The Hypoglossal Nerve (XII) is the Most Commonly Injured Cranial Nerve During Carotid Endarterectomy
The correct answer is D. XII (Hypoglossal nerve). According to evidence from multiple sources, the hypoglossal nerve (XII) is the most frequently injured cranial nerve during carotid endarterectomy procedures 1, 2.
Incidence of Cranial Nerve Injuries During Carotid Endarterectomy
Cranial nerve injuries occur in approximately 5.6% of carotid endarterectomy (CEA) procedures 2. The specific distribution of these injuries is:
- Hypoglossal nerve (XII): 3.3% - highest incidence 2
- Recurrent laryngeal branch of vagus nerve (X): 2.6% 2
- Glossopharyngeal nerve (IX): 0.7% 2
- Facial nerve (VII): 0.4% 2
Risk Factors for Hypoglossal Nerve Injury
Several anatomical and surgical factors increase the risk of hypoglossal nerve injury:
- High carotid bifurcation - requires more extensive dissection 1
- Atheromatous lesions extending into the internal carotid artery beyond the exposed surgical field 3
- Reoperative CEA due to accumulated scar tissue 3
- Lesions at or above the level of the second cervical vertebra 3
Mechanism of Injury
The hypoglossal nerve is particularly vulnerable during CEA because:
- It crosses the external carotid artery near the carotid bifurcation
- It must be mobilized during exposure of the distal internal carotid artery
- It can be injured during:
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
Prognosis
Most cranial nerve injuries following CEA are transient and show improvement within weeks. In one study, all patients showed improvement within a few weeks with no residual disability at follow-up (ranging from two weeks to 14 months) 2.
Prevention Strategies
To minimize the risk of hypoglossal nerve injury:
- Thorough knowledge of regional anatomy is essential 1, 4
- Careful surgical technique with gentle tissue handling 1
- Identification and protection of cranial nerves during dissection 1
- Avoid excessive retraction
- Minimize dissection above the hypoglossal nerve when possible
Other Important Considerations
While the hypoglossal nerve is most commonly injured, injuries to the vagus nerve (X) through its recurrent laryngeal branch are also significant, causing vocal cord paralysis and hoarseness 2, 5. Contralateral laryngeal nerve palsy is a relative contraindication to CEA, as bilateral nerve palsies could compromise the airway 3.
Patients with high-risk anatomical features such as high carotid bifurcation, prior neck surgery, or radiation therapy may benefit from careful preoperative planning and consideration of alternative approaches 3.