Mechanical Thrombectomy for Ischemic Stroke: How It Works and Why It Matters

Not all intracranial haemorrhages require surgical evacuation — most are managed medically. When the bleed is causing raised intracranial pressure, because the brain is inside a closed skull and any extra volume risks herniation, we have to evacuate it. There are several techniques — minimally invasive surgery, stereotactic drainage, or open decompressive surgery — and that's the neurosurgeon's domain. Our endovascular role is in identifying and occluding the underlying vascular cause, the aneurysm or AVM, that caused the bleed in the first place.

Think of it like a blocked drainage system under a city. A surgeon's approach is to dig down from outside to reach the blockage. Our approach is to enter the drainage system from where it begins and navigate a map through the system to the blockage, clearing it from within — you don't have to dig the ground. Access is through a needle puncture in the groin or wrist, and from there the catheters track through the blood vessels all the way to the brain.

Age is not a criterion for us. We have treated patients in their 90s and even at 100 years of age and seen them recover. Age alone is never a reason to withhold intervention.

The key risk factors are hypertension and smoking. Blood hits the vessel wall repeatedly, the wall weakens and bulges into an aneurysm, and the body tries to repair itself — but if blood pressure is chronically elevated, or tobacco smoke is weakening the vessel wall, or there's an underlying genetic factor causing weak collagen, that repair mechanism gets overwhelmed and the aneurysm develops over time. This is different from AVMs, which are congenital and present from birth — aneurysms are acquired lesions that develop over a lifetime.

We're usually talking about narrowing at the carotid bifurcation in the neck, where the common carotid artery splits into the external carotid, supplying the face, and the internal carotid, supplying the brain. Stenosis of 50% or more on catheter angiography, or 60% or more on non-invasive imaging like CT or MR angiography, is considered significant and needs treatment. When we say severe stenosis, we mean 70% to 99% narrowing.

The American Stroke Association classified mechanical thrombectomy as a Class I treatment, the highest level of medical evidence, and stroke care has not looked back since.

The Number Needed to Treat for acute stroke intervention within 6 hours is 2.6, meaning one in every 2.6 patients treated has a meaningfully better outcome because of the procedure. For comparison, the NNT for angioplasty in a heart attack is 28, for thrombolysis in pulmonary embolism it is 34, and for bypass surgery to prevent cardiac death it is 25, making thrombectomy one of the most effective treatments in modern medicine.

Large vessel strokes account for only about one third of all strokes, but they cause 75 to 90 percent of the death and disability that follows stroke, which is why rapid access to thrombectomy matters so much.

In hospitals without an on-site neurointervention team, the patient receives initial thrombolysis locally and is then transferred to a specialist centre for thrombectomy. The strategy works only within a limited geographic radius, since the patient must generally reach the specialist centre within 4 to 5 hours of symptom onset.