Cytomegalovirus is the most frequent cause of congenital infection and it occurs in approximately 1 % of newborns [3]. In the Buzzi Children’s Hospital series of 3147 fetal MR studies collected from 2001 to 2014 (unpublished data), a proven CMV infection was found in 105 cases, whereas toxoplasmosis in 12, rubella in 2, and parvovirus infection in 7.

Approximately 30–40 % of infected mothers transmit the virus to the fetus. In most cases, the infection is asymptomatic, but 10–15 % of asymptomatic cases at birth and two thirds of neonates with symptomatic infection develop neurological sequelae [3, 4] such as mental retardation, epilepsy, motor deficits, and deafness. The clinical course is generally described as static; however, disease progression has been demonstrated in some cases [5]. The infection can be diagnosed by PCR performed on amniotic fluid, fetal blood, or, in the case of the newborn, by urine analysis or PCR of cerebrospinal fluid or blood.

The infection results in different neuroradiological patterns according to the stage of gestation [1, 6]:

Abnormalities of the temporal polar regions are highly suggestive of congenital CMV infection [3] (Figs. 8.8 and 8.9). The MR imaging pattern of congenital CMV after birth could partly resemble the pattern of the congenital muscular dystrophies, in which a combination of cortical abnormalities and white matter lesions can be seen. However, in congenital muscular dystrophies, hypotonia and muscle weakness are very often present and patients show other abnormalities on MRI, particularly of the brainstem and cerebellum, which usually allow the correct diagnosis. When cortical malformations are absent and white matter abnormalities are the predominant MRI features, the static course of CMV-related encephalopathy and the unrevealing metabolic screening allow to rule out classic leukodystrophies and some inherited disorders such as Aicardi– Goutières syndrome and pseudo-TORCH syndrome, which have a progressive course [3, 7].

Cytomegalovirus infection-related cerebral abnormalities are well identified by MRI, with the exception of calcifications, which are better appreciated on computed tomography (Fig. 8.3) [3, 8–10]. US is able to identify areas of parenchymal hyperechogenicity, ventricular septa, periventricular necrosis, and calcification, as well as ventriculomegaly [11]. Recent efforts are directed toward the early identification of brain lesions in prenatal life. US can detect some CMV infection-associated brain anomalies, but it is substantially influenced by technical and anatomical factors. Fetal MRI is reported to provide substantial additional information, since it is able to identify almost all CMV-related lesions, even at an early gestational age, including major abnormalities such as microencephaly (sometimes missed by US if not associated with microcephaly) and cortical anomalies, with important implications in prognostic evaluation and pregnancy management [12]. Fetal MRI can also identify temporal pole lesions and their evolution throughout gestation: dilatation of temporal horns is the first anomaly followed by white matter T2-weighted hyperintensity and cystic lesions (Figs. 8.8 and 8.9).