Rete mirabile of the ICA: Report of three cases

Abstract

Carotid rete mirabile is an arterial meshwork, occurring at the cavernous portion of the internal carotid artery (ICA). Rete mirabile in humans is not present during normal development of the intracranial circulation and hence is considered as a collateral pathway that develops as a consequence of segmental agenesis of the ICA. We report three cases of this rare entity encountered at our institute.

Keywords: Carotid; artery; embryology; humans; rete.

Figure 1.

(a) Lateral view of right CCA shows non-visualization of right ICA. (b), (c) AP and lateral view of right ECA, respectively, shows multiple collaterals from right IMA and APA reconstituting the right ICA at the cavernous segment. Right ophthalmic artery is ectatic (black arrow). (d) Right ECA AP view demonstrating intracranial filling: the supraclinoid segment of right ICA, A1 segment of ACA and M1 segment of MCA are ectatic. There is a posterosuperiorly directed aneurysm at the ICA bifurcation. Flow through Acom is filling the contralateral ACA and MCA. (e) Bone window of CT Brain shows hypoplastic right carotid canal. (f), (g) AP and lateral view of left VA shows tortuous and ectatic P1 segment of right PCA with aneurysms. Left PCA was fetal. (h) Lateral view of left CCA shows normal calibre of cervical ICA and ECA. (i) Lateral view of left ICA: Note the normal calibre of ICA until the origin of PCom and non-visualisation of ICA distal to Pcom. Left ophthalmic artery (black arrow) is dilated. Multiple collaterals in the orbit (white arrow) arising from the OA are retrogradely opacifying the ACA. Left PCom and PCA are markedly tortuous and ectatic with few aneurysms in the PCA. (j) Lateral view of left ECA shows collaterals from left IMA along with intercavernous branches from left ICA opacifying the right cavernous ICA. (k), (l), (m) AP and left anterior oblique view of right subclavian artery and AP view of the aortic arch shows marked tortuosity and ectasia in proximal right subclavian artery. CCA: Common carotid artery; AP: anteroposterior; ECA external carotid artery; IMA: internal maxillary artery; APA: ascending pharyngeal artery; ICA: internal carotid artery; MCA: middle cerebral artery; Acom: anterior communicating artery; ACA: anterior cerebral artery; VA vertebral artery; PCA: posterior cerebral artery; Pcom: posterior communicating artery; OA: ophthalmic artery.

Figure 2.

(a) CT brain scan shows subarachnoid haemorrhage in interpeduncular cistern (was also noted in suprasellar cistern, bilateral sylvian fissures, left temporal and right parietal sulcal spaces). (b) 3D view of right vertebral artery injection shows basilar tip aneurysm and a small superiorly directed aneurysm in P1 segment of right PCA. (c) CT bone window at skull base: Bilateral hypoplastic carotid canals are noted. (d) AP view of right CCA shows non-visualisation of ICA from origin. (e), (f) AP and lateral view of right ECA shows collaterals from the IMA reconstituting the ICA at the cavernous segment. An attenuated calibre ICA is seen opacifying and filling attenuated calibre ipsilateral ACA and MCA. (g) AP view of left CCA non-visualisation of ICA from origin. (h), (i) AP and lateral view of left ECA shows collaterals from the IMA reconstituting the ICA at the cavernous segment. An attenuated calibre ICA is seen opacifying and filling attenuated calibre ipsilateral ACA and MCA.

Figure 3.

(a) Axial FLAIR image of MRI brain scan shows gliosis and volume loss in left cerebral hemisphere. (b) Lateral view of right CCA injection shows non-visualisation of right ICA from its origin. (c), (d) AP view of right ECA shows collaterals from IMA and APA reconstituting the right ICA at the petrous segment. Distal right ICA is of normal calibre and is predominantly filling the right MCA territory. (e) AP view of left CCA shows significant narrowing of left ICA with non-visualisation of ICA beyond the OA, this was secondary to moyamoya. (f) AP view of right VA shows segmental non visualisation of distal V2 segment with reformation of V3 segment through collaterals from APA and deep cervical arteries. Dilated tortuous ASA and PSA systems were seen. Cross-filling across PCom is filling bilateral MCA and ACA territories.