Hypoglossal Nerve (CN XII) is the Most Commonly Injured Cranial Nerve During Carotid Endarterectomy
The hypoglossal nerve (CN XII) is the most commonly injured cranial nerve during carotid endarterectomy procedures. 1, 2
Incidence of Cranial Nerve Injuries During CEA
According to research evidence, cranial nerve injuries occur in approximately 5.6% of carotid endarterectomy procedures, with the following distribution:
- Hypoglossal nerve (CN XII): 3.3% of cases 2
- Vagus nerve (CN X): 2.6% of cases (causing vocal cord paralysis) 2
- Glossopharyngeal nerve (CN IX): 0.7% of cases 2
- Facial nerve (CN VII): 0.4% of cases (specifically the marginal mandibular branch) 2
Risk Factors for Hypoglossal Nerve Injury
The American Heart Association and American College of Radiology guidelines identify several risk factors that increase the likelihood of hypoglossal nerve injury during CEA:
- High carotid bifurcation requiring more extensive dissection 1
- Atheromatous lesions extending into the internal carotid artery beyond the exposed surgical field 1
- Reoperative CEA with accumulated scar tissue 1
- Lesions at or above the level of the second cervical vertebra 1
- Prior neck surgery or radiation therapy 1
Anatomical Considerations
The hypoglossal nerve is particularly vulnerable during CEA due to its anatomical course:
- It originates in the dorsal medulla
- Traverses the premedullary cistern
- Enters the hypoglossal canal
- Travels within the carotid space to innervate the tongue musculature 1
This path brings the nerve in close proximity to the surgical field during carotid endarterectomy, making it susceptible to injury.
Clinical Presentation of Hypoglossal Nerve Injury
Patients with hypoglossal nerve injury typically present with:
- Tongue deviation toward the affected side when protruded
- Dysarthria
- Difficulty with mastication
- Dysphagia 1
Prevention of Cranial Nerve Injuries
The American College of Surgeons recommends the following measures to minimize the risk of cranial nerve injuries during CEA:
- Thorough knowledge of regional anatomy
- Careful surgical technique with gentle tissue handling
- Identification and protection of cranial nerves during dissection
- Avoidance of excessive retraction 1
Prognosis
Most cranial nerve injuries following CEA are transient and show improvement within weeks. In the study by the International Union of Angiology, all patients with cranial nerve injuries showed improvement within a few weeks, and none had residual disability at the last follow-up (two weeks to 14 months) 2.
Clinical Implications
- Contralateral laryngeal nerve palsy is a relative contraindication to CEA, as bilateral nerve palsies could compromise the airway 1
- Patients with high-risk anatomical features may benefit from careful preoperative planning and consideration of alternative approaches 1
- Patients manifesting symptoms of cranial nerve dysfunction should undergo thorough otolaryngological evaluation and long-term follow-up 2