What is a rete mirabile (network of blood vessels) anomaly?

What is Rete Mirabile Anomaly?

Rete mirabile is a rare congenital vascular anomaly consisting of an abnormal network of fine, anastomosing arterial vessels that replaces a normal parent artery, typically compensating for hypoplastic, aplastic, or stenotic native vessels. 1, 2

Anatomical Definition and Embryology

• Rete mirabile (Latin for "wonderful net") represents a congenital aberrant arterial collateral network resulting from abnormal embryonic activity during native vessel formation 1
• This vascular plexus is a normal physiological structure in lower mammals but does not exist in normal human embryological development 2, 3, 4
• In humans, it appears as a pathological compensatory mechanism when the definitive adult artery fails to develop properly 2

Location and Types

The anomaly most commonly affects:

• Carotid circulation: Arterial plexus at the cavernous region supplying the intradural internal carotid artery when the cavernous portion is aplastic—termed carotid rete mirabile (CRM) 3, 4
• Vertebral arteries: Segmental occlusion with tortuous collaterals 3
• Combined carotid and vertebral rete mirabile (CVRM): Bilateral involvement of both systems, which is extremely rare 5, 2, 3
• Posterior inferior cerebellar artery (PICA): Exceptionally rare, with minimal literature documentation 1

Clinical Significance and Complications

The primary clinical concern is the risk of hemorrhagic complications, as these abnormal vascular networks can be associated with:

• Subarachnoid hemorrhage from rupture of associated aneurysms 1, 3
• Spinal artery aneurysm formation due to hemodynamic stress on collateral pathways 3
• Pial arteriovenous fistulas in rare associations 2
• Ischemic cerebrovascular events, particularly in pediatric cases 4

Associated Vascular Pathology

• Rete mirabile may coexist with other vascular disorders including vein of Galen aneurysmal malformations 5
• Intracranial aneurysms and systemic vascular disorders (such as pseudoxanthoma elasticum) can accompany CRM 4
• The abnormal hemodynamics create stress on collateral vessels, particularly cervical spinal arteries, increasing aneurysm risk 3

Diagnostic Approach

Digital cerebral angiography is the gold standard for diagnosis, revealing the characteristic fine meshwork of anastomosing vessels replacing the parent artery 1, 5, 2

Key angiographic findings include:

• Hypoplasia or aplasia of the internal carotid arteries bilaterally 4
• Abnormal vascular network from the external carotid system around the cavernous portion of the internal carotid arteries 3, 4
• Development of ophthalmic arteries as collateral pathways 4
• In CVRM cases, detailed evaluation of cervical spinal arteries is mandatory to detect or rule out aneurysms 3

Clinical Presentation

Patients may present with:

• Hemorrhagic stroke symptoms from aneurysm rupture (most serious presentation) 1, 3
• Pulsatile tinnitus interfering with daily activities 2
• Neurological deficits including slurred speech, proptosis, vomiting, and altered consciousness 5
• Acute hemiplegia in pediatric cases 4
• Some patients remain asymptomatic with incidental discovery 5, 2

Management Considerations

Treatment options depend on presentation and associated complications:

• Endovascular coil embolization for ruptured aneurysms to prevent rebleeding 3
• Conservative medical management for asymptomatic or minimally symptomatic cases 5, 2
• Open surgical or endovascular treatment for associated arteriovenous fistulas (though patients may decline intervention) 2

Critical Pitfall

In patients with CVRM presenting with subarachnoid hemorrhage, detailed evaluation of cervical spinal arteries is essential, as aneurysm formation in these collateral vessels is a reasonable consequence of hemodynamic stress and represents a treatable cause of hemorrhage 3