Neurointerventional Thrombectomy
On this page
Direct answer
Six hours used to be the ceiling for stroke intervention; thrombectomy trials have lifted it to twenty-four in selected patients. Mechanical thrombectomy — stent retrievers or contact aspiration via a groin or wrist access — removes clot from an occluded large vessel (internal carotid terminus, M1 middle cerebral artery, basilar artery) and is standard care within six hours of onset in eligible patients, and between six and twenty-four hours when perfusion imaging demonstrates a small core infarct with substantial salvageable mismatch, per the DAWN and DEFUSE-3 selection logic. Non-contrast CT with ASPECTS scoring (a 10-point topographic scale; 6 or more generally favoured) plus CT angiography to show the occlusion, with perfusion imaging in the extended window, constitute the imaging pathway. Intravenous thrombolysis within four-and-a-half hours remains the foundation and is bridged, not replaced, by thrombectomy.
What you must remember
- Imaging pathway: non-contrast CT to exclude haemorrhage, CT angiography (head and neck) to identify large vessel occlusion, ASPECTS on CT (0-10; 6 or more is the conventional threshold), CT or MR perfusion for the extended window.
- Time tiers: standard window within 6 hours of onset or last-known-well; extended window 6-24 hours for selected patients with favourable perfusion mismatch (small core, large penumbra) — the DAWN and DEFUSE-3 legacy.
- Target vessels: internal carotid terminus, M1 middle cerebral artery, tandem lesions, and basilar artery, where recent trials support thrombectomy for severe posterior-circulation strokes.
- Devices: stent retrievers that entrap clot for withdrawal, and contact (aspiration) catheters that suction it directly — often combined, with first-pass reperfusion as the procedural goal.
- Reperfusion grading: modified TICI, with 2b (greater than 50% territory filling) or 3 (complete) counted as successful reperfusion and correlating with outcome.
- Bridging, not replacing: eligible patients receive intravenous alteplase (or increasingly tenecteplase) within 4.5 hours and proceed directly to thrombectomy; thrombolysis is never withheld in anticipation of thrombectomy.
- Post-procedure care: blood pressure management after reperfusion (commonly systolic below about 180, tighter after successful reperfusion), observation for haemorrhagic transformation, and access-site checks.
- Contraindications that matter: large established core infarct (low ASPECTS), extensive early changes, and haemorrhage — not age alone; stroke severity (NIHSS) is selection input.
Running an extended-window case
A 71-year-old is found unwell at 7 a.m., last seen well at 10 p.m. the previous night — an onset of about nine hours, beyond both the thrombolysis and standard thrombectomy windows. She has right hemiparesis, aphasia and NIHSS 16. Non-contrast CT shows subtle early ischaemia with ASPECTS 8 and no haemorrhage; CT angiography demonstrates a left M1 occlusion. Perfusion imaging shows a small core with a large mismatch volume — the physiology that DAWN and DEFUSE-3 codified. She goes to the angiography suite: femoral access, a guide catheter in the left internal carotid, and a stent retriever with contact aspiration achieve mTICI 3 on the first pass. Systolic pressure is held below 180, tighter after reperfusion; she returns to the stroke unit for haemorrhage surveillance. Imaging selection did all the work here — time alone no longer disqualifies, but physiology must replace it: core, mismatch, collaterals and clinical severity. Every examinable element — ASPECTS, mismatch, mTICI, bridging logic — sits in this one patient's night.
Window and bridging confusions
Presenting thrombectomy as an alternative to thrombolysis is the commonest conceptual slip — eligible patients get both, sequentially; the correct framing is "bridging therapy". Second, misquoting the windows: six hours is the standard cut-off, twenty-four the extended ceiling with imaging selection, and the two regimes rest on different evidence bases (the HERMES collaboration versus DAWN/DEFUSE-3). Third, forgetting what ASPECTS measures — it grades early ischaemic change on non-contrast CT from 10 downward, not vessel patency or infarct volume; a low score means an already-large core and a poor candidate. Fourth, imaging incompleteness: a stroke CT that stops at the head misses cervical tandem occlusions, and treatment planning depends on the neck vessels — "CT angiography from arch to vertex" is the viva phrase to quote.
Frequently asked questions
Which patients qualify for mechanical thrombectomy?
Those with anterior circulation large vessel occlusion (internal carotid terminus, M1) within 6 hours, and selected patients from 6 to 24 hours with small core infarcts and substantial perfusion mismatch on imaging.
What is the ASPECTS score and its thrombectomy threshold?
A 10-point topographic grading of early ischaemic change on non-contrast CT across the middle cerebral artery territory; a score of 6 or more generally defines a favourable candidate.
What devices are used for thrombectomy?
Stent retrievers that ensnare the clot for retrieval, and large-bore contact aspiration catheters that suction it directly — often combined, with balloon-guider flow arrest to limit distal embolisation.
Does intravenous thrombolysis remain necessary before thrombectomy?
Yes, when the patient is eligible within 4.5 hours — lysis is administered without delay and thrombectomy follows as bridging therapy, not as a substitute.
What perfusion findings define the extended window?
A small established core infarct (tens of millilitres) with a large ischaemic penumbra — the core-mismatch profile demonstrated as clinically effective in the DAWN and DEFUSE-3 trials.