Cranial Nerve Injury After Carotid Endarterectomy: Incidence, Risk Factors, and Time Trends

Abstract

Objective/background: To review the incidence of post-carotid endarterectomy (CEA) cranial nerve injury (CNI), and to evaluate the risk factors associated with increased CNI risk.

Methods: The study was a meta-analysis. Pooled rates with 95% confidence intervals (CIs) were calculated for CNIs after primary CEA. Odds ratios (ORs) were calculated for potential risk factors. A fixed-effects model or a random effects model (Mantel-Haenszel method) was used for non-heterogeneous and heterogeneous data, respectively. Meta-regression analysis was performed to examine the influence of publication year upon CNI rate.

Results: Twenty-six articles, published between 1970 and 2015, were included in the meta-analysis, corresponding to 20,860 CEAs. Meta-analysis revealed that the vagus nerve was the most frequently injured cranial nerve (pooled injury rate 3.99%, 95% CI 2.56-5.70), followed by the hypoglossal nerve (3.79%, 95% CI 2.73-4.99). Fewer than one seventh of these injuries are permanent (vagus nerve: 0.57% [95% CI 0.19-1.10]; hypoglossal nerve: 0.15% [95% CI 0.01-0.39]). A statistically significant influence of publication year on the vagus and hypoglossal nerve injury rate was found, with the injury rate having decreased from about 8% to 2% and 1%, respectively, over the last 35 years. Urgent procedures (OR 1.59, 95% CI 1.21-2.10; p = .001), as well as return to the operating room for a neurological event or bleeding (OR 2.21, 95% CI 1.35-3.61; p = .002) were associated with an increased risk of CNI, whereas no statistically significant association was found between CNIs and the type of anaesthesia, the use of a patch, redo operation, and the use of a shunt.

Conclusion: The vagus nerve appears to be the most frequently injured cranial nerve after CEA, followed by the hypoglossal nerve, with only a small proportion of these injuries being permanent. The CNI rate has significantly decreased over the past 35 years to a point indicating that CNIs should not be considered a major influencing factor in the decision making process between CEA and stenting.

Keywords: Carotid; Cranial nerve injury; Endarterectomy; Meta-analysis; Risk factors; Time trend.