AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

Primary intra-axial brain tumors account for approximately two thirds of all brain neoplasms, whereas the remaining one third is made up of metastases. As a group, gliomas are the most common brain tumors and include astrocytomas, oligodendrogliomas, ependymomas, and choroid plexus tumors. Astrocytomas account for approximately 80% of all gliomas and are the most common supratentorial tumor in all age groups.

The classification of astrocytomas is currently histologic, and the new World Health Organization (WHO) classification of brain tumors is the most widely accepted system. This system has essentially replaced the Kernohan classification because its grades most closely correspond with the prognosis. The first edition was published in 1979 and was the result of nearly a decade of work. In 1993, a second edition incorporated immunohistochemical findings. A working group of experts who convened in July 1999 in Lyon, France, created the current system. Instead of dividing tumors into glial or nonglial categories, tumors are divided by their tissue of origin. Astrocytomas fall into the largest category of tumors of neuroepithelial tissue. The other categories are tumors of peripheral nerves, tumors of the meninges, lymphomas and hematopoietic neoplasms, germ-cell tumors, tumors of the sellar region, and metastatic tumors.

WHO classification of astrocytic tumors

• WHO grade II astrocytoma - Diffuse astrocytoma
  • Fibrillary astrocytomas
  • Protoplasmic astrocytomas
  • Gemistocytic astrocytoma
• WHO grade III astrocytoma - Anaplastic astrocytomas
• WHO grade IV astrocytoma - Glioblastoma
  • Giant-cell glioblastoma
  • Gliosarcoma
• WHO grade II astrocytoma - Pleomorphic xanthoastrocytoma
• WHO grade II astrocytoma - Choroid glioma
• Pilocytic astrocytomas
• Subependymal giant-cell astrocytomas

Pilocytic astrocytomas and subependymal giant-cell astrocytomas are in category 1 of the Systemized Nomenclature of Medicine (SNOMED) classification scheme. This category is defined as tumors of low or uncertain malignant potential or borderline malignancy. The remaining astrocytic tumors are category 3, or malignant. SNOMED category 2 denotes an in situ lesion, and category 0 denotes a benign lesion.

Gliomatosis cerebri is defined as an infiltrative neoplasm involving at least 2 lobes of the brain. Although it is currently defined as an epithelial neoplasm of uncertain origin, many authors believe it to be of glial origin.

Astrocytomas are often divided into circumscribed or infiltrating tumors. Pilocytic astrocytomas and subependymal giant-cell astrocytomas are circumscribed group because they tend to respect anatomic boundaries and because they do not invade. Grade II, III, and IV astrocytomas are infiltrating because of their tendency to insinuate and invade. Tumor cells are often found distant from the imaged mass. Pleomorphic xanthoastrocytomas occupy an intermediate position; although they are well circumscribed and slow growing, malignant progression may occur.

Diffuse astrocytomas (WHO grade II astrocytomas) demonstrate slow growth, moderate hypercellularity, occasional nuclear atypia, and diffuse infiltration of neighboring brain structures. These lesions have a tendency for malignant transformation, possibly dedifferentiating all the way to glioblastoma. Included in this group are protoplasmic, gemistocytic, fibrillary, and mixed variants.

Anaplastic astrocytomas (WHO grade III astrocytomas) demonstrate hypercellularity, moderate nuclear atypia, prominent mitotic activity, and diffuse infiltration. These tumors are most often the result of dedifferentiation of a grade II astrocytoma.

Glioblastomas (WHO grade IV astrocytomas) are the most malignant astrocytic tumors. They demonstrate marked nuclear atypia, high mitotic activity, microvascular proliferation, and areas of coagulative necrosis. This group includes glioblastoma multiforme (GBM) and 2 variants: giant-cell glioblastoma and gliosarcoma. Although a glioblastoma may represent a dedifferentiated grade II or III astrocytoma, most are primary glioblastomas and do not derive from a less malignant precursor.

Pleomorphic xanthoastrocytoma (WHO grade II astrocytomas) are histologically characterized by pleomorphic and lipid laden cells. When high mitotic activity or areas of necrosis are present, the term anaplastic pleomorphic xanthoastrocytoma is used.

The 2000 WHO revision added a new entity, namely, chordoid glioma. This tumor is low grade and typically involves the third ventricle of middle-aged women. Although the tumor histologically resembles a chordoma, immunohistochemical staining revealed glial-type qualities.

Pilocytic astrocytomas are generally well circumscribed and often cystic. Subependymal giant-cell astrocytomas are also well circumscribed; they are seen in patients with tuberous sclerosis.

Brain-tumor imaging has dramatically progressed over the past few decades with the development and refinement of CT, MRI, positron emission tomography (PET), and, most recently, advanced magnetic resonance (MR) sequences.

Pathophysiology

To date, the pathophysiology of astrocytoma remains is not clearly understood, though continuing research is being conducted to evaluate possible molecular pathways. Specific genes believed to play a role in astrocytoma pathogenesis include PTEN/MMAC1, DMBT1 (deleted in malignant brain tumor-1), EGFR, TP53, P16, PDGFR, and retinoblastoma cell-cycle regulatory genes. Research is also directed against disease syndromes with increased rates of astrocytomas, including neurofibromatosis 1 and 2, tuberous sclerosis, and Li-Fraumeni cancer syndrome.

Frequency

United States

Astrocytomas are the most common supratentorial intra-axial tumor in all age groups and the most common brain tumor in children. Among children, astrocytoma is second only to leukemia in cancer prevalence.

The incidence of astrocytoma is 1.22 cases per 100,000 person-years for individuals aged 0-19 years and 1.29 cases per 100,000 person-years for those aged 0-14 years. In general, the incidence of grade I or II tumors decreases with age, whereas that of grade III or IV tumors increases with age. In the 1995-1999 study involving the Central Brain Tumor Registry, the incidence of pilocytic astrocytoma peaked at ages 0-14 years, and the incidence of grade III or IV astrocytoma peaked at ages 65-74 years.

The prevalence of pediatric malignant brain tumors is estimated to be 7.9 cases per 100,000 population, affecting approximately 21,000 children in the United States. The prevalence for adults is 29.5 per 100,000 persons; therefore, more than 81,000 adults in the United States are living with a malignant brain tumor. The most common malignant brain tumor in adults is GBM.

Mortality/Morbidity

The Table below shows mortality rates, as described in the Surveillance, Epidemiology, and End Results report of data collected in 1973-1999.

*ND is no data.

Sex

Supratentorial low-grade astrocytomas are more common in male individuals than in female individuals, with a male-to-female ratio of 2:1. Choroid glioma is most frequent in women. No sex predilection is observed in the other types of astrocytomas.

Age

Incidences of the types of astrocytomas depend on the patient's age. Pilocytic astrocytomas are most common in children and adolescents aged 5-15 years. Low-grade astrocytomas are most common in adults aged 25-40 years. The incidence of anaplastic astrocytomas peaks at 40-50 years. The peak incidence of GBM is in those aged 45-70 years.

Anatomy

Supratentorial astrocytomas are most common in adults. The most common locations are the cerebral hemispheres, but the hypothalamus, optic chiasma, and corpus callosum are also commonly affected.

Infratentorial astrocytomas are most common in children. These tumors most often involve the cerebellum, followed by the brainstem.

Diffuse astrocytomas preferentially involve the cerebral hemispheres. Two thirds of diffuse astrocytomas involve the frontal or temporal lobes. Glioblastomas most often involve the subcortical white matter of the cerebral hemispheres. About 98% of pleomorphic xanthoastrocytomas are supratentorial (most often in the temporal lobes) and typically superficial (in the cerebrum and meninges). Choroid glioma most often involves the third ventricle. Pilocytic astrocytomas occur throughout the CNS. The most common locations include the cerebellum, optic nerve and/or chiasm, hypothalamus, thalamus, basal ganglia, cerebral hemispheres, brainstem, and (uncommonly) spinal cord. Subependymal giant-cell astrocytomas most often originate from the walls of the lateral ventricles in patients with tuberous sclerosis.

Clinical Details

Because of its occupation of a confined space and its relatively soft parenchyma, the brain is especially vulnerable to the mass effect and edema a neoplastic process causes. The effects of a tumor on the brain depend on the characteristics of the occupied brain and the nature of the tumor. Mass effect is less deleterious in atrophic brain than in normal brain because the vault increases the space for displacement of the brain parenchyma. Of course, an aggressive tumor causes more mass effect and edema than does a benign tumor.

Furthermore, the location of the tumor is of fundamental importance. For example, tumor involving a frontal lobe may simply cause personality changes, whereas one that affects the medulla or obstructs the third ventricle most likely results in a poor outcome. Increased intracranial pressure associated with an intracranial mass is an important cause of brain herniation and associated morbidity and mortality.

Increased intracranial pressure, which is observed in 50-75% of patients, causes the most common initial presentations of patients with brain tumors. These presentations include seizures, headache, vomiting, changes in behavior, and changes in mental status. These same changes can also be the result of direct tumoral invasion. Seizures occur in 25-50% of patients. Focal neurologic changes can occur when certain anatomic areas are affected. Children often present with behavioral changes and bulging fontanels.

Preferred Examination

The diagnosis of astrocytoma ultimately requires a tissue sample.

At present, contrast-enhanced MRI is the imaging modality of choice. The large amount of streak artifact in the posterior fossa that can be encountered with CT does not affect MRI. The sensitivity of MR studies is 82-100%, and the specificity is 81-100%. The excellent intrinsic contrast of conventional MRI makes it a sensitive study. The addition of contrast material and additional sequences can substantially improve the specificity. Additional techniques include MR spectroscopy (MRS), which allows clinicians to characterize the chemical composition of the mass by determining the presence and/or alteration of components such as lactate, N-acetylaspartate (NAA), choline (Cho), and myo-inositol (Ins).

Two investigational sequences are often helpful in difficult cases, though the resultant images should be interpreted with caution. The first is perfusion-weighted imaging improves characterization of the tumor and aids in equivocal cases when other causes of signal abnormality are suggested, such as with demyelinating lesions, infarcts, and abscesses. The second is diffusion-tensor imaging, which can demonstrate the relationship of the tumor to white matter tracts.

Although MRI has distinct advantages over CT, contrast-enhanced CT is still used at many centers as the imaging modality for the evaluation of intra-axial mass lesions. The sensitivity of contrast-enhanced CT is 65-100%, and the specificity is 72-100%. Positive aspects of CT include relatively short scanning times, decreased cost, and an open environment for patients with claustrophobia.

Limitations of Techniques

MRI and CT can depict the gross morphologic characteristics of the tumor, its relationship with adjacent tissue, and certain aspects of the chemical composition of the tumor (with MRS). Perfusion-weighted and diffusion-tensor images must be interpreted with caution.

Tumor margins are often difficult to determine with accuracy. Studies have demonstrated that the extent of tumoral involvement in grades I-III astrocytomas is underestimated when current conventional imaging is used. Although MRS has been useful, it also causes underestimation of the tumor burden. Tumor cells have been demonstrated well beyond the margin of any imaging abnormality.

Although imaging is instrumental in diagnosing the tumor and in evaluating the extent of disease or recurrence, only biopsy helps in determining the grade of tumor.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Other Problems to be Considered

Supratentorial mass in an adult

Astrocytoma
Oligodendroglioma
Ependymoma
Metastasis
Meningioma
Lymphoma
Pineal gland tumors
Infarct

Supratentorial mass in a child

Astrocytoma
Ganglioglioma
Primitive neuroectodermal tumors
Dysembryoplastic neuroectodermal tumors
Ependymoma
Pleomorphic xanthoastrocytomas

Infratentorial mass in an adult

Astrocytoma
Metastasis
Hemangioblastoma
Medulloblastoma
Ependymoma
Meningioma
Cerebellar-pontine angle schwannoma
Infarct

Infratentorial mass in a child

Astrocytoma (usually pilocytic)
Medulloblastoma
Ependymoma
Epidermoid inclusion cyst
Craniopharyngioma

Astrocytomas can occur in the white mater of the spinal cord (mostly in children).

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Plain-film radiography does not play a role in the diagnosis of astrocytoma

CT SCAN

Section 5 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

The appearance of astrocytoma on CT partly depends on its grade. Low-grade astrocytomas typically appear as homogeneous areas of decreased attenuation. They are relatively well circumscribed, and 20% have associated calcification. Although low-grade tumors usually do not enhance, rare tumors demonstrate minimal enhancement.

Specific low-grade tumors have imaging characteristics that can increase the specificity of CT. Pilocystic astrocytomas often appear as a cystic lesion with an eccentric mural nodule that strongly enhances after the administration of contrast agent. Subependymal giant-cell astrocytomas are typically near the foramen of Monro and usually occur in patients with tuberous sclerosis. Pleomorphic xanthoastrocytomas are typically supratentorial, cortically based masses with strong heterogeneous enhancement. The adjacent dura and meninges often enhances, creating the dural-tail appearance.

Grade III astrocytomas appear more heterogeneous. Edema is often appreciated, calcification is rare, and the enhancement pattern is usually more pronounced.

Grade IV astrocytomas are even more heterogeneous than tumors of other grades on CT, and they almost always enhance strongly. Calcification is uncommon. Hemorrhage and necrosis is common. Extensive edema and mass effect are usually appreciated. This grade often involves both hemispheres by spreading by means of the corpus callosum or commissures.

MRI

Section 6 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

MRI has increased the sensitivity and specificity in imaging astrocytomas. With the advent of the new techniques (MRS, perfusion-weighted imaging, and diffusion-tensor imaging), specificity has further improved.

MRS allows cerebral metabolites to be assessed by suppressing the signal of water and by interrogating for entities, including NAA, Cho, creatine (Cr), lactate, and lipids. The 2 main MRS techniques are single-voxel spectroscopy and chemical-shift imaging. Single-voxel spectroscopy is used to detect the signal from a single region during 1 measurement. Chemical-shift imaging uses additional phase-encoding pulses to obtain signals.

With cerebral gliomas, MRS is used to assess the spectral pattern, metabolite intensities, and ratios to help grade the tumor and/or predict treatment response. MRS can also help in evaluating for tumoral recurrence and treatment response. The intensity of NAA is correlated with neuronal density and viability. Cho is involved in the turnover of cell membranes and neurotransmitters. Cr serves as a reserve for high-energy phosphates in the cytosol of neurons. Cerebral lactate is always abnormal and indicates ineffective cellular oxidative metabolism. Free lipids are present in areas of necrosis. Compared with normal tissues, cerebral gliomas consistently show lowered NAA intensity, elevated Cho (indicating increased membrane metabolism), and a stable or reduced Cr concentration. An Ins peak is described in certain low-grade tumors.

Perfusion-weighted imaging involves several image acquisitions during the first pass of a bolus of contrast agent. This method allows the imager to determine the relative cerebral blood volume (rCBV). In general, the greater the rCBV, the higher the grade of tumor. Lack of notable flow indicates a nonneoplastic etiology with abnormal signal intensity, such as demyelination. Of note, mixed oligodendrogliomas can have low rCBV. Besides the prognostic information it provides, perfusion-weighted imaging can increase the yield of brain biopsy and help in differentiating recurrent neoplasm from radiation necrosis.

Diffusion-tensor imaging is an experimental sequence that allows the imager to evaluate the structure and orientation of the white matter tracts. This sequence takes advantage of the fact that myelin restricts diffusion of water molecules in directions perpendicular to the fiber orientation. This sequence can help in determining whether neoplasm involves white matter pathways, improving the precision of surgical planning and the placement of radiation ports.

Although not used in the diagnosis of astrocytomas, functional MRI (fMRI) deserves mention because it can be an important part of presurgical planning. A blood oxygen–dependent sequence is applied as the patient performs various tasks involving motor, sensory, visual, auditory, and language functions. Increased blood flow to a part of the brain is correlated with increased metabolic activity. The results are used determine whether tumor involves vital structures (eloquent areas), a finding that may possibly affect surgical decisions.

Low-grade astrocytomas are typically hyperintense on T2-weighted images. On T1-weighted images, most low-grade astrocytomas are hypointense relative to white matter. Contrast enhancement may be absent or, at best, mild. Exceptions include the mural nodule of pilocytic astrocytoma and the strong heterogeneous enhancement of pleomorphic xanthoastrocytomas. Astrocytomas are often associated with enhancement of the adjacent dura and meninges, giving the dural-tail appearance. MRS may show an elevated Cho peak and decreased NAA peak. An elevated Cho-Cr ratio or a depressed NAA-Cr ratio suggests tumor. This holds true for all high-grade tumors and many, but not all, low-grade tumors. (Some low-grade tumors may not have an elevated Cho peak.) Perfusion MR studies fail to demonstrate increased rCBV.

Grade III astrocytomas often invade structures without destroying them, causing their ill-defined borders. The mass is inhomogeneous and bright on T2-weighted images. Surrounding edema and/or tumor infiltration is usually appreciated. Enhancement is usually seen. MR perfusion demonstrates increased relative cerebral flow volume.

Grade IV astrocytomas (GBM) are usually discovered as bulky disease, and necrosis is a hallmark of this grade. These lesions usually enhance peripherally, in a nodular and irregular manner, and they cause a large amount of mass effect and edema. These tumors often cross the corpus callosum, giving them a typical butterfly shape. Areas of hemorrhage and necrosis are common, and spectroscopy demonstrates high Cho, high lactate, high lipid, and low NAA values. Short–echo time (TE) studies demonstrate an absent or low myo-inositol peak. Perfusion studies demonstrate elevated rCBV.

ULTRASOUND

Section 7 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Ultrasonography plays a role in the intraoperative assessment of nonsuperficial masses. Using ultrasonography, the surgeon can plan the best surgical approach before excision or biopsy.

NUCLEAR MEDICINE

Section 8 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Primary brain tumors generally have increased glucose metabolism on [18F]fluorodeoxyglucose (FDG) PET studies. The degree of metabolic activity is correlated with both the grade of the tumor and the patient's prognosis. Low-grade tumors may demonstrate little to no increased uptake, whereas grade IV lesion often have uptake that overshadows that of the gray matter.

The heterogeneous nature of grade III or IV lesions is a specific feature for which PET helpful. Obtaining samples from active areas is of vital importance for accurate grading. PET can be used to guide stereotactic biopsy to obtain a representative sample.

PET has also been used to assess the response to therapy, and it can be used to detect transformation of a low-grade lesion to a high-grade one.

ANGIOGRAPHY

Section 9 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Angiography is being used in several ongoing trials to assess the intratumoral treatment of grade III and IV astrocytoma.

INTERVENTION

Section 10 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Interventional neuroradiology may play an important role in the future treatment of astrocytoma with intratumoral chemotherapy. In general, current treatment is limited to traditional approaches.

Medical/Legal Pitfalls

• Medical and legal pitfalls of imaging of astrocytoma primarily consist of missed or delayed diagnosis.
• With CT, the scarcity of edema and mass effect with low-grade lesions may make the true extent of pathology difficult to ascertain. Furthermore, small lesions may not be visible if contrast material is not used.
• As many as 4% of grade III or IV lesions do not enhance on imaging.
• Finally, because of the inhomogeneity of high-grade tumors, stereotactic biopsy of an area of necrosis instead of the tumor can delay accurate diagnosis.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Normal pattern on single-voxel magnetic resonance spectroscopy (MRS) of 4 key molecules show relative heights and typical values. N-acetylaspartate (NAA) peaks at 2.0 ppm (tallest peak). Creatine (Cr) peaks at 3.0 ppm. Choline (Cho) peaks at 3.2 ppm. Myo-inositol (MI) peaks at 3.6 ppm.
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Media type:  MRI

Media file 2:  Pilocytic astrocytoma in a 20-year-old man. Top row (left to right), Sagittal, coronal, and axial contrast-enhanced T1-weighted MRIs. Bottom row: Axial fluid-attenuated inversion recovery (FLAIR), diffusion, and apparent diffusion coefficient (ADC) images. Note the cystic mass with an intensely enhancing mural nodule in the inferior cerebellar vermis, as well as the mass effect on the brainstem, upper cervical cord, cerebellum, and fourth ventricle.
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Media type:  MRI

Media file 3:  Grade II astrocytoma in a 27-year-old woman. Nonenhanced CT scan shows a heterogeneous, ill-defined, hypoattenuating area in the right temporal lobe.
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Media type:  CT

Media file 4:  Grade II astrocytoma in a 30-year-old man. Nonenhanced T2-weighted MRI shows a well-circumscribed area of increased signal intensity in the left temporal lobe.
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Media type:  MRI

Media file 5:  Low-grade astrocytoma in a 52-year-old woman. Top row (left to right), Nonenhanced CT scan, fluid-attenuated inversion recovery (FLAIR) MRI, and diffusion-weighted MRI. Bottom row (left to right), Single-voxel spectroscopic image showing with region of interest, spectrum, and perfusion image. Images show an ill-defined, hypoattenuating lesion in the right centrum semiovale extending to the left side through the body of the corpus callosum. The lesion has increased signal intensity on the FLAIR image. The true nature of the lesion cannot be easily established on anatomic imaging. Magnetic resonance spectroscopy (MRS) shows mild elevation of the choline (Cho) peak in relation to the N-acetylaspartate (NAA) peak with an inverted lactate peak. The findings are compatible with a low-grade neoplasm.
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Media type:  MRI

Media file 6:  Grade II astrocytoma. Left, Fluid-attenuated inversion recovery (FLAIR) image demonstrates an area of increased signal intensity in the parietooccipital region. Right, Perfusion MRI demonstrates decreased relative cerebral blood volume (rCBV), consistent with a low-grade neoplasm. The final pathologic diagnosis was a grade II astrocytoma.
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Media type:  CT

Media file 7:  Grade III astrocytoma in a 33-year-old woman. Nonenhanced studies (right) show a mixed-attenuation lesion (solid and cystic areas) in the right parietal lobe with adjacent vasogenic edema. After contrast enhancement (left), the solid component is enhancing.
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Media type:  CT

Media file 8:  Grade III astrocytoma in a 33-year-old woman. Top row (left to right), Axial nonenhanced and contrast-enhanced T1-weighted, proton density–weighted, and fluid-attenuated inversion recovery (FLAIR) MRIs. Bottom row (left to right), Sagittal nonenhanced and contrast-enhanced T1-weighted MRIs, axial diffusion-weighted images, and axial apparent diffusion coefficient (ADC) map. T1-weighted images demonstrate a well-defined area of mixed signal intensity in the right parietal lobe extending to the corpus callosum with adjacent vasogenic edema. Mixed areas represent hemorrhage. Contrast-enhanced images show minimal enhancement of the lesion. Also appreciated is dural enhancement secondary to previous intervention.
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Media type:  MRI

Media file 9:  Grade III astrocytoma in a 71-year-old man. Contrast-enhanced (left) and nonenhanced (right) images show a cystic lesion with thick walls in the left parietal lobe, with thick rim enhancement on the enhanced image. Moderate surrounding vasogenic edema causes mass effect on the atrium of the left lateral ventricle.
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Media type:  CT

Media file 10:  Grade III astrocytoma in a 71-year-old man. Top row (left to right), Axial nonenhanced and contrast-enhanced T1-weighted, proton density–weighted, and fluid-attenuated inversion recovery (FLAIR) MRIs. Bottom row (left to right), Sagittal nonenhanced and contrast-enhanced T1-weighted MRIs, axial diffusion-weighted images, and axial apparent diffusion coefficient (ADC) map. Images show a cystic, well-defined lesion in the left parietal region with surrounding vasogenic edema and a thick rim enhancement on enhanced images. Diffusion and ADC images shows no evidence of acute restriction.
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Media type:  MRI

Media file 11:  Image show no evidence of recurrence in a 37-year-old woman with a history of grade 3 astrocytoma who underwent resection 7 years ago. Coronal contrast-enhanced T1-weighted, diffusion-weighted, and apparent diffusion coefficient (ADC) imaging were initially performed, followed by multivoxel magnetic resonance spectroscopy (MRS) and perfusion imaging. Because findings on cross-sectional imaging were not conclusive, additional studies were performed. MRS shows low levels of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in an area of encephalomalacia, with a normal spectrum in the rest of the brain. Perfusion imaging shows no increased activity in the area of concern. These findings are compatible with gliosis.
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Media type:  MRI

Media file 12:  Grade IV astrocytoma in a 73-year-old man. Top row (left to right), Nonenhanced CT images and fluid-attenuated inversion recovery (FLAIR) MRI. Bottom row, Axial nonenhanced and enhanced and coronal enhanced T1-weighted MRIs. CT demonstrates an inhomogeneous area of abnormal attenuation in the right temporal lobe that extends to the parietal region, with surrounding edema and mass effect. Enhanced MRI demonstrates heterogeneous enhancement, extensive vasogenic edema, and mass effect. Note the ependymal and subependymal enhancement involving the adjacent lateral ventricle and enhancement of the adjacent dura; this finding is consistent with spread.
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Media type:  MRI

Media file 13:  Recurrent grade IV astrocytoma in the region of the right caudate and putamen in a 76-year-old man. Top row (left to right), Nonenhanced CT scan, nonenhanced T1-weighted MRI, T2-weighted MRI, and fluid-attenuated inversion recovery (FLAIR) MRI. Second row from top (left to right): Diffusion-weighted MRI, apparent diffusion coefficient (ADC) map, and axial and coronal contrast-enhanced T1-weighted MRIs. Third row from top: Perfusion-weighted MRIs show increased flow in the caudate and putamen but not in the other areas of abnormal signal intensity. Bottom row: Axial spectroscopic image shows the 2 regions of interest in the right caudate corresponding to the multivoxel spectra. Note the large, infiltrating mass centered in the right basal ganglia and extending to the right frontal lobe, temporal lobe, and insula. Image shows thick peripheral enhancement and central necrosis. Multivoxel spectroscopy demonstrates decreased N-acetylaspartate (NAA), elevated choline, and elevated lactate values in thecaudate.
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Media type:  MRI

Media file 14:  A, Image in a patient after resection of a left frontoparietal, high-grade astrocytoma. Positron emission tomography (PET) demonstrates increased activity in this region, consistent with recurrence. B, Image in another patient being evaluated for recurrence of a high-grade astrocytoma. Image shows no abnormally increased activity to suggest recurrence.
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Media type:  Image

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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• Grainger R, Allison D, Andreas A, et al, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 4th ed. London: Churchill Livingstone;2001.
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• Harrer JU, Parker GJ, Haroon HA, et al. Comparative study of methods for determining vascular permeability and blood volume in human gliomas. J Magn Reson Imaging. Nov 2004;20(5):748-57.
• Hsu YY. Metabolism, perfusion and diffusion MR images of cerebral gliomas. Acta Neurol Taiwan. 2002;11:173-180.
• Kaye AH, Laws ER Jr. Brain Tumors: An Encyclopedic Approach. 2nd ed. Philadelphia, Pa: Churchill Livingstone;2001.
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Article Last Updated: Jun 27, 2006