Glioneuronal Tumors
Glioneuronal tumors comprise a heterogeneous group of focal, low-grade glial tumors that include—among others— pleomorphic xanthoastrocytoma (PXA), dysembryoplastic neuroepithelial tumor (DNET), and ganglioglioma.
Unlike diffuse infiltrative low-grade gliomas (WHO grade II), these tumors are typically well circumscribed, cortical or superficially located, and most often present with seizures, particularly in children and young adults. Management is primarily surgical, aiming for maximal safe resection and—when applicable—improvement or complete remission of seizure activity.
What are glioneuronal tumors and how do they differ from other low-grade gliomas?
These are focal, often cortical tumors with glial and/or neuronal components, exhibiting distinct biology and prognosis compared with diffuse infiltrative gliomas.
Diffuse low-grade gliomas (e.g., WHO grade II astrocytoma or oligodendroglioma) are characterized by infiltrative growth, extending into surrounding normal brain tissue. In contrast, many glioneuronal tumors are more localized, better demarcated, and often involve superficial cortical regions.
How common are they and at what ages do they occur?
These tumors are less common than diffuse low-grade gliomas and primarily affect children and young adults.
Although relatively uncommon, glioneuronal tumors are clinically significant because of their strong association with epilepsy and their generally favorable prognosis after appropriate surgical treatment.
- PXA: most often in children, adolescents, and young adults.
- DNET: classically in children/adolescents with long-standing, drug-resistant epilepsy.
- Ganglioglioma: predominantly in pediatric populations, often associated with temporal lobe epilepsy.
What is the typical clinical presentation and why are they associated with epilepsy?
Seizures are the most common presentation, reflecting frequent cortical involvement in epileptogenic brain regions.
Common presentations include:
- Focal seizures (with or without impaired awareness), often of temporal lobe origin.
- Secondary generalization in some patients.
- In larger lesions: headache, nausea, or mass effect (less common in DNET).
- Focal neurologic deficits depending on lesion location (less frequent at presentation).
Epilepsy may result not only from the tumor itself but also from associated cortical irritability or coexisting focal cortical dysplasia, particularly in DNET.
Main subtypes (PXA, DNET, ganglioglioma): key features
While grouped together, each glioneuronal tumor subtype has characteristic clinical, imaging, and biologic features.
Pleomorphic Xanthoastrocytoma (PXA)
- Rare tumor (small fraction of astrocytic neoplasms).
- Typically superficial and supratentorial, with a predilection for the temporal lobe.
- Seizures are common; larger lesions may cause mass effect.
- Often cystic with a mural nodule and variable enhancement.
DNET (Dysembryoplastic Neuroepithelial Tumor)
- Classically cortical and well circumscribed.
- Associated with long-standing drug-resistant epilepsy.
- Typically shows minimal edema, little mass effect, and limited contrast enhancement.
Ganglioglioma
- Mixed tumor with neuronal and glial components.
- Most commonly located in the temporal lobe.
- One of the most frequent tumors encountered in temporal lobe epilepsy.
- Often contains calcifications and mixed cystic/solid elements.
What do MRI and CT show—diagnostic imaging patterns?
MRI with contrast is the imaging modality of choice. Certain patterns are suggestive, but definitive diagnosis remains histologic.
General features: lesions are often well defined and cortical/superficial.
- PXA: frequently cystic with mural nodule, variable enhancement, superficial cortical location.
- DNET: multinodular appearance, minimal or absent enhancement, little edema or mass effect.
- Ganglioglioma: heterogeneous, cystic and/or solid mass, variable enhancement, frequent calcifications.
Why are histopathology and WHO grading important?
Histologic diagnosis defines tumor biology, recurrence risk, and the need for adjuvant therapy.
Most glioneuronal tumors are classified as low-grade (WHO grade I or II), with slow growth. However, certain entities—especially PXA and rarely ganglioglioma—may exhibit anaplastic features, altering follow-up and treatment strategy.
Imaging alone is insufficient. Histopathologic evaluation (and molecular profiling when applicable) is essential for accurate diagnosis and prognosis.
What is first-line treatment and why is surgery central?
Maximal safe surgical resection is the treatment of choice, offering durable tumor control and improved seizure outcomes.
In PXA, DNET, and ganglioglioma, surgery:
- provides definitive diagnosis,
- reduces or eliminates the epileptogenic focus,
- improves prognosis, particularly when gross total resection is achieved.
What does “maximal safe resection” mean and how does it relate to seizure control?
The goal is to remove as much tumor as possible without compromising neurologic function, recognizing that extent of resection influences seizure outcome.
Maximal safe resection accounts for:
- proximity to eloquent cortex (speech, motor, vision),
- use of mapping, neuronavigation, and microsurgical techniques,
- possible coexistence of cortical dysplasia or peritumoral epileptogenic cortex.
In DNET and ganglioglioma, completeness of resection often correlates with excellent seizure control. In PXA, gross total resection primarily improves oncologic control and reduces recurrence risk.
Is there a role for radiotherapy or chemotherapy?
In most glioneuronal tumors, adjuvant therapy is not routine.
Radiotherapy and/or systemic therapy may be considered when:
- resection is incomplete with residual disease,
- there is tumor recurrence,
- anaplastic features are present (e.g., anaplastic PXA),
- biologic behavior suggests a more aggressive course.
What to expect after surgery: recovery, seizure control, follow-up
Postoperative course depends on tumor location, extent of resection, and whether epilepsy or mass effect was the dominant issue.
Typical elements include:
- Postoperative MRI to document extent of resection.
- Individualized follow-up schedule (clinical and imaging).
- For epilepsy patients: close collaboration with neurology for antiepileptic management and seizure outcome assessment.
Seizure improvement may be immediate or gradual. Duration of preoperative epilepsy and completeness of resection strongly influence long-term seizure freedom.
Prognosis and risk of recurrence or malignant transformation
Overall prognosis is excellent, especially after complete resection, though risk profiles differ by subtype.
- DNET: extremely slow growth; recurrence after complete resection is rare.
- Ganglioglioma: excellent prognosis with total resection; anaplastic transformation is rare.
- PXA: generally favorable prognosis, but higher risk of aggressive behavior when anaplastic features are present.
Frequently asked questions & when to seek a second opinion
If seizures remain drug-resistant, is the tumor always the cause?
Not exclusively. Peritumoral epileptogenic cortex or associated cortical dysplasia may contribute, underscoring the importance of comprehensive preoperative evaluation.
Is radiotherapy required after surgery?
Usually not. It is considered mainly in cases of residual disease, recurrence, or anaplastic histology.
What is the imaging study of choice?
Contrast-enhanced brain MRI is the reference standard. CT is useful for rapid assessment or detecting calcifications.
When should I seek urgent care?
- New or worsening seizures.
- New weakness, speech or visual disturbances, balance problems.
- Signs of increased intracranial pressure (severe headache, vomiting, confusion).
At Neuroknife, management is individualized, aiming for maximal safe resection and optimal seizure control when epilepsy is the primary clinical issue.
When should you seek specialized neurosurgical evaluation?
If you have epilepsy with persistent seizures despite appropriate medication and imaging reveals a focal lesion consistent with PXA, DNET, or ganglioglioma, early neurosurgical consultation helps define a safe, effective treatment strategy.
Final decisions depend on lesion location, proximity to eloquent cortex, epilepsy history, and feasibility of safe resection.
Schedule an appointment or request a second opinion© Neuroknife — Original physician-authored medical content, provided exclusively for patient education and informational purposes.