Neurovascular Anatomy

Cerebral Arterial Supply - Brain's Blood Pipes

• Circle of Willis (CoW): Anastomotic arterial ring at the base of the brain.
  • Formed by: Internal Carotid Arteries (ICAs) & Vertebrobasilar system (Basilar artery).
  • Components: Anterior Communicating (AComA), Posterior Communicating (PComA), ACA (A1), PCA (P1).
  • Crucial for collateral blood flow, especially if a major artery is occluded.
• Major Cerebral Arteries & Territories:
  • Anterior Cerebral Artery (ACA):
    • Supplies: Medial aspects of frontal and parietal lobes, corpus callosum (anterior part), leg-foot area of motor/sensory cortex.
    • Pathology: Contralateral leg > arm weakness/sensory loss, frontal lobe signs (e.g., abulia, grasp reflex).
  • Middle Cerebral Artery (MCA): Largest cerebral artery; most common site of cerebrovascular accident (CVA).
    • Supplies: Lateral convexity of cerebral hemisphere (frontal, parietal, temporal lobes), basal ganglia, internal capsule.
    • Pathology: Contralateral hemiplegia (face/arm > leg), sensory loss, aphasia (dominant hemisphere), neglect (non-dominant hemisphere).
  • Posterior Cerebral Artery (PCA):
    • Supplies: Occipital lobe, inferior-medial temporal lobe, thalamus, midbrain.
    • Pathology: Contralateral homonymous hemianopia with macular sparing, memory impairment, visual agnosia.
• Lenticulostriate Arteries: Small, deep penetrating branches from MCA; supply basal ganglia & internal capsule. Prone to hypertensive damage (Charcot-Bouchard microaneurysms).

⭐ The Middle Cerebral Artery (MCA) is the most common artery involved in ischemic stroke, often leading to significant neurological deficits due to its large supply territory.

Cerebral Venous Drainage - Brain's Drain System

• Overview: Valveless system; superficial & deep veins drain into dural venous sinuses.
• Superficial Veins: Drain cortex.
  • Superior cerebral veins → Superior Sagittal Sinus (SSS).
  • Superficial middle cerebral vein → Cavernous or Sphenoparietal sinus.
  • Anastomotic veins: Trolard (superior), Labbé (inferior).
• Deep Veins: Drain deep structures (e.g., basal ganglia, thalamus).
  • Internal cerebral veins + Basal veins of Rosenthal → Great Cerebral Vein (of Galen).
  • Great Vein of Galen → Straight Sinus.
• Dural Venous Sinuses: Endothelium-lined channels between dural layers.
  • Unpaired: Superior Sagittal (SSS), Inferior Sagittal (ISS), Straight, Occipital.
  • Paired: Cavernous, Transverse, Sigmoid, Superior & Inferior Petrosal, Sphenoparietal.
  • Confluence of Sinuses (Torcular Herophili): SSS, Straight, Occipital, Transverse sinuses meet.
• Clinical Correlation:
  • Cavernous Sinus Thrombosis: Risk from infections in 'danger area' of face. Affects CN III, IV, V1, V2, VI & Internal Carotid Artery (ICA).

  ⭐ The Cavernous Sinus is critical: CN VI (Abducens) and the ICA pass through it. CN III (Oculomotor), IV (Trochlear), V1 (Ophthalmic), and V2 (Maxillary) are in its lateral wall. (📌 Mnemonic for lateral wall contents: "Oh To Ogle Marilyn" or simply O TOM).

Spinal Cord Vasculature - Cord's Lifelines

• Arterial Supply:
  • Anterior Spinal Artery (ASA): single; supplies anterior 2/3 (motor, spinothalamic).
  • Posterior Spinal Arteries (PSAs): paired; supply posterior 1/3 (dorsal columns).
  • Segmental/Radicular Arteries: reinforce.
    • Artery of Adamkiewicz: major to lumbosacral cord. 📌 Typically T9-T12 (left).
• Venous Drainage:
  • Anterior & posterior spinal veins.
  • Internal vertebral venous plexus (Batson's).

⭐ Anterior Cord Syndrome (ASA occlusion): bilateral loss of motor function, pain, and temperature sensation below the lesion. Proprioception and vibration (dorsal columns) are preserved.

Clinical Neurovascular Syndromes - When Pipes Go Wrong

• Ischemic Strokes (85%):
  • Anterior Circulation:
    • ACA (Anterior Cerebral Artery): Contralateral leg > arm weakness/sensory loss, grasp reflex, abulia, urinary incontinence.
    • MCA (Middle Cerebral Artery): Contralateral face/arm > leg weakness/sensory loss, aphasia (dominant hemisphere), neglect (non-dominant hemisphere), homonymous hemianopia.

      ⭐ MCA is the most commonly affected artery in stroke.

    • 📌 Arm > Leg = MCA; Leg > Arm = ACA.
  • Posterior Circulation:
    • PCA (Posterior Cerebral Artery): Contralateral homonymous hemianopia (often with macular sparing), visual agnosia, memory loss.
    • Vertebrobasilar Syndromes: Vertigo, nystagmus, diplopia, dysarthria, dysphagia, ataxia, crossed deficits (e.g., Wallenberg syndrome).
  • Lacunar Strokes: Small, deep infarcts (basal ganglia, thalamus, pons, internal capsule). E.g., pure motor, pure sensory, ataxic hemiparesis, dysarthria-clumsy hand.
• Hemorrhagic Strokes (15%):
  • Intracerebral Hemorrhage (ICH): Hypertension (commonest cause). Locations: basal ganglia (putamen), thalamus, pons, cerebellum.
  • Subarachnoid Hemorrhage (SAH): Sudden severe "worst headache of life", nuchal rigidity, photophobia. Ruptured berry aneurysm (commonest). Xanthochromia in CSF after ~12 hours.

High‑Yield Points - ⚡ Biggest Takeaways

• Circle of Willis: Key for collateral flow; common site for berry aneurysms (e.g., AComA).
• MCA stroke: Most frequent; contralateral face/arm weakness/sensory loss, aphasia (Broca's/Wernicke's).
• ACA stroke: Contralateral leg/foot weakness/sensory loss; frontal lobe signs.
• PCA stroke: Contralateral homonymous hemianopia; thalamic pain, memory issues.
• Lenticulostriate arteries: Supply deep structures (basal ganglia, internal capsule); site of lacunar infarcts.
• Wallenberg syndrome: Caused by PICA occlusion; ipsilateral facial numbness, contralateral body pain/temp loss.