Most Commonly Injured Cranial Nerve During Carotid Endarterectomy
The hypoglossal nerve (CN XII) is the most commonly injured cranial nerve during carotid endarterectomy. 1, 2
Cranial Nerve Injury Rates
Based on the available evidence, the incidence of cranial nerve injuries during carotid endarterectomy (CEA) shows the following pattern:
- Hypoglossal nerve (CN XII): 3.3% of cases 2
- Vagus/Recurrent laryngeal nerve (CN X): 2.6% of cases 2
- Glossopharyngeal nerve (CN IX): 0.7% of cases 2
- Facial nerve (CN VII): 0.4% of cases 2
Risk Factors for Hypoglossal Nerve Injury
Several anatomical and surgical factors increase the risk of hypoglossal nerve injury during CEA:
- High carotid bifurcation requiring more extensive dissection 1
- Atheromatous lesions extending beyond the exposed surgical field 1
- Lesions at or above the level of the second cervical vertebra 3
- Reoperative CEA with accumulated scar tissue 3, 1
- Prior radical neck surgery or radiation 3
Anatomical Considerations
The hypoglossal nerve is particularly vulnerable during CEA because:
- It crosses the external carotid artery and must be mobilized during exposure of the carotid bifurcation
- It originates in the dorsal medulla and travels within the carotid space to innervate the tongue musculature 1
- It forms part of an anatomical triangle with the vagus nerve and pharyngeal veins in approximately 17.3% of cases 4
Clinical Presentation of Hypoglossal Nerve Injury
Patients with hypoglossal nerve injury may present with:
- Tongue deviation toward the affected side when protruded
- Dysarthria
- Difficulty with mastication
- Dysphagia 1
Prognosis
Most cranial nerve injuries following CEA are transient and show improvement within weeks to months. In the study by International Angiology, all patients showed improvement within a few weeks, and none had residual disability at the last follow-up (two weeks to 14 months) 2.
Prevention Strategies
To minimize the risk of hypoglossal nerve injury during CEA:
- Thorough knowledge of regional anatomy is essential 1, 5
- Careful surgical technique with gentle tissue handling 1
- Identification and protection of cranial nerves during dissection 1
- Avoidance of excessive retraction 1
- Careful ligation and division of the inferior pharyngeal vein 4
Clinical Implications
While unilateral single nerve injury is usually well tolerated, bilateral or combined nerve injuries can pose a serious threat to life 5, 4. This is particularly important to consider in patients with contralateral laryngeal nerve palsy, which is a relative contraindication to CEA 3, 1.