A neonate had suffered from a teratogenic insult during embryonic growth that has affected the mesencephalic pa of his developing neural tube. In the presented cast of his ventricular system (left lateral view), which of the following areas might have suffered

The cerebral aqueduct (D) is the cavity of the midbrain that develops from the mesencephalon. The lateral ventricle (A) is the cavity of telencephalon and the third ventricle (C) is the cavity of diencephalon. The interventricular foramen of Monro (B) serves as the communication between the two. The fouh ventricle (E) is the cavity of the rhombencephalon.