Hypoglossal Nerve (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
Cranial Nerve Injury Rates During Carotid Endarterectomy
According to the evidence, the pattern of cranial nerve injuries during carotid endarterectomy shows:
- Hypoglossal nerve (XII): 3.3% of cases 2
- Vagus nerve (X): 2.6% of cases (causing vocal cord paralysis) 2
- Glossopharyngeal nerve (IX): 0.7% of cases 2
- Facial nerve (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 carotid endarterectomy:
- High carotid bifurcation requiring more extensive dissection 1
- Atheromatous lesions extending into the internal carotid artery beyond the exposed surgical field 1
- Reoperative carotid endarterectomy 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 carotid endarterectomy 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 it into close proximity with the surgical field during carotid endarterectomy, making it the most frequently injured cranial nerve during this procedure.
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 Strategies
To minimize the risk of hypoglossal nerve injury during carotid endarterectomy:
- Employ careful surgical technique with gentle tissue handling
- Identify and protect cranial nerves during dissection
- Avoid excessive retraction
- Maintain thorough knowledge of regional anatomy 1
Prognosis
Most cranial nerve injuries following carotid endarterectomy, including hypoglossal nerve injuries, are transient and show improvement within weeks 1, 2. In the study by 2, all patients showed improvement within a few weeks, and none had residual disability at the last follow-up (ranging from two weeks to 14 months).