A 52-year-old woman from Mumbai is admitted with acute onset right-sided hemiparesis and aphasia. CT head shows left MCA territory infarction. Cerebral angiography reveals complete occlusion of the left internal carotid artery (ICA) at its origin, with excellent cross-filling via a prominent anterior communicating artery (AComm) from the right anterior cerebral artery (ACA). The infarct core is small. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Analysis This patient has acute left ICA occlusion with excellent collateral circulation via the Circle of Willis (prominent AComm providing cross-filling). The small infarct core indicates that collaterals are maintaining perfusion to the penumbra — a favourable scenario for mechanical thrombectomy. ## Why Mechanical Thrombectomy is the Next Step **Key Point:** The presence of: - Small infarct core (salvageable penumbra) - Excellent collateral circulation (prominent AComm) - Acute presentation (within intervention window) ...makes this patient an ideal candidate for mechanical thrombectomy to restore antegrade flow through the left ICA and MCA. **High-Yield:** Good collateral circulation (assessed by angiography or CTA) is a strong predictor of better outcomes after thrombectomy because it indicates the penumbra is still viable. The Circle of Willis is the primary source of collaterals in ICA occlusion. ## Circle of Willis Anatomy & Collateral Function | Structure | Function in ICA Occlusion | | --- | --- | | **Anterior Communicating Artery (AComm)** | Allows cross-filling from contralateral ACA to ipsilateral ACA territory | | **Posterior Communicating Artery (PComm)** | Allows filling from ipsilateral PCA (via vertebrobasilar system) to MCA territory | | **Leptomeningeal collaterals** | Surface vessels connecting ACA, MCA, PCA territories | **Clinical Pearl:** A "prominent" AComm (as in this case) indicates it is patent and large enough to provide robust collateral flow — this is a favourable prognostic sign in acute ICA occlusion. ## Management Algorithm ```mermaid flowchart TD A[Acute ICA occlusion on angiography]:::outcome --> B{Collateral<br/>circulation?}:::decision B -->|Poor collaterals| C[Large infarct core likely]:::outcome C --> D[Limited thrombectomy benefit]:::action B -->|Excellent collaterals<br/>Small infarct core| E[Mechanical thrombectomy]:::action E --> F[Restore ICA/MCA flow]:::action F --> G[Salvage penumbra]:::outcome ``` **Tip:** Angiography in acute stroke not only identifies the occlusion but also grades collateral circulation — this is critical for patient selection for thrombectomy. Excellent collaterals = good outcome potential.