Brain Blood Vessels and Intracerebral Bleeds

Course Information

• Class: Year 2 Semester 1
• Course: Medicine
• Lecturer: Dr. Vijayalakshmi S B
• Date: 06/11/2024
• Topic: Brain blood vessels and intracerebral bleeds

Learning Outcomes

• Describe the blood supply to the brain and spinal cord
• Identify the areas supplied by individual arteries
• Describe the Circle of Willis
• Define "stroke" and differentiate between ischaemic and hemorrhagic stroke causes
• Explain the effect of focal lesions caused by strokes in major cortical functional areas

Blood Supply to the Brain

• Anterior system: Internal carotid arteries supply most of the forebrain, except the occipital lobe.
• Posterior system: Vertebro-basilar arteries supply the spinal cord, brainstem, cerebellum, and occipital lobes.
• Connecting system: The two systems are connected via the Circle of Willis.

Blood Supply

• Internal carotid arteries
• Vertebral arteries

Vertebrobasilar System

• Two vertebral arteries arise from the subclavian artery.
• Ascend in transverse foramina.
• Enter foramen magnum.
• Release posterior inferior cerebellar artery (PICA)
• Release posterior and anterior spinal arteries.
• Merge into a single basilar artery.

Vertebral Arteries and Spinal Cord

• Anterior spinal arteries unite to form a single anterior spinal artery.
• Two posterior spinal arteries travel vertically.
• Spinal arteries are supplemented by radicular arteries entering intervertebral foramina arising from segmental arteries.
• Artery of Adamkiewicz is located in the lower thoracic or upper lumbar region.

Branches of the Basilar Artery

• Formed at the ponto-medullary junction.
• Anterior Inferior Cerebellar Arteries (AICA)
• Labyrinthine arteries
• Pontine arteries
• Superior cerebellar arteries
• Posterior cerebral arteries
• Communicate to internal carotid artery (ICA) via posterior communicating arteries (PCA)

Pontomedullary Junction

• Location of the basilar artery formation.
• Contains various arteries.

Internal Carotid Artery

• Cervical part of the ICA enters the carotid foramen/canal.
• Passes through the carotid canal as the petrous part of the ICA.
• Opens into the top part of the foramen lacerum and travels through the cavernous sinus (cavernous part).
• Cerebral part of the ICA joins the Circle of Willis.

Branches of the Internal Carotid Artery

• Ophthalmic
• Through the optic canal to the eye.
• Anterior choroidal artery
• To choroid plexus, enters the inferior tip of the lateral ventricle.
• Also supplies optic chiasma, optic tract, lateral geniculate body (thalamus), and part of the internal capsule.
• A branch to the pituitary gland.
• Posterior communicating artery
• Two terminal branches
• Leading to communicating arteries and middle cerebral arteries.

Anterior Cerebral Artery

• Supplies the orbital surface of the frontal lobe, medial aspect of hemisphere (except occipital lobe), upper border of frontal and parietal lobes.
• Supplies the lower limb.
• Supplies perineum, micturition, and defecation functions.
• Medial striate arteries supply basal ganglia and the anterior limb and genu of the internal capsule.

Middle Cerebral Artery

• Supplies the lateral fissure and lateral aspect of the hemisphere (except anterior cerebral strip and occipital lobe).
• Supplies the lateral aspects of the frontal, parietal, and temporal lobes.
• Medially supplies the anterior temporal lobe.
• Supplies speech areas (Broca's and Wernicke's areas) and auditory areas.
• Lateral striatal or lenticulostriate arteries supply basal ganglia and internal capsule.

Posterior Cerebral Artery

• Supplies the occipital lobe and infero-medial temporal lobe.
• Usually a terminal branch of the basilar artery.
• Rarely, may receive blood supply via posterior communicating artery.

Blood Supply of Central Cerebral Areas

• Basal ganglia, internal capsule.
• Anterior choroidal and striate arteries.

Internal Capsule

• Anterior limb - frontopontine fibers, thalamus to prefrontal.
• Genu - corticobulbar fibers.
• Posterior limb - corticospinal and sensory fibers, corticobulbar fibers.
• Retrolentiform - fibers to auditory and visual cortex.

Striate Arteries

• Various names (lenticulostriate, thalamostriate, long central artery).
• Medial striate arteries: anterior cerebral artery, internal capsule, nearby basal ganglia, and parts of the hypothalamus.
• Lateral striate arteries: middle cerebral artery and anterior choroidal arteries, nearby basal ganglia, and putamen.
• Central branches of posterior cerebral arteries including branches from posterior communicating arteries and supply thalamus and third ventricle.

Stroke

• Sudden development of focal neurological deficits due to impaired cerebral blood flow.
• Types: ischaemic and hemorrhagic.
• Common causes: spontaneous cerebrovascular accidents (CVA), cerebral thrombosis, cerebral hemorrhage, cerebral embolism, subarachnoid haemorrhage.
• Transient Ischaemic Attacks (TIAs): neurologic symptoms due to ischemia (e.g., carotid or vertebrobasilar stenosis). Symptoms last a few minutes (but can be up to an hour), with symptoms like staggering, dizziness, light-headedness, fainting, and paraesthesia. TIAs are a risk factor for stroke.

FAST

• Face: Has the face fallen on one side? Can they smile?
• Arms: Can they raise both arms and keep them there?
• Speech: Is their speech slurred?
• Time: Time to call 999 immediately if you see any of these signs.

Stroke Symptoms

• Cerebral hemispheres: contralateral symptoms.
  • Anterior cerebral: contralateral hemiplegia and anaesthesia
  • Middle cerebral: contralateral hemiplegia and anaesthesia, possible aphasia
  • Posterior cerebral: contralateral hemianopia
• Vertebrobasilar: mix of contralateral and ipsilateral symptoms
• Brainstem: varies depending on the specific area affected.
• Cerebellar hemispheres: ipsilateral symptoms, with cerebellar signs (balance and coordination problems), including involvement of superior cerebellar, AICA and PICA.

Middle Cerebral Artery (MCA) Stroke

• Contralateral motor and sensory loss (sparing lower limb and perineum).
• Possible speech deficits if the dominant hemisphere is involved.
• Supplies lateral striatal or lenticulostriate arteries to basal ganglia and the internal capsule.

PICA Syndrome (Lateral Medullary Syndrome)

• Lateral medulla is supplied by the PICA.
• Symptoms: ipsilateral pain and temperature loss from the face, vertigo, nystagmus, tinnitus, ipsilateral Horner's syndrome (ptosis, meiosis, anhydrosis), contralateral pain and temperature loss in the body, loss of taste from ipsilateral tongue, hoarseness/dysphagia, and involvement of cranial nerves.

Medial Medullary Syndrome

• Medial part of the medulla is supplied by the vertebral artery.
• Symptoms: contralateral hemiparesis, impaired position and tactile discrimination, ipsilateral tongue paralysis (involving hypoglossal nerve and nucleus).

Subarachnoid Hemorrhage

• High-density blood in the subarachnoid space.

Venous Drainage of the Brain

• Drained by a system of veins that empty into dural sinuses.
• Sinuses drain into the right and left internal jugular veins.
• Cerebral veins are divided into superficial and deep cerebral veins.
  • Superficial: superficial middle cerebral vein, superior anastomotic vein of Trolard, inferior anastomotic vein of Labbé
  • Deep: great cerebral vein of Galen, basal vein of Rosenthal, internal cerebral vein

Venous Drainage of the Spinal Cord

• Posterior lateral spinal veins, posterior median spinal vein, anterior median spinal vein, anterior lateral spinal veins.
• Drainage of veins from the spinal cord to the venous system.

Video Links (for further learning)

• Provide links to videos about specific stroke types.

This quiz focuses on the anatomy of brain blood vessels, specifically the blood supply to the brain and spinal cord. It covers key topics such as the Circle of Willis, types of strokes, and the impact of focal lesions. Test your understanding of these critical vascular concepts in medicine.