Reviewed for medical accuracy by Dr Evelyne Jonniaux, Medical Advisor
Last updated 17 September 2026
For a symptomatic carotid stenosis, what matters most is not the degree of narrowing, it is the delay. Operated within two weeks, 5 patients need treating to prevent one stroke. Operated after three months, 125 do. The same procedure, on the same lesion, at 25 times lower yield.
The questions we get asked
What is the real benefit in symptomatic stenosis?
It is clear in tight stenoses. The North American trial gives 26 percent of strokes on the affected side at two years under medical treatment, against 9 percent after surgery. For stenoses of 50 to 69 percent the benefit exists but 15 patients must be treated to prevent one event. Below 50 percent there is no benefit, and the pooled analysis shows that below 30 percent surgery does harm.
Why does the delay matter so much?
Because stroke risk peaks in the days following the first symptoms and declines thereafter. The analysis of 5,893 patients gives a number needed to treat of 5 within two weeks and 125 beyond twelve weeks. The authors explicitly conclude that the operation should take place within two weeks of the last symptoms.
Two other factors strongly change the yield: the number needed to treat is 9 in men against 36 in women, and 5 after 75 against 18 before 65.
And if the stenosis causes no symptoms?
This is the most disputed question in the specialty, and it has just been retried. The medical arm has collapsed over the decades: 11 percent of events at five years in the 1995 American trial, against 5.3 to 6 percent at four years in the medical arms of the trial published in January 2026. Medicine has closed much of the gap that surgery used to fill.
That new trial gives an asymmetric and awkward result. Stenting does significantly better than medical treatment alone, 2.8 against 6 percent. Endarterectomy does not do significantly better, 3.7 against 5.3 percent. Two parallel trials within the same protocol reach opposite conclusions on the same question, when twenty years of literature established that the two techniques are equivalent.
The cautious reading: the absolute benefit of revascularisation in asymptomatic stenosis, if it still exists, is of the order of 2 to 3 points over four years, at the limit of detectability. “Benefit not demonstrated” is not “no benefit”, and the reverse is equally true.
Does surgery protect memory?
No. The cognitive outcomes of the same trial, prespecified and covering 2,165 patients, show no difference at four years, after stenting or after surgery, on any of the five tests.
What the figures say
| Finding | Figure | Source |
|---|---|---|
| Tight symptomatic stenosis, strokes at 2 years | 26 against 9 percent | NASCET, N Engl J Med, 1991 |
| Stenosis of 50 to 69 percent, number needed to treat | 15 | NASCET, N Engl J Med, 1998 |
| Surgery within 2 weeks against after 12 weeks | 5 to treat against 125 | Rothwell et al., Lancet, 2004 |
| Asymptomatic stenosis, medical arm | 11 percent at 5 years in 1995, 5.3 to 6 percent at 4 years in 2026 | ACAS, 1995 and CREST-2, 2026 |
| Stenting against medical treatment alone, asymptomatic | 2.8 against 6 percent | CREST-2, N Engl J Med, 2026 |
| Endarterectomy against medical treatment alone | 3.7 against 5.3 percent, not significant | CREST-2, 2026 |
Three widespread claims to correct. “Under modern treatment the risk is below 1 percent a year”: the published figure is a four-year cumulative incidence on a composite endpoint, not an annual stroke rate. “Stenting is riskier than surgery”: the trials give 1 percent disabling stroke or death in both arms, and the new trial finds stenting superior where surgery is not. And “endarterectomy prevents cognitive decline” is refuted.
What Noria Health does, and does not do
We organise a vascular surgery consultation with a specialist team near Brussels, duplex ultrasound and review of existing imaging included, and confirm feasibility within 24 to 48 hours.
We do not handle any acute situation. Weakness on one side, difficulty speaking or loss of vision, even briefly, mean emergency care immediately: the benefit of any intervention collapses with time, and that is the central message of this page.
Who reviewed this page
Noria Health editorial team.
See also: all our articles on vascular surgery.
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