What does a post-stenotic aneurysm of the left vertebral artery near the C2 vertebra mean for an adult patient?

Post-Stenotic Aneurysm of the Left Vertebral Artery Near C2

A post-stenotic aneurysm (PSA) of the left vertebral artery near C2 is an abnormal focal dilation of the vessel wall that develops downstream from a stenotic (narrowed) segment, typically located in the V2 or V3 segment of the vertebral artery at the level of the second cervical vertebra.

Anatomical Context

The vertebral artery near C2 corresponds to the V2 and V3 segments 1:

• V2 segment: Extends through the transverse foramina from C6 to C2 2
• V3 segment: Exits the C2 transverse foramen, courses laterally and posteriorly around the superior articular process of C2, then travels across the posterior arch of C1 toward the foramen magnum 1

The V3 segment is particularly vulnerable to mechanical injury due to its connection to highly mobile cervical vertebrae (C1 and C2) 1.

Pathophysiology of Post-Stenotic Aneurysm

Post-stenotic aneurysms develop due to hemodynamic stress 2:

• A stenosis (narrowing) creates turbulent flow and increased pressure distal to the narrowed segment
• This abnormal hemodynamic force weakens the arterial wall downstream
• Progressive dilation occurs, forming an aneurysm
• The aneurysm may be fusiform (circumferential dilation) or saccular (focal outpouching) 2

Clinical Significance and Risks

Stroke Risk

Vertebral artery aneurysms near C2 pose significant risk for posterior circulation stroke 3:

• Vertebral artery atherosclerosis causes approximately 20% of posterior circulation strokes 2
• Aneurysms can cause stroke through two mechanisms: thromboembolism (clot formation within the aneurysm that breaks off) or hemodynamic compromise 2

Dissection Risk

The V3 segment is particularly prone to dissection due to mechanical vulnerability, with an incidence of approximately 1.3 per 100,000 in patients under 45 years 1.

Rupture Risk

While rare, vertebral artery aneurysms can rupture, causing subarachnoid hemorrhage 4, 5.

Clinical Presentation

Patients may present with 1:

• Posterior circulation symptoms: Dizziness, vertigo, diplopia, perioral numbness, blurred vision, tinnitus, ataxia, bilateral sensory deficits 2
• Headache and neck pain 1
• Nausea and visual disturbances 1
• Horner syndrome (ptosis, miosis, anhidrosis) if dissection is present 1
• Acute stroke symptoms: Dysarthria, vertigo, cerebellar signs 3

Critical caveat: Many patients remain asymptomatic until a catastrophic event occurs 6.

Diagnostic Evaluation

CTA or contrast-enhanced MRA are superior to ultrasound for evaluating vertebral artery pathology near C2 1:

• Sensitivity and specificity of 94-95% for CTA and MRA versus 70% for ultrasound 2
• Neither MRA nor CTA reliably delineates vertebral artery origins, but they excel at visualizing the V2-V3 segments 2

Digital subtraction angiography (DSA) remains the gold standard for definitive characterization before intervention 3.

Management Approach

Medical Management

All patients require aggressive medical therapy regardless of intervention plans 2:

• Antiplatelet therapy (aspirin, clopidogrel, or combination aspirin-dipyridamole)
• Statin therapy for atherosclerotic disease
• Blood pressure control
• Risk factor modification (smoking cessation, diabetes management)

Anticoagulation Considerations

For acute presentations with evidence of thrombus, anticoagulation for at least 3 months is recommended 2.

Endovascular Intervention

Endovascular treatment options include 3, 6, 5:

• Flow-diverting stents: Increasingly used for fusiform and dissecting aneurysms, promoting aneurysm thrombosis while preserving parent vessel 3
• Stent-supported coil embolization: Can be used but carries risk of recurrence 5
• Parent vessel occlusion with coil embolization: Definitive treatment if patient tolerates test balloon occlusion and has adequate contralateral vertebral artery flow 5

Important consideration: The left vertebral artery arises directly from the aortic arch in approximately 5% of individuals rather than from the subclavian artery, which affects surgical planning 2.

Surgical Options

Open surgical repair with vein graft reconstruction is possible but rarely performed in the modern era, reserved for cases unsuitable for endovascular treatment 7.

Follow-Up Requirements

Close clinical and imaging surveillance is mandatory 5:

• Patients treated with stent-supported coiling require particularly vigilant follow-up due to recurrence risk 5
• Repeat imaging at 4-6 weeks, then periodically based on initial treatment response
• Any new posterior circulation symptoms warrant immediate re-evaluation

Key Clinical Pitfalls

• Do not assume asymptomatic means benign: Vertebral artery injuries and aneurysms can remain silent until catastrophic events 6
• Do not rely on ultrasound alone: CTA or MRA is essential for adequate visualization of the V2-V3 segments 1
• Do not overlook contralateral vertebral artery status: Treatment decisions depend heavily on whether the patient can tolerate sacrifice of the affected vessel 5
• Do not miss associated aortic arch variants: Aberrant vertebral artery origins affect treatment planning 2