13 MAGNETIC RESONANCE ANGIOGRAPHY: FRONTAL AND LATERAL VIEWS

Vasculature



Lateral projection



89



Femorocerebral Angiography



Pericallosal artery



Multiple branches of

middle cerebral artery



Callosomarginal artery



Anterior cerebral artery



Frontopolar artery



Medial orbitofrontal artery



Ophthalmic artery



Parieto-occipital

and

Posterior temporal

branches of

Posterior

cerebral artery

Posterior communicating artery



Supraclinoid,

Cavernous,

Petrous, and

Cervical segments

of internal caroid artery



Frontal projection



Right anterior cerebral artery

Anterior choroidal artery

Left anterior cerebral artery

Medial and lateral

lenticulostriate arteries



Anterior communicating artery



Middle cerebral artery

Frontopolar artery

Ophthalmic artery

Supraclinoid,

Cavernous,

Petrous, and

Cervical

segments of

internal carotid artery



7.14  ANGIOGRAPHIC ANATOMY OF THE

�INTERNAL CAROTID CIRCULATION

The top plate is an angiogram that is a lateral view of the ICA

circulation after injection of a radiopaque contrast agent into

the ICA. The major branches of the ICA, particularly the ACA

and MCA, are delineated. The bottom plate is an �angiogram



that is a frontal view of the ICA circulation after injection of

a radiopaque contrast agent into the common carotid artery.

The major branches of this arterial system are delineated.

MRA is used commonly to investigate the status of the cerebral arteries, but angiography with contrast agents can provide excellent anatomical details for teaching purposes.



90



Overview of the Nervous System



Arteries of Posterior Cranial Fossa



Crura of fornix



Lateral and medial

geniculate bodies

of left thalamus



choroid plexuses

of lateral ventricles



Right

Left



Posterior horn of right lateral ventricle

Right and

left pulvinars



Septum pellucidum

Corpus callosum



Splenium of

corpus callosum



Anterior cerebral arteries

Longitudinal

(interhemispheric) fissure



Right posterior

pericallosal artery



Heads of caudate nuclei



Parieto-occipital and

Calcarine branches

of right posterior

cerebral artery



Thalamogeniculate arteries

Medial and lateral

lenticulostriate arteries



Left superior colliculus



Anterior choroidal artery



Superior vermian artery

Posterior medial choroidal

artery (to choroid plexus

of 3rd ventricle)



Anterior cerebral artery

Optic (II) nerve

and ophthalmic artery

Middle cerebral artery

Thalamoperforating arteries



Left posterior cerebral artery

with anterior and posterior

temporal branches



V



Posterior communicating artery



VIII



Left interior carotid artery

Superior cerebellar artery



Posterior lateral choroidal artery



IV



III



VI



Lateral marginal branch of

superior cerebellar artery



VII



Basilar artery



IX

X



Pontine branches

Interior auditory (labyrinthine) artery



Inferior vermian artery (in phantom)

Choroidal point and choroidal artery

to 4th ventricle



XI



Anterior inferior cerebellar artery



Tonsillohemispheric branches



Posterior inferior cerebellar artery

Anterior meningeal branch of vertebral artery

Left vertebral artery



Outline of 4th ventricle (broken line)

Posterior meningeal branch of vertebral artery

Left posterior spinal artery



Anterior

spinal artery



7.15  VERTEBROBASILAR ARTERIAL SYSTEM

The vertebral arteries unite at the midline to form the basilar

artery. Medial penetrating branches extend into medial zones

of the brain stem, supplying wedgelike territories. Infarcts in

these branches can produce “alternating hemiplegias,” contralateral motor deficits )>>corticospinal system damage above

the decussation of the pyramids), and ipsilateral brain stem/

cranial nerve signs and symptoms. The vertebral and basilar

arteries also give rise to larger short and long circumferential

branches, such as the posterior inferior cerebellar artery, the

anterior inferior cerebellar artery, and the superior cerebellar artery. Strokes in these arterial territories generally produce a constellation of ipsilateral brain stem sensory, motor,

and autonomic symptoms and contralateral somatosensory

symptoms. For example, an infarct in the posterior inferior �cerebellar artery results in loss of pain and temperature



�

sensation

on the contralateral body and the ipsilateral face.

The end branch of the basilar artery is the PCA, which distributes to the visual cortex and inferior temporal lobe. Occlusion

results in contralateral hemianopsia.

CLINICAL POINT

The vertebrobasilar system gives rise to several types of arterial

�bra�nches. Those located most medially are the paramedian branches.

An infarct in such a branch commonly involves ipsilateral damage

to a cranial nerve and its function as well as contralateral hemiplegia

because of involvement of the corticospinal tract before it decussates

on its way to the spinal cord. These infarcts are known as alternating hemiplegias. The short and long circumferential arteries distribute

into more lateral territories, and infarcts commonly result in a complex mixture of sensory, motor, and autonomic symptoms, as seen in

the lateral medullary syndrome resulting from an infarct in the posterior inferior cerebellar artery.



Vasculature



91



Arteries of Posterior Cranial Fossa

Vertebral Angiograms: Arterial Phase



A. Lateral projection



Posterior lateral choroidal arteries

Superior cerebellar arteries

Posterior cerebral arteries

Thalamoperforating arteries



Posterior pericallosal artery

Parieto-occipital

Posterior temporal

Calcarine



Inferior vermian artery

Tonsillohemispheric branches



Posterior communicating arteries

Basilar artery

Anterior inferior cerebellar artery



B. Frontal projection



Branches of posterior cerebral artery



Posterior inferior cerebellar artery

Vertebral artery



Posterior cerebral arteries

Superior cerebellar arteries



Anterior inferior

cerebellar arteries

Basilar artery



Inferior vermian branches

or

Right and left posterior

inferior cerebellar arteries

and

Left hemispheric branch

of left posterior inferior cerebellar artery



Vertebral artery



7.16  ANGIOGRAPHIC ANATOMY OF THE

�VERTEBROBASILAR SYSTEM

These figures show angiograms of both lateral and frontal views of the vertebrobasilar )>>posterior) circulation after



injection of a radiopaque contrast agent into the vertebral artery. The major arterial branches of this system are delineated.



92



Overview of the Nervous System



Hypothalamic vessels



Primary plexus of

hypophyseal portal system

Long hypophyseal

portal veins



Anterior branch

Posterior branch



Short hypophyseal

portal veins



Superior hypophyseal artery (from internal carotid

artery or posterior communicating artery)



Artery of trabecula



Capillary plexus of

infundibular process



Trabecula



Posterior lobe

Efferent vein to cavernous sinus

Anterior lobe

Secondary plexus of hypophyseal portal system

Stalk



Anterior lobe

Posterior

lobe



Cavernous sinus



Efferent vein to

cavernous sinus

Lateral branch

and

Medial branch

of

Inferior hypophyseal artery

(from the internal carotid artery)



Efferent vein to

cavernous sinus



7.17  VASCULAR SUPPLY TO THE Â�HYPOTHALAMUS

AND THE PITUITARY GLAND

The superior hypophyseal arteries )>>from the ICA or the posterior communicating artery) supply the hypothalamus and infundibular stalk and anastomose with branches of the inferior

hypophyseal artery )>>from the ICA). A unique aspect of this arterial distribution is the hypophyseal portal system, whose primary

plexus derives from small arterioles and capillaries that then send

branches into the anterior pituitary gland. This plexus allows

neurons producing hypothalamic releasing factors and inhibitory

factors to secrete these factors into the hypophyseal portal system,

which delivers a very high concentration directly into the secondary plexus in the anterior pituitary. Thus, anterior pituitary cells

are bathed in releasing and inhibitory factors in very high concentrations. This private vascular communication channel allows

the hypothalamus to exert fine control, both directly and through

feedback, over the secretion of anterior pituitary hormones.



Internal carotid artery

Posterior communicating artery

Superior hypophyseal artery

Portal veins

Lateral hypophyseal veins

Inferior hypophyseal artery

Posterior lobe veins



Inferior aspect



CLINICAL POINT

The primary hypophyseal portal system coalesces into long hypophyseal portal veins that give rise to a secondary hypophyseal plexus. This

�arrangement allows the secretion of releasing and inhibitory factors

from nerve endings, whose cell bodies are located in the hypothalamus

and other structures, into a private vascular system, to be delivered to

the pituicytes in the anterior pituitary gland in extraordinarily high

concentrations. The ultimate control of the releasing and inhibitory

factors profoundly influences neuroendocrine secretion and its downstream �effects in the entire body. For example, corticotrophin releasing

hormone or factor induces the release of adrenocorticotropic hormone

from the anterior pituitary, which is released into the systemic circulation and activates the adrenal cortex to release cortisol and other steroid

hormones. This hypothalamo-pituitary-adrenal system helps to regulate

glucose metabolism, insulin secretion, immune responses, adipose distribution, and a host of other vital functions. The corticotrophin releasing hormone neurons are under extensive regulatory control by neural

inputs, hormonal feedback, and inflammatory mediators; these neurons

help to orchestrate stress reactivity for the organism as a whole.



Vasculature



Anterior View



93



Posterior View

Posterior inferior cerebellar artery



Posterior cerebral artery

Superior cerebellar artery



Posterior spinal arteries



Basilar artery

Anterior inferior cerebellar artery



Vertebral artery



Posterior inferior cerebellar artery



Posterior radicular arteries



Anterior spinal artery

Vertebral artery

Anterior radicular arteries



Cervical

vertebrae



Deep cervical artery

Ascending cervical artery



Ascending cervical artery

Deep cervical artery



Subclavian artery



Subclavian artery

Anterior radicular artery



Posterior radicular arteries

Posterior intercostal artery

Posterior intercostal arteries

Thoracic vertebrae



Artery of Adamkiewicz

(major anterior radicular artery)



Anterior radicular artery



Posterior radicular arteries



Lumbar artery

Anastomotic loops to

posterior spinal arteries



Lumbar arteries

Lumbar vertebrae

Anastomotic loops to anterior spinal artery

Lateral sacral (or median sacral) artery



Lateral sacral (or median sacral) artery



Sacrum



7.18  ARTERIAL BLOOD SUPPLY TO THE SPINAL

CORD: LONGITUDINAL VIEW

The major arterial blood supply to the spinal cord derives from

the anterior spinal artery and the paired posterior spinal arteries, both branches of the vertebral artery. The actual blood flow

through these arteries, derived from the posterior circulation,

is inadequate to maintain the spinal cord beyond the cervical

segments. Radicular arteries, deriving from the aorta, provide



major anastomoses with the anterior and posterior spinal arteries and supplement the blood flow to the spinal cord. The

largest of these anterior radicular arteries, often from the L2

region, is the artery of Adamkiewicz. Impaired blood flow

through these critical radicular arteries, especially during surgical procedures that involve abrupt disruption of blood flow

through the aorta, can result in spinal cord infarct.



94



Overview of the Nervous System



Arteries of Cervical Cord

Exposed from the Rear



Basilar artery

Posterior inferior cerebellar artery

Vertebral artery

Anterior spinal artery

Spinal ramus

Posterior spinal artery

Posterior radicular artery

Pre-laminar branch



Anterior spinal artery

Post-central branch

Anterior central artery

Spinal ramus

Neural branch

Anterior radicular artery

Posterior radicular artery

Internal spinal arteries

Posterior central artery

Pre-laminar branch

Posterior spinal artery



Arteries of Spinal Cord Diagrammatically Shown in Horizontal Section



7.19  ANTERIOR AND POSTERIOR SPINAL

�ARTERIES AND THEIR DISTRIBUTION

The anterior and posterior spinal arteries travel in the subarachnoid space and send branches into the spinal cord. The

anterior spinal artery sends alternating branches into the anterior median fissure to supply the anterior two thirds of the

spinal cord. Occlusion of one of these branches can result in

ipsilateral flaccid paralysis in muscles supplied by the affected

segments, ipsilateral spastic paralysis below the affected level



)>>resulting from upper motor neuron axonal damage), and

contralateral loss of pain and temperature sensation below

the affected level )>>resulting from damage to the anterolateral

spinothalamic/spinoreticular system). The posterior spinal

artery branches supply the dorsal third of the spinal cord. Occlusion affects the ipsilateral perception of fine discriminative

touch, vibratory sensation, and joint position sense below the

level of the lesion )>>resulting from damage to fasciculi gracilis

and cuneatus, the dorsal columns).



Vasculature



95



Posterior spinal arteries

Anterior spinal artery

Anterior radicular artery

Posterior radicular arteries

Branch to vertebral body and dura mater

Spinal branch

Dorsal ramus of posterior intercostal artery

Posterior intercostal arteries

Paravertebral anastomosis

Prevertebral anastomosis

Aorta



Section through Thoracic Spine

Right posterior spinal artery

Peripheral branches from pial plexus

Central branches to right side of spinal cord



Central branches to left side of spinal cord

Left posterior spinal artery



Anterior radicular artery



Pial arterial plexus

Posterior radicular artery



Anterior spinal artery



Schema of Arterial Distribution



7.20  ARTERIAL SUPPLY TO THE SPINAL CORD:

CROSS-SECTIONAL VIEW

The major contribution to the arterial blood supply of the spinal cord below the cervical segments derives from the radicular arteries )>>top). This intercostal blood supply also distributes

to adjacent bony and muscular structures. The penetrating

vessels supplying the spinal cord derive from central branches

of the anterior spinal artery and from a pial plexus of vessels

that surround the exterior of the spinal cord.

CLINICAL POINT

Alternating branches arise from the anterior spinal artery into the anterior two thirds of the spinal cord. Following an infarct in the anterior spinal artery, acute radiating leg pain is experienced. Depending



Zone supplied by penetrating

branches from pial plexus

Zone supplied by central branches

Zone supplied by both central branches

and branches from pial plexus

Posterior radicular artery

Anterior radicular artery

Pial arterial plexus



on the level, acute flaccid paraparesis or quadraparesis occurs, resolving to spastic paraparesis or quadraparesis with hyperreflexia as the

result of the upper motor neuron lesion resulting from damage to the

bilateral lateral funiculi. Only at the level of the infarct, where �lower

motor neurons are lost, does flaccid paralysis remain, along with

hyporeflexia. Bilateral plantar extensor responses are seen. Bilateral

loss of pain and temperature sensation is seen because of ischemia to

the anterolateral territory of the spinothalamic/spinoreticular protopathic system. Descending fibers for control of the bladder and bowel

travel in the lateral funiculus and are damaged by an anterior artery

infarct. In a lesion of the anterior spinal artery above the T1 level,

bilateral damage to descending central sympathetic fibers regulating

T1 intermediolateral cell column outflow produces bilateral Horner’s

syndrome, with bilateral ptosis, myosis, and anhidrosis.



96



Overview of the Nervous System



Galea aponeurotica

Pericranium



Calvaria



Arachnoid granulation



Superior sagittal sinus

Emissary vein



Tributary of superficial

temporal vein



Skin



Falx cerebri



Cerebral hemisphere



Diploic vein



Pia mater



Epidural space (potential)



Superior cerebral vein



Dura mater

Subdural space



Cerebral artery

Arachnoid

Subarachnoid space



venous system

7.21  MENINGES AND SUPERFICIAL

CEREBRAL VEINS

The superior sagittal sinus and other dural sinuses receive

venous blood from a variety of veins, including superficial

cerebral veins draining blood from the cortical surface, meningeal veins draining blood from the meninges, diploic veins

draining blood from channels located between the inner and

outer tables of the calvaria, and emissary veins, which link the

venous sinuses and diploic veins with veins on the surface of

the skull. These channels do not have valves and permit free

communication between these venous systems and the venous

sinuses. This is a significant factor in the possible spread of infections from foci outside the cranium to the venous sinuses.



CLINICAL POINT

Arachnoid granulations act as one-way valves that convey cerebrospinal fluid into the dural sinus, channeling it back into the venous circulation. The cerebral veins also extend across the subarachnoid space

and enter into the superior sagittal sinus. With severe head trauma,

these bridging veins can be torn, with resultant venous bleeding into

the subdural space; this bleed dissects the dura from the arachnoid and

becomes a space-occupying mass. It also brings about cerebral edema

and swelling. Acute subdural hematomas can be life-threatening, especially in young individuals with head trauma. Chronic subdural hematomas often occur in the elderly with relatively minor trauma; the

bridging veins tear because of some mild atrophy of the underlying

hemisphere, making the course of the bridging veins more extended

and more vulnerable to tearing. Slow accumulation of subdural blood

eventually can result in increased intracranial pressure with headache,

lethargy, confusion, seizures, and focal neurological abnormalities.

Surgical drainage is often performed for large subdural hematomas,

whereas small hematomas regress naturally in the elderly.



Vasculature



97



Scalp, Skull, Meningeal, and Cerebral Blood Vessels

Superior sagittal sinus

Diploic vein



Arachnoid Cerebral vein penetrating subdural space to enter sinus (bridging veins)

granulation

Dura mater (two layers)



Emissary vein

Frontal and parietal tributaries

of superficial temporal vein

Frontal and parietal branches

of superficial temporal artery

Arachnoid granulation

indenting skull (foveola)

Venous lacuna

Inferior sagittal sinus



Epidural space (potential)

Arachnoid

Subarachnoid space

Pia mater

Middle meningeal

artery and vein

Deep middle and

superficial temporal

arteries and veins



Thalamostriate and

internal cerebral veins

Deep and

superficial middle

cerebral veins



Diploic and Emissary Veins of Skull

Parietal emissary vein

Frontal diploic vein



Posterior temporal diploic vein

Occipital emissary vein

Occipital diploic vein



Anterior temporal diploic vein



7.22  VEINS: SUPERFICIAL CEREBRAL,

�MENINGEAL, DIPLOIC, AND EMISSARY

Venous blood drains from the skull, the meninges, and the

cerebral cortex into the superior sagittal sinus and other



Mastoid emissary vein



�

dural

sinuses. This is a point of vulnerability where �potential

�infections and contamination from the more superficial

�venous drainage networks can be allowed into the central

�venous sinus channels.



98



Overview of the Nervous System

Optic (II) nerve

Intercavernous (circular) sinus and pituitary gland

Internal carotid artery

Cavernous sinus

Sphenoparietal sinus

Superficial middle cerebral vein

Oculomotor (III) nerve

Trochlear (IV) nerve

Trigeminal (V) nerve

Middle meningeal vein

Abducens (VI) nerve

Superior petrosal sinus

Petrosal vein

Facial (VII) nerve and nervus intermedius

Vestibulocochlear (VIII) nerve

Glossopharyngeal (IX) nerve

Vagus (X) nerve

Jugular foramen

Sigmoid sinus

Accessory (XI) nerve

Hypoglossal (XII) nerve

Transverse sinus

Great cerebral vein (of Galen)

Opening of an inferior cerebral vein



Falx cerebri (cut)

Superior ophthalmic vein

Basilar plexus



Cavernous sinus



Tentorial artery



Superior and

inferior

petrosal

sinuses



Tentorium cerebelli

Straight sinus

Falx cerebri (cut)

Confluence of sinuses

Superior sagittal sinus

Falx cerebri

Inferior sagittal sinus

Great cerebral vein (of Galen)

Sphenoparietal sinus

Intercavernous sinus

Superior petrosal sinus

Straight sinus

Inferior petrosal sinus

Sigmoid sinus

Jugular foramen

Transverse sinus

Confluence of sinuses

Occipital sinus



7.23  VENOUS SINUSES

The falx cerebri and tentorium cerebelli, protrusions of fused

inner and outer dural membranes, confine the anterior, middle, and posterior fossae of the skull. Outer )>>superior sagittal)

and inner )>>inferior sagittal) venous channels, found in split

layers of the dura, drain blood from the superficial and deep

regions of the central nervous system, respectively, into the

jugular veins. The great cerebral vein of Galen and the straight

sinus merge with the transverse sinus into the confluence of

sinuses to drain the deep, more posterior regions of the central

nervous system. Infection can be introduced into the cerebral

circulation through these sinuses. Venous sinus thrombosis

can cause stasis )>>a backup of the venous pressure), which results in inadequate perfusion of the regions where drainage

should occur. The protrusions of dura, such as the tentorium

cerebelli and falx cerebri, are tough, rigid membranes through

which portions of the brain can herniate when intracranial

pressure increases.



CLINICAL POINT

Venous sinus thrombosis commonly occurs with infection. �Cavernous

sinus thrombosis can occur as the result of infection in the �paranasal

sinuses or middle ear or following a furuncle in the region of the face.

Anterior cavernous sinus thrombosis can result in severe pain and

headache, ipsilateral visual loss, exophthalmos )>>protrusion of the eyeball), edema of the eyeball )>>chemosis), and palsies of the extraocular

nerves )>>III, IV, VI) and V1 )>>ophthalmic division) that traverse the

�sinus. This lesion can expand to cause hemiparesis and can involve the

interconnected cavernous sinus of the other side, the superior petrosal

sinuses, and other venous structures.

The petrosal sinuses can undergo a process of thrombosis caused

by the spread of infection in the middle ear. An inferior petrosal sinus

thrombosis may cause damage to the VI )>>abducens) nerve; a superior petrosal sinus thrombosis can result in damage to the semilunar

ganglion, producing facial pain. If the transverse sinus is thrombosed,

cranial nerve deficits in nerves IX, X, and XI may occur.