ModulePublishedclinician-educationstroke-escalationimaging

Posterior communicating (PCoA) aneurysm — CN III palsy warning sign, CTA/DSA detection, and urgency (Advanced)

Advanced course: a PCoA aneurysm can compress the 3rd cranial nerve and may present with new drooping eyelid and pupil changes. Learn why this is urgent, and how CTA/MRA/DSA and CT rule out hemorrhage.

ClinicianCaregiver, SurvivorAdvanced24 minGrade 11

Educational only

Educational only — not medical advice.

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If a patient develops new or worsening stroke symptoms, reduced consciousness, seizure, severe headache, airway/swallowing danger, or unstable vital signs, activate emergency response and follow local stroke escalation protocols.

Key takeaways

  • Recognize CN III palsy (ptosis + eye movement limits) as a possible aneurysm emergency
  • Explain why pupil involvement is a key red flag (high-level)
  • Explain imaging pathway: CT for hemorrhage, CTA/MRA for aneurysm screening, DSA for detail
  • Know what questions to ask about rupture risk and next steps

Why this matters

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Clinical frame

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Core clinical idea

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Assessment and workup

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Clinical reasoning pathway

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Management and team actions

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Common pitfalls

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Patient-safe explanation

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Escalation and safety signals

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Applied case

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Clinical scenario

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Common misconceptions

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Reflect

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Key takeaways

  • Recognize CN III palsy (ptosis + eye movement limits) as a possible aneurysm emergency
  • Advanced stroke care requires reconciling the clinical syndrome with timing, imaging, medication risk, patient context, and local pathway capacity.
  • A safe plan names escalation thresholds, responsible clinicians, patient-facing instructions, and the next step if results or symptoms change.

Practice check

What you’ll practice

These questions are untimed. After you answer all of them, you’ll see your score and a clear next lesson or reference step.

0 of 4 answered

Question 1

1. A learner is applying this lesson on Posterior communicating (PCoA) aneurysm — CN III palsy warning sign, CTA/DSA detection, and urgency. Which approach best reflects advanced clinical reasoning?

Question 2

2. Which actions show safe handling of Posterior communicating (PCoA) aneurysm — CN III palsy warning sign, CTA/DSA detection, and urgency? Select all that apply.

Question 3

3. Match each reasoning element to its role in Posterior communicating (PCoA) aneurysm — CN III palsy warning sign, CTA/DSA detection, and urgency.

Question 4

4. For Posterior communicating (PCoA) aneurysm — CN III palsy warning sign, CTA/DSA detection, and urgency, a normal or non-specific early test result is enough to stop reassessment when the clinical syndrome still suggests risk.

References

  1. Tier 1American Heart Association/American Stroke Association2023
    2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage
  2. Tier 2RadiologyInfo.org2025
    CT Angiography of the Head
  3. Tier 2RadiologyInfo.org2025
    Magnetic Resonance Imaging (MRI) - Head
  4. Tier 2RadiologyInfo.org2025
    Cerebral Angiography