Blood supply of the nervous system

Objectives Describe the main arteries supplying the CNS. Follow up each artery to its destination. Describe the circle of Willis and its branches. Discuss the principle of end artery type of circulation. Describe venous drainage of the brain.

CEREBRAL ARTERIAL SUPPLY It is composed of two arterial systems: Carotid System Vertebro Basilar System

Arteries of brain Two sources Internal carotid artery: supplies anterior 2/3 of cerebral hemisphere and parts of diencephalon Vertebral artery: supplies posterior 1/3 of cerebral hemisphere and parts of diencephalon, brain stem and cerebellum

Posterior cerebral artery Vertebrobasilar System Vertebral Artery A branch of the first part of subclavian artery Its course is divided into 4 parts The 4th part enters the cranial cavity through the foramen magnum on the side the medulla The two vertebral arteries approach each other and join together in the median plane at the lower border of the pons to form the basilar artery Basilar artery Formed by the union of the two vertebral arteries at the lower border of the pons Ascends on the front of the pons lodged in the basilar groove Ends at the upper border of the pons by dividing into 2 Posterior cerebral arteries (PCA) Posterior cerebral artery Basilar artery Vertebral artery

Branches of the 4th part of vertebral artery Anterior spinal artery Posterior spinal artery Medullary branches, to the antero-medial part of the medulla Posterior inferior cerebellar artery, supplies the posterior part of the inferior surface of cerebellum. It gives medullary branches to the postero-lateral part of the medulla, and a choroid branch Posterior cerebral artery Basilar artery Superior cerebellar artery Pontine branches Labyrinthine artery Vertebral artery Anterior inferior cerebellar artery Anterior spinal artery Posterior inferior cerebellar artery Posterior spinal artery

Basilar artery Anterior inferior cerebellar arteries, supplies the anterior part of inferior surface of cerebellum Labyrinthine artery, enters the internal acoustic meatus to supply the membranous labyrinth Pontine branches, run transversely and supply the pons Superior cerebellar arteries, supply the superior surface of cerebellum 2 Posterior cerebral arteries end divisions

Posterior cerebral artery Superior cerebellar artery Choroid plexus of lateral ventricle Posterior cerebral artery Superior cerebellar artery Anterior choroid a Pontine branches Internal carotid a Labyrinthine artery Basilar artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery Anterior spinal artery Posterior spinal artery Vertebral artery

Posterior communicating a Internal Carotid Artery One of the two terminal branches of the common carotid artery Reaches the cranial cavity by passing through the carotid canal Terminates lateral to the optic chiasma by dividing into Anterior & Middle Cerebral Arteries Terminal part of ICA Anterior cerebral a Optic chiasma Middle cerebral a Anterior choroid a Posterior communicating a

Branches of internal carotid artery Hypophyseal arteries, arise inside the cavernous sinus and supply the hypothalamus and neurohypophysis Anterior choroidal artery, forms the choroid plexus of the lateral ventricle. Posterior communicating artery, runs backwards to join the posterior cerebral artery Ophthalmic artery, runs into the optic canal to the orbit Terminal branches: Anterior cerebral artery (ACA) Middle cerebral artery (MCA)

Anterior communicating a Posterior communicating a Anterior cerebral a Anterior communicating a Middle cerebral a Anterior choroid a Internal carotid a Posterior communicating a Posterior cerebral a Choroid plexus of lateral ventricle

Anterior communicating a Circle of Willis An arterial circle on the base of the brain It joins the 2 arterial systems It surrounds the optic chiasma in front of the cerebral peduncles Anterior communicating a Anterior cerebral a Optic chiasma Internal carotid a Posterior communicating a Posterior cerebral a Basilar a

It is formed of: 2 Anterior cerebral arteries 2 Internal carotid arteries 2 Posterior cerebral arteries 2 Posterior communicating arteries 1 Anterior communicating artery

Branches: Perforating arteries (Anterior& Posterior): Numerous small vessels that penetrate the surface of the brain through the anterior and posterior perforating substances. APA supplies: Large part of Basal Ganglia, Optic chiasma, Internal capsule & Hypothalamus PPA supplies: Ventral portion of Midbrain, parts of Subthalamus and Hypothalamus

Anterior Cerebral Artery (ACA) Course One of the two terminal branches of ICA Takes origin lateral to the optic chiasma Runs medially above the optic nerve to reach the longitudinal fissure Continues on the medial surface of the cerebral hemisphere above the corpus callosum Its proximal part is connected to its fellow of the opposite side by the anterior communicating artery Terminates by turning upward in front of the parieto-occipital sulcus Anterior Cerebral Artery (ACA) Corpus callosum Parieto-occipital sulcus Anterior cerebral a Terminal part of ICA Anterior cerebral a Posterior cerebral a Terminal part of ICA

Anterior perforated substance Rostrum of corpus callosum Branches of ACA: Central branches Pass through the anterior perforated substance Supply anterior part of hypothalamus, rostrum of corpus callosum, septum pellucidum, head of caudate nucleus, anterior part of lentiform nucleus & anterior half of anterior limb of internal capsule. Callosal Branches They supply all parts of the corpus callosum except the splenium (supplied by posterior cerebral artery) Thalamus Septum pellucidum Anterior perforated substance Optic chiasma Rostrum of corpus callosum Posterior cerebral a Posterior perforated substance hypothalamus Optic chiasma

Anterior cerebral artery Genu of corpus callosum Head of caudate nucleus Lentiform nucleus Internal capsule Thalamus

superolateral surface Cortical branches The cortical branches are distributed to the following areas: Medial surface as far back as the parieto-occipital sulcus Upper inch of supero-lateral surface, in front of the parieto-occipital sulcus Medial part of the orbital surface Parieto-occipital sulcus Upper inch of superolateral surface Medial part of orbital surface

Middle Cerebral Artery (MCA) Course One of the two terminal branches of ICA Takes origin lateral to the optic chiasma Runs laterally in the depth of the lateral sulcus Terminates on the surface of insula by breaking into terminal branches Insula Lateral cerebral a Anterior cerebral a Middle cerebral a

Body of corpus callosum Branches of MCA: Central branches Pass through the anterior perforated substance They are called striate arteries, as they supply the corpus striatum ( lentiform nucleus, caudate nucleus) and internal capsule NB. Occlusion of (or hemorrhage from) striate arteries leads to contralateral hemiplegia Striate arteries Corpus striatum Cortical branches of middle cerebral a Middle cerebral a Anterior cerebral a Lateral ventricle Septum pellucidum Body of corpus callosum

The cortical branches are distributed to the following areas: All the Supero-lateral surface, EXCEPT: Upper inch (supplied by anterior cerebral artery) Lower inch (supplied by posterior cerebral artery) Occipital lobe (supplied by posterior cerebral a) Lateral part of orbital surface Temporal pole & insula Area supplied by anterior cerebral a. Area supplied by posterior cerebral a.

Posterior Cerebral Artery (PCA) Course One of the two terminal branches of basilar artery at the upper border of the pons Runs backwards around the side of the cerebral peduncle of the midbrain Reaches the medial surface of the occipital lobe, below the splenium of corpus callosum, where it divides into 2 terminal branches which run in the: Calcarine sulcus Parieto-occipital sulcus Cerebral peduncle Posterior cerebral a

Central branches: Differentiated into medial & lateral groups The medial group pierce the posterior perforated substance, while the lateral group pierce the side of the cerebral peduncle They supply the thalamus, hypothalamus, cerebral peduncles & geniculate bodies Posterior choroidal branches (Medial & lateral) -The medial posterior choroidal supplies the tectum of midbrain and choroid plexus of 3rd ventricle -The lateral posterior choroid supplies the choroid plexus of lateral ventricle ICA Thalamus Anterior choroid a Hypothalamus Choroid plexus of lateral ventricle Medial posterior chroid a Posterior cerebral a Lateral posterior choroid a

Cortical areas supplied by posterior cerebral a Cortical branches The cortical branches are distributed to the following areas: Tentrorial surface (behind the temporal pole) Lower inch of supero-lateral surface All surfaces of the occipital lobe Temporal pole Cortical areas supplied by posterior cerebral a

Lateral surface Medial surface Cortical areas supplied by ACA Cortical areas supplied by MCA Cortical areas supplied by PCA

Summary of the arterial supply of the brain Cortical Distribution of Cerebral Arteries The Cerebral cortex is supplied by cortical branches of: Anterior cerebral; all medial surface (except the occipital lobe), medial half of orbital surface and upper inch of lateral surface (in front of parieto-occipital sulcus) Middle cerebral; all lateral surface (except the upper inch, lower inch and occipital lobe), lateral half of orbital surface, insula & temporal pole Posterior cerebral; all surfaces of occipital lobe, tentorial surface (behind the temporal pole), lower inch of lateral surface

Internal capsule; supplied by central branches of: MCA ACA Anterior choroidal artery (from Internal Carotid) Corpus Striatum; supplied mainly by central (striate) branches of MCA Thalamus; supplied mainly by central branches of PCA Midbrain; supplied by: PCA Medial posterior choroidal (also from PCA) Pons; mainly supplied by the Basilar artery and its pontine branches Medulla Oblongata; supplied by medullary branches of: Vertebral arteries Posterior inferior cerebellar arteries. Anterior & posterior spinal arteries Cerebellum; supplied by the three pairs of cerebellar arteries: Posterior Inferior Cerebellar, Anterior Inferior Cerebellar, Superior Cerebellar Labyrinth; labyrinthine artery (from Basilar Artery)

Arterial Disorders Stroke: Aneurysm Angioma Sudden occlusion Hemorrhage Aneurysm Angioma

Occlusion of ACA Manifestations: 1. Motor & sensory disturbances in the contralateral distal leg 2. Difficulty in the Prefrontal lobe functions: Cognitive thinking, Judgment, Motor initiation and Self monitoring

Occlusion of MCA Manifestations: 1. Contralateral weakness of: Face, Arm & Hand (more than leg) 2.Contralateral sensory loss of: 3. Visual field cut (damage to optic radiation) 4. Aphasia (language disturbances ) Broca's: production Wernicke's: comprehension

Occlusion of PCA Manifestations: 1. Visual disturbances Contralateral homonymous hemianopia (visual field loss on the same side of both eyes)

Bilateral lesions: cortical blindness Cortical blindness is the loss of vision due to damage to the visual portion of the occipital cortex in the brain. (Anton Babinski`s syndrome)patients having cortical blindness but unaware they cannot see or insist that they can see 2. Memory impairment If the temporal lobe is affected

Cerebral Venous Drainage (A) Superficial (cortical) veins: Found in the Subarchnoid space Drain the cortical surfaces (B) Deep veins: Drain the deeper structures These veins are thin walled and devoid of valves. They ultimately drain into the Dural Venous Sinuses

Venous drainage of the cerebral hemisphere Superior cerebral veins Run on the lateral surface above the lateral fissure Drain into the superior sagittal sinus and suprerficial middle cerebral vein Inferior cerebral veins Run on the lateral surface below the lateral fissure Drain into the superficial middle cerebral vein and the transverse sinus Superior sagittal sinus Superior cerebral v Superior anastomotic v Superficial middle cerebral v Inferiro anastomotic v Inferior cerebral v

Superficial middle cerebral vein Runs in the superficial part of the lateral sulcus Its posterior end is connected to the superior sagittal sinus and transverse sinus by the superior and inferior anastomotic veins Its anterior part curves medially to terminate in the cavernous sinus

Deep Cerebral Veins Drain the internal structures (basal ganglia, internal capsule, thalamus) They merge to form two Internal Cerebral Veins. The two veins unite in the midline to form the Great Cerebral vein. This short vessel is continuous with the Straight Sinus

Superficial middle cerebral v Deep middle cerebral vein Runs in the depth of the lateral sulcus Terminates at the anterior perforated substance where it shares in the formation of the BASAL vein Anterior cerebral vein Runs on the medial surface with the anterior cerebral artery Striate veins Drain the corpus striatum Emerges through the anterior perforated substance and joins the anterior cerebral vein and deep middle cerebral vein to form the BASAL vein Anterior cerebral v Deep middle cerebral v Superficial middle cerebral v Basal vein Great cerebral v

Superficial middle cerebral v Basal vein Formed at the anterior perforated substance by the union of: Anterior cerebral vein Deep middle cerebral vein Striate veins Runs around the side of the midbrain to terminate in the GREAT CEREBRAL VEIN Anterior cerebral v Deep middle cerebral v Superficial middle cerebral v Basal vein Great cerebral v

Internal cerebral vein Thalamostriate vein Runs in the groove between thalamus and caudate nucleus Drains the thalamus, corpus striatum, internal capsule and septum pellucidum Unites with the choroid veins (behind the interventricular foramen) to form the internal cerebral vein Choroid veins Drain the choroid plexuses of lateral and third ventricles Unite with the thalamostriate veins to form the internal cerebral vein Internal cerebral vein Thalamostriate vein Caudate nucleus Choroid vein Choroid plexus of lateral ventricle Basal vein Great cerebral vein Straight sinus

Internal cerebral vein Inferior sagittal sinus Formed behind the interventricular foramen by the union of: Thalamostriate vein Choroid veins Runs backwards and unites with its fellow of the opposite side to form the Great Cerebral Vein Great cerebral vein Formed by the union of the two Internal Cerebral Veins It also receives the basal veins Runs backwards and unites with the Inferior Sagittal Sinus to form the Straight Sinus Internal cerebral vein Great cerebral v Inferior sagittal sinus Internal cerebral v Thalamostriate vein Choroid vein Choroid plexus of lateral ventricle Basal vein Great cerebral vein Basal v Straight sinus Straight sinus

Dural venous sinuses The venous blood from the deep areas of the brain is collected into channels called the venous sinuses. The dural venous sinuses of the brain are formed by layers of dura matter lined by endothelium. The main venous sinuses are : 1 superior sagittal sinus 1 inferior sagittal sinus 1 straight sinus 2 transverse sinus or lateral sinuses 2 sigmoid sinuses The sigmoid sinuses situated close to the mastoid air sinuses continue as internal jugular veins

Dural sinus Location Receives Superior sagittal Superior border of falx cerebri Superior cerebral, diploic, and emissary veins and CSF Inferior sagittal Inferior margin of falx cerebri A few cerebral veins and veins from the falx cerebri Straight Junction of falx cerebri and tentorium cerebelli Inferior sagittal sinus, great cerebral vein, posterior cerebral veins, superior cerebellar veins, and veins from the falx cerebri Occipital In falx cerebelli against occipital bone Communicates inferiorly with vertebral plexus of veins Confluence of sinuses Dilated space at the internal occipital protuberance Superior sagittal, straight, and occipital sinuses

Transverse (right and left) Horizontal extensions from the confluence of sinuses along the posterior and lateral attachments of the tentorium cerebelli Drainage from confluence of sinuses (right-transverse and usually superior sagittal sinuses; left-transverse and usually straight sinuses); also superior petrosal sinus, and inferior cerebral, cerebellar, diploic, and emissary veins Sigmoid (right and left) Continuation of transverse sinuses to internal jugular vein; groove parietal, temporal, and occipital bones Transverse sinuses, and cerebral, cerebellar, diploic, and emissary veins Cavernous (paired) Lateral aspect of body of sphenoid Cerebral and ophthalmic veins, and emissary veins from pterygoid plexus of veins and sphenoparietal sinuses

Superior petrosal (paired) Superior margin of petrous part of temporal bone Cavernous sinus, and cerebral and cerebellar veins Inferior petrosal (paired) Groove between petrous part of temporal bone and occipital bone ending in internal jugular vein Cavernous sinus, cerebellar veins, and veins from the internal ear and brainstem Basilar Clivus, just posterior to sella turcica of sphenoid Connect bilateral inferior petrosal sinuses and communicate with vertebral plexus of veins

Important structures related to cavernous sinus The internal carotid artery and the sixth cranial nerve, which travel through it In the lateral wall, the third and fourth cranial nerves, and the ophthalmic and maxillary divisions of the fifth cranial nerve. The pituitary gland, which lies medially in the sella turcica The veins of the face, which are connected with the cavernous sinus via the facial vein and inferior ophthalmic vein, and are an important route for the spread of infection from the face The superior and inferior petrosal sinuses, which run along the upper and lower borders of the petrous part of the temporal bone

Dangerous area of the face It is the area between the root of the nose and 2 angles of the mouth. - The veins in this region are connected to cavernous sinus through the facial vein so any infection in this area may lead to cavernous sinus thrombosis.

Venous Disorders Infarcation. Sinus thrombosis: (SSS thrombosis) can complicate ear infection . Cavernous S thrombosis (as a complication of infection in the dangerous area of the face) Obstruction of venous drainage of the brain leads to Cerebral swelling (edema) and raised ICP

Arterial Supply of the Spinal Cord The spinal cord is supplied by the anterior and posterior spinal arteries, in addition to the radicular arteries Anterior spinal arteries They arise from the 4th part of vertebral artery on each side Arteries of both sides unite together forming a single anterior spinal artery The anterior spinal artery descends in front of the anterior median fissure of the spinal cord Posterior spinal arteries They also arise from the 4th part of the vertebral artery on each side Each artery divides into 2 branches The 2 branches descend on each side of the dorsal roots of spinal nerves

Radicular arteries Their origin varies according to the region through which the spinal cord descends From above downwards, they arise from the following arteries: Vertebral Ascending cervical Superior intercostal Posterior intercostal Subcostal Upper lumbar They pass through the intervertebral foramina and divide into ventral and dorsal branches

AICA = lateral inferior pontine Anterior Cerebral Artery -Loss of sensation and motor to lower limb - Medial motor & somatosensory motor Middle Cerebral Artery -Loss of sensation and motor to upper limb and face - Lateral motor & somatosens Posterior Cerebral Artery = Webers or Benedikts (red nucleus) Lose CST: contra weakness Lose CN 3: (Oculomotor-eyes down and out-ipsi BENEDIKTS: Webers + Ataxia Superior Cerebellar Artery = lateral superior pontine -Sup Cerebellar Ped=output from cerebellum = Ataxia Basilar Artery = locked in Median Pontine Syndrome *Only move eyes up & down -CST & Facial Nucleus -Abducens N & Pontine gaze enter PICA =lateral medullary:Wallenberg -Inf Cerebellar peduncle=Ataxia -Trigeminal-Spinal tract & Nucl V= pain/temp from face-ipsi -STT=pain & temp from body-contra -CN 10=Nucl Solitarius-no taste -Desc symp fibers: Horner’s AICA = lateral inferior pontine -Middle Cerebellar Ped= ATAXIA, posture probl. -CN 8-Vestibular Nuclei=vertigo -Trigeminal-CN V Spinal Tract= lose pain & temp from face- ipsi -STT= pain & temp from body contr -Desc symp fibers: Horner’s Vertebral Artery = lateral medullary -same as PICA Anterior Spinal Artery = medial medullary -CST & ML/DL= contra -CN 12-Hypoglossal=ipsi tongue deviation