Bilateral segmental agenesis of carotid and vertebral arteries with rete mirabile and the prominent anterior and posterior spinal arteries as compensations

Revised concept of rete-like collateral formation: Rete mirabile does not exist in humans

The carotid rete is a physiological network between the external and internal carotid arteries (ICA) in lower vertebrates. However, true carotid rete does not exist in humans. This review aimed to contrast the physiological function of human "rete-like collaterals" with that of lower vertebrate "rete mirabile". An explanation for the development of rete-like collaterals in human intracranial arteries was also discussed. The rete mirabile (carotid, vertebral, spinal, and thoracic) in lower vertebrates has a specific physiological role and does not form vasculature for the same purpose in humans. Therefore, the term "rete mirabile" should not be used for cases reported in humans. Instead, "rete-like collaterals" is preferred. In the literature, rete-like or arterial anastomosis was observed in the ICA cavernous portion and the intradural arteries. Based on the hypothesis of the segmental concept, it applies to the ICA and intracranial arteries. Whether in the ICA, middle cerebral artery, posterior cerebral artery, or posterior inferior cerebellar artery, the segmental concept is the same and should be considered to have formed secondary collaterals after segmental regress or dysgenesis of affected arteries. Summarily, the significance of this review lies in its reevaluation of vascular structures previously described as "carotid rete" in humans to a true and preferred term, "rete-like collaterals". It also provides insights into the historical context and potential genetic factors associated with the formation of arteries in humans, contributing to a better understanding of human vascular anatomy.

Lethal subarachnoid haemorrhage in a patient with rete mirabile network of the posterior circulation with associated aneurysm

Rete mirabile (RM), an arterial network normally existing in some vertebrate animals interconnecting the extracranial and intracranial arterial circulation, can rarely be found in humans whether asymptomatic or presenting with cerebral ischaemia or haemorrhage. Encompassing diverse angiographic characteristics and similarities with other arterial malformations, proper diagnosis and differential diagnosis is challenging. We hereby describe an unusual RM case variant, presenting to us with lethal subarachnoid haemorrhage owing to a ruptured small aneurysm associated with the RM network. Angiography disclosed an absent P1 segment of the posterior cerebral artery (PCA) and an RM network anastomosing the basilar apex with the normal distal PCA. Brain death was confirmed on the fifth day after admission and attributed to the severity of subarachnoid haemorrhage (SAH). This is an exceedingly rare case representing an intradural-to-intradural RM anastomosis in a patient presenting with lethal SAH. RM epidemiology, pathophysiology, presentation, angiographic findings and prognosis are reviewed.

Unilateral cervical and petrosal segment agenesis of the internal carotid artery with rete mirabile

The carotid rete mirabile (RM) is a physiological network between the internal and external carotid arterial systems. In this paper, an extremely rare case is presented, in which internal-external carotid artery anastomoses and a dilated ascending pharyngeal artery, due to unilateral agenesis of the cervical and petrous segments of the internal carotid artery (ICA), is presented.

Isolation of right internal carotid artery, persistent proatlantal 1 artery and rete mirabile in a child with 22q11 deletion syndrome

We report a case of a 2-year-old girl with 22q11 deletion syndrome who underwent studies for cardiac murmur. Ultrasound, computed tomography angiography and digital subtraction angiography revealed an aberrant right subclavian artery and an isolated right internal carotid artery (ICA) originating from the right pulmonary artery. A right carotid rete mirabile (CRM) and a proatlantal (Pa) type 1 artery were also found. We hypothesize that Pa type 1 persistence and CRM development are secondary to the reversal of flow of the isolated ICA.

Rete mirabile associated with pial arteriovenous fistula: imaging features with literature review

A rete mirabile is a vascular network of intercommunicating small arteries or arterioles that replace the definitive adult artery supplying the brain. It supplies the brain in lower mammals but is not seen in normal human embryological development. A 26-year-old man presented with worsening tinnitus that was interfering with his sleep. On CT and digital subtraction angiography he was found to have a temporal lobe pial arteriovenous fistula with bilateral carotid and vertebral rete mirabile. The patient was offered open surgical and endovascular treatment options for pial arteriovenous fistula but he refused both and opted for conservative medical management. At 6-month follow-up he continued to have pulsatile tinnitus but was otherwise neurologically normal. We present the first described association of rete mirabile with pial arteriovenous fistula and discuss its clinical presentation and imaging features, with a review of the literature for bilateral carotid and vertebral rete mirabile.

Carotid rete mirabile associated with subarachnoid hemorrhage from intracranial aneurysm: A case report and systematic review

Carotid rete mirabile (CRM) is a rare physiological vascular network in humans that is most often found in Eastern populations. This paper describes a CRM associated with an aneurysmal subarachnoid hemorrhage (aSAH) and discusses the details of the patient's treatment. A 28-year-old woman was admitted to our service with clinical signs and symptoms of a spontaneous aSAH. Computed tomography revealed a diffuse and extensive SAH (Fisher group IV), while an angiogram showed an abnormal collateral network in the right carotid system and a hypoplastic aspect to the internal carotid artery (ICA) on the same side. In addition, a saccular aneurysm with a diameter of 9.5 mm was present in the ophthalmic segment of the left ICA. This case is extremely uncommon. To avoid rebleeding in the patient, we successfully treated the patient by clipping the aneurysmal lesion. No procedure was performed for the CRM.