What Is Oligodendroglioma?
Oligodendroglioma is a diffuse infiltrative brain tumor that develops from oligodendrocytes, the cells that produce the myelin sheathing nerve fibers, and accounts for roughly 5% of all primary intracranial tumors. It is usually located in the white matter of the cerebral hemispheres, most often the frontal lobe, and typically occurs in young-to-middle-aged adults aged 35-50. Because of its cortical location, many patients present with epilepsy (seizures) as the sole symptom for a long period. Having the most favorable prognosis among diffuse gliomas makes it special in terms of recognizing and planning it correctly.
The Diagnosis Is Made by 1p/19q and IDH
MRI is the principal imaging method; the tumor typically appears as a cortical-subcortical lesion that is hyperintense on T2/FLAIR, and the calcification often seen on CT aids the diagnosis. However, the definitive diagnosis is made only by molecular examination of tissue obtained at surgery: under the 2021 WHO classification, demonstration of both an IDH1/IDH2 mutation and 1p/19q co-deletion is mandatory for the diagnosis of oligodendroglioma. Without these tests, oligodendroglioma cannot be diagnosed; IDH-mutant tumors without 1p/19q co-deletion fall into the astrocytoma category. For this reason, surgery is a critical step both for treatment and for an accurate molecular diagnosis.
Classification and the Treatment Decision
In the 2021 WHO classification, the term 'anaplastic oligodendroglioma' has been removed; the tumor is classified only as grade 2 or grade 3, and there is no grade 4 oligodendroglioma. Treatment is planned according to grade, extent of resection, molecular profile, age and the patient's condition. The first step is the widest safe surgical resection; awake craniotomy and cortical mapping are used for tumors near critical functional (eloquent) areas. For low-grade cases, options include close surveillance, the brain-penetrant IDH inhibitor vorasidenib (approved for certain grade 2 cases after surgery), and radiotherapy with chemotherapy when needed. For grade 3 cases, the standard approach is radiotherapy combined with chemotherapy (PCV or temozolomide).
The Surgical Process and Preserving Function
Because oligodendroglioma is a tumor that infiltrates the surrounding brain, the aim of surgery is the widest possible resection while preserving function. During preparation a detailed neurological examination, contrast MRI, and when needed functional MRI and DTI tractography, a multidisciplinary meeting and an anaesthetic assessment are carried out. If the tumor is close to critical areas such as speech or movement, awake craniotomy and cortical mapping are preferred to reduce the risk of permanent loss. Because of calcification and increased vascularity, the bleeding risk may be somewhat higher than in some gliomas; this is taken into account in surgical planning. After surgery there is usually 24–48 hours of intensive care and a few days in hospital; the extent of resection is assessed with a control MRI.
Prognosis and Realistic Expectations
Thanks to 1p/19q co-deletion and IDH mutation, oligodendroglioma has the most favorable prognosis among diffuse gliomas and responds to radiotherapy and chemotherapy; the PCV regimen is supported by long-term follow-up data. Prognosis varies with age, extent of resection, tumor grade and molecular features. Because low-grade tumors may transform to higher grade over time, close follow-up is recommended. The risks of surgery (bleeding, infection, a temporary or permanent neurological deficit, edema, seizures) are discussed openly. We do not promise a guaranteed result; expectations are shared clearly before surgery.