Glioma: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Gliomas are primary brain tumors arising from glial cells — astrocytes, oligodendrocytes, or ependymal cells — and are the most common malignant primary brain tumors, representing approximately 80% of malignant intracranial neoplasms. Approximately 25,000 new glioma cases are diagnosed annually in the US. The WHO 2021 brain tumor classification integrates histological and molecular features, defining grades 1–4 based on IDH mutation status, 1p/19q codeletion, TERT promoter mutation, CDKN2A/B homozygous deletion, and EGFR amplification. IDH mutation status is the single most important molecular marker, distinguishing IDH-mutant tumors (grades 2–3 astrocytomas, oligodendrogliomas, and grade 4 IDH-mutant astrocytoma) from IDH-wildtype glioblastoma (grade 4), which is the most common and aggressive subtype with a median survival of only 12–15 months despite multimodal therapy. Gliomas account for the greatest proportion of cancer-related years of life lost of any malignancy in younger adults, given their predilection for patients in the 4th–6th decades of life.

Prior cranial ionizing radiation is the only well-established environmental risk factor for glioma development. Hereditary predisposition syndromes account for a minority of glioma cases: NF1 (neurofibromatosis type 1) predisposes to pilocytic astrocytoma; Li-Fraumeni syndrome (TP53 germline mutation) increases risk of high-grade glioma; Lynch syndrome (MMR gene mutations) and BRCA1/2 carriers have elevated glioma risk. IDH1/2 somatic mutations are the fundamental molecular driver of grade 2–3 gliomas and grade 4 IDH-mutant astrocytoma, arising in oligodendrocyte precursor cells of the frontal lobe in younger patients. IDH-wildtype glioblastoma typically harbors EGFR amplification, PTEN deletion, TERT promoter mutation, and chromosome 10 monosomy as key genomic alterations. No confirmed causal link to mobile phone radiofrequency radiation has been established in large prospective studies. Pesticide and solvent exposure and family history are weak risk factors.

Symptoms reflect tumor location within the brain and the degree of mass effect, peritumoral edema, and seizure activity. New-onset epileptic seizures — partial (focal) or generalized — are the most common presenting feature of low-grade gliomas, occurring in 70–80% of patients, due to cortical irritation by the slowly growing infiltrative tumor. High-grade gliomas (grade 3–4) more commonly cause subacute progressive neurological deficits: contralateral arm or leg weakness, aphasia (dominant hemisphere), visual field defects, cognitive and personality changes, and headaches from raised intracranial pressure (worse in the morning, associated with nausea and vomiting). Rapid clinical deterioration over days to weeks is characteristic of glioblastoma. Temporal lobe tumors cause memory impairment, mood changes, and complex partial seizures. Brainstem gliomas cause diplopia, dysphagia, facial weakness, and gait disturbance.

MRI with gadolinium contrast is the diagnostic standard and should be obtained without delay when glioma is suspected. Low-grade IDH-mutant gliomas appear as T2/FLAIR hyperintense non-enhancing lesions, typically in the frontal or insular cortex. High-grade gliomas show ring enhancement with a necrotic center on T1-post-contrast imaging and marked surrounding edema on T2/FLAIR. Perfusion MRI and MR spectroscopy supplement conventional imaging. Surgical biopsy or resection is required for definitive WHO 2021 molecular classification: IDH1/2 mutation testing (IHC for IDH1 R132H, sequencing for non-canonical IDH2 mutations), 1p/19q codeletion status (FISH or chromosomal microarray), TERT promoter mutation, MGMT promoter methylation, CDKN2A/B homozygous deletion, EGFR amplification, and H3 K27M/G34 mutations for pediatric tumors. DNA methylation array provides the most accurate integrated molecular classification. Gliomas are not staged using TNM — WHO grade (1–4) and molecular subtype define prognosis and treatment.

Maximal safe surgical resection is the first step for all glioma grades: extent of resection correlates directly with improved survival and seizure control. For grade 2 IDH-mutant gliomas, resection followed by PCV chemotherapy (procarbazine, lomustine/CCNU, vincristine) plus 54 Gy radiotherapy (RTOG 9802 trial) extends median OS beyond 13 years for 1p/19q-codeleted oligodendroglioma. Grade 3 anaplastic gliomas: radiotherapy plus temozolomide (CATNON trial). Grade 4 glioblastoma (Stupp protocol): concurrent temozolomide (75 mg/m2 daily) plus 60 Gy in 30 fractions, followed by adjuvant temozolomide (150–200 mg/m2 for 5 days every 28 days) for 6 cycles; MGMT-methylated tumors derive the greatest benefit. Tumor treating fields (TTFields, Optune device) improve median OS from 16.0 to 20.9 months (EF-14 trial) when added to adjuvant temozolomide for newly diagnosed GBM in eligible patients. Bevacizumab is used for recurrent GBM symptom control. IDH-mutant specific therapies: vorasidenib (IDH1/2 inhibitor) improved PFS in grade 2 IDH-mutant gliomas (INDIGO trial, 2023).

Prognosis varies dramatically by molecular subtype. IDH-mutant oligodendroglioma (grade 2): median survival greater than 14 years; 15–20 year survivors documented. IDH-mutant astrocytoma (grade 2): median survival approximately 10 years. IDH-mutant astrocytoma (grade 3): median survival 5–7 years. IDH-wildtype glioblastoma (grade 4): median survival approximately 15 months with Stupp protocol; MGMT-methylated GBM achieves median OS of approximately 21 months. IDH mutation status is the single strongest prognostic factor — IDH-mutant tumors survive 2–3 times longer than IDH-wildtype at equivalent grades. MGMT promoter methylation predicts temozolomide benefit in GBM. The prognosis for Glioma: Causes, Symptoms, Diagnosis and Treatment varies depending on severity at diagnosis, the patient's overall health, and how promptly treatment is initiated. With early diagnosis and appropriate management, many patients achieve good outcomes and maintain quality of life. Regular follow-up with healthcare providers is essential to monitor progress, adjust treatment as needed, and detect any complications early. Adherence to prescribed treatments and lifestyle modifications significantly improves long-term prognosis.

No confirmed modifiable environmental risk factors exist for sporadic glioma. Patients with hereditary predisposition syndromes (NF1, Li-Fraumeni syndrome with TP53 germline mutation) should undergo annual brain MRI surveillance beginning at the time of genetic diagnosis to detect early-stage glioma. Minimizing cranial radiation delivered for other medical conditions — particularly in pediatric patients — reduces secondary glioma risk. Patients with germline TP53 mutations warrant surveillance by a multidisciplinary cancer genetics team following the Li-Fraumeni surveillance protocol, which includes annual brain MRI. No chemoprevention has proven effective for glioma prevention. Population-based screening with MRI for asymptomatic glioma is not cost-effective or recommended given the low incidence. First-degree relatives of glioma patients do not require routine screening in the absence of a known hereditary syndrome.

Seek urgent neurological evaluation for any new-onset seizure in an adult — this should always be investigated with brain MRI before being attributed to idiopathic epilepsy. Progressive or persistent headaches that are new for you, particularly when worse in the morning or associated with nausea and vomiting, require neuroimaging. Any new focal neurological deficit — progressive arm or leg weakness, new speech difficulty (word-finding difficulty, slurred speech), unexplained visual field loss, or personality or behavioral changes noted by family — warrants urgent brain MRI without delay. Rapidly progressive cognitive decline over days to weeks may indicate high-grade glioma and is a neurological emergency. Known glioma patients who experience worsening headaches, new or more frequent seizures, or any decline in function between scheduled appointments should contact their neuro-oncology team without waiting for the next routine visit.