Snapshot A 5-year-old male presents with an unprovoked convulsive episode that lead to right-sided hemiparesis. On physical exam, a port wine stain is appreciated, affecting the ophthalmic and maxillary division of the trigeminal nerve on the left side of the face. Head CT shows brain calcifications. Introduction Congenital vascular disorder characterized by port wine stain (capillary malformation of the face, nevus flammeus) primarily in V1 or V2 distribution of the trigeminal nerve capillary-venous malformation (eye and brain) Etiology GNAQ gene somatic mosaic mutation GNAQ gene product is involved in regulating intracellular signaling pathways this is a non-inherited disease Associated with: leptomeningeal angioma usually ipsilateral to port wine stain seizures capillary-venous malformation intellectual disability behavioral problems ophthalmologic involvement glaucoma visual field defect Presentation Symptoms port wine stain seizures intellectual disability behavioral problems decreased visual acuity and/or visual field defect Evaluation Clinical findings port wine stain MRI of the brain with gadolinium (preferred) shows leptomeningeal capillary-venous malformation if MRI is not available, head CT may show brain calcification ("tram-tracking" sign) Differential Klippel-Trenaunay-Weber syndrome Beckwith-Wiedemann syndrome Treatment No specific treatment Prognosis, Prevention, and Complications Complications glaucoma seizures hemiparesis mental retardation