Subarachnoid Hemorrhage Overview

Subarachnoid Hemorrhage (SAH)

• A hemorrhage of the cerebral vessel, primarily the circle of Willis, into the subarachnoid space.

Etiology

• Traumatic Causes:

  • Blunt force trauma
  • Penetrating trauma

• Non-Traumatic Causes:

  • Aneurysmal Causes:
    • Types of Aneurysms:
      • Saccular (Berry) Aneurysm: Asymmetric ballooning of the vessel
      • Fusiform (Dolichoectatic) Aneurysm: Symmetrical dilation of the vessel
      • Pseudoaneurysm: Dissection of the vessel creating a false aneurysm
      • Mycotic Aneurysm: Infected aneurysm containing infectious material
    • Contributing Factors:
      • Hypertension: Increases stress on the vessel wall
      • Sympathomimetics: Cocaine, Methamphetamines
      • Smoking: Nicotine
      • Ethanol: Alcohol use
      • Oral Contraceptives/Pregnancy: Hormonal changes
  • Genetic Causes:
    • Connective Tissue Defects: Marfan syndrome, Ehlers-Danlos syndrome, polycystic kidney disease
    • Abnormal Growth/Dysplasia: Fibromuscular dysplasia
  • Infective Causes:
    • Infective Endocarditis: Vegetations on valves release infective materials, leading to vessel wall degradation.

Pathophysiology

• Stress on the vessel wall leads to weakening, dilation, and eventual rupture.
• Genetic defects and infections increase susceptibility to aneurysm formation and rupture.

Common Locations for Aneurysms

• Anterior Communicating Artery: 30%
• Posterior Communicating Artery: 25%
• MCA Bifurcation: 20%
• ICA Terminus: 7.5%
• Basilar Tip: 7%
• Anterior Cerebral Artery: 4%
• PICA: 3.5%

Triggers for Rupture

• Acute rise in blood pressure
• Painful stimulus
• Anger fits

Clinical Features

• Headache: "Worst headache of their life" or "thunderclap headache"
• Meningeal Signs: Photophobia, neck stiffness, positive Kernig's and Brudzinski's signs
• Increased Intracranial Pressure (ICP): Nausea, vomiting, cranial nerve deficits, posturing, Cushing's triad (high blood pressure, low heart rate, irregular respirations)
• Focal Deficits: Stroke symptoms

Hunt and Hess Score

• Asymptomatic/Mild Headache: Score 1
• Moderate/Severe Headache with Cranial Nerve Deficits: Score 2
• Lethargy, Confusion, Focal Deficits: Score 3
• Stupor, Early Posturing: Score 4
• Comatose, Decerebrate Posturing: Score 5

Diagnostics

• Non-Contrast CT Scan: Identifies blood in sulci, cisterns, and ventricles and hydrocephalus.
• Modified Fischer Score: Determines risk of vasospasm based on CT findings.
• CT Angiogram: Identifies aneurysms and reversible cerebral vasoconstriction syndrome.
• Digital Subtraction Angiogram: Gold standard for visualizing vessels.
• Lumbar Puncture: Identifies blood or xanthochromia in CSF when CT is inconclusive.

Treatment

• Initial Management:

  • Airway, Breathing, Circulation (ABC): Secure airway, manage ICP, and control blood pressure.
  • External Ventricular Drain (EVD): Indicated for high Hunt-Hess score, intraventricular hemorrhage, and hydrocephalus.

• Blood Pressure Control:

  • Pre-Coiling/Clipping Goal: Systolic BP < 160 mm Hg.
  • Medications: Nicardipine, labetalol, hydralazine, enalapril.

• Securing the Aneurysm:

  • Coiling or Clipping: Must be done within 24 hours. Decision based on age, aneurysm neck size, hemodynamic stability, and location.

• Managing Complications:

  • Rebleeding:
    • Temporary Measures: Aminocaproic acid, tranexamic acid, cryoprecipitate, platelet transfusion.
  • Vasospasm:
    • Prevention/Treatment: Nimodipine, induced hypertension, intra-arterial dilators (verapamil, milrinone).
  • Other Complications:
    • Seizures: Anti-epileptic medications
    • Pyrexia: Cooling measures (cooling blankets, arctic sun, ZOLL catheter, cold infusions) and anti-shivering medications (magnesium, buspirone, bromocriptine, propofol, opioids)
    • Cerebral Salt Wasting: Fludrocortisone, normal saline infusions, 3% hypertonic saline infusions, salt tablets.

This quiz covers the fundamentals of subarachnoid hemorrhage (SAH), including its etiology, traumatic and non-traumatic causes, and types of aneurysms. Learn the contributing factors and genetic causes associated with SAH. Perfect for healthcare students or anyone interested in neurology.