Neurology · MU Sofia

58. Cerebral circulation: anatomy, physiology, pathology, classification of acute disorders, examination methods in cerebrovascular diseases

Covers the anterior and posterior arterial supply of the brain, including the Circle of Willis, and the normal cerebral blood flow and its autoregulation with the factors that alter it. It then describes the main pathological mechanisms, classifies acute disorders into ischaemic (TIA and stroke) and haemorrhagic types, and lists clinical features of stroke. It closes with examination methods: clinical assessment, CT and MRI, vascular imaging, ultrasound, cardiac evaluation and laboratory tests.

Inside: 1 section · 1 labelled picture · 15 flashcards · 2 min

Topic 58 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 324 words (2 min of reading), with 15 flashcards.

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  1. Cerebral circulation - anatomy, physiology and pathology. Classification of the acute disorders of the cerebral ciruclation. Methods of examination in the cerebrovascular diseases.

Cerebral circulation - anatomy, physiology and pathology. Classification of the acute disorders of the cerebral ciruclation. Methods of examination in the cerebrovascular diseases.

Anatomy of Cerebral Circulation

The brain receives blood from two arterial systems:

A. Internal Carotid System (Anterior Circulation)

Branches: Anterior cerebral artery (ACA). Middle cerebral artery (MCA)

Supplies: Frontal lobe. Parietal lobe. Lateral cerebral hemispheres

B. Vertebrobasilar System (Posterior Circulation)

Formed by: Two vertebral arteries → basilar artery

Branches: Posterior cerebral artery (PCA)

Supplies: Brainstem. Cerebellum. Occipital lobe. Thalamus

Circle of Willis: Arterial anastomosis connecting anterior and posterior circulations.

Function: Collateral blood supply during vascular occlusion.

Physiology of Cerebral Circulation

Cerebral Blood Flow (CBF)

Normal: ≈ 50 mL/100 g brain tissue/min

Autoregulation: Maintains constant cerebral blood flow despite BP changes.

  • Mechanisms: Vasodilation. Vasoconstriction

Factors Affecting CBF: Blood pressure. PaCO₂ (↑ CO₂ → vasodilation). PaO₂. Intracranial pressure (ICP)

Pathology of Cerebral Circulation

Main Mechanisms: Thrombosis. Embolism. Hemorrhage. Hypoperfusion

  • Result: Cerebral ischemia. Cerebral infarction. Intracranial hemorrhage

Classification of Acute Disorders of Cerebral Circulation

A. Ischemic Cerebrovascular Disease (≈80–85%)

1. Transient Ischemic Attack (TIA): Neurological deficit <24 h (usually <1 h). No permanent infarction

2. Ischemic Stroke (Cerebral Infarction)

  • Causes: Thrombotic. Embolic. Hemodynamic (hypoperfusion)

B. Hemorrhagic Cerebrovascular Disease

1. Intracerebral Hemorrhage (ICH): Bleeding into brain parenchyma.

  • Common cause: Hypertension

2. Subarachnoid Hemorrhage (SAH): Bleeding into subarachnoid space.

  • Most common cause: Ruptured berry aneurysm

Clinical Manifestations of Stroke

Sudden onset of: Hemiparesis/hemiplegia. Facial weakness. Aphasia. Sensory loss. Visual field defects. Ataxia. Altered consciousness

Examination Methods in Cerebrovascular Diseases

A. Clinical Examination

  • Neurological Assessment: Consciousness. Cranial nerves. Motor function. Sensory function. Reflexes. Coordination. Speech

B. Neuroimaging

CT Brain (First-line Emergency Test)

  • Detects: Hemorrhage. Large infarction

MRI Brain

  • More sensitive for: Early ischemia. Brainstem lesions

C. Vascular Imaging

CT Angiography (CTA)

  • Visualizes: Arterial stenosis. Occlusion. Aneurysms

MR Angiography (MRA): Non-invasive vessel assessment.

Digital Subtraction Angiography (DSA): Gold standard for vascular anatomy.

D. Ultrasound

Carotid Duplex Ultrasound

  • Evaluates: Carotid stenosis. Plaques

Transcranial Doppler: Measures intracranial blood flow.

E. Cardiac Evaluation

ECG

  • Detects: Atrial fibrillation. Echocardiography. Searches for cardiac embolic source.

F. Laboratory Tests: CBC. Blood glucose. Lipid profile. Coagulation studies. Electrolytes

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