Tegmental Heterotopia in Phace Syndrome: A Previously Undescribed Feature

PHACE syndrome is a rare pediatric disorder characterized by posterior fossa malformations, large segmental facial hemangiomas, arterial anomalies, cardiac defects, and eye abnormalities. Neuronal migration disorders, including supratentorial heterotopia, have been previously reported as minor criteria. We describe two novel cases of infratentorial neuroglial heterotopia involving the tectal plate, a feature not previously documented in PHACE syndrome. Case 1 involved a 6-week-old infant with a right facial segmental hemangioma and ventricular septal defect. Brain MRI revealed two 5-mm nodular lesions posterior to the tectal plate, isointense to brain parenchyma and non-enhancing, consistent with infratentorial neuroglial heterotopia. MR angiography showed right internal carotid artery dolichoectasia with absent communicating arteries. Case 2 involved a neonate with prenatal posterior fossa cyst and right cerebellar hypoplasia. MRI demonstrated a 7-mm tectal plate lesion with similar characteristics; no significant vascular anomalies were observed. These findings expand the neuroimaging spectrum of PHACE syndrome to include tectal plate heterotopia, which might result from hypothetical vascular-related neuronal migration mechanism. Recognition of this anomaly on standard axial MRI sequences, including prenatal imaging, may facilitate earlier diagnosis and better characterization of brainstem malformations in PHACE syndrome. This is particularly relevant because infantile hemangiomas are not yet clinically apparent in utero or immediately after birth. Further studies are warranted to determine prevalence, clinical relevance, and pathophysiologic mechanisms underlying this distinct anomaly.