What causes transient tongue swelling in carotid artery dissection?

Carotid Artery Dissection and Transient Tongue Swelling: Pathophysiological Mechanism

Transient tongue swelling in carotid artery dissection is caused by mechanical compression of the hypoglossal nerve (CN XII) by the intramural hematoma that forms during dissection of the internal carotid artery. 1

Pathophysiological Mechanism

Anatomical Basis

• The hypoglossal nerve (CN XII) travels in close proximity to the internal carotid artery (ICA) in the carotid space
• The nerve exits the skull through the hypoglossal canal and courses caudally within the carotid space before traveling anteriorly to innervate the tongue 2

Dissection Process and Nerve Compression

1. Initial Event: Arterial dissection begins with an intimal tear in the arterial wall 3
2. Hematoma Formation: Blood enters between the layers of the vessel wall, creating a false lumen and initiating an intramural hematoma 3
3. Nerve Compression: The expanding hematoma in the carotid artery wall directly compresses the adjacent hypoglossal nerve 4, 1
4. Acute Phase: The initial compression causes edema of the tongue musculature on the affected side, presenting as acute tongue swelling 1
5. Chronic Phase: With persistent compression, denervation leads to muscle atrophy and fat tissue replacement in the chronic stage 1

Clinical Presentation

Acute Phase (Tongue Swelling)

• Presents as unilateral tongue swelling that can mimic angioedema 5, 1
• Often misdiagnosed initially as allergic reaction or angioedema 5
• Typically occurs on the same side as the carotid dissection 1

Progression

• Swelling persists despite antihistamines and corticosteroids (distinguishing it from allergic angioedema) 1
• Eventually progresses to unilateral tongue weakness and deviation toward the affected side 4, 1
• May be accompanied by other symptoms of carotid dissection:
  • Unilateral head or neck pain
  • Horner syndrome (ptosis, miosis, anhidrosis)
  • Pulsatile tinnitus 3

Diagnostic Considerations

Imaging

• MRI with fat-saturated T1 sequences: Best for visualizing the intramural hematoma and nerve compression 3
• MRA/CTA: Shows the dissection flap and vessel lumen narrowing 2, 3
• Carotid Duplex Ultrasonography: May identify the dissection flap and differential flow in true and false lumens 2

Differential Diagnosis

• Allergic angioedema
• Hereditary angioedema
• Infection/abscess
• Trauma
• Other causes of hypoglossal nerve palsy 5, 1

Clinical Implications

Recognition

• Acute tongue swelling should prompt consideration of carotid dissection, particularly in young or middle-aged patients without obvious allergic triggers 1
• Persistence of swelling despite antihistamines and steroids should raise suspicion 1

Management

• Antithrombotic therapy (anticoagulation or antiplatelet therapy) for 3-6 months to prevent ischemic complications 3
• Monitoring for progression of dissection or pseudoaneurysm formation 3
• Endovascular intervention may be considered for persistent symptoms despite medical therapy 3

Prognosis

• Tongue swelling typically resolves over time as the dissection heals 1
• Risk of recurrent stroke or TIA is approximately 12% 3

Special Considerations

• Cocaine use has been associated with carotid dissection causing hypoglossal nerve injury and acute tongue swelling 6
• Carotid dissection should be considered in the differential diagnosis of patients presenting with isolated acute tongue swelling, particularly when other causes have been ruled out 1

This unique presentation of carotid artery dissection highlights the importance of recognizing unusual manifestations of vascular pathology to ensure prompt diagnosis and appropriate management.