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Imaging in Juvenile Pilocytic Astrocytoma

  • Author: Simon S Lo, MD; Chief Editor: James G Smirniotopoulos, MD  more...
 
Updated: Oct 27, 2015
 

Overview

Juvenile pilocytic astrocytomas occur more often in children and young adults. They are the most common astrocytic tumors in children, accounting for 80-85% of cerebellar astrocytomas and 60% of optic gliomas.

Juvenile pilocytic astrocytomas usually arise in the cerebellum, brainstem, hypothalamic region, or optic pathways, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. The most common site of occurrence of juvenile pilocytic astrocytoma is the cerebellum.[1]

These tumors are usually discrete, indolent lesions associated with cyst formation. The cysts may be unilocular or multilocular, with an associated tumor nodule.

The most common presenting symptoms are associated with increased intracranial pressure resulting from mass effect or hydrocephalus. Symptoms may include headache, nausea, vomiting, irritability, ataxia, and visual complaints, depending on the site of occurrence.[1, 2, 3, 4, 5, 6, 7, 8]

CT and MRI scans

The classic juvenile pilocytic astrocytoma arises in a cerebellar hemisphere; it is easily seen on computed tomography (CT) and magnetic resonance imaging (MRI) scans, as a well-circumscribed lesion with an associated macrocyst. The nodular portion of the lesion usually demonstrates homogeneous contrast enhancement. Calcification is present in 10% of juvenile pilocytic astrocytomas. Other low-grade gliomas are typically hypoattenuating or hypointense, poorly defined, nonenhancing lesions on CT and MRI scans.[9, 10]

Preferred examination

The preferred examination is MRI (demonstrated in the images below).[11, 12, 13, 14, 15, 16, 17]

Juvenile pilocytic astrocytoma (JPA). Axial T1-wei Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI without intravenous gadolinium contrast enhancement shows a cystic JPA in the right cerebellar hemisphere (same patient and tumor as in the next 2 images below).
Juvenile pilocytic astrocytoma (JPA). Axial T2-wei Juvenile pilocytic astrocytoma (JPA). Axial T2-weighted MRI shows a cystic JPA in the right cerebellar hemisphere. The fluid in the cyst has a higher signal intensity than that of the solid component. Peritumoral vasogenic edema is present.
Juvenile pilocytic astrocytoma (JPA). Axial T1-wei Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI obtained with intravenous gadolinium-based contrast agent shows a cystic JPA with an enhancing component in the cyst in the right cerebellar hemisphere.

Pilocytic astrocytomas are typically treated with surgery; MRI scans are useful in outlining the contrast-enhancing tumor. The tumor should be completely resected whenever possible. Cyst wall enhancement may be seen on MRI scans; when such enhancement is present, resection of the entire cyst is indicated.[18, 19, 20, 21, 22, 17] Use of radiologic findings alone to identify low-grade gliomas results in an incorrect diagnosis in as many as 50% of cases.

Intervention

In patients in whom tumor resection is incomplete, the clinical course is often benign; postoperative stabilization of the disease is achieved, despite positive findings of tumor in surgical margins. For this reason, postoperative radiation therapy in these patients is controversial. Frequent follow-up with MRI is helpful.

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Computed Tomography

Supratentorial juvenile pilocytic astrocytomas

Juvenile pilocytic astrocytomas may occur anywhere in the central nervous system. On CT scans, these astrocytomas cannot be reliably differentiated from other more diffuse or aggressive tumors on the basis of imaging characteristics alone. CT scans may show hypoattenuating areas, isoattenuating areas, or both. Enhancement varies from none to extensive, with varying degrees of necrosis and cyst formation.

Supratentorial malignant glioma, ependymoma, and oligodendroglioma may have similar appearances. Lower-grade tumors tend to be homogeneous and well circumscribed. Peritumoral edema is mild, and no hemorrhage is present. Higher-grade tumors have more surrounding edema, are more heterogeneous in density, and may have areas of hemorrhage. A CT scan of a juvenile pilocytic astrocytoma is provided below.

Juvenile pilocytic astrocytoma (JPA). Axial CT sca Juvenile pilocytic astrocytoma (JPA). Axial CT scan obtained with intravenous contrast material shows a contrast-enhancing JPA with cystic components in the cerebellum.

Optic nerve and optic chiasm hypothalamic juvenile pilocytic astrocytomas

A subset of astrocytic tumors occurs in patients with NF1. These tumors may involve the optic nerves, the optic chiasm, and the optic tracts. Most are juvenile pilocytic astrocytomas, but their imaging characteristics are not specific with regard to their histologic features. Varying degrees of cystic change and enhancement are demonstrated. These tumors may appear smooth, fusiform, eccentric, or lobulated. CT scanning demonstrates the intraorbital optic nerves and is sensitive in the detection of the tumors. About 20% of juvenile pilocytic astrocytomas have microscopic calcifications; these calcifications are less frequently seen on CT scans than on other types of images.

Posterior fossa juvenile pilocytic astrocytomas

Among pediatric tumors of the posterior fossa, astrocytomas are second in frequency only to medulloblastoma. Approximately 75% of cerebellar astrocytomas are of the pilocytic type; imaging does not help in predicting their histologic features because fibrillary forms may have similar appearances.

Imaging characteristics are most typical for cerebellar tumors during the first decade of life. The typical presentation of a juvenile pilocytic astrocytoma is of a large cerebellar hemispheric or vermian mass that is predominantly cystic in a child younger than 10 years. Nonenhanced CT scans show hypoattenuation or isoattenuation. Tumor contrast enhancement is homogeneous or heterogeneous, depending on the extent of the cystic necrotic changes.

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Magnetic Resonance Imaging

Supratentorial juvenile pilocytic astrocytomas

On T1-weighted images, the signal intensity is generally low; on T2-weighted images, the signal intensity is increased. Enhancement patterns are similar to those depicted on CT scans. MRI images of juvenile pilocytic astrocytomas are provided below.

Juvenile pilocytic astrocytoma (JPA). Axial T1-wei Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI without intravenous gadolinium contrast enhancement shows a cystic JPA in the right cerebellar hemisphere (same patient and tumor as in the next 2 images below).
Juvenile pilocytic astrocytoma (JPA). Axial T2-wei Juvenile pilocytic astrocytoma (JPA). Axial T2-weighted MRI shows a cystic JPA in the right cerebellar hemisphere. The fluid in the cyst has a higher signal intensity than that of the solid component. Peritumoral vasogenic edema is present.
Juvenile pilocytic astrocytoma (JPA). Axial T1-wei Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI obtained with intravenous gadolinium-based contrast agent shows a cystic JPA with an enhancing component in the cyst in the right cerebellar hemisphere.
Juvenile pilocytic astrocytoma (JPA). Sagittal T1- Juvenile pilocytic astrocytoma (JPA). Sagittal T1-weighted MRI obtained with intravenous gadolinium-based contrast agent shows a JPA with enhancement in the hypothalamic area.

Optic nerve and optic chiasm hypothalamic juvenile pilocytic astrocytomas

Optic chiasm hypothalamic gliomas cannot be distinguished on the basis of their site of origin and are considered to be a single entity. On T1-weighted images, the signal intensity is low. On T2-weighted images, the signal intensity is generally increased. The increase in T2-weighted signal intensity may extend as far as the optic radiations, but such findings do not correlate directly with the presence of tumor. Enhancement is similar to that seen on CT scans. Use of fat-saturated T1-weighted postcontrast MRI of the intraorbital optic nerves is a sensitive method for demonstrating the tumor.

Posterior fossa juvenile pilocytic astrocytomas

The signal intensity is low with T1-weighted sequences and high with T2-weighted sequences. Enhancement patterns are similar to those seen on CT scans. MRI is less sensitive to calcium than is CT scanning.

Vermian tumors are often associated with hydrocephalus. Three general tumor patterns are found.

Less than 10% are solid. These tumors may enhance in a homogeneous or a heterogeneous fashion.

Approximately 50% are simple cysts with a single mural nodule. On CT and MRI scans, the nodule enhances homogeneously, but the associated cyst wall usually does not. Likewise, no histologic evidence of tumor is present in the cyst wall. For this kind of tumor, removal of the mural nodule may be sufficient for treatment.

About 40-45% consist of multilocular cysts. These are actually necrotic tumors; they have a cystlike appearance. The periphery or cyst wall enhances. Histologic evidence of tumor is present in the cyst wall. Cure requires resection of the entire wall. Imaging shows clear-cut enhancement of the non-necrotic portions of the tumor.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis.

NSF/NFD has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see FDA Information on Gadolinium-Based Contrast Agents or Medscape.

Degree of confidence

Specific findings on MRI may be suggestive of juvenile pilocytic astrocytomas, but they are not diagnostic for this disease. Metastatic disease, neoplasm, and high-grade glioma cannot be excluded on the basis of radiographic findings. With regard to tumors of the posterior fossa, the most common possibilities in the differential diagnosis are medulloblastoma and ependymoma. Metastases are rare in childhood. Medulloblastomas are typically isoattenuating to hyperattenuating on nonenhanced CT scans.

Ependymomas may extend laterally or inferiorly to the foramina of Luschka or Magendie; extension is to the cerebellopontine angle or through the foramen magnum, respectively. They are isoattenuating to hyperattenuating on nonenhanced CT scans. About 50% of ependymomas exhibit small multifocal calcifications on CT scans. The major differential diagnostic consideration for optic chiasm/hypothalamic glioma is craniopharyngioma.

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Angiography

Angiography is usually not useful in the diagnosis of juvenile pilocytic astrocytoma except to exclude an aneurysm in the presence of a suprasellar tumor mass.

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Contributor Information and Disclosures
Author

Simon S Lo, MD Associate Professor of Radiation Oncology, Case Western Reserve University School of Medicine; Director of Radiosurgery Services and Neurologic Radiation Oncology, UH Seidman Cancer Center, Case Comprehensive Cancer Center; Chair, American College of Radiology Appropriateness Criteria Expert Panel in Bone Metastasis

Simon S Lo, MD is a member of the following medical societies: American College of Radiology, American Medical Association, American Society for Radiation Oncology, Radiological Society of North America

Disclosure: Nothing to disclose.

Coauthor(s)

Sameer R Keole, MD Assistant Professor of Radiation Oncology, Mayo Medical School; Senior Associate Consultant, Department of Radiation Oncology, Mayo Clinic; Adjunct Assistant Professor, Department of Radiation Oncology, Oklahoma University Health Science Center

Sameer R Keole, MD is a member of the following medical societies: American Medical Association, American Society for Radiation Oncology

Disclosure: Nothing to disclose.

Kenneth J Levin, MD Director, Department of Radiation Oncology, Henry Ford West Bloomfield Hospital

Kenneth J Levin, MD is a member of the following medical societies: American Medical Association, American Society for Radiation Oncology, Michigan State Medical Society, Oakland County Medical Society, American Society of Clinical Oncology

Disclosure: Nothing to disclose.

Andrew E Sloan, MD, FACS Peter D Cristal Chair of Neurosurgical Oncology, Director, Brain Tumor and Neuro-Oncology Center, Vice-Chair of Research Affairs, Department of Neurological Surgery, Case Western Reserve University School of Medicine, University Hospital/Case Medical Center

Andrew E Sloan, MD, FACS is a member of the following medical societies: American Association for the Advancement of Science, American Association for Cancer Research, American Association of Neurological Surgeons, American College of Surgeons, American Society for Radiation Oncology, Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Karl Kish, MD Chief, Section of Neuroradiology, Department of Radiology, Harper University Hospital

Karl Kish, MD is a member of the following medical societies: Radiological Society of North America

Disclosure: Nothing to disclose.

Eric L Chang, MD Professor and Chair, Department of Radiation Oncology, Keck School of Medicine of the University of Southern California; Medical Director, Department of Radiation Oncology, Norris Cancer Hospital; Medical Director, Department of Radiation Oncology, LAC+USC Medical Center; Medical Director, Department of Radiation Oncology, Children’s Hospital of Los Angeles; Adjunct Professor, Department of Radiology, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center

Eric L Chang, MD is a member of the following medical societies: American College of Radiology, American Radium Society, American Society for Radiation Oncology, California Medical Association, North American Skull Base Society, Children's Oncology Group, American Society of Clinical Oncology, Los Angeles County Medical Association, Radiation Therapy Oncology Group, International Stereotactic Radiosurgery Society, Paediatric Radiation Oncology Society

Disclosure: Received honoraria from AbbVie for consulting.

James Fontanesi, MD Clinical Professor of Radiation Oncology, Oakland University, William Beaumont School of Medicine

James Fontanesi, MD is a member of the following medical societies: American Medical Group Association, American Society for Radiation Oncology, Radiological Society of North America, Children's Oncology Group, American Society of Clinical Oncology

Disclosure: Nothing to disclose.

Specialty Editor Board

Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand

Disclosure: Nothing to disclose.

Chief Editor

James G Smirniotopoulos, MD Professor of Radiology, Neurology, and Biomedical Informatics, Program Director, Diagnostic Imaging Program, Center for Neuroscience and Regenerative Medicine (CNRM), Uniformed Services University of the Health Sciences

James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Head and Neck Radiology, American Society of Neuroradiology, Association of University Radiologists, Radiological Society of North America, American Society of Pediatric Neuroradiology

Disclosure: Nothing to disclose.

Additional Contributors

Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR Professor Emeritus of Radiology, Louisiana State University Health Sciences Center, New Orleans; Clinical Professor of Radiology, Tulane University School of Medicine

Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, Louisiana State Medical Society, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, Royal College of Radiologists, Royal Society of Medicine, Orleans Parish Medical Society, American Society of Spine Radiology, American Society of Functional Neuroradiology, Southern Radiology Conference

Disclosure: Nothing to disclose.

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Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI without intravenous gadolinium contrast enhancement shows a cystic JPA in the right cerebellar hemisphere (same patient and tumor as in the next 2 images below).
Juvenile pilocytic astrocytoma (JPA). Axial T2-weighted MRI shows a cystic JPA in the right cerebellar hemisphere. The fluid in the cyst has a higher signal intensity than that of the solid component. Peritumoral vasogenic edema is present.
Juvenile pilocytic astrocytoma (JPA). Axial T1-weighted MRI obtained with intravenous gadolinium-based contrast agent shows a cystic JPA with an enhancing component in the cyst in the right cerebellar hemisphere.
Juvenile pilocytic astrocytoma (JPA). Sagittal T1-weighted MRI obtained with intravenous gadolinium-based contrast agent shows a JPA with enhancement in the hypothalamic area.
Juvenile pilocytic astrocytoma (JPA). Axial CT scan obtained with intravenous contrast material shows a contrast-enhancing JPA with cystic components in the cerebellum.
 
 
 
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