Chapter 121 Low-Grade Gliomas : Astrocytoma, Oligodendroglioma, and Mixed Glioma

• Youmans,Neurological Surgery • Greenberg,Handbook of Neurosurgery

Epidemiology

• 15% of all brain tumors in adults• Classified,WHO grade II

– diffuse infiltrating astro cytoma : fibrillary, protoplasmic, and gemistocytic variants

– oligodendroglial– ependymal, or mixed cellular histology

• Youmans,Neurological Surgery

Spatial definition

• Type 1: – solid tumor only without infiltration of brain parenchyma– Most amenable to surgical resection. Most favorable

prognosis– Includes gangliogliomas, pilocytic astrocytomas,

pleomorphic xanthoastrocytomas, and some protoplasmic astrocytomas (no oligodendrogliomas are in this group)

Spatial definition• Type 2 :

– solid tumor associated with surrounding tumor-infiltrated brain parenchyma

– Surgical resection may be possible, depending on tumor location

– Often low-grade astrocytomas

• Type 3: – infiltrative tumor cells without solid tumor tissue– Risk of neurologic deficit may preclude surgical resection. – Usually oligodendroglioma

• Greenberg,Handbook of Neurosurgery

Clinical presentation• Typically arise in the frontal lobes, followed by temporal

and parietal lobe lesion• Presentation

– seizures with most remaining otherwise neurologically intact– increase intracranial pressure (head ache, nausea, vomiting,

lethargy, papilledema)– focal neurological deficits (weakness, sensory disturbance or

neglect, visual neglect, agnosia, aphasia)– impaired executive function (altered per sonality, disinhibition,

apathy)

• Youmans,Neurological Surgery

Neuroradiology• CT

– one of an either discrete or diffuse hypodense to isodense mass lesion

– minimal or no enhancement with intravenous contrast administration– calcification : oligodendrogliomas or mixed oligoastrocyro mas

• MRI– T1 : hypointense to isointense – T2 : hyperintense– most LGGs do not show gadolinium enhancement on MRl– display a tendency to reside within and extend along white matter

tracts (e.g., corpus callosum, subcortical white matter)

• Youmans,Neurological Surgery

Neuroradiology• Positron emission tomography (PET) and single-photon

emis sion computed tomography (SPECT)– usually shows reduced uptake offluorodeoxyglucose compared

to the rest of the brain– the characterization of tumor grade because LGGs are typically

hypometabolic compared with high-grade lesions

• Youmans,Neurological Surgery

Treatment