What is the most likely pathologic mechanism in a 63-year-old female with increasing headaches and sudden onset of focal neurological deficit, including weakness in her right arm?

Rupture of a Berry Aneurysm is the Most Likely Pathologic Mechanism

The most likely pathologic mechanism in this 63-year-old female with progressively worsening headaches, recent irritability, and sudden right arm weakness is the rupture of a berry aneurysm (saccular aneurysm). 1

Clinical Presentation Analysis

• The patient's presentation includes several key features consistent with aneurysmal subarachnoid hemorrhage (aSAH):
  • Progressive headaches over 5 weeks described as "achy and steady" - likely representing a sentinel or warning headache 1, 2
  • Recent personality change (irritability and anger) - suggesting evolving neurological impact 1
  • Sudden onset of focal neurological deficit (right arm weakness) - a classic sign of ruptured aneurysm with resulting hemorrhage 3

Pathophysiologic Mechanisms

• Berry aneurysms (saccular aneurysms) are the most common type of intracranial aneurysm and frequently rupture, causing subarachnoid hemorrhage 1
• The progressive headache pattern over 5 weeks likely represents a sentinel or warning leak from the aneurysm, which occurs in 10-43% of patients before major rupture 1, 2
• The sudden onset of focal neurological deficit (right arm weakness) indicates a more significant rupture with localized effect on brain tissue 3

Differential Diagnosis Analysis

Let's analyze each option:

1. Tearing of the middle meningeal artery: This typically causes epidural hematoma following trauma, which is not present in this case history 1

2. Inflammation of the temporal artery: Temporal arteritis typically presents with new-onset headache, jaw claudication, visual disturbances, and systemic symptoms in older adults. While the patient's age is appropriate, the focal neurological deficit and progressive course are not typical 4

3. Tearing of a bridging vein: This causes subdural hematoma, typically following trauma, and presents with more gradual onset of symptoms without the preceding weeks of headache 1

4. Rupture of a Charcot-Bouchard aneurysm: These microaneurysms typically cause hypertensive intracerebral hemorrhage in deep brain structures. While possible, the clinical course with weeks of preceding headache is more consistent with saccular aneurysm rupture 1

5. Rupture of a berry aneurysm: This best explains the clinical presentation with:

   • Warning/sentinel headache preceding major rupture 1, 2
   • Behavioral changes (irritability) 1
   • Sudden focal neurological deficit 3

Key Clinical Pearls

• Sentinel headaches occur in up to 43% of patients with aneurysmal SAH within 2-8 weeks before major rupture 1
• The classic description of "worst headache of my life" is reported by 80% of patients with aneurysmal SAH who can give a history 1
• Focal neurological deficits occur in approximately 10% of aneurysmal SAH cases and are associated with poorer outcomes 3
• Mechanisms of focal deficits in aneurysmal SAH include:
  • Intraparenchymal hematoma (45.5%)
  • Early cerebral infarction (22.7%)
  • Parenchymal compression by subarachnoid thrombus (18.2%)
  • Seizure with Todd's paralysis (13.6%) 3

Management Implications

• Immediate neuroimaging (non-contrast CT) is essential for diagnosis 1
• If CT is negative but clinical suspicion remains high, lumbar puncture should be performed to evaluate for xanthochromia 1, 2
• Early neurosurgical or endovascular intervention is critical to prevent rebleeding, which carries high mortality 1
• Nimodipine should be administered to reduce vasospasm-related neurological deficits 5

Common Pitfalls to Avoid

• Misdiagnosis of aneurysmal SAH occurs in up to 12% of cases, with failure to obtain neuroimaging being the most common error 1
• Dismissing headache without recognizing "red flags" such as:
  • Progressive worsening over weeks
  • Change in personality or cognition
  • Sudden onset of focal neurological deficit 6
• Delaying treatment after diagnosis, as the risk of rebleeding is highest in the first 24 hours (3-4%) 1