What does a tortuous course of the left Internal Carotid Artery (ICA) near the skull base without dissection indicate?

Tortuous Course of the Left Internal Carotid Artery: Clinical Significance and Management

A tortuous course of the left internal carotid artery (ICA) near the skull base without dissection is generally a benign anatomical variant that rarely causes clinical symptoms and does not require specific intervention in most cases.

What is Carotid Artery Tortuosity?

Carotid artery tortuosity refers to an elongation and abnormal curvature of the carotid artery, which can occur in the internal carotid artery (ICA), common carotid artery (CCA), or both. This anatomical variation is characterized by:

• Elongation of the vessel with altered course
• Can present as simple tortuosity (curved), kinking (angulation), or coiling (loop formation)
• Most commonly affects the internal carotid artery 1
• May be unilateral or bilateral

Clinical Significance

Epidemiology and Risk Factors

• More common in females, particularly those over 60 years of age 2
• Often bilateral (48% of cases) but when unilateral, more frequently occurs on the left side 2
• Associated risk factors include:
  • Advanced age
  • Hypertension
  • Atherosclerosis
  • Congenital factors (incomplete descent of the third aortic arch) 3

Clinical Implications

1. Stroke Risk: Current evidence suggests that carotid tortuosity alone is not clearly associated with increased stroke risk 2

2. Blood Flow Dynamics: In severe cases of kinking or coiling, there may be:

   • Increased maximal systolic velocity at the level of tortuosity 2
   • Potential for turbulent flow, though this rarely causes hemodynamic compromise

3. Surgical Considerations: Important anatomical consideration during:

   • Head and neck surgeries
   • Carotid endarterectomy
   • Intubation procedures 3

4. Relationship to Atherosclerosis:

   • Mild atheromatous plaques are more common in patients with carotid tortuosity
   • Moderate and large plaques are less common in tortuous vessels 2
   • Tortuosity itself is not considered a marker of atherosclerotic vascular disease 2

Diagnostic Evaluation

When a tortuous ICA is identified on CTA, the following should be considered:

1. Differentiation from Dissection: The CTA finding specifically notes "no dissection," which is important as dissection would require different management. CTA has high sensitivity (51-98%) and specificity (67-100%) for detecting carotid dissection 4.

2. Assessment of Stenosis: Determine if there is associated stenosis, which would be more clinically significant than tortuosity alone.

3. Further Imaging: Additional imaging is generally not required if:

   • No neurological symptoms are present
   • No significant stenosis is identified
   • No dissection is present

Management Approach

Asymptomatic Patients

• No specific treatment is required for asymptomatic carotid tortuosity without stenosis 2
• Standard cardiovascular risk factor modification should be continued if indicated for other reasons

Patients with Associated Stenosis

• If significant stenosis (>70%) is present along with tortuosity:
  • Medical therapy including antiplatelet therapy and statins is indicated 5
  • Revascularization may be considered if stenosis is severe (>70-80%) and symptomatic 5

Surgical Considerations

• If surgery is required for significant stenosis in a tortuous vessel, special techniques may be needed:
  • Standard endarterectomy may lead to angulation occlusion due to loss of the stenting effect provided by plaque
  • Eversion endarterectomy with transection and lower reimplantation of the ICA on the common carotid artery may be optimal 6

Key Points for Clinicians

• Tortuous carotid arteries are often incidental findings on imaging studies
• The finding alone, without dissection or significant stenosis, is generally benign
• Current evidence suggests tortuosity is more of a "curiosity" than a clinically significant finding 2
• No specific follow-up is required for asymptomatic patients with isolated tortuosity
• Awareness of this anatomical variant is important for surgeons operating in the head and neck region

In summary, a tortuous course of the left ICA near the skull base without dissection is typically an anatomical variant that requires no specific intervention. It should be documented in the patient's medical record for future reference, particularly if head or neck surgery is ever contemplated.