Sonographic assessment of normal and abnormal patterns of fetal cerebral lamination.

OBJECTIVES: Prenatal development of the brain is characterized by gestational age-specific changes in the laminar structure of the brain parenchyma before 30 gestational weeks. Cerebral lamination patterns of normal fetal brain development have been described histologically, by postmortem in-vitro magnetic resonance imaging (MRI) and by in-vivo fetal MRI. The purpose of this study was to evaluate the sonographic appearance of laminar organization of the cerebral wall in normal and abnormal brain development. METHODS: This was a retrospective study of ultrasound findings in 92 normal fetuses and 68 fetuses with abnormal cerebral lamination patterns for gestational age, at 17-38 weeks' gestation. We investigated the visibility of the subplate zone relative to the intermediate zone and correlated characteristic sonographic findings of cerebral lamination with gestational age in order to evaluate transient structures. RESULTS: In the normal cohort, the subplate zone-intermediate zone interface was identified as early as 17 weeks, and in all 57 fetuses examined up to 28 weeks. In all of these fetuses, the subplate zone appeared anechoic and the intermediate zone appeared homogeneously more echogenic than did the subplate zone. In the 22 fetuses between 28 and 34 weeks, there was a transition period when lamination disappeared in a variable fashion. The subplate zone-intermediate zone interface was not identified in any fetus after 34 weeks (n=13). There were three patterns of abnormal cerebral lamination: (1) no normal laminar pattern before 28 weeks (n=32), in association with severe ventriculomegaly, diffuse ischemia, microcephaly, teratogen exposure or lissencephaly; (2) focal disruption of lamination before 28 weeks (n=24), associated with hemorrhage, porencephaly, stroke, migrational abnormalities, thanatophoric dysplasia, meningomyelocele or encephalocele; (3) increased prominence and echogenicity of the intermediate zone before 28 weeks and/or persistence of a laminar pattern beyond 33 weeks (n=10), associated with Type 1 lissencephaly or CMV infection. There was a mixed focal/diffuse pattern in two fetuses. In CMV infection, the earliest indication of the infection was focal heterogeneity and increased echogenicity of the intermediate zone, which predated the development of microcephaly, ventriculomegaly and intracranial calcification. CONCLUSIONS: The fetal subplate and intermediate zones can be demonstrated reliably on routine sonography before 28 weeks and disappear after 34 weeks. These findings represent normal gestational age-dependent transient laminar patterns of cerebral development and are consistent with histological studies. Abnormal fetal cerebral lamination patterns for gestational age are also visible on sonography, and may indicate abnormal brain development.

Malignant transformation of an intraaxial-supratentorial neurenteric cyst - case report and review of the literature.

Neurenteric cysts are "rare benign mass forming developmental abnormalities" that usually affect young adults. Neurenteric cysts are thought to be derived from primitive endoderm, and form as a result of faulty endodermal-notochordal separation at 3 weeks of embryogenesis. Neurenteric cysts are lined by simple-to-pseudostratified respiratory/gastrointestinal-like epithelium; as such, these lesions closely resemble colloid and Rathke's cleft cysts. Anatomically, neurenteric cysts most frequently arise in an intradural-extraaxial location anterior to the cervical-thoracic spinal cord. Intracranial neurenteric cysts are uncommon but have a tendency to reside in the infratentorial compartment. Malignant transformation of the epithelial component of neurenteric cysts is decidedly rare. Of the 3 reported cases of neurenteric cysts with malignant transformation, all were intracranial (2 infratentorial and 1 supratentorial) and extraaxial. We describe a 58-year-old female with a supratentorial-intraaxial lesion that is consistent with a neurenteric cyst exhibiting malignant transformation into an invasive mucinous papillary cystadenocarcinoma. Areas of direct transition between typical benign neurenteric cyst epithelia and malignant epithelia (i.e., carcinoma in situ), highlighted by an abrupt change in the Ki-67 proliferative index, were identified, and supported the primary nature of this brain neoplasm. Metastatic workup at the time of presentation was unremarkable, and immediately up until being lost to follow-up 38 months after gross total resection, routine follow-up MR imaging had not detected a recurrence. To our knowledge, this would be the first reported case of malignant transformation within a supratentorial-intraaxial neurenteric cyst.