**9. Destructive cerebral lesions**

prenatally diagnosed by ultrasound and MRI. The classification of intracranial hemorrhages includes five major types: intraventricular hemorrhage, cerebellar, subdural, primary subarachnoid hemorrhages, and other intraparenchymal hemorrhages. Intraventricular hemorrhage is the most common variety of neonatal intracranial hemorrhages and is characteristic of the immature brain. Intraventricular hemorrhages are subdivided according to their severity into four grades: the first three grades are limited to the ventricles, while the fourth grade

The outcome of bleeding into the ventricles ranges from hemorrhage absorption and resolution without residual deficit, to brain damage, with neurological and mental deficits, epilepsy and in extreme cases to fetal or neonatal death. Different scoring systems have been developed to predict the prognostic significance of fetal intraventricular hemorrhage. They depend upon ventricular enlargement and the presence or absence of brain parenchymal damage [72–79].

*Vein of Galen aneurysmal malformation* is a rare congenital malformation (1% of all abnormalities of the fetal cerebral arteriovenous system [80]. It occurs in isolation, although there have been reported cases related to cardiac abnormalities or cystic hygroma. The current hypothesis is the early occurrence (between the 6 and 11 WA), as a result of the persistence of an abnormal connection between the primitive choroidal vessels and the proximal region of the prosencephalic median vein. The persistence of the connection leads to the appearance of some abnor-

mal arteriovenous shunts and the formation of the vein of Galen (**Figures 27** and **28**).

**Figure 27.** Massive intraparenchymatous hemorrhage in a case of fetal/neonatal alloimmune thrombocytopenia.

**Figure 28.** The same case. The fetus has had a complete normal neurosonogram in mid-trimester.

includes parenchymal involvement.

58 Congenital Anomalies - From the Embryo to the Neonate

Spontaneous antenatal subdural hemorrhage is rare [71].

The destructive lesions may include an extremely wide range of conditions: hydranencephaly, tumors/mass lesions, cysts, periventricular leukomalacia, infections, dysplasias, intracranial hemorrhage, and other lesions. Identification of these abnormalities can be extremely helpful in providing the patients with management options. Moreover, it has the potential to modulate the neonatal therapy [81–85].

*Hydranencephaly* is a severe congenital condition: most of the cerebral hemispheres are replaced by a membranous sac. The pathogenic mechanism and the prognosis remain controversial. Still, fetal and postnatal neuroimaging data and histopathologic findings suggest an early bilateral internal carotid artery occlusion occurring at 8–12 WA [81].

Fetal brain *tumors* are rare and have a different histologic pattern [84]. The definitive diagnosis relies on histopathology. The distinction between potentially curable tumors and tumors rapidly fatal after birth is extremely difficult. Moreover, some intracranial masses are not real tumors. Among the histological structure, we mention teratoma, glioblastoma, fetus-in-fetu, craniopharyngioma, and hemangioma.

The acronym TORCH is used to refer to congenital *infections*: toxoplasmosis, other infections (syphilis, varicella zoster, and parvovirus B19), cytomegalovirus, and herpes simplex virus. Zika virus has emerged as an important worldwide congenital infection. Many maternal and fetal symptoms are common. All mentioned infections may cause neurologic damage (ventriculomegaly, intraventricular adhesions, subependymal cysts, intracerebral calcifications, and microcephaly). The Zika virus leads to a more severe spectrum of CNS abnormalities and affects mildly other organ systems [85]. All congenital infections have rather nonspecific ultrasound findings. For the imagist professional, the awareness of imaging features of common congenital infections may facilitate early diagnosis and may, at times, lead to prompt initiation of therapy.

*Periventricular leukomalacia* has been reported in preterm and growth-restricted fetuses and neonates, and in monochorionic complicated pregnancies. It manifests as punctate white matter lesions or focal white matter necrosis. In clinical settings, cranial US has a limited sensitivity in detecting them. MRI is a more useful tool [78, 86].

Unfortunately, *cortical dysplasias*, involved as an epileptogenic substrate, are the most subtle lesions to identify, diagnose, and characterize [87, 88]. Improved MRI techniques with a multimodality approach (magnetoencephalography, positron emission tomography) will probably increase sensitivity and specificity for identifying them.

The most used classification [88] tried to unify the terminology of cortical dysplasias, which are seen as a subset of all malformations of cortical development. This proposal is based on histopathologic data, clinical and imaging findings, being currently under review [87] (**Figures 29**–**31**).

The above division of CNS congenital anomalies is an arbitrary one. In the most severe cases, several types of cortical malformation may be found simultaneously. Moreover, many types

Fetal Central Nervous System Abnormalities http://dx.doi.org/10.5772/intechopen.76208 61

**Figure 34.** Complete agenesis of the corpus callosum. Cystic dilatation of the fourth ventricle and enlarged posterior fossa, with upward displacement of the tentorium, torcula, and transverse sinuses. Confirmation of the absence of CC

**Figure 33.** Complete agenesis of the corpus callosum. Unilateral voluminous intracerebral cyst. Severe unilateral asymmetric ventriculomegaly. Subsequently, the short-term and long-term evolution was completely normal.

**Figures 32**–**34** show several examples of such associated abnormalities.

succed one another, or overlap in time.

by means of conventional autopsy.

**Figure 29.** Benign, small dimensions, non-evolving intracerebral cyst: 28 WA (a and b), 30 WA (c), and postpartum, by means of transfontanellar ultrasound assessment (d).

**Figure 30.** Porencephaly.

**Figure 31.** Arachnoid cyst.

**Figure 32.** Midline abnormality and unilateral asymmetric borderline ventriculomegaly.

The above division of CNS congenital anomalies is an arbitrary one. In the most severe cases, several types of cortical malformation may be found simultaneously. Moreover, many types succed one another, or overlap in time.

**Figures 32**–**34** show several examples of such associated abnormalities.

**Figure 33.** Complete agenesis of the corpus callosum. Unilateral voluminous intracerebral cyst. Severe unilateral asymmetric ventriculomegaly. Subsequently, the short-term and long-term evolution was completely normal.

**Figure 31.** Arachnoid cyst.

**Figure 30.** Porencephaly.

means of transfontanellar ultrasound assessment (d).

60 Congenital Anomalies - From the Embryo to the Neonate

**Figure 32.** Midline abnormality and unilateral asymmetric borderline ventriculomegaly.

**Figure 29.** Benign, small dimensions, non-evolving intracerebral cyst: 28 WA (a and b), 30 WA (c), and postpartum, by

**Figure 34.** Complete agenesis of the corpus callosum. Cystic dilatation of the fourth ventricle and enlarged posterior fossa, with upward displacement of the tentorium, torcula, and transverse sinuses. Confirmation of the absence of CC by means of conventional autopsy.
