Cognitive Outcomes After Stenting and Endarterectomy: A Systematic-Review and Meta-Analysis

This systematic review and meta-analysis of 68 studies indicates that carotid revascularization (both endarterectomy and stenting) is associated with cognitive improvement, particularly on MoCA tests at long-term follow-up, while finding no significant difference in cognitive outcomes between the two procedures despite limited comparative evidence.

The Gist

Imagine your brain is a bustling city, and the carotid arteries are the main highways delivering fresh blood (the fuel) to keep the city running smoothly. When these highways get clogged with plaque (stenosis), the city might start to dim, leading to "traffic jams" in thinking, memory, and focus. Doctors have two main ways to fix these highways: Carotid Endarterectomy (CEA), which is like a surgeon physically scraping the gunk off the road, and Carotid Artery Stenting (CAS), which is like inserting a metal scaffold to hold the road open.

For a long time, doctors knew these procedures prevented strokes, but they weren't sure if fixing the road actually made the city's "thinking" better. This paper is a massive "report card" that gathered data from 68 different studies (involving nearly 4,700 patients) to answer that question.

Here is what the paper found, broken down simply:

1. The "Before and After" Picture (Single-Arm Studies)

The researchers looked at groups of people who had only one type of surgery and compared their brain tests before and after.

• The "MoCA" Test vs. The "MMSE" Test: Think of the MMSE as a basic driver's license test—it checks if you can read a sign and remember a few things. It's good, but it might miss small improvements. The MoCA is like a complex navigation challenge; it's much more sensitive and catches tiny changes in attention and memory.
• The Results:
  • When they used the MoCA (the sensitive test), both surgery groups showed a clear improvement in thinking skills after the procedure. It was like the city lights getting brighter.
  • When they used the MMSE (the basic test), the results were a bit foggy. There was a slight improvement, but it wasn't always statistically clear, especially right after surgery.
  • Time Matters: The improvements tended to get stronger the longer you waited after the surgery (more than 6 months), suggesting the brain takes time to fully recover and adapt to the new, clear highway.

2. The "Head-to-Head" Race (Comparing the Two Surgeries)

The big question was: Does one surgery fix the thinking better than the other? Is the "scaffold" (stent) better than the "scraping" (endarterectomy)?

• The Verdict: The paper found no clear winner. When they directly compared the two groups, the difference in thinking scores was essentially zero.
• The Catch: There weren't many studies that directly compared the two side-by-side. It's like trying to decide between two brands of tires by looking at only a few race cars. The data was too thin to say for sure if one is better, so the researchers concluded: We don't have enough evidence to pick one over the other based on thinking skills alone.

3. Who Got the Most Help?

The study looked at specific groups of people to see if the surgery worked better for some than others.

• Symptomatic Patients: People who had already had warning signs (like a mini-stroke or TIA) seemed to get a bigger boost in their thinking scores after the "scraping" surgery (CEA) compared to those who had no symptoms yet.
• Baseline Scores: Interestingly, patients who started with lower thinking scores seemed to gain more ground after the surgery. It's like a runner who is far behind the pack gaining the most ground when the track is cleared.

4. The "Foggy" Parts (Limitations)

The authors are very honest about the flaws in the data, using some helpful metaphors:

• Different Rulers: Every study used different tests and measured at different times. It's like trying to compare the height of trees when some people measured in feet, some in meters, and some only measured the trunk while others measured the branches. This made the data "heterogeneous" (messy).
• No Control Group: Most studies didn't have a group of people who didn't get surgery to compare against. It's hard to know if the brain got better because of the surgery or just because the brain naturally recovers or because the patients got better at taking the test the second time (practice effects).
• Observational Data: Most of the studies were just watching what happened (observational) rather than a strict, controlled experiment. This means other factors (like how healthy the patient was generally) might have influenced the results.

The Bottom Line

This paper tells us that fixing the clogged neck arteries is generally associated with better thinking scores, especially when measured with sensitive tools like the MoCA. However, we cannot say that one surgery (stenting) is better for the brain than the other (endarterectomy).

The authors conclude that while the "lights seem brighter" after surgery, we need much stricter, head-to-head studies with better measuring tools before we can tell a patient, "Choose this surgery because it will make you smarter." For now, the choice between the two procedures should probably be based on other factors (like stroke risk or anatomy), not on a promise of cognitive improvement, because the evidence for that specific benefit isn't strong enough yet.

Technical Summary

Technical Summary: Cognitive Outcomes After Stenting vs. Endarterectomy

Problem Statement
Carotid artery stenosis is a recognized risk factor for vascular dementia and cognitive impairment, driven by mechanisms such as chronic hypoperfusion and subclinical ischemic injury. While carotid endarterectomy (CEA) and carotid artery stenting (CAS) are established interventions for stroke prevention in patients with severe stenosis, their specific effects on cognitive function remain unclear. Prior literature presents inconsistent findings, ranging from postoperative cognitive improvement to transient decline or no change. Furthermore, the heterogeneity of cognitive assessment tools and study designs has historically prevented robust comparisons between these two revascularization strategies. This systematic review and meta-analysis aims to synthesize evidence regarding global and domain-specific cognitive outcomes following CEA and CAS, and to determine if one procedure offers a cognitive advantage over the other.

Methodology
Adhering to PRISMA guidelines, the authors conducted a systematic review of literature published between January 2000 and November 2025 across PubMed, Embase, Web of Science, and the Cochrane Library.

• Inclusion Criteria: Studies involving adults ($\ge$18 years) with carotid stenosis undergoing CEA, CAS, or direct comparison of both, reporting validated cognitive outcomes (global screening via MMSE or MoCA, or domain-specific testing).
• Data Synthesis: The review included 68 studies (4,659 patients). Quantitative meta-analysis was performed for 27 studies focusing on global cognition (MMSE and MoCA), while 41 studies underwent qualitative synthesis for domain-specific outcomes.
• Statistical Approach: Random-effects meta-analyses were employed to account for between-study heterogeneity.
  • Single-arm analyses: Used standardized mean change to evaluate within-group improvements for CEA and CAS separately.
  • Head-to-head analyses: Used mean difference to compare CAS versus CEA directly.
  • Time Stratification: Outcomes were stratified into early follow-up ($\le$6 months) and late follow-up ($>$6 months).
  • Bias Assessment: Risk of bias was evaluated using RoB-2 (RCTs), ROBINS-I (non-randomized comparative), and the Newcastle-Ottawa Scale (single-arm). Meta-regression was utilized to assess the influence of covariates such as symptomatic status and baseline cognitive function.

Key Results

• Global Cognition (Single-Arm):
  • CEA: Associated with positive mean changes in global scores. MMSE showed non-significant early changes (0.51 points) but late changes approached significance (0.59 points). MoCA scores demonstrated significant improvement at both early (0.81 points) and late (1.33 points) intervals.
  • CAS: MMSE scores showed significant improvement only at late follow-up (>6 months; 1.12 points). MoCA scores showed substantial and significant improvements at both early (2.59 points) and late (2.93 points) intervals.
  • Heterogeneity: High heterogeneity ($I^2 > 50\%$) was observed in most comparisons, particularly for CAS MoCA outcomes.
• Head-to-Head Comparisons:
  • Direct comparisons between CEA and CAS revealed no statistically significant differences in cognitive change for either MMSE or MoCA at early or late follow-up intervals.
  • These comparisons were limited by small sample sizes (e.g., $k=8$ for MMSE $\le$6 months) and wide confidence intervals, preventing definitive conclusions regarding procedural equivalence.
• Domain-Specific Outcomes:
  • Qualitative synthesis indicated that cognitive domains (memory, attention, executive function, processing speed) were mostly stable or improved. Declines were rarely reported and typically isolated.
• Moderators:
  • Meta-regression identified baseline cognitive function as a significant negative moderator in several subgroups (e.g., lower baseline scores correlated with greater improvement).
  • Symptomatic status was a significant positive moderator for CEA-MoCA outcomes, suggesting greater gains in symptomatic patients.
• Publication Bias: Funnel plot asymmetry tests were generally non-significant, though trim-and-fill analyses suggested potential shifts in pooled estimates for specific CAS subgroups, indicating the need for cautious interpretation of single-arm improvements.

Key Contributions and Significance
The paper provides the first comprehensive synthesis of cognitive outcomes specifically comparing CEA and CAS. Its primary contributions include:

1. Differentiation of Assessment Tools: The review highlights that MoCA appears more sensitive than MMSE in detecting cognitive changes post-revascularization, particularly in the early postoperative period and for CAS procedures.
2. Clarification of Procedural Comparison: The analysis explicitly states that current evidence does not support a clear cognitive advantage of either CEA or CAS. The lack of significant difference in head-to-head analyses suggests that procedural choice should not be guided by anticipated cognitive benefits based on current data.
3. Clinical Implications: The findings support the consideration of cognition as a relevant outcome in carotid disease management but emphasize that cognitive benefit cannot yet be used as a primary driver for procedural selection.
4. Methodological Recommendations: The authors advocate for standardized neuropsychological testing (favoring MoCA over MMSE for sensitivity) and the necessity of prospective, adequately powered comparative studies with true control groups to isolate the effects of revascularization from practice effects and regression to the mean.

Conclusion
Carotid revascularization is associated with measurable improvements in global cognitive screening scores, particularly when assessed via MoCA. However, these findings are derived largely from observational data with high heterogeneity. Crucially, the review finds no evidence that one revascularization strategy (stenting vs. endarterectomy) yields superior cognitive outcomes over the other. Future research must prioritize standardized, longitudinal, and blinded comparative designs to definitively characterize the cognitive trajectory of these interventions.