Imaging of congenital intracranial tumors in fetus and infant.

Dr/ ABD ALLAH NAZEER. MD.

Primary central nervous system (CNS) tumors are a common group of neoplasms in the infant population, being second only to leukemia in frequency. CNS tumors of the fetus represent only 10% of all antenatal tumors, ranking behind extra cranial teratomas, neuroblastomas, and soft-tissue tumors.Intracranial teratoma is the most common fetal brain tumor, accounting for approximately half of all reported cases. It is followed in frequency by astrocytomas of varying grades, lipomas, choroid plexus papillomas, craniopharyngiomas, and primitive neuroectodermal tumors. With regard to anatomic distribution, the majority of fetal CNS tumors are supratentorial.Congenital brain tumors most commonly arise from the pineal gland, suprasellar area, or cerebral hemispheres; however, imaging or even autopsy are frequently unable to determine the origin of these lesions. The tumors most commonly become clinically manifest in the third trimester of pregnancy, sometimes in patients with a normal ultrasound (US) scan obtained recently as 2 weeks before the clinical diagnosis.Diagnosis earlier in pregnancy, particularly before 30 weeks gestation, portends a particularly deleterious prognosis, with reported mortality rates as high as 96.9%.

Histological type and mortality rate of main CNS tumors.

Imaging modalities.US and/or MRI as well as the Multislice CT Scan.

Congenital Teratoma.Intracranial teratomas are rare, accounting for 0.5-2.0% of intracranial tumors. They comprise 50% of congenital brain tumors (those presenting in the first 60 days of life).

Teratomas are typically benign tumors containing elements of all 3 germinal layers: ectoderm, mesoderm and endoderm. They develop from embryonic cells which become “misinvolved” during formation of the primitive streak in the 3rd week of life. Some of these cells become “misenfolded” as intracranial rests of tissue.

Contrast enhanced CT of congenital teratoma shows a centrally located heterogeneous mass containing cystic/solid components and severe hydrocephalus.

Axial T1 (left) and T2 (right) images of a congenital teratoma (arrows). The mass is centrally located and has a heterogeneous appearance. There is hydrocephalus.

Heterogeneous suprasellar mass lesion, proved by histopathology teratoma.

Right frontal teratoma with hemorrhagic component.

Astrocytoma of infancy.Astrocytoma of infancy is a rare tumour that is present itself as a hemispheric mass of voluminous size in infants. It reveals well-circumscribed dural base mass lesion . The tumors are associated with good prognosis.

Right frontal Oligodendroglioma.

Desmoplastic astrocytoma of right fronto-temporo-parietal lobe.

juvenile pilocytic astrocytoma of the cerebellum

Neoplasms of the choroid plexus account for 0.4%-0.6% of all intracranial tumors.2%-4% of pediatric brain tumors, and 10%-20% of brain tumors in children younger than 1 year of age. Most choroid plexus tumors (about 80%) occur as the benign, slowly growing

choroid plexus papilloma, a WHO grade I tumor with a favorable overall prognosis. Choroid plexus tumors have long been associated with hydrocephalus and symptoms related to increased intracranial pressure. In most cases, the increased intraventricular pressure is secondary to an increase in the production of CSF by the tumor. Histologic examination of choroid plexus papillomas reveals an appearance quite similar to that of normal nonneoplastic choroid plexus tissue. Prominent fronds of fibrovascular connective tissue surrounded by columnar or cuboidal cells without significant mitotic activity are typical.

Choroid plexus glomus of the lateral ventricle.

Choroid plexus glomus at the lateral ventricle.

Medulloblastoma.Medulloblastoma is the most common malignant braintumor of infancy and comprises approximately 20% of all primary central nervous system tumors occurring inpatients less than 18 years. Medulloblastoma is believed to arise from the precursor cells of the external granule layer of the developing cerebellum and is predominantly composed of densely packed cells with round-to-oval hyperchromatic nuclei with generally abundant mitotic activity.The etiologies of infant medulloblastoma are unknownfor most patients.

Axial T2 (A) and contrast-enhanced T1 (B) images of a 3-year-old with a medulloblastoma

Supratentorial Primitive neuroectodermal Tumors.Supratentorial primitive neuroectodermal tumors, by definition occurring in the cerebrum or suprasellar region, are composed of undifferentiated or poorly differentiated neuroepithelial cells that may show differentiation along various cell lines. Supratentorial primitive neuroectodermal tumors are infrequent, accounting for approximately 2.5% of childhood brain tumors, with peak incidence in the first 3 years of life. Although morphologically indistinguishable from medulloblastoma, cytogenetic and molecular genetic studies have now demonstrated that supratentorial primitive neuroectodermal tumors are distinct.

Hemorrhagic primitive neuroectodermal tumor of the right frontal lobe in a 4-month-old infant.

Atypical Teratoid/Rhabdoid Tumors

Atypical teratoid/rhabdoid tumors usually present early in life and may constitute as many as 20% of all embryonal tumors. However, the atypical teratoid/rhabdoid tumors have been reported all throughout childhood and into early adulthood. The clinical presentation of atypical teratoid/rhabdoid tumors is indistinguishable from that of medulloblastoma or supratentorial primitive neuroectodermal tumors. About 50% of atypical teratoid/rhabdoid tumors arise in the posterior fossa, 40% are supratentorial, and the rest are pineal, spinal, or multifocal.67 Their location can be intra-axial, extra-axial, or both as they often invade through the meningeal and ependymal boundaries.Leptomeningeal spread occurs in one third of cases atpresentation.

Axial T2 (A) and contrast-enhanced T1 (B) images of an 8-month-old with a large rhamboid tumor arising in the posterior right lateral ventricle.

MR images of a boy with a hemorrhagic AT/RT in the frontal lobe.

Neonatal craniopharyngioma. Craniopharyngioma is a rare neonatal tumor, although it is the most common tumor of the parasellar region in childhood. Only a few cases have been antenatally diagnosed. inception time.

Craniopharyngioma of fetus 26 weeks with supra-sellar echogenic mass.

Craniopharyngioma of 2 months infant.

Craniopharyngioma of 8 months infant.

Congenital craniopharyngioma.

Ependymomas arise from ependymal cells that line the ventricles and passageways in the brain and the center of the spinal cord. Ependymal cells produce cerebrospinal fluid (CSF). These tumors are classified as supratentorial or infratentorial. In children, most ependymomas are infratentorial tumors that arise in or around the fourth ventricle. According to the WHO classification of brain tumors, ependymal tumors are classified into the following four main subtypes:Subependymoma (WHO Grade I).Myxopapillary ependymoma (WHO Grade I).Ependymoma (WHO Grade II).Anaplastic ependymoma (WHO Grade III).

Post-contrast MR image demonstrating an ependymoma in the cerebello-pontine angle.

Hemangioma is a common benign vascular neoplasm that closely resembles normal vessels and can be found in all organs of the human body. Vascular lesions can be classified as infantile hemangiomas or vascular malformations on the basis of their natural history, location, cellular turnover, and histologic characteristics. Hemangiomas are the most common tumor of infancy. It is estimated that they occur in 1%–2% of the population in general and in up to 10% of white persons. They occur more frequently in girls than in boys (3:1 ratio), and their prevalence is higher in premature infants. Hemangiomas are present at birth in 30%–40% of cases, with the remainder generally being appreciated in the first months of life. More than one-half are located in the head and neck, with the most common sites of involvement being the mid-cheek, upper lip, and upper eyelid.Other common involved organ systems include: liver, central nervous system, intestine and lungs.

Multiple intra-cerebral hemangioma by ultrasound study.

Multiple intra-cerebral hemangioma with hemorrhage.

Nasal gliomas occur near the root of the nose (where the cranial portion of the nose joins the forehead), are composed of dysplastic glial tissue, and are congenital nonneoplastic lesions best categorized as heterotopia. A nasal glioma may be connected to the brain by a stalk of tissue in up to 15% of cases, but the stalk does not contain a direct fluid-filled tract that communicates with the subarachnoid spaces. Nasal gliomas are intranasal in 30% of cases, extranasal in 60%, and mixed in 10%.Treatment requires surgical excision. Close follow-up of these patients is of paramount importance because of the possibility of postoperative CSF rhinorrhea and intracranial infectious complication. If there is an intracranial extension that cannot be safely and adequately repaired via the initial extracranial approach, a frontal craniotomy is recommended to prevent any complication. Overall, recurrence rates of 4 to 10% have been reported.

MDCT shows nasopharyngeal mass lesion with extension to the skull base and brain, proved histopathologically as nasal glioma.

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