Incidence of Tongue Deviation After Carotid Endarterectomy
Cranial nerve palsy, including hypoglossal nerve injury causing tongue deviation, is a recognized complication of CEA, though the major guidelines cite it as a known risk without providing specific incidence rates. 1
Reported Incidence Rates
The incidence of tongue deviation after CEA varies considerably depending on how rigorously it is assessed:
Historical estimates suggest hypoglossal nerve damage occurs in approximately 5% of carotid endarterectomies, though this figure represents clinically apparent cases. 2
Up to 20% of patients may experience some degree of hypoglossal nerve injury when carefully examined, though many of these deficits are mild or go unnoticed by patients. 3
In contemporary surgical series with systematic evaluation, the rate appears lower - one prospective study of 28 patients using detailed perceptual and instrumental assessments found no significant long-term tongue dysfunction, suggesting that with modern surgical technique, permanent hypoglossal nerve injury is uncommon. 4
A recent 2021 surgical series reported mild tongue deviation in 1 of 6 patients (approximately 17%) undergoing CEA, with complete recovery at follow-up, attributed to surgical retraction rather than nerve transection. 5
Clinical Context and Risk Factors
The risk of cranial nerve injury, including hypoglossal nerve palsy causing tongue deviation, is influenced by several anatomical and technical factors:
High carotid bifurcation or lesions extending beyond the exposed surgical field increase the technical challenge and risk of cranial nerve injury during CEA. 1
Prior radical neck surgery, radiation therapy, or reoperation are associated with higher risk of cranial nerve complications (OR 1.95 for reoperation versus primary surgery, p<0.018). 1
Contralateral laryngeal nerve palsy is a relative contraindication to CEA because bilateral nerve palsies could compromise the airway, highlighting the importance of detecting unilateral deficits before contralateral surgery. 1, 3
Important Clinical Distinctions
Most hypoglossal nerve injuries are temporary and resolve without permanent functional disability, even if tongue hemiplegia persists, because the vast majority of patients compensate well for unilateral hypoglossal nerve dysfunction. 2
Permanent symptomatic dysfunction is rare - when it occurs, it may be due to aberrant reinnervation rather than persistent denervation, causing abnormal coactivation of tongue muscles and resulting in dysarthria beginning 4 months after surgery. 2
Bilateral hypoglossal nerve injury is poorly tolerated and causes potentially serious impairment of speech and risk of aspiration, making careful preoperative assessment critical in patients who may undergo staged bilateral procedures. 3
Common Pitfalls
Failing to systematically examine for cranial nerve deficits preoperatively and within 24 hours postoperatively, as recommended by guidelines (Class I, Level of Evidence C), may result in missed injuries that could influence decisions about contralateral surgery. 1
Not recognizing that mild tongue deviation may be related to surgical retraction rather than nerve transection, which has important prognostic implications as retraction injuries typically resolve completely. 5
Underestimating the functional impact of bilateral hypoglossal nerve injury when planning staged bilateral CEA procedures, as unilateral deficits are generally well-tolerated but bilateral deficits cause severe disability. 3