Most Commonly Injured Cranial Nerve During Carotid Endarterectomy
The hypoglossal nerve (CN XII) is the most commonly injured cranial nerve during carotid endarterectomy. 1
Incidence of Cranial Nerve Injuries
Based on the available evidence, cranial nerve injuries occur in approximately 5.6% of carotid endarterectomy procedures 1. The specific distribution of these injuries shows:
- Hypoglossal nerve (CN XII): 3.3% 1
- Vagus nerve (CN X): 2.6% (manifesting as vocal cord paralysis) 1
- Glossopharyngeal nerve (CN IX): 0.7% 1
- Facial nerve (CN VII): 0.4% (specifically the marginal mandibular branch) 1
Anatomical Considerations
The hypoglossal nerve is particularly vulnerable during carotid endarterectomy due to its anatomical course:
- CN XII arises from the dorsal medulla, traverses the premedullary cistern, and enters the hypoglossal canal 2
- It then travels within the carotid space to innervate the tongue musculature 2
- This proximity to the surgical field makes it susceptible to injury during dissection and retraction
Risk Factors
High carotid bifurcations significantly increase the risk of hypoglossal nerve injury during the procedure 2. This anatomical variation requires more extensive dissection in the superior portion of the surgical field where the hypoglossal nerve traverses.
Prevention of Nerve Injuries
To minimize the risk of cranial nerve injuries during carotid endarterectomy:
- Thorough knowledge of regional anatomy is essential 2, 3
- Careful surgical technique with gentle tissue handling 2
- Identification and protection of cranial nerves during dissection 2
- Awareness of potential anatomical variations, such as non-recurrent laryngeal nerves 4
Clinical Course of Nerve Injuries
Most cranial nerve injuries following carotid endarterectomy are transient:
- Patients typically show improvement within a few weeks 1
- Complete resolution is common, with no residual disability reported in follow-up periods ranging from two weeks to 14 months 1
- Injuries generally result from trauma during dissection, retraction, or carotid clamping rather than direct transection 1, 5
Clinical Significance
While most injuries are temporary, they can cause significant functional impairment:
- Hypoglossal nerve injury leads to ipsilateral tongue weakness and deviation
- Vagal injury causes hoarseness due to vocal cord paralysis
- Glossopharyngeal nerve injury, though less common, can result in severe functional disability 6
Therefore, the answer is D. XII (Hypoglossal nerve).