Figure 8: Case 8: Two transvaginal views of the fetal brain at 22 weeks, showing abundant intracranial calcifications (arrows) in the deep white matter.
The brain is easily imaged in the second and third trimesters because of differences in echogenicity between brain parenchyma and specular reflections from the coverings of the brain. Normally echogenic structures in the fetal brain include the choroid plexus, leptomeninges, ventricular walls, deep penetrating veins, and the cerebellar vermis7,9. Aside from these areas, all of which conform to known anatomic landmarks in the brain, an intracranial echogenic mass is likely to be associated with significant pathology.
Intracranial teratomas tend to be echogenic complex masses with cystic and solid components. They may grow rapidly, distorting normal intracranial structures, and may extend extracranially as well3,10,14. Other common intracranial tumors of the neonate include primitive neuroectodermal tumors, astrocytomas, malignant germ cell tumors and choroid plexus neoplasms1,15. It may be difficult to differentiate an intracranial hemorrhage from tumor; in addition, hemorrhage may occur within a tumor.
Fetal intracranial hemorrhages are rare and may result in hydrocephalus4,6,8,11,12.
Lipoma of the corpus callosum is a rare congenital anomaly presenting as a highly echogenic mass in a characteristic midline location in the interhemispheric fissure. The lipoma may extend into the lateral ventricles and involve the choroid plexus. In approximately 50% of cases, there is partial or complete agenesis of the corpus callosum2,13. Prognosis for the fetus with corpus callosum lipoma is variable. Symptoms may include seizures, headache, mental retardation, hemiparesis, vomiting and vertigo in 50% of patients13. Surgical resection is not carried out for these stable lesions which do not produce and enlarging mass; therefore, management is directed towards the treatment of symptoms2.
Intracranial calcifications tend to be punctate and scattered, often in a periventricular location, without disturbing midline structures. These calcifications are often associated with infection inutero and may result in micro- or macrocephaly, as well as sensory neural loss5.
The cases described in this report show that diagnostic possibilities for an echogenic mass in the fetal brain include lesions composed of blood, fat or calcium. Echogenic masses in the brain, particularly those causing shift of midline structures, usually carry a poor prognosis.
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