Acute Ischemic Stroke

If you or a loved one is having a stroke caused by a blocked brain artery, every minute matters. For large-vessel strokes, a procedure called mechanical thrombectomy can physically pull the clot out and restore blood flow, often reversing what looks like a devastating neurological injury.

What Is Acute Ischemic Stroke (Large-Vessel Occlusion)?

A stroke happens when blood flow to part of the brain is suddenly cut off. About 87% of strokes are ischemic (caused by a clot), and roughly one in three involves a large-vessel occlusion (LVO) — a clot stuck in one of the main arteries feeding the brain.

With every minute of an untreated LVO, about 1.9 million neurons die. But modern imaging can find brain cells that are starving but not yet dead even many hours later — which is why patients who would have been sent home untreated ten years ago are now leaving the hospital walking and talking today.

At a Glance

A large-vessel occlusion (LVO) is a stroke caused by a clot blocking one of the big arteries supplying the brain — the kind most likely to cause major disability
Mechanical thrombectomy uses a catheter threaded from the groin or wrist up into the brain artery to physically remove the clot
Eligible patients can be treated up to 24 hours from when they were last known well if imaging shows salvageable brain tissue
IV clot-busting medication (tPA or tenecteplase) is given first when the patient qualifies; thrombectomy is done in addition
UChicago Medicine is a Comprehensive Stroke Center with a 24/7 neuroendovascular team

Symptoms

The BE FAST warning signs

B — Balance: sudden trouble with balance or dizziness
E — Eyes: sudden blurred, double, or lost vision
F — Face: one side of the face droops
A — Arm: one arm drifts down when trying to hold both up
S — Speech: slurred, garbled, or nonsensical speech
T — Time: call 911 right away and note the time symptoms started

Symptoms suggesting large-vessel occlusion

Complete weakness or paralysis of one side of the body
Inability to speak or understand speech (aphasia)
Looking forcefully to one side (gaze deviation)
Ignoring one side of the world entirely (neglect)
In basilar artery strokes: sudden coma, crossed weakness, 'locked-in' symptoms

Call 911 immediately. Do not drive yourself.

Diagnosis

Non-contrast CT scan — rules out bleeding in the brain
CT angiogram (CTA) — shows every major brain artery; where we find the large-vessel occlusion
Perfusion imaging (CTP or MRI) — shows the core (already dead tissue) and penumbra (starving but salvageable tissue). Small core + large penumbra = green light for thrombectomy even 6-24 hours after symptom onset.
NIH Stroke Scale (NIHSS) — scores neurological exam on a 0-42 scale. Score ≥6 combined with LVO generally meets criteria for thrombectomy.

Types

Anterior circulation LVO

Internal carotid artery (ICA) — biggest, most devastating strokes (T occlusion)
Middle cerebral artery, M1 — most common LVO; causes severe weakness and language problems or neglect
Middle cerebral artery, M2 — treatable with higher technical challenge

Posterior circulation LVO

Basilar artery occlusion — frequently fatal without treatment. ATTENTION and BAOCHE trials (2022) confirmed thrombectomy doubles chance of good functional recovery.
Vertebral artery occlusion — treated when threatening the basilar artery

Treatment

IV thrombolysis — alteplase (tPA) or tenecteplase

Given within ~4.5 hours of last known well time if no contraindications. Tenecteplase is now preferred at many centers — given as a single fast push. Does not replace thrombectomy — it's a first punch.

Mechanical thrombectomy — pulling the clot out

Catheter threaded from groin or wrist up into the blocked brain artery. Two tools remove the clot:

Stent retriever — self-expanding mesh that traps the clot like a fishing net, then pulled out
Aspiration catheter — large-bore catheter that sucks the clot out directly (ADAPT technique)

Goal: TICI 2b or 3 reperfusion — more than half, ideally all, of the blocked territory reopened.

The extended window — 6 to 24 hours

DAWN trial (6-24h) and DEFUSE-3 trial (up to 16h) proved that patients with small core / large penumbra mismatch on imaging benefit dramatically from thrombectomy. Wake-up strokes now routinely treated.

Outcomes

Factor	Independent at 90 days (mRS 0-2)	What to know
No thrombectomy (medical only)	~19%	Pooled control arm from HERMES
Thrombectomy, any TICI	~46%	Pooled thrombectomy arm from HERMES
Thrombectomy, TICI 2b/3 reperfusion	~50-60%	Substantial reperfusion drives outcome
Thrombectomy, TICI 3 (complete)	~60-70%	Best-case scenario
Extended window 6-24h (DAWN)	49% vs 13% medical	Mismatch-selected patients
Basilar artery occlusion (ATTENTION)	~46% mRS 0-3 vs 23% medical	Life-saving for a once-uniformly-fatal stroke

Every 30 minutes saved from onset to reperfusion adds about a 10% absolute gain in the chance of a good outcome.

References

Berkhemer OA, et al. MR CLEAN — a randomized trial of intraarterial treatment for acute ischemic stroke. NEJM. 2015;372(1):11-20. PMID: 25517348
Goyal M, et al. ESCAPE — randomized assessment of rapid endovascular treatment of ischemic stroke. NEJM. 2015;372(11):1019-1030. PMID: 25671798
Goyal M, et al. HERMES — endovascular thrombectomy after large-vessel ischaemic stroke: meta-analysis. Lancet. 2016;387(10029):1723-1731. PMID: 26898852
Nogueira RG, et al. DAWN — thrombectomy 6 to 24 hours after stroke with mismatch between deficit and infarct. NEJM. 2018;378(1):11-21. PMID: 29129157
Albers GW, et al. DEFUSE-3 — thrombectomy for stroke at 6 to 16 hours with selection by perfusion imaging. NEJM. 2018;378(8):708-718. PMID: 29364767
Tao C, et al. ATTENTION — trial of endovascular treatment of acute basilar-artery occlusion. NEJM. 2022;387(15):1361-1372. PMID: 36239644

Our Specialists

Omer Doron, MD, PhD

Neurosurgery

Jehad Zakaria, MD

Neurosurgery

Sean P. Polster, MD

Neurosurgery

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