Anat 6.2 Blood Supply of CNS_zulueta

Anatomy  6.2    

 

January  24,  2012   Dr.  Zulueta  

Blood Supply of the CNS

  OUTLINE   I.  The  Brain   II.  Internal  Carotid  Artery   A.Middle  Cerebral  Artery   B.Anterior  Cerebral  Artery   III.  Vertebral  Artery  System              A.  Posterior  Cerebral  Artery   IV.  Circle  of  Willis              A.  Middle  Meningeal  Artery   V.  Venous  Drainage  of  the  Brain   VI.  The  Spinal  Cord  

  Objectives:   • Describe  the  origin  and  course  of  the  arterial  blood  supply  of  the  brain:   o Internal  carotid  artery  system   o Vertebral  artery  system   o Circle  of  Willis   • Describe  the  general  distribution  of  the  different  branches  of  arteries  that   supply  the  various  regions  of  the  brain   • Describe  the  venous  drainage  of  the  brain   • Describe  the  arterial  supply  and  venous  drainage  of  the  spinal  cord     *  Texts  in  Comic Sans MS  are  from  the  lecture.     o Ma’am  gave  the  lecture  with  mostly  pictures  so  most  texts  lifted  from   the  audio  are  describing  figures.   *Texts  in  Times New Roman  are  lifted  from  the  book  

I.  The  Brain   • One  of  the  most  metabolically  active  organs  of  the  body   consuming  large  amounts  of  oxygen  and  glucose    requires   continuous  blood  flow     • It  uses  20%  of  the  body's  oxygen  consumption  and  up  to  2/3  of   the  liver's  glucose  production.  As  the  brain  only  stores  minimal   amounts  of  oxygen  and  glucose,  it  needs  a  continuous  blood  flow   to  supply  the  brain  with  them.  (If  you  lose  blood  supply  to  any   area  of  the  brain,  you’d  lose  consciousness  for  15  seconds.  If  you   lose  blood  supply  for  3-­‐5  minutes,  you’d  be  in  coma.)   • Any  damage  to  the  brain  is  irreparable     • Diving  reflex   o Blood  flow  is  concentrated  on  areas  which  needs  continuous   blood  supply  (brain  &  heart)  when  in  shock   o Usually  kidneys  are  the  ones  depleted  by  blood  supply   • Arterial  supply  consists  of  2  major  interconnected  systems:   o Internal  Carotid  System(Anterior)   o Vertebral  Artery  System(Posterior)    Some books say basilar artery system, the basilar artery is formed by the union of two vertebral arteries, so it’s the same actually

 The  vertebral  artery  arising  from  subclavian  artery  pass   through  vertebral  foramen  and  pass  through  the  biggest   foramen  (foramen  magnum)    Vertebral  veins  don’t  pass  through  foramen  magnum,  only   vertebral  arteries              

Group  5  |  Dave,  Bamba,  Precious,  Jaela  

 

 

  Fig.  1  Blood  Supply  to  the  CNS  

This figure shows the origin of both systems - the anteriorly   placed INTERNAL CAROTID SYSTEM supplies most of the TELENCEPHALON and the DIENCEPHALON, while the posteriorly placed VERTEBRAL ARTERY SYSTEM or the vertebral-basilar system supplies the SPINAL CORD, the BRAINSTEM, the CEREBELLUM and the INFERIOR and POSTERIOR parts of the CEREBRUM. The internal carotid, along with the external carotid, which supplies the face, the scalp and other extracranial structures, arises from the COMMON CAROTID in the neck.

II.  INTERNAL  CAROTID  ARTERY   • Start  in  the  neck  from  the  bifurcation  of  common  carotid  artery   into  Internal  Carotid  Artery  +  External  Carotid  Artery   • Perforates  the  skull  through  Carotid  canal  of  the  temporal  bone  in   the  floor  of  the  middle  cranial  fossa,  passes  forward  through  the   cavernous  sinus  just  lateral  to  the  sellaturcica   • Turns/bends  medial  to  the  anterior  clinoid  process  and  perforates   the  dura  mater     • Have  many  turns  called  carotid  siphon  (only  in  radiographs)   • Divides into the anterior and middle cerebral arteries Major  Intracranial  Branches  of  ICA  before  it  terminates:   • Hypophyseal  arteries   o Supply  the  pituitary  glandand  constitute  part  of  the   hypophyseal  portal  system   • Ophthalmic  artery   o Will  give  rise  to  central  retinal  artery  (the  sole  supply  of  the   retina,  the  nervous  part  of  the  eye  and  essentially  you  will  be   blind  if  occluded).  Terminal branches also supply the frontal scalp, ethmoid and frontal sinuses, and the dorsum of the nose.   • Posterior  communicating  artery   o Which  anastomoses  with  the  posterior  cerebral  artery  forming   part  of  the  circle  of  Willis    

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• Anterior  choroidal  artery   o Supplies  the  choroid  plexus(secretes  Cerebrospinal  fluid)  in  the   inferior  horn  of  the  lateral  ventricle,  the  optic  tract,  and  parts  of   the  thalamus,  basal  ganglia,  and  the  ventral  part  of  the  internal   capsule.     o It  varies  a  great  deal  in  size  and  importance  in  different   individuals  and  may  instead  branch  from  the  middle  cerebral   artery.   • Anterior  cerebral  artery  (ACA)   o When  ICA  goes  up  near  interhemispheric  fissure.  Its  cortical   branches  supply  the  entire  medial  surface  of  the  cerebral   cortex  as  far  back  as  the  parietooccipital  cortex.  Also  supplies   the  “leg  area”  of  the  precentralgyrus.   • Middle  cerebral  artery  (MCA)   o When  the  ICA  branches  to  the  lateral  sylvian  fissure.   o  Largest branch of the ICA and its cortical branches supply the entire lateral surface of the hemisphere except for the portion supplied by the anterior cerebral artery (ACA), the occipital pole, and the inferolateral surface supplied by the posterior cerebral artery (PCA).  

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    Fig.  2  Branches  of  Internal  Carotid  Artery     This  figure  shows  the  branches  of  both   the  ICAs  seen  inferiorly  from  the     base   of   the   brain   -­‐   the   ophthalmic,   the   posterior   communicatingthe   anterior  cerebral,  and  the  middle  cerebral  arteries.    

 

   

 

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Fig.  3B  Arterial  Supply   Side  Note:  Ma’am  discussed  about  how  to  locate  the  cranial  nerves:     CN I o There are two boobs (mammillary bodies) - two pairs of boobs in the brainstem which are Superior and Inferior colliculi. You’ll see olfactory tract and bulb (must know the difference) are beside Interhemispheric fissure. The free nerve endings are actually in the nose. CN II o Optic nerve and optic chiasm- ma’am differentiated the two with the optic tract CN III o Upper pons (rostral pons) – occupied by the CN III (Oculomotor nerve) CN IV o Very small nerve arising from posterior part of brain – Trochlear nerve (CN IV) – usually like a strand of dirt (as thin as the strand of hair CN V o Occupying lateral pons - motor and sensory component CN VI Pons and medulla junction o pontomedullary junction in between is the Abducens nerve (CN VI) CN VII, VIII, IX, X o Lateral pontomedullary junction – VII and VIII are always together Facial Nerve (CN VII) the biggest while IX and X are together CN XI o Dorsolateral sulcus – you will see rootlets of Spinal Accessory Nerve which innervates trapezius and sternocleidomastoid CN XII o Ventrolateral sulcus– you will see rootlets of Hypoglossal nerve which innervates all intrinsic muscles except palatoglossus

       

  Fig.  3A  Arterial  Supply  

Group    5|  Dave,  Bamba,  Precious,  Jaela

 

     

             

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A.  Middle  Cerebral  Artery   • “Direct  communication”  of  the  ICA   • Supplies  the  dorsolateral  surface  of  the  cerebral  hemispheres   o The  MCA  is  regarded  as  the  direct  communication  of  the   INTERNAL  CAROTID  ARTERY,  passing  laterally  to  the  Sylvian   fissure  and  is  distributed  in  a  fanlike  fashion  supplying  the   dorsolateral  surface  of  the  cerebral  hemisphere.   • Branches  from  stem  or  M1  segment  (initial  part  of  the  MCA  

KEY  FUNCTIONAL  AREAS  OF  MCA:   • Superior  branches   o Sensorimotor  cortex  (except  legs)  -­‐  surrounding  the   Rolandic  fissure   o Frontal  eye  fields-­‐  important  for  bilateral  eye   coordination   o Broca’s  area  (language  expression)   • Inferior  branches   o Wernicke’s  area  (language  comprehension)   o Auditory  cortex   o Optic  radiations  

o As it passes laterally, the stem gives off a series of 6-12 long, small diameter penetrating vessels that travel upward to supply the basal ganglia and much of the internal capsule called the LATERAL STRIATE ARTERIES (Together with the medial striate arteries, which are branches of the ACA also supplying the basal ganglia and internal capsule, they are collectively called LENTICULOSTRIATE ARTERIES)

o Once  in  the  Sylvian  fissure  itself,  the  MCA  stem  divides  into  two   main  cortical  branches  that  supply  the  entire  lateral  surface  of   the  brain  as  well  as  the  insula:    Superior  (upper  or  suprasylvian)  MCA  branch    Inferior  (lower  or  infrasylvian)  MCA  branch   • MCA  supplies:     1. Inferior  frontal  gyrus   o BA  44  &  45  (Motor  speech  area/Broca’s  area)     Function:  Language  expression     located  at  the  back  of  the  temporal  lobe  and  traverse  the   gyrus  of  Heschel  (Wornikke’s  area  BA  22   2. Precentralgyrus   o BA  4  (Primary  motor  area)     3. Postcentralgyrus   o BA  3,  1,  2  (Primary  somatosensory  area)   4. Superior  temporal  gyrus   o BA  22  (Wernicke’s  area)     Function:  Language  comprehension   5. Frontal  Eye  fields   o BA  8   This  can  also  be  affected  if  MCA  occluded    

Fig.  4  Right  Lateral  view  of  right   hemisphere   On this lateral view of the cerebral hemisphere, in blue is seen the superior or suprasylvian branches of the MCA supplying the inferior and lateral frontal lobe and the anterolateral parietal lobe and the inferior or infrasylvian branches of the MCA supplying the lateral temporal, the lateral occipital and the posterior parietal lobes.

 

 

  Clincial  Correlation   Occlusion  in  the  MCA  may  produce:   • Severe  contralateral  hemiparesis  (marked  in  UE  and  face)   • Contralateral  sensory  loss  mainly  the  face  and  the  arm   • Severe  aphasia  (if  dominant  hemisphere  is  involved   Broca’s/Wernicke’s)  problem  in  understanding  and  speaking    If  there  is  occlusion  in  UE  than  L  –  occlusion  in  MCA    LE  than  UE  –  more  ACA  than  MCA  involvement   Only  weaness  (paresis)    not  paralysis,  why  is  that?   If  you  affected  the  peripheral  nerve  itself,  for  example  you  have  affected  the   radial  nerve.  Radial  nerve  supplies  the  upper  extremities  such  that  if  you   affected  it,  there  is  difficulty  in  extension  of  the  arm  and  forearm  and  there  is   paralysis.  But  if  you  affected  only  the  pathway,  (will  be  discussed  by  Dr.   Calilao  on  Motor  Pathway)  you  will  only  have  weakness.  

 

 

Group    5|  Dave,  Bamba,  Precious,  Jaela

Fig  5.  Branches  of  ICA  

    B.  Anterior  Cerebral  Artery   • is  a  smaller  branch  of  the  Internal  Carotid  Artery  that  passes   rostromedially,  dorsal  to  the  optic  nerve  and  approaches  the   corresponding  artery  of  the  opposite  side  along  the   interhemispheric  fissure   • Anterior  branch  of  Internal  carotid  artery  supplying  the  medial   aspect  of  the  frontal  and  parietal  lobes   • Branches:   o Anterior  communicating  artery  -­‐  which  allows  collateral  flow   into  the  opposite  hemispheres  if  the  ICA  is  occluded  on  either   side.   o Orbital  branches  and  frontopolar  artery   o Callosomarginal  artery   o Pericallosal  artery  

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o Medial  striate  artery  or  recurrent  artery  of  Heubner  (part  of  

III.  VERTEBRAL  ARTERY  SYSTEM  

the  lenticulostriate  arteries)  is an early branch near the base of the artery which sends off deep penetrating branches to supply the anteromedial part of the HEAD OF THE CAUDATE NUCLEUS, adjacent parts of the INTERNAL CAPSULE and PUTAMEN, and parts of the SEPTAL NUCLEI.

   

 

   

  Fig.  6  Medial  View  of  Cerebral  Hemisphere  

On the medial view of the cerebral hemisphere, the Ant CEREBRAL Artery sweeps forward into the interhemispheric fissure and then runs up and over the genu of the corpus callosum, giving off orbital branches and the frontopolarartery supplying the orbital, the frontal pole and the medial aspect of the frontal lobe. As it turns backwards, it forms one branch that stays immediately adjacent to the corpus callosum (the pericallosal artery) while a second branch runs in the cingulate sulcus just superior to the cingulategyrus (the callosomarginal artery)

  KEY  FUNCTIONAL  AREAS  OF  ACA:   • Septal  area   • Sensorimotor  cortex  for  the  lower  extremities   • Motor  planning  areas  in  the  medial  frontal  lobe  anterior  to   the  precentral  gyrus     CLINICAL  CORRELATON   Occlusion  in  the  ACA  may  produce:   • Contralateral  hemiparesis  and  hemisensory  loss  greatest   in  the  lower  limb   • Inability  to  identify  objects  correctly,  apathy  and   personality  changes  (frontal  and  parietal  lobes)   • Inhibition  of  primitive  reflexes  in  the  frontal  lobe  such  as   rooting  reflex                           Group    5|  Dave,  Bamba,  Precious,  Jaela

 

 

Fig.7  Vertebral  Arteries  

The VERTEBRAL ARTERIES usually arise from the subclavian arteries. They course through the CERVICAL TRANSVERSE FORAMINA, run medially and ascend into the FORAMEN MAGNUM where they pierce the dura and enter the cranial cavity. They would then join to form a SINGLE BASILAR ARTERY, which would later bifurcate to form the POSTERIOR CEREBRAL ARTERIES, whose branch the POSTERIOR COMMUNICATING ARTERY joins with the ipsilateral INTERNAL CAROTID ARTERYjoining both systems.

  The   Vertebral   Artery   System   is   from   the   1st   part   of   Subclavian   artery.  It:   • Perforates   the   intervertebral   foramen   of   the   upper   6   cervical   vertebrae   • Enters   cranial   cavity   through   the   foramen   magnum   [medulla   +   vertebral  artery]   • Terminates   into   a   big   artery   at   the   level   of   the   pons   „³   Basilar   artery   • The   entire   blood   supply   of   medullary   oblongata,   pons,   mesencephalon  and  cerebellum     Divided  into  2  Branches   1. Vertebral  artery   • ascend  on  the  ventrolateral  surface  of  the  brainstem   Branches  are:     • Spinal  arteries-­‐  2  posterior  and  1  anterior   • A  pair  of  POSTERIOR  SPINAL  ARTERIES   o branches and descends along the posterolateral surface of the spinal cord AND two anterior branches join to form a single midline ANTERIOR SPINAL ARTERYthat supplies the medial regions of the lower medulla and the upper spinal cord. These arteries form an ANASTOMOTIC system with the RADICULOSPINAL ARTERIES, which supply the spinal cord

• Meningeal   arteries   supply   the   bone   and   dura   mater   in   the  

posterior  cranial  fossa • Posterior  inferior  cerebellar  arteries  (PICA)   o Supplies   inferior   and   posterior   surface   of   the   cerebellum,   lateral  1/3  of  medulla  and  the  choroid  of  the  4th  ventricle   • Medullary  (bulbar)  branches   o Small branches that are distributed to the medulla oblangata

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2. Basilar  artery  -­‐  Formed  by  fusion  of  the  two  vertebral  arteries  at   medullary   pontine/pontomedullary   junction   and   further   divided   into(arranged  from  caudal  to  rostral):   • Anterior  inferior  cerebellar  arteries  (AICA)   o At  point  of  fusion   o  supply  the  lateral  region  of  the  caudal  pons,  upper  medulla,   and  portions  of  the  inferior  surface  of  the  cerebellum;     • Internal  auditory  (labyrinthine)  arteries   o Enter  internal  acoustic  meatus  with  CN  7  and  8   o Sometimes  arise  from  AICA   o Supplies  the  inner  ear   • Pontine  arteries   o paramedian,  circumferential  (short  and  long)   o have  paramedian  branches  supplying  the  medial  pons,  short   circumferential  branches  supplying  the  ventrolateral  surface   of   the   pons   and   long   circumferential   branches   which   anastomose   with   the   AICA   and   the   superior   cerebellar   arteries  to  supply  most  of  the  pontinetegmentum;   • Superior  cerebellar  arteries   o Before  termination   o At  upper  pons  and  end  at  dorsal  surface  of  cerebellum,  pons,   and  superior  cerebellar  peduncle   o Supplies   rostral   pons,   superior   surface   of   the   cerebellum,   pineal  gland,  and  the  superior  medullary  velum.   • Posterior  cerebral  arteries  (PCA)   o terminal  branches  of  the  basilar  artery.      

  A.  Posterior  Cerebral  Artery  [PCA]               • Terminal  branch  of  the  basilar  artery   • Cortical brances supply the inferolateral and medial surfaces of the temporal lobe (visual cortex). Central branches supply parts of the thalamus and the midbrain. A choroidal branch supplies the choroid plexus and third ventricle • From   parieto-­‐occipital   sulcus   and   posterior   to   it   (Preoccipital   notch)   • Also   supplies   the   Reticular   Activating   System   (RAS)   for   maintenance  of  consciousness   • Branches:   o Calcarine  artery    An   important   branch   of   the   Post   Cerebral   Artery   which   supplies  the  visual  cortex  at  the  occipital  lobe.   o Posterior  choroidal  arteries    Arise  from  the  Posterior  Cerebral  Art  to  supply  portions  of   the  midbrain,  the  thalamus,  and  the  choroid  plexus  of  the   3rd  ventricle.   *So   the   main   blood   supply   of   the   choroid   plexus   at   different   levels   are:   rd

(lateral  ventricles,  anterior  choroidal  a.  [ICA  (or  MCA)];  3  ventricle,  posterior   th choroidal  a.  [PCA];  4  ventricle,  PICA  

o Deep   perforating   branches-­‐   As   each   Post   Cerebral   Artery   passes   around   the   cerebral   peduncles,   it   forms   a   series   of   branches   to   the   midbrain   and   gives   rise   to   Deep   perforating   branches    Supply much of the hypothalamus and the thalamus (of the diencephalon). The small branches to the midbrain supply especially the RETICULAR ACTIVATING SYSTEM (or RAS) whose function is maintenance of consciousness.

KEY  FUNCTIONAL  AREAS  OF  PCA:   • Diencephalon:  All  with  the  word  “thalamus”   • Midbrain   • Primary  visual  cortex   • Hippocampal  formation  (memory)  

 

CLINICAL  CORRELATON   Occlusion  in  the  PCA  may  produce:   • Contralateral  homonymous  hemianopsia  =  Bigger  blindspot   -­‐Due  to  occlusion  of  Calcarine  artery                                      -­‐Remember!  NOT  BLINDNESS                    -­‐It  is  the  occlusion  of  OPTHALMIC  ARTERY  that  causes              blindness   • Bilateral  occlusion:  defect  of  memory  

 

Fig.  8  Vertebral  Artery  System  

  IV.  CIRCLE  OF  WILLIS   • Also  called  “circulus  arteriosus”   • Formed  by  the  junction  of  the  basilar  artery  and  the  2  ICAs   through  the  presence  of  2  posterior  and  1  anterior   communicating  arteries   • Gives  of  2  types  of  arteries:   1.  Central   2.  Cortical   **Aside from the cortical branches from the different arteries, which form part of the circle, there are CENTRAL

     

  Fig.  9  Vertebral  Artery  System  (Gross)  

Group    5|  Dave,  Bamba,  Precious,  Jaela

ARTERIES which penetrate the substance of the brain and supply deep structures. The 2 groups of central arteries within the circle itself are the ANTERIOR MEDIAL and the POSTERIOR MEDIAL GROUPS.

 

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Table  1.  Arteries  to  Specific  Brain  Areas  

• Little  exchange  between  brain  halves  (functionally  separate):   equalize  flow  but  functionally  inadequate     • Compensates  if  there  is  occlusion  to  other  arteries   • Encircles  the  optic  chiasm,  tuber  cinereum  and  interpeduncular   region   • Anteromedial  group  –  Central  arteries  arise  from  anterior   communicating  artery  and  ACA   • Posteromedial  group  –  Originates  from  PCA  and  posterior   communicating  arteries  

Corpus striatum & internal capsule

Lenticulostriate(supplied mainly fromlateral striate from MCA and medial striate from ACA) and anterior choroidal arteries (from ICA)

Thalamus

PCA (from basilar-vertebral system), posterior communicating (from ICA)

Midbrain

PCA, superior cerebellar (both from basilar-vertebral system)

Pons

Superior cerebellar arteries, Pontine a. and AICA (from basilar-vertebral system) and PICA (from vertebral)

Medulla oblongata

AICA PICA Basilar Vertebral Ant and Post Spinal

Cerebellum

Superior cerebellar, AICA and PICA

Notes: The circle of Willis is highly over-rated as a source of effective

collateral circulation. Normally, there is little exchange of blood between brain halves because of the equality of blood pressure. Blood normally does not flow around the arterial circle. Though interconnected, the two systems are functionally separate. The anastomotic channels do serve to equalize flow to various parts of the brain and prevent neurological damage. However, the communicating arteries are often functionally inadequate if

   

occlusion occurs acutely. In fact, various combinations of hypoplastic and asymmetrical arterial circles commonly occur.

                           

 

1.  Anterior  cerebral  artery   (callosomarginal  and   pericallosal  arteries)   2.  Middle  cerebral  artery   3.  Posterior  cerebral       artery   4.  Medial  striate  arteries   to  the  internal  capsule,   globuspallidus  and   amygdala     5.  Lateral  striate  arteries   to  the  caudate  nucleus,   putamen  and  internal   capsule  

Fig.  11  Arteries  to  Specific  Brain  Areas  

 

A    

B  

 

Fig.  10  A  and  B  The  Circle  Of  Willis  

Group    5|  Dave,  Bamba,  Precious,  Jaela

 

 

A.  Middle  Meningeal  Artery   • Periosteal  branch  of  the  external  carotid  artery   • supplies  no  CNS  tissue   • enters  the  cranial  cavity  through  the  foramen  spinosum   • usually  ruptured  by  fracture  of  the  lateral  skull  vault   • bleeding  between  the  dura  and  overlying  skull(extradural  or   epidural  hematoma)     V.  VENOUS  DRAINAGE  OF  THE  BRAIN   • Do  NOT  run  along  course  of  cerebral  arteries   •  Devoid  of  valves   • External  veins  divided  into  superficial  and  deep  groups,  which   drain  the  cortex  and  subcortical  white  matter  areas  respectively,   and  piercing  the  arachnoid  and  dura  mater,  they  drain  into  the   dural  venous  sinuses  and  ultimately  into  the  internal  jugular  veins.   o Deep  Cerebral  Veins      It  just  follows  venae  comitantes;  will  eventually  drain  into   that  set  of  veins    

Page  6  of  10    

o Branches  of  Superficial  Cerebral  Veins:    External  cerebral  veins    Superior  cerebral  veins  –  empty  into  superior  sagittal  sinus    Superficial  middle  cerebral  vein  –  drains  lateral  surface  of   cerebral  hemisphere  and  empties  into  the  cavernous  sinus    Deep  middle  cerebral  vein  –  drains  the  insula    Basal  veins    from  anterior  cerebral,  striate  and  deep  middle  cerebral   veins  and  empty  into  the  great  cerebral  vein;  drains  into   straight  sinus    Internal  cerebral  veins    From  thalamostriate,  septal  and  choroidal  vv.    Great  cerebral  vein  of  Galen    formed  by  the  2  internal  cerebral  veins  and  empty  into  the   straight  sinus           A                         The superior cerebral veins drain the cortex and pass upward to empty into the superior sagittal sinus. The superficial middle

cerebral veinruns inferiorly in the lateral sulcus following the course of the middle cerebral artery and drains the lateral surface of the cerebral hemispheres emptying into the cavernous sinus. A superior anastomotic vein may connect the superficial middle cerebral vein with the superior sagittal sinus.

B  

The internal cerebral vein drains the interior of each hemisphere while the basal veindrains the cerebrum anteriorly. These two empty into the great cerebral vein of Galen, which in turn drains into the straight sinus. Take note that the superficial and deep cerebral veins are interconnected by numerous anastomotic channels.

 

Veins  to  specific  brain  areas   o Midbrain – drained by veins that open into the basal or great cerebral veins o Pons- drained by veins that open into the basal vein, cerebellar veins, or neighboring sinuses o Medulla oblongata – drained by veins opening into the spinal veins and neighboring sinuses o Cerebellum – drained by veins emptying into the great cerebral vein or adjacent sinuses Dural  Venous  Sinuses   o Superior  sagittal  sinus      Runs  along  the  superior  margin  of  the  falx  cerebri  from  the   foramen  caecum  to  the  confluence.   o Inferior  sagittal  sinus      Runs  along  the  inferior  border  of  the  falx  cerebri  and  caudally   joins  the  RECTUS  or  STRAIGHT  SINUS,  which  is  located  at  the   junction  of  the  falx  cerebri  and  the  tentorium  cerebelli  and   then  empties  into  the  confluence.   o Rectus  (straight)  sinus       At  the  junction  of  falxcerebri  and  tentorium  cerebelli    Empties  into  the  confluence   o Confluence  of  the  sinuses      located  near  the  internal  occipital  protuberance  where  the   superior  sagittal,  the  straight,  the  occipital  and  the   transverse  sinuses  meet  (SST)   o Transverse  sinuses      arise  laterally  from  the  confluence  and  curve  downward  and   backward  as  the  SIGMOID  SINUSES,  which  eventually  open   into  the  INTERNAL  JUGULAR  VEIN.       o Sigmoid  sinuses      Turned  backwards     Pass  into  jugular  foramen  (not  the  internal  jugular  vein)     Eventually  drain  into  Internal  jugular  vein   o Cavernous  sinus      an irregular network of communicating venous channels on either side of the sphenoid sinus, the sellaturcica, and the

pituitary

CAROTID

gland.

ARTERY

It and

encloses CRANIAL

the

INTERNAL

NERVES

3,

4,

ophthalmic 5, and 6. The cavernous sinus of each side is connected with the other by the basilar venous plexus and venous channels running anterior and posterior to the hypophysis.

Group    5|  Dave,  Bamba,  Precious,  Jaela

 

Page  7  of  10    

 

Fig.  15  Dural  Venous  Sinuses  of  the  Brain   *note:   The   SUPERIOR   PETROSAL   SINUS   connects   the   cavernous   sinus   with   the   transverse   sinus,   while   the   INFERIOR   PETROSAL   SINUS   connects   the   cavernous  sinus  with  the  bulb  of  the  internal  jugular  vein.     The cavernous sinus also receives anastomotic branches from the veins draining the face and maxilla. Also note that the brainstem and the cerebellum are drained by numerous veins that parallel the arteries and form the BASILAR VENOUS PLEXUS, which also empties into the great cerebral vein via the basal veinsor the internal cerebral veins. The basilar venous plexus and the occipital sinus also make connections with the internal vertebral or epidural venous plexus. The significance of this I will point out when we discuss the venous drainage of the spinal cord.

VI.  THE  SPINAL  CORD   • Blood  supply:  perforating  vessels  from  network  of  pial  arteries   o 1  anterior  and  2  posterior  spinal  arteries  (insufficient  to  supply   the  cord  beyond  the  cervical  levels.)    1  anterior  spinal  artery  =  supply  anterior  horn,  lateral  horn,   central  gray  and  basal  part  of  the  posterior  horn     2  posterior  spinal  arteries  =  supply  Posterior  horn  and   posterior  funiculi   o Radicular  arteries     supply  the  NERVE  ROOTS    Branch  off  from  the  vertebral/cervical  arteries  in  the  neck,   intercostals  arteries  in  the  thorax,  lumbar  arteries  in  lumbar   region  and  the  abdominal  aorta   o Radiculospinal  or  segmental  medullary  arteries  –  supply  the   RADICULOSPINAL  or  SEGMENTAL  MEDULLARY  ARTERIES    arise  from  branches  of  the  aorta  and  anastomose  with  the   anterior  and  posterior  spinal  arteries  at  different  levels    each  supply  about  6  spinal  cord  segments  with  the  exception   of  the  GREAT  ANTERIOR  SEGMENTAL  MEDULLARY  ARTERY   OF  ADAMKIEWICZ,  which  usually  enters  the  left  second   lumbar  ventral  root,  ranging  between  T10-­‐L4,  and  supplies   most  of  the  caudal  1/3  of  the  cord   Group    5|  Dave,  Bamba,  Precious,  Jaela

 

 

   

Fig.  16  Anterior  Blood  Supply  of  the  Spinal  Cord  

*The anterior spinal artery forms a circumferential plexus with the posterior spinal arteries called the VASOCORONA. * The anterior spinal artery supplies the anterior 2/3 of the cord including the base of the posterior horn, while each posterior spinal artery supplies the ipsilateral posterior horn and dorsal columns. *Below

the

cervical

level,

the

RADICULOSPINAL

or

the

SEGMENTAL MEDULLARY ARTERIES supply both the roots and

the cord as they join with the spinal artery, augmenting its path. *Each of these radiculospinal arteries supply about 6 spinal cord segments

with

the

exception

of

the

GREAT

ANTERIOR

SEGMENTAL MEDULLARY ARTERY OF ADAMKIEWICZ, which usually enters the left

second lumbar ventralroot, ranging

between T10-L4, and supplies most of the caudal 1/3 of the cord.

 

Page  8  of  10    

Question:  The  dorsal  horn  of  the  spinal  cord  is  supplied  by  what   artery?    Radicular  arteries  accompany  the  spinal  nerves  and  bifurcate  to   form  a  VENTRAL  or  ANTERIOR  RADICULAR  ARTERY  and  a  DORSAL   or  POSTERIOR  RADICULAR  ARTERY  to  supply  the  ventral  and   dorsal  never  roots  respectively.    Radiculospinal  arteries  connect  with  the  anterior  spinal  artery  to   also  supply  the  cord  -­‐SULCAL  ARTERIES  arise  from  the  anterior   spinal  artery  and  courses  in  the  ANTERIOR  MEDIAN  FISSURE  to   supply  approximately  2/3  of  the  anterior  cross-­‐sectional  area  of   the  cord  (Sulcal  means  central)     • Venous  Supply   o Parallels  with  arterial  supply  (venae  comitantes)   o Internal  vertebral  venous  plexus  (epidural  venous  plexus)    Between  the  dura  mater  and  the  vertebral  periosteum     Have  connections  thoracic,  abdominal  and  intercostals  veins   and  external  venous  plexus     Internal  vertebral  venous  plexus  =  External  vertebral  venous   plexus  =  Systemic  venous  system   o Because  of  these  connections,  infection  or  carcinoma  from   pelvic  or  abdominal  organs  may  spread  to  the  brain    

 

  Fig.  17  Anterior  and  Posterior  Blood  Supply  of  the   Spinal  Cord  

*Along its course, the spinal cord is supplied anteriorly and posteriorly from arteries which enter the spinal canal through the intervertebral foramina in company with the spinal nerves.

  CLINICAL  CORRELATION   • Any  infection  from  angular  vein  or  facial  vein  can  enter  cavernous   sinus  =    Cavernous  sinus  thrombosis     • Each  side  is  connected  by  basilar  venous  plexus     • Where  ophthalmic  vein  and  sphenoparietal  sinus  drain     • Drain  into  the  superior  and  inferior  petrosal  sinuses     • Superior  petrosal  drains  into  sigmoid  „³  IJV  „LInferiorpetrosal   drains  directly  to  IJV     • Emissary  Veins    -­‐No  valves    -­‐For  emergency  drainage  in  case  IJV  is  occluded   -­‐Can  be  a  pathway  for  extracranial  infection,  leading  to  infected   thrombosis        

Group    5|  Dave,  Bamba,  Precious,  Jaela

 

   

Fig.  18  Venous  Drainage  of  the  Spinal  Cord  

Notes: There are usually 3 anterior and 3 posterior spinal veins. They are arranged longitudinally, communicate with each other, and are drained by up to 12 anterior and posterior medullary and radicular veins. These veins join the INTERNAL VERTEBRAL (or EPIDURAL) VENOUS PLEXUS [point bottom], lying in the extradural or epidural space.

Page  9  of  10    

As mentioned earlier, this INTERNAL VERTEBRAL VENOUS PLEXUS passes superiorly through the foramen magnum to communicate with the dural sinuses and basilar venous plexus in the skull. The INTERNAL VERTEBRAL VENOUS PLEXUS also communicates with the EXTERNAL VERTEBRAL VENOUS PLEXUS on the external surface of the vertebrae and thus connect directly to the systemic venous system. These connections may act as a route for spread of infection or carcinoma from the pelvic or abdominal organs to the brain.

stress  stress    stress    stress    stress    stress    stress    stress    stress    stress     stress    stress  stress  stress    stress    stress    stress    stress    stress    stress     stress    stress    stress    stress  stress  stress    stress    stress    stress    stress     stress    stress    stress    stress    stress    stress  stress  stress    stress    stress     stress    stress    stress    stress    stress    stress    stress    stress  stress  stress     stress    stress    stress    stress    stress    stress    stress    stress    stress    stress   stress    stress    stress    stress    stress    stress    stress    stress    stress    stress     stress    stress    stress    stress    stress    stress    stress    stress    stress    stress     stress    stress    stress    stress    stress    stress    stress    stress    stress    stress     stress    stress    stress    stress    stress    stress  stress  stress    stress    stress     stress    stress    stress    stress    stress    stress    stress    stress  stress  stress     stress    stress    stress    stress    stress    stress    stress    stress    stress    stress  

A  

 

I  AM  UNDER  A  LOT  OF  STRESS  

 

   

      The anterior spinal artery forms a circumferential plexus with the posterior spinal arteries called the VASOCORONA . The anterior spinal artery supplies the anterior 2/3 of the cord including the

base of the posterior horn [point], while each posterior spinal artery supplies the ipsilateral posterior horn and dorsal columns

      Group    5|  Dave,  Bamba,  Precious,  Jaela

 

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