PHACEing a challenging diagnosis: Should we expand the phenotype?

PHACE syndrome is a challenging but important prenatal diagnosis due to its protean clinical consequences. The 'tilted telephone receiver' sign (TTRS), consisting of asymmetric cerebellar volume reduction and marked counterclockwise, Dandy-Walker-like upward vermis rotation on prenatal MRI and ultrasound has high specificity for PHACE. Recently, a case report of the prenatal imaging findings in an infant with PHACE described more mild upward vermis rotation and cerebellar clefting. It recommended consideration of expansion of the currently accepted phenotype to improve prenatal detection of the condition. We describe a case with imaging features essentially indistinguishable from the recently published case of PHACE with mild upward vermis rotation, asymmetric cerebellar hemispheric volume loss and a cerebellar hemispheric cleft. Our patient did not have PHACE postnatally at 1 year of follow up. Neurodevelopmental testing in infancy demonstrated mildly atypical development. Fetuses with asymmetric cerebellar hemispheric volume loss, a cleft in the smaller hemisphere and only mild upward vermis rotation, consistent with the proposed 'expanded PHACE phenotype' do not always have PHACE. Erroneously adverse prenatal prognostic counselling may result from such prenatal phenotypic expansion.
(© 2024 Royal Australian and New Zealand College of Radiologists.)