Agenesis of Bilateral Internal Carotid Arteries in the PHACE Syndrome

We read with interest the paper by Weon et al,¹ in which they described the case of a 14-year-old girl with a complex association of agenesis of the bilateral internal carotid arteries with transcranial collaterals from the external carotid artery, agenesis of the vertebrobasilar system, hypoplasia of the right cerebellar hemisphere, absence of the inferior cerebellar vermis, and facial capillary hemangioma. PHACE syndrome is a constellation of anomalies that includes posterior fossa abnormalities, hemangiomas, arterial abnormalities, aortic coarctation and cardiac abnormalities, and eye abnormalities.² The acronym has been subsequently expanded to “PHACES” to include sternal defects, which may be associated in a minority of patients.² Among arterial anomalies occurring in patients with PHACE syndrome, Weon et al noted that agenesis of major arteries, such as the internal carotid and vertebral arteries, is usually unilateral and occurs ipsilaterally to the cutaneous lesion.

In a 2001 paper with a coincidentally similar title³ that was unfortunately not cited by Weon et al, we described 3 patients with PHACE syndrome, one of whom had a complex arterial abnormality bearing some similarities to that described by Weon et al. This patient was a female neonate with bilateral agenesis of the internal carotid arteries, as shown by MR angiography and confirmed by the absence of the carotid canals on the bone window setting of brain CT. Unlike Weon et al’s case, in our case the anterior circulation was reconstituted by a huge basilar trunk via enlarged posterior communicating arteries, whereas the external carotid artery branches did not contribute to the anterior circulation except for the right ophthalmic artery originating from a branch of the right middle meningeal artery. Thus, to the best of our knowledge, Weon et al’s is the second report on bilateral agenesis of the internal carotid arteries in the setting of PHACE syndrome.

Other features of our case included tricuspid atresia, right hemispheric cerebellar cortical dysplasia (until then a novel feature of PHACE syndrome), and a remarkably minor cutaneous expressivity with a capillary hemangioma of the right pinna in the absence of the disfiguring hemifacial hemangioma that is found in most patients with PHACE syndrome.² We did not find ophthalmologic abnormalities or sternal defects, and also the other 2 cases from our series,³ as well as an additional, unpublished case that we recently observed, did not display the full phenotypic spectrum of the syndrome. Thus, we agree with Weon et al that the PHACE syndrome is heterogeneous and that absence of one or more components is the rule. We also believe that all patients with a facial hemangioma (regardless of size) should undergo neuroradiologic, cardiologic, and ophthalmologic investigations to disclose possible associated abnormalities. It is hoped that future research will establish more precise diagnostic criteria and, one hopes, disclose the genetic background to what we believe is not merely an association of findings—etymologically, a syndrome—but rather a true vascular phakomatosis.

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