Low-Grade Gliomas (LGG)

What are low-grade gliomas (LGG)?

These are primary glial tumors that often grow slowly, but they are not “harmless”—they require proper assessment and a clear, long-term strategy.

LGG most commonly include tumors such as astrocytoma and oligodendroglioma. Their biology may vary substantially, which is why morphology alone is no longer enough. Molecular classification (e.g., IDH status, 1p/19q codeletion) improves prediction of tumor behavior and helps guide the most appropriate treatment plan.

How common are they and what is the general outlook?

Primary brain tumors can cause significant morbidity, and outcomes depend strongly on tumor type and molecular biology.

In many low-grade gliomas, survival after diagnosis can extend for many years, in contrast to high-grade tumors (such as glioblastoma), where expected survival is typically shorter. In LGG, prognosis is particularly influenced by:

• Extent of maximal safe resection (more safe tumor removal is generally better).
• Molecular profile (IDH, 1p/19q, etc.).
• Age, functional status (KPS), and tumor size.
• Location (proximity to eloquent brain regions).

What symptoms do they cause and why are seizures so frequent?

Seizures are the most common first symptom, because LGG often irritate the cortex without immediately causing major neurologic deficits.

In LGG, seizures very commonly represent the first clinical manifestation (often focal seizures). Because these tumors grow slowly, the brain may adapt to subtle changes and symptoms can remain mild or overlooked for a long time.

Other possible symptoms include:

• Subtle, progressive weakness, imbalance, speech or memory difficulties.
• Headache (more often when edema is present).
• Changes in concentration, performance, or “unexplained” fatigue and slowed thinking.

Focal seizures may be subtle (e.g., brief confusion, unusual sensations, transient speech disturbance). These episodes warrant proper evaluation.

How is the diagnosis made (MRI, EEG) and what can MRI show—and not show?

MRI is central, but it cannot always reliably distinguish low-grade from higher-grade tumors without histologic and molecular confirmation when indicated.

• Brain MRI (with/without contrast): defines the lesion’s extent, characteristics, and relationship to eloquent areas.
• EEG: helpful when seizure diagnosis is unclear or to document epileptiform activity.

Clinically, lack of strong contrast enhancement often suggests lower-grade disease, but it is not absolute. Final characterization is based on the overall picture and, when appropriate, tissue diagnosis with molecular profiling.

Is there heredity? NF1 & Li-Fraumeni—what does this mean in practice?

Most LGG are sporadic, but certain hereditary syndromes can increase risk.

The vast majority of LGG are not driven by strong familial inheritance. However, conditions such as Neurofibromatosis type 1 (NF1) and Li-Fraumeni syndrome may be associated with increased risk.

In NF1, a classic example is optic pathway glioma (optic nerve/chiasm/hypothalamus), often low grade (frequently WHO grade I, though some cases can be grade II).

Medical management: anti-seizure medication and what you should know

After a confirmed seizure, anti-seizure therapy is commonly initiated. Choice of medication depends on efficacy, tolerability, and interactions.

Many centers prefer monotherapy with levetiracetam because it has fewer drug interactions (especially with oncologic medications) compared with older agents such as phenytoin.

Practical points:

• If episodes are unclear, EEG can support diagnosis and characterization.
• Levetiracetam may cause irritability or mood changes in some patients.
• Treatment is individualized with the goal of effective seizure control and good quality of life.

Steroids: when they help, what to expect, and side effects to watch for

Corticosteroids can be very effective when edema causes symptoms, but dosing and duration must be carefully managed.

Corticosteroids (e.g., dexamethasone) reduce vasogenic edema and may improve symptoms within hours, with maximal effect over a few days. They are commonly used around the time of surgery or during episodes of significant edema.

Common side effects we monitor for:

• Gastric irritation, insomnia, mood changes.
• Hyperglycemia (especially in diabetes).
• Fluid retention, increased appetite, facial puffiness.

The goal is the lowest effective dose, with tapering when safe, while monitoring for symptom recurrence.

Surgical strategy: biopsy or resection—when and why?

The surgical plan balances maximal safe tumor removal, the need for tissue diagnosis, and neurologic risk.

Core options include:

• Resection, aiming for maximal safe removal.
• Stereotactic biopsy, when resection is not safe or feasible (deep, small, diffuse, or multifocal lesions).

Biopsy can confirm diagnosis, but it may occasionally be non-diagnostic if the sample is not representative. Therefore, decisions are individualized to combine diagnostic certainty with meaningful therapeutic benefit.

Modern surgical safety: navigation, ultrasound, mapping, awake craniotomy

Advanced techniques allow a greater extent of resection with lower neurologic risk, especially near eloquent areas.

At Neuroknife, we use tools such as:

• Neuronavigation for precise intraoperative orientation.
• Intraoperative ultrasound for real-time localization of subcortical lesions.
• Microsurgical technique (microscope, ultrasonic aspirator) for tissue preservation and control.
• Functional mapping to identify eloquent cortex and subcortical pathways.
• Awake craniotomy when lesions are adjacent to critical speech or motor regions.

Functional mapping is often what makes maximal safe resection truly achievable.

Molecular markers (IDH, 1p/19q, MGMT): why they change prognosis and treatment

Molecular classification is not a “detail”—it meaningfully guides prognosis, treatment decisions, and follow-up strategy.

Examples:

• IDH1/IDH2 mutations: common in LGG and generally associated with more favorable outcomes.
• 1p/19q codeletion: characteristic of oligodendroglioma with important prognostic and treatment implications.
• MGMT: more commonly discussed in high-grade gliomas for predicting response to alkylating chemotherapy.

Adjuvant therapies & structured follow-up: who is considered higher risk?

Some patients can be managed with close surveillance, while higher-risk features may support earlier adjuvant treatment.

Decisions are based on factors such as:

• Tumor size (e.g., > 4 cm).
• Residual tumor on postoperative MRI.
• Age and functional status (KPS).
• Location in eloquent cortex and feasibility of further safe resection.

Because LGG may slowly enlarge over time, follow-up relies on serial MRIs and careful comparative review— sometimes across longer intervals to confidently document progression.