebri. At the point in the back of the head where the falx cerebri merges with the tentorium, the superior sagittal sinus is joined by the straight sinus, which runs in the midline along the attachment of the tentorium and carries blood from deep regions of the brain. Venous blood from the superior sagittal sinus and straight sinus is then distributed to the two transverse sinuses in the torcular Herophili (“winepress of Herophilus,” after Herophilus of Alexandria); from each transverse sinus, blood drains into the sigmoid sinus, which then

Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.

11 438 · 11 Blood Supply and Vascular Disorders of the Central Nervous System

Sphenoparietal	Falx cerebri
sinus

Inferior sagittal sinus

Superior sagittal sinus

Transverse sinus

Straight sinus

Internal jugular vv.

Fig. 11.17 Dural venous sinuses

Cavernous sinus

Inferior petrosal sinus Superior petrosal sinus Tentorium

Sigmoid sinus

continues below the jugular foramen as the internal jugular vein. The sinuses are often asymmetric, and there are a number of anatomical variants of the venous drainage pattern in the region of the torcular.

Bloodfromthebraindrainsnotonlyintotheinternaljugularsystem,butalso, by way of the pterygoid plexus, into the venous system of the viscerocranium. The cavernous sinus, formed by a double fold of dura mater at the base of the skull, also drains some of the venous blood from basal regions of the brain. It mainly receives blood from the temporal lobe and from the orbit (by way of the superior and inferior ophthalmic veins). It drains into a variety of venous channels. One of these is the sigmoid sinus, to which it is connected by the superior and inferior petrosal sinuses. Some of its blood also enters the pterygoid plexus.

Pathologically elevated venous pressure in the cavernous sinus, caused, for example, by the intracavernous rupture of an aneurysm of the internal carotid artery, causes reversal of flow in these veins, resulting in chemosis and exophthalmos.

Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.

Blood Supply of the Spinal Cord · 439 11

Blood Supply of the Spinal Cord

Arterial Anastomotic Network

The spinal cord receives blood from an anastomotic network of arteries on its surface. There are three named longitudinal arteries, but these are multiply interconnectedastheytraveldownthespinalcord,sothatthevascularpatternresemblesachainofanastomosesratherthanthreedistinct,independentvessels.

Anterior spinal artery. The unpaired (single) anterior spinal artery runs down the ventral surface of the spinal cord at the anterior edge of the anterior median fissure. It receives segmental contributions from a number of arteries (see below) and supplies the ventral part of the spinal gray matter through perforating vessels known as the sulco-commissural arteries. These arteries branch off segmentally from the anterior spinal artery and run transversely through the median fissure, from which they enter the parenchyma. Each sulco-com- missural artery supplies one half of the spinal cord. Important structures supplied by the anterior spinal artery include the anterior horns, the lateral spinothalamic tract, and part of the pyramidal tract (Fig. 11.18).

Posterolateral spinal arteries. The posterolateral spinal arteries are the major longitudinal vessels on the dorsal side of the spinal cord; they run down the cord between the posterior roots and the lateral columns on either side. Like the anterior spinal artery, they arise from a confluence of segmental arteries; this confluence can be incomplete in places. The posterolateral spinal arteries supply the posterior columns, the posterior roots, and the dorsal horns

(Fig. 11.18). The longitudinal axes are connected by radicular anastomoses. These supply the anterior and lateral columns through perforating branches.

The arteries of the spinal cord are interconnected by many anastomoses. Thus, proximal stenosis or occlusion of one of these arteries is usually asymptomatic. In the periphery, however, the arteries of the spinal cord are functional end arteries; intramedullary embolic occlusion of a sulco-commissural artery therefore causes infarction of the spinal cord.

Arteries Contributing to the Arterial Network of the Spinal Cord

The embryonic spinal cord receives its blood supply from segmental arteries, in accordance with the metameric segmentation of the spine. Over the course of development, many of these arteries regress, leaving only a few major ones to supply the cord. There is no way to know which of the original segmental arteries has persisted in the mature individual, except by angiography. Yet the blood

Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.

11 440 · 11 Blood Supply and Vascular Disorders of the Central Nervous System

Posterolateral spinal a.

Posterolateral spinal a.

		Anterior
		spinal a.
	Lateral	Vascular
	spinothalamic
		corona
	tract

Anterior spinothalamic

tract

Lateral corticospinal Sulcotract

commissural a.

			Postero-
Anterior spinal a.			lateral spinal a.
Fig. 11.18 Arterial network of the spinal cord

supply of the spinal cord does receive relatively constant contributions from a number of segmental levels (Fig. 11.19).

In the upper cervical region, the anterior spinal artery receives most of its blood from the vertebral artery. In principle, both vertebral arteries may supply blood to the anterior spinal artery, but the vertebral artery of one side is usually dominant. Further down the cord, the anterior and posterior longitudinal vessels receive most of their blood either from the vertebral artery or from cervical branches of the subclavian artery (or both). Spinal cord arteries preferentially arise from the costocervical or thyrocervical trunk. From T3 downward, the anterior spinal artery is fed by aortic branches: the thoracic and lumbar segmental arteries, in addition to the branches that they give off to the musculature, connective tissue, and bones, also contribute a few branches to the anterior spinal artery or the posterolateral spinal artery. These spinal branches are the segmental spinal cord arteries that did not regress during embryonic development. Each one divides into an anterior and a posterior branch, which

Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.

Vertebral a.

Anterior radicular a. of C4–C5

Anterior radicular a. of C6–C8

Costocervical trunk

Thyrocervical trunk

Common carotid a.

Brachiocephalic trunk

Aorta

Anterior spinal a.

Posterior intercostal a. of T4–T6

Great radicular a.

(of Adamkiewicz)

Posterior intercostal a. of T9–L1

Blood Supply of the Spinal Cord · 441 11

Fig. 11.19 Contributions of the segmental arteries to the arterial network of the spinal cord.

After Thron A in Poeck K and Hacke W: Neurologie, 11th ed., Springer, Berlin/Heidelberg, 2001.

enter the spinal canal with the anterior and posterior root, respectively. Because the spinal cord elongates to a lesser extent than the vertebral column during development, each radicular artery enters the spinal cord some distance above its level of origin. There is usually one particularly large segmental artery supplying the lower spinal cord, which is called the great radicular artery or, more commonly, the artery of Adamkiewicz. The developmental “ascent” of the spinal cord makes this artery join the anterior spinal artery at an acute angle (hairpin configuration).

Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.