Intracranial Tumors

Fetal intracranial tumors are rare. The incidence has been estimated at 0.34 per million live births.

Embryonic tumors are thought to derive from embryologically dsplaced cells. Brain tumors have been produced in animals by the use of chemical and viral teratogens. The relevance of these experiments to human brain neoplasms is unclear.

There are several classifications of congenital brain tumors (Table 1). Teratomas, by far the most frequent variety diagnosed antenatally, may contain well-differentiated structures, such as hair, bone, or muscle, or undifferentiated structures. In the latter case, they have a tendency toward malignancy. Teratomas usually occur in the pineal region, the suprasellar region, or the fourth ventricle. Most of the teratomas diagnosed antenatally are large and cause major distortion of the surrounding brain tissues and are often associated with macrocrania.^1-3 Epidermoid tumors (also known as "cholesteatomas") derive from epithelial cells and frequently appear as cystic lesions, containing a leaflike material, that originate from the desquamation of the internal epithelial lining. They are most commonly located at the level of the cerebellopontine angle, suprasellar region, and temporal lobe. Dermoid tumors are characterized by the presence of desquarnated epithelium, sebaceous secretions, and hair. They are often connected with the skin surface by a dermal sinus and usually occur in the posterior fossa. Germinomas originate from germ cells and are usually solid lesions occurring in the pineal and suprasellar regions. Tumors originating from differentiated germ cells include choriocarcinoma (trophoblastic cells), endodermal sinus tumor (yolk sac), embryonal carcinoma, and teratoma. Medulloblastoma only arises in the posterior fossa. It is a very malignant lesion that appears as a soft, friable mass often with internal necrosis.

Craniopharyngioma is the most frequent supratentorial tumor in children. It derives from remnants of the craniopharyngeal duct, consists of both cystic and solid components, and occurs in the suprasellar region. Among the tumors that derive from ependymal cells, the one that is most frequently congenital in origin is the choroid plexus papilloma. Tuberous - sclerosis, neurofibromatosis, and systemic angiomatosis of the CNS and eye are autosomal dominant diseases that are characterized by the presence of intracranial tumors. In tuberous sclerosis, multiple neuroglial nodules occur in the cerebral cortex or ventricular system. Neurofibromatosis is associated with brain tumors, such as acoustic neurinoma, multiple meningioma, and glioma. Systemic angiomatosis of the CNS and eye is characterized by the presence of cerebellar hemangioblastoma. The colloid cyst of the third ventricle is thought to derive from the epithelium that forms the roof of the thela choroidea and is located in the anterior portion of the third ventricle.

In a review of 48 cases diagnosed antenatally, teratomas accounted for 62% of cases. Neuroepithelial tumors were present in 15%, lipomas in 10% and craniopharyngiomas in 6%.¹

The origin of tumors diagnosed in utero is frequently difficult to ascertain, given the large dimensions of the mass. Most of the lesions are however supratentorial, in contrast to the more frequent infratentorial location of brain tumors occurring in older children.

Fetal intracranial tumors are frequently associated with macrocephaly, ventricular enlargement, intracranial calcifications and hemorrage. Ventriculomegaly is most frequently caused by obstruction to cerebro-spinal fluid circulation. However, overproduction of fluid may however occur with teratomas and choroid plexus papillomas. Polyhydramnios occur in 40% of cases. In most cases, the mechanism is probably related to failrue of swallowing, whether this is neurologically induced r is the consequence of mechanical obstruction to the pharynx. Hydrops has also been reported, most frequently as a consequence of arteriovenous shunting within the large tumoral mass, causing high output cardiac failure.¹

Facial dysmorphism is frequent with large tumors. There is well established association between interhemispheric lipomas and agenesis of the corpus callosum.⁴

There is no established association between fetal and neonatal tumors and chromosomal aberrations.

A relatively small number of cases of brain tumors have been described in the literature and has been extensively reviewed.1-3, 5, 6 A brain tumor is suspected when mass-occupying lesions, cystic areas, or solid areas are seen within the fetal head or when there is a change in shape or size of the normal anatomic structures (e.g., a shift in the midline). Although ultrasound can detect some fetal intracranial tumors, usually it does not allow a specific diagnosis of the histologic variety.2 Schlembach and associates1 have extensively reviewed the antenatal liturature and have found that fetal teratomas, astrocytomas and craniopharyngiomas have a similar appearance, that is a complex mass distorting the brain architecture, possibly associated with macrocephaly, ventriculomegaly and intracranial calcifications. Intracranial teratomas usually cause major distortion of intracranial anatomy and tend to grow outside the fetal skull. Intracranial lipomas are well-defined echogenic areas, usually located in the midline, in the position normally occupied by the corpus callosum, and/or within the bodies of lateral ventricles. Choroid plexus tumors appear as large choroid plexuses, and may be associated wit ventriculomegaly and subarachnoid space enlargement.7 Choroid plexus papillomas and carcinoma have a similar sonographic appearance and probably can not be differentiated prenatally. Papillomas however are by far more frequent in the prenatal and neonatal period.5

Frequently, tumors have an aspecific antenatal appearance that may be compatible with hemorrhage and/or hydrocephalus.

The natural history of fetal brain tumors is variable. The available data suggest however that even very severe lesions may develop rapidly in late gestation. In fact, several cases have been reported in which midtrimester sonograms were unremarkable.

Teratomas may be associated with increased maternal serum and amniotic fluid alphafetoprotein.1, 3

Magnetic resonance may be helpful to better differentiate normal cerebral parenchyma from the tumor mass, as well as to identify external components of the tumor. 1, 5

The differential diagnosis of brain tumors include other space occupying intracranial lesions. At times, it may be particularly challenging to distinguish between a tumor and a fresh intraparenchymal hemorrage. Cerebral hemorrage lacks the mass effect that is usually found with tumors. In these cases, serial sonograms (in 2-3 weeks most severe intracranial hemorrages are expected to result in cavitation, ventriculomegaly, and blood clot formation) or antenatal MRI allow a specific diagnosis.

Unfortunately, most intracranial tumors will be manifest only in late gestation. It has been remarked that midtrimester sonograms are frequently unremarkable.

Magnetic resonance usually provides significant additional information. Most intracranial tumors appear as a large intracranial masses. A specific diagnosis of the histologic type is usually impossible but the outcome in general is poor. Choroid plexus tumors and lipomas that have a better prognosis usually have a specific appearance.

The prognosis of congenital tumors is variable and is frequently poor for those cases diagnosed in utero. In the review of 48 cases by Schlembach and associates¹ the mortality rate was 77%. No clear data are available with regard to the degree of neurological impairment in survivors, but this is expected to be high as well. The histologic type of the tumor is certainly a major factor. In a postnatal series,the one year survival rate of teratomas was only 7%, compared with 44% of astrocytomas.⁸ Choroid plexus papillomas have a much better outcome (the five year survival rate for papillomas is 100% and for carcinoma 40%)and intracranial lipomas haveassociated with a survival rate of 100% and no developmental handicap.⁸ Unfortunately, there are limitations to the antenatal diagnosis of the specific type of tumor. Large complex mass distorting intracranial anatomy (usually teratomas, astrocytomas or craniopharyngiomas) were found to have an overall survival rate of only 14%.¹

Pregnancy termination can be offered to the parents before viability. Many cases however will be diagnosed only in late gestation. In the presence of a large complex mass distorting cerebral anatomy, the prognosis is generally poor and a conservative management should be offered to the couple.

TABLE 1. CLASSIFICATION OF CONGENITAL INTRACRANIAL TUMORS

Embryonic tumors

Teratoma

Epidermoid

Dermoid

Germinal tumors

Germinoma

Embryonal carcinoma

Choriocarcinoma

Endodermal sinus tumor

Teratoma

Neuroblastic tumors

Medulloblastoma

Neuroblastoma

Retinoblastoma

Tumors related to embryonal remnant tissues

Craniopharyngioma

Chordoma

Tumors of ependymal origin

Ependymoma

Subependymal mixed glioma

Choroid plexus papilloma

Glioblastoma mu(tiforme

Malignant astrocytoma

Tumors associated with genetic diseases

Tuberous sclerosis (Bourneville's disease)

Neurofibromatosis (Von Recklinghausen's disease)

Systemic angiomatosis of the CNS and eye (Von Hippel- Lindau's disease)

Colloid cyst of the third ventricle

Heterotopia and hamartoma

Lipoma

Vascular tumors: hemangioblastoma

Adapted from Mori:- Neuroradiology and Neurosurgery. New York, Thieme-Stratton, 1985; Wilson et al. In: Newton, Potts (eds): Radiology of the Skull and Brain.

Anatomy and Pathology. St. Louis, CV Mosby, 1977

1. Schlembach D, Bornemann A, Rupprecht T, Beinder E. Fetal intracranial tumors detected by ultrasound: a report of two cases and review of the literature. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 1999;14(6):407-18. Epub 2000/02/05.

2. D'Addario V, Pinto V, Meo F, Resta M. The specificity of ultrasound in the detection of fetal intracranial tumors. Journal of perinatal medicine. 1998;26(6):480-5. Epub 1999/05/04.

3. Sherer DM, Onyeije CI. Prenatal ultrasonographic diagnosis of fetal intracranial tumors: a review. American journal of perinatology. 1998;15(5):319-28. Epub 1998/06/27.

4. Pilu G, Sandri F, Perolo A, Pittalis MC, Grisolia G, Cocchi G, Foschini MP, Salvioli GP, Bovicelli L. Sonography of fetal agenesis of the corpus callosum: a survey of 35 cases. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 1993;3(5):318-29. Epub 1993/09/01.

5. Anselem O, Mezzetta L, Grange G, Zerah M, Benard C, Marcou V, Fallet-Bianco C, Adamsbaum C, Tsatsaris V. Fetal tumors of the choroid plexus: is differential diagnosis between papilloma and carcinoma possible? Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2011;38(2):229-32. Epub 2011/07/30.

6. Doren M, Tercanli S, Gullotta F, Holzgreve W. Prenatal diagnosis of a highly undifferentiated brain tumour--a case report and review of the literature. Prenatal diagnosis. 1997;17(10):967-71. Epub 1997/11/14.

7. Pilu G, De Palma L, Romero R, Bovicelli L, Hobbins JC. The fetal subarachnoid cisterns: an ultrasound study with report of a case of congenital communicating hydrocephalus. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 1986;5(7):365-72. Epub 1986/07/01.

8. Wakai S, Arai T, Nagai M. Congenital brain tumors. Surgical neurology. 1984;21(6):597-609. Epub 1984/06/01.

9. Pencalet P, Sainte-Rose C, Lellouch-Tubiana A, Kalifa C, Brunelle F, Sgouros S, Meyer P, Cinalli G, Zerah M, Pierre-Kahn A, Renier D. Papillomas and carcinomas of the choroid plexus in children. Journal of neurosurgery. 1998;88(3):521-8. Epub 1998/03/06.

Pilu, G, Buyukkurt S: Congenital intracranial tumors. Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology, www.visuog.org, (January 2013).

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