Prenatal ultrasonographic detection of unilateral cerebral ventriculomegaly 
arises suspicion of pathological condition related to cerebrospinal fluid flow 
obstruction or cerebral parenchimal pathology. Dyke-Davidoff-Masson syndrome is 
a rare condition characterized by cerebral hemiatrophy, calvarial thickening, 
skull and facial asymmetry, contralateral hemiparesis, cognitive impairment and 
seizures. Congenital and acquired types are recognized and have been described, 
mainly in late childhood, adolescence and adult ages. We describe a female 
infant with prenatal diagnosis of unilateral left ventriculomegaly in which 
early brain MRI and contrast enhanced-MRI angiography, showed cerebral left 
hemiatrophy associated with reduced caliber of the left middle cerebral artery 
revealing the characteristic findings of the Dyke-Davidoff-Masson syndrome. 
Prenatal imaging, cerebral vascular anomaly responsible for the cerebral 
hemiatrophy and the early clinical evolution have never been described before in 
such a young child and complete the acquired clinical descriptions in older 
children. Differential diagnosis, genetic investigations, neurophysiologic 
assessments, short term clinical and developmental follow up are described. 
Dyke-Davidoff-Masson syndrome must be ruled out in differential diagnosis of 
fetal unilateral ventriculomegaly. Early clinical assessment, differential 
diagnosis and cerebral imaging including cerebral MRI angiography allow the 
clinicians to diagnose also in early infancy this rare condition.