eMedicine Specialties > Neurology > Neuro-oncology
Low-Grade Astrocytoma: Differential Diagnoses & Workup
Updated: Jan 8, 2010
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Other Problems to Be Considered
Brainstem syndromes
Cerebritis or cerebral abscess
Cavernous angioma or arteriovenous malformation
Hamartoma
Stroke or infarct
Workup
Laboratory Studies
No specific laboratory test is available for low-grade glioma. If an endocrine abnormality is suggested, then the appropriate studies may be ordered, but laboratory tests are not indicated routinely for diagnosis of low-grade glioma.
Imaging Studies
Both CT scan and MRI can aid in the diagnosis of low-grade glioma. Generally, MRI is considered the study of choice. However, in an emergency setting a noncontrast CT scan may be ordered first.
Computed tomography
Patients with new-onset headache, seizure, weakness, or numbness frequently undergo a CT scan first. Typical CT findings of a low-grade glioma show lower attenuation than the surrounding brain (see image below). A mild mass effect may be noted. Obstructive hydrocephalus can be confirmed. Low-grade gliomas also may show evidence of calcification. If a contrast CT scan is obtained, the tumor usually does not enhance.
A 28-year-old male taxi driver presented to the emergency department after having a seizure. Noncontrast head CT scan was obtained showing the typical appearance of a low-grade astrocytoma. The lesion in the mesial left frontal lobe was hypodense on CT scan.
Magnetic resonance imaging
On MRI, low-grade gliomas show decreased signal relative to surrounding brain on T1 sequences (see following images).
Preoperative MRI of the brain of a 28-year-old male taxi driver who presented to the emergency department after having a seizure. On T1-weighted sequences, the tumor does not enhance and shows decreased signal intensity compared to normal brain. These findings are consistent with low-grade astrocytoma.
For tumors, MRI has the advantage of showing the lesion in multiple planes. This image, a T1-weighted sagittal image of the brain of a 28-year-old male taxi driver who presented to the emergency department after having a seizure, shows the tumor along the mesial aspect of the frontal lobe. Note that mass effect is minimal, typical of a low-grade lesion.
Coronal T1-weighted gadolinium-enhanced MRI of the brain shows the tumor of a 9-year-old boy who presented with headaches and gradual onset of a right hemiparesis. Note the heterogeneous enhancement of the tumor.
Sagittal T1-weighted MRI of the brain shows juvenile pilocytic astrocytoma of a 9-year-old boy who presented with headaches and gradual onset of right hemiparesis. Stereotactic surgery has made resection of these low-grade tumors in this deep location feasible.
A 3-year-old boy presented with speech regression. MRI of the brain revealed a tumor in the left mesial temporal lobe. This T1-weighted gadolinium-enhanced image shows an enhancing tumor involving the hippocampus, uncus, and amygdala. The surgical pathologic studies revealed a low-grade mixed tumor of astrocytes and atypical neurons, a ganglioglioma.
On T2 sequences, higher signal reflects both the tumor and surrounding edema (see following images). Pilocytic astrocytomas often are associated with a cyst, which may be particularly prominent on T2-weighted sequences.
T2-weighted sequences of an MRI of the brain of a 28-year-old male taxi driver who presented to the emergency department after having a seizure show increased signal intensity compared with normal brain. The radiologic appearance is typical of low-grade astrocytoma.
A 9-year-old boy presented with headaches and gradual onset of right hemiparesis. MRI of the brain was obtained. The T2-weighted sequence in this MRI shows a tumor in the left thalamus, which is a typical location for a juvenile pilocytic astrocytoma. Note the relatively well-circumscribed nature of the lesion.
MRI of the spinal cord is also the study of choice if an intramedullary low-grade astrocytoma is suspected. On MRI, widening of the spinal cord and frequently an associated cyst are noted. The tumor may show a variable degree of enhancement.
Other Tests
- Electroencephalography (EEG) may be performed on a patient with new-onset seizures; however, no EEG findings are specific to low-grade glioma. However, generalized, diffuse slowing and/or epileptogenic spikes can be seen over the area of the tumor.
- Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging sometimes are used to try to differentiate low-grade gliomas from either high-grade tumors or other types of pathology. Typically, low-grade gliomas show hypometabolism via PET or SPECT while high-grade gliomas are hypermetabolic. This information may be useful in guiding further therapy.
Procedures
Lumbar puncture is generally contraindicated in patients with elevated intracranial pressure, which may occur in the setting of a brain tumor. Cerebrospinal fluid (CSF) studies do not aid in the diagnosis of low-grade glioma.
Histologic Findings
As briefly reviewed already, the histologic findings in low-grade astrocytomas depend on the type of tumor. Low-grade infiltrating astrocytomas are characterized by mild cellular proliferation and atypia. High-grade features, such necrosis or endothelial cell proliferation, are not present.
Pilocytic astrocytomas show piloid (hairlike) cells in 2 patterns: dense fascicles and loose arrangements. They also may show some degree of microvascular proliferation and necrosis, but these do not indicate malignant potential in these relatively well-circumscribed tumors. Pilocytic astrocytomas frequently are associated with a cyst.
Pleomorphic xanthoastrocytoma have a high degree of astrocytic pleomorphism as well as lipidized giant cells. Usually no necrosis or endothelial proliferation is noted. Subependymal giant-cell astrocytomas demonstrate several types of cells, typically including small elongated cells as well as giant, multinucleated globoid cells.
More on Low-Grade Astrocytoma |
| Overview: Low-Grade Astrocytoma |
 Differential Diagnoses & Workup: Low-Grade Astrocytoma |
| Treatment & Medication: Low-Grade Astrocytoma |
| Follow-up: Low-Grade Astrocytoma |
| Multimedia: Low-Grade Astrocytoma |
| References |
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Further Reading
Keywords
low grade astrocytoma, central nervous system neoplasms, primary brain tumor, treatment, symptoms, glioblastoma multiforme, GBM, juvenile pilocytic astrocytoma, JPA, pleomorphic xanthoastrocytoma, PXA, subependymal giant-cell astrocytoma, SGCA, low-grade astrocytoma, CNS neoplasm, glioma
