The CT scanner in posterior fossa tumours of childhood

Imaging tumors of the pediatric central nervous system

Primary tumors of the central nervous system (CNS) are the second most common neoplasms in children and the leading cause of death in this patient population. The primary objective of this article is to describe the most common pediatric brain tumors and to offer an overview of their respective imaging features, primarily on magnetic resonance imaging. Precise anatomic characterization is essential for developing an appropriate differential diagnosis. Once equipped with this critical information, physicians should be better able to make firm diagnoses, leading to improved disease management and patient outcomes in the setting of CNS tumors of childhood.

Clinical and neuroradiologic findings in infants with intracranial ependymomas. Pediatric Oncology Group

Typical clinical characteristics, neuroradiologic findings, and initial neuroradiologic studies were reviewed for 40 patients <3 years of age with intracranial ependymomas, who were treated in the Pediatric Oncology Group (prolonged postoperative chemotherapy and delayed radiation for children <3 years of age with malignant brain tumors). The study included 16 females and 24 males, aged 3 to 35 months, who were diagnosed and registered in the study between 1986 and 1990. Commonly, patients presented with vomiting (70%), ataxia (53%), headache (28%), lethargy (28%), increased head circumference (23%), and irritability (23%). Duration of symptoms before diagnosis ranged from 1 day to 11 months. Thirty-five tumors (88%) were infratentorial; average tumor size was 4.3 (+/-1.4) x 4.2 (+/-1.7) x 4.1 (+/-1.8) cm at presentation. Noncontrast CT scans were performed on 23 patients; 13 (57%) were isodense to surrounding brain tissue and 13 (57%) were calcified. Contrast CT scans of 29 patients revealed that 28 (97%) were enhanced. Of the 15 T1-weighted MRI scans, 10 (67%) demonstrated low-signal intensity tumors, and 15 (94%) of the 16 T2-weighted scans revealed high-signal tumors. Forty-three percent of the tumors were cystic. Blood was observed within only 2 tumors and peritumoral edema was uncommon. Twenty-five percent of the ependymomas extended out to involve the dura, and 97% of the infratentorial tumors showed characteristic plasticity. Hydrocephalus was present in 34 (85%) children.

Posterior cranial fossa tumours in childhood

We reviewed clinical and CT findings in 133 posterior cranial fossa tumours in children. All had histological diagnosis, apart from 20 cases of brain stem glioma. The majority were intra-axial tumours, including 53 medulloblastomas (40%), 31 cerebellar astrocytomas (23%), 28 brain stem gliomas (21%), 14 ependymomas (11%), and single cases of ganglioglioma, haemangioblastoma and teratoma. Extra-axial tumours formed only 3%, including 2 chordomas and 2 schwannomas. The clinical data and CT findings are reviewed. Cerebellar astrocytoma involved the sexes equally, while medulloblastoma, brain stem glioma, and ependymoma were more common in males. Most cerebellar astrocytomas were in the midline, and presumably arose from the vermis. The frequency of calcification was similar to that in previous reports, being highest in ependymoma (69%), followed my medulloblastoma (29%), cerebellar astrocytoma (17%), and brain stem glioma (8%).

Medulloblastoma with extensive calcification

Calcification in cases of medulloblastoma has been described with varying frequency (10%-15.4%) on computed tomographic (CT) scan. Usually these calcifications are small in size and speckled. The authors report a case of medulloblastoma with extensive calcification in the lateral hemisphere of the cerebellum in an 18-year-old boy.

Cystic medulloblastoma

In children medulloblastoma is a commonly encountered posterior fossa midline tumour in which cystic degeneration is not uncommon. A cystic medulloblastoma without solid component has, however, not been described. We report a 12-year-old boy with a posterior fossa midline cystic lesion on CT with surgical and histological confirmation of the diagnosis.

Computed tomography in management of medulloblastomas

The neuroradiological studies of 116 patients with histologically verified medulloblastomas, which had been examined with plain and contrast-enhanced computed tomography (CT), were reviewed. The typical CT appearances of a well-defined, hyperdense enhancing mass in the vermis, with surrounding oedema, occurred in 60% of this series. Atypical features include calcification (17%), cystic or necrotic regions (47%) or poorly defined margins and lack of enhancement (7%). Such features in a vermis mass presenting in the first decade, especially in a boy, should not be considered against the diagnosis of medulloblastoma, but may be misleading when the tumour predominantly involves a cerebellar hemisphere.

Posterior fossa lesions in childhood and infancy. A CT study

Forty-three children with CT studies demonstrating abnormalities in the posterior fossa are presented. Tumors constitute the largest group of lesions (53.5%). Their mean size at time of diagnosis was 39.5 mm. Astrocytomas, medulloblastomas, and ependymomas were the most frequent tumors and their CT features are described and discussed. The congenital group of lesions comprised 18.6% of the cases--the most frequent anomaly being arachnoid cyst. In the miscellaneous group (23.3%), cases with atrophy were the most frequent. The cerebellar hemispheres were the most involved sites (39.5%). Lesions located at the tentorial hiatus or near the clivus were rather rare.

Cystic adult medulloblastomas

The computed tomography scans of four patients who had a medulloblastoma are reviewed. In all the cases, atypical findings were present--specifically, cystic or lucent areas within the tumor. The importance of this uncommon finding associated with adult medulloblastoma is discussed.

Medulloblastomas: a review of modern management with a report on 75 cases

The authors summarize the 8-year experience of a tertiary medical center with 75 cases of medulloblastoma in Saudi Arabia. A discussion of the evolution of modern management of this difficult problem ensues. As 5-year survival statistics approach 80% in some institutions, attention is being focused on the long-term effects of modern therapy and the quality of life led by these children.

The value of skull radiography in children with intracranial tumours

A consecutive series of 106 children with intracranial tumours has been reviewed with special reference to the findings of cranial computed tomography (CT) and plain skull radiography. This review showed that if cranial CT is to be performed, routine plain skull radiographs provide no further information of value in diagnosis. Special projections of the optic canal or internal auditory meatus may be of value in selected patients.

Parameters of infiltration in posterior fossa tumours of childhood using a high resolution CT scanner

The computed tomographic changes in 23 posterior fossa tumours of childhood scanned on a GE 8800 scanner have been compared with the detailed operative reports in order to evaluate morphological features indicative of infiltration. The study indicated that the cyst wall of a cystic astrocytoma was always easily enucleated and was free from infiltration and that a sharp enhancing edge of a medulloblastoma or centrally necrotic astrocytoma was usually also not the site of infiltration. Other features however were found to be unreliable.

Computed tomography of posterior fossa ependymomas in childhood

In reviewing 10 children with surgically proven posterior fossa ependymomas, various computed tomographic representations were seen. Calcification, seen in 50% of the cases, was the single most important finding suggesting the diagnosis of ependymoma. The appearance of two of our ependymomas mimicked the "typical" appearance of medulloblastomas. A case of calcified brainstem ependymoma is presented, to our knowledge, the first such case studied with computed tomography.

Pencil gliomas of the aqueduct of Sylvius. Report of two cases

✓ The authors present the cases of two young adults with low-grade astrocytomas limited to the aqueductal region of the tectum of the mesencephalon. The characteristic presentation of hydrocephalus without brain-stem signs is described. Careful radiological examination, including computerized axial tomography, failed to reveal any evidence of tumor. The diagnosis was established at postmortem examination. Literature review yielded 12 previous cases of similar presentation.

Computerized tomographic findings in medulloblastomas

Twenty patients with intracranial medulloblastoma were analyzed by CT. All patients presented with symptoms of headache, and in eight clinical findings consistent with intracranial hypertension were the only neurological abnormalities. In 16 cases, the medulloblastoma appeared as midline posterior fossa mass and in four cases it was located laterally in the cerebellar hemisphere. The fourth ventricle appeared abnormal and there was evidence of obstructive hydrocephalus in all cases. The lesion was hyperdense in 14 cases but in only one was there evidence of calcification; the neoplasm appeared isodense in six. Post-contrast enhancement was visualized in all cases; this was homogeneous in 18 and had a ring-pattern of variable thickness in two others.

The role of computed tomography in the diagnosis and management of brain tumors

This review article emphasizes the role of computed tomography in the diagnosis and management of brain tumors. The head CT scan has become one of the most precise noninvasive tests in the neurosciences. It has given clinicians more information than they were able to obtain in the past. The subject is covered by subdividing it into several categories: detection of true tumor extent, radiation treatment planning, the immediate postoperative period, treatment responses, failure patterns, detection of radiation-induced damage, and the potential to predict histopathology. The paper is illustrated with examples that emphasize the advantages and some of the limitations of computed tomography as it exists today.