Agenesis of bilateral internal carotid arteries and posterior fossa abnormality in a patient with facial capillary hemangioma: presumed incomplete phenotypic expression of PHACE syndrome

Abstract

PHACE syndrome is a neurocutaneous syndrome with the following features: posterior fossa malformations of the brain, large facial hemangiomas, arterial anomalies, cardiac anomalies and aortic coarctation, and eye abnormalities. We report a rare case of bilateral internal carotid artery agenesis with transcranial collaterals from the external carotid arteries and agenesis of the vertebrobasilar system in a possible PHACE syndrome. We suggest that the patient had an incomplete phenotypic expression of the PHACE syndrome. Although the phenotypic spectrum is broad and is still largely unexplored, the extent of the cephalic neural crest cells insulted genetically or by other causes at a certain time during the development of the embryo might explain the variable phenotypic expression of PHACE syndrome.

Fig 1.

On axial (A) and coronal (B) T2-weighted images, hypoplasia of the right cerebellar hemisphere and absence of the inferior cerebellar vermis are present. Note that the abnormally dilated basilar artery with numerous small signal intensity void structures corresponds with the collateral networks at the prepontine cistern. On MR angiography (C, -D), both internal carotid arteries are not seen, and the distal portion of internal carotid arteries is reconstituted from the external carotid arteries.

Fig 2.

Injection of right external carotid artery (A and B) and left external carotid artery (C and D) demonstrates the reconstitution of the distal internal carotid artery by branches of the internal maxillary arteries, middle meningeal arteries, deep temporal arteries, artery of the foramen rotundum, ascending pharyngeal arteries, and collaterals of the occipital artery. Injection of the left vertebral artery (E and F) shows the discontinuation between the vertebral arteries and the abnormally dilated proximal basilar artery with collateral branches mainly from the left vertebral artery.

Fig 3.

Normal internal carotid arteries are not seen in the carotid spaces, and no carotid canals are noted on the bone window setting of the brain CT (A) and T1-weighted brain MRI (B).

Fig 4.

Injection of the innominate artery (A) and CT scan obtained at the level of thoracic inlet (B) demonstrate the unusual subclavian artery turning like a screw.